add bt polling speedtest

Update external dependencies

See merge request akwizgran/briar!788

.gitignore

@@ -20,6 +20,7 @@ local.properties
 .idea/*
 !.idea/runConfigurations/
 !.idea/codeStyleSettings.xml
+!.idea/codeStyles
 .gradle
 build/
 *.iml

.gitlab-ci.yml

@@ -8,8 +8,6 @@ cache:
 before_script:
   - set -e
   - export GRADLE_USER_HOME=$PWD/.gradle
-  # Accept the license for the Android build tools
-  - echo y | /opt/android-sdk/tools/bin/sdkmanager "build-tools;26.0.2"
   # Download OpenJDK 6 so we can compile against its standard library
   - JDK_FILE=openjdk-6-jre-headless_6b38-1.13.10-1~deb7u1_amd64.deb
   - if [ ! -d openjdk ]

.idea/codeStyles/Project.xml

@@ -0,0 +1,261 @@
+<component name="ProjectCodeStyleConfiguration">
+  <code_scheme name="Project" version="173">
+    <option name="RIGHT_MARGIN" value="100" />
+    <AndroidXmlCodeStyleSettings>
+      <option name="USE_CUSTOM_SETTINGS" value="true" />
+    </AndroidXmlCodeStyleSettings>
+    <JavaCodeStyleSettings>
+      <option name="ANNOTATION_PARAMETER_WRAP" value="1" />
+      <option name="CLASS_COUNT_TO_USE_IMPORT_ON_DEMAND" value="99" />
+      <option name="NAMES_COUNT_TO_USE_IMPORT_ON_DEMAND" value="99" />
+      <option name="PACKAGES_TO_USE_IMPORT_ON_DEMAND">
+        <value />
+      </option>
+      <option name="IMPORT_LAYOUT_TABLE">
+        <value>
+          <package name="android" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="com" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="junit" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="net" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="org" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="java" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="javax" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="" withSubpackages="true" static="true" />
+          <emptyLine />
+        </value>
+      </option>
+      <option name="JD_ALIGN_PARAM_COMMENTS" value="false" />
+      <option name="JD_ALIGN_EXCEPTION_COMMENTS" value="false" />
+    </JavaCodeStyleSettings>
+    <Objective-C-extensions>
+      <file>
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Import" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Macro" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Typedef" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Enum" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Constant" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Global" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Struct" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="FunctionPredecl" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Function" />
+      </file>
+      <class>
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Property" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Synthesize" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="InitMethod" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="StaticMethod" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="InstanceMethod" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="DeallocMethod" />
+      </class>
+      <extensions>
+        <pair source="cpp" header="h" fileNamingConvention="NONE" />
+        <pair source="c" header="h" fileNamingConvention="NONE" />
+      </extensions>
+    </Objective-C-extensions>
+    <XML>
+      <option name="XML_LEGACY_SETTINGS_IMPORTED" value="true" />
+    </XML>
+    <codeStyleSettings language="Groovy">
+      <indentOptions>
+        <option name="USE_TAB_CHARACTER" value="true" />
+        <option name="SMART_TABS" value="true" />
+      </indentOptions>
+    </codeStyleSettings>
+    <codeStyleSettings language="JAVA">
+      <option name="RIGHT_MARGIN" value="80" />
+      <option name="ALIGN_MULTILINE_PARAMETERS" value="false" />
+      <option name="ALIGN_MULTILINE_RESOURCES" value="false" />
+      <option name="ALIGN_MULTILINE_FOR" value="false" />
+      <option name="SPACE_BEFORE_ARRAY_INITIALIZER_LBRACE" value="true" />
+      <option name="CALL_PARAMETERS_WRAP" value="1" />
+      <option name="METHOD_PARAMETERS_WRAP" value="1" />
+      <option name="RESOURCE_LIST_WRAP" value="1" />
+      <option name="EXTENDS_LIST_WRAP" value="1" />
+      <option name="THROWS_LIST_WRAP" value="1" />
+      <option name="EXTENDS_KEYWORD_WRAP" value="1" />
+      <option name="THROWS_KEYWORD_WRAP" value="1" />
+      <option name="METHOD_CALL_CHAIN_WRAP" value="1" />
+      <option name="BINARY_OPERATION_WRAP" value="1" />
+      <option name="TERNARY_OPERATION_WRAP" value="1" />
+      <option name="FOR_STATEMENT_WRAP" value="1" />
+      <option name="ARRAY_INITIALIZER_WRAP" value="1" />
+      <option name="ASSIGNMENT_WRAP" value="1" />
+      <option name="ASSERT_STATEMENT_WRAP" value="1" />
+      <option name="PARAMETER_ANNOTATION_WRAP" value="1" />
+      <option name="VARIABLE_ANNOTATION_WRAP" value="1" />
+      <option name="ENUM_CONSTANTS_WRAP" value="1" />
+      <indentOptions>
+        <option name="USE_TAB_CHARACTER" value="true" />
+        <option name="SMART_TABS" value="true" />
+      </indentOptions>
+    </codeStyleSettings>
+    <codeStyleSettings language="XML">
+      <option name="FORCE_REARRANGE_MODE" value="1" />
+      <indentOptions>
+        <option name="CONTINUATION_INDENT_SIZE" value="4" />
+        <option name="USE_TAB_CHARACTER" value="true" />
+        <option name="SMART_TABS" value="true" />
+      </indentOptions>
+      <arrangement>
+        <rules>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>xmlns:android</NAME>
+                  <XML_NAMESPACE>Namespace:</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>xmlns:.*</NAME>
+                  <XML_NAMESPACE>Namespace:</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:id</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:name</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>name</NAME>
+                  <XML_NAMESPACE>^$</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>style</NAME>
+                  <XML_NAMESPACE>^$</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*</NAME>
+                  <XML_NAMESPACE>^$</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:layout_width</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:layout_height</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:layout_.*</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:width</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*:height</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*</NAME>
+                  <XML_NAMESPACE>http://schemas.android.com/apk/res/android</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+          <section>
+            <rule>
+              <match>
+                <AND>
+                  <NAME>.*</NAME>
+                  <XML_NAMESPACE>.*</XML_NAMESPACE>
+                </AND>
+              </match>
+              <order>BY_NAME</order>
+            </rule>
+          </section>
+        </rules>
+      </arrangement>
+    </codeStyleSettings>
+  </code_scheme>
+</component>

.idea/codeStyles/codeStyleConfig.xml

@@ -0,0 +1,5 @@
+<component name="ProjectCodeStyleConfiguration">
+  <state>
+    <option name="USE_PER_PROJECT_SETTINGS" value="true" />
+  </state>
+</component>

bramble-android/build.gradle

@@ -9,13 +9,13 @@ apply plugin: 'de.undercouch.download'
 
 android {
 	compileSdkVersion 27
-	buildToolsVersion '26.0.2'
+	buildToolsVersion '27.0.3'
 
 	defaultConfig {
 		minSdkVersion 14
 		targetSdkVersion 26
-		versionCode 1700
+		versionCode 10001
-		versionName "0.17.0"
+		versionName "1.0.1"
 		consumerProguardFiles 'proguard-rules.txt'
 	}
 
@@ -36,23 +36,79 @@ dependencies {
 
 dependencyVerification {
 	verify = [
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
+			'com.android.tools.analytics-library:protos:26.1.2:protos-26.1.2.jar:52672a0b42b572a06aecc3535d5068eb46c0e15d129b9f1085d3c16a1da5cdbb',
+			'com.android.tools.analytics-library:shared:26.1.2:shared-26.1.2.jar:5c7e0eda18c6f87feeb83628c707e8aaa3298b41fb72e38efe31ad1675f9e8e9',
+			'com.android.tools.analytics-library:tracker:26.1.2:tracker-26.1.2.jar:06f97aa0adf44ffb06f8681c6a79d9be153a08f61d21eddc42b8d3db96df4282',
+			'com.android.tools.build:apksig:3.1.2:apksig-3.1.2.jar:40696a4559124d1d57873d208857eee059d48859239d569c7d18374ac644a8be',
+			'com.android.tools.build:builder-model:3.1.2:builder-model-3.1.2.jar:d49bfa2a135c9562b6ca7aa4342036cfa1582c7074c2d1d93d1dae8b3a134e17',
+			'com.android.tools.build:builder-test-api:3.1.2:builder-test-api-3.1.2.jar:dfe2a50b740d41b11189101062434d4283d18647e89a492ad51710c719363e9f',
+			'com.android.tools.build:builder:3.1.2:builder-3.1.2.jar:b60f825a42e2efe8433619fbc759f3d9effecab718279048d36881188ceb1d14',
+			'com.android.tools.build:gradle-api:3.1.2:gradle-api-3.1.2.jar:e58bcc5b893e4583ab0f5c8ef89c4dbcce202b405a9d7fcc116d21e5357d4893',
+			'com.android.tools.build:manifest-merger:26.1.2:manifest-merger-26.1.2.jar:9c61c27ea5266573107b954acf1216d398f4d7e7ae6fad6409d6b2b767eb091c',
+			'com.android.tools.ddms:ddmlib:26.1.2:ddmlib-26.1.2.jar:18a2a5fbef36882f07d03c2b9e59eba05cf8248177bf5cbff736e4b582804c44',
+			'com.android.tools.external.com-intellij:intellij-core:26.1.2:intellij-core-26.1.2.jar:37c5acf279f1ae3e85b1a5be3c9f15f43bde7b08f978eefefffb9c4035760c52',
+			'com.android.tools.external.com-intellij:kotlin-compiler:26.1.2:kotlin-compiler-26.1.2.jar:152df0bee7580326c77316b669a9d96e3b09efb1d45f545dce4147271b0b8944',
+			'com.android.tools.external.org-jetbrains:uast:26.1.2:uast-26.1.2.jar:02d39582206d3f5fc0a6cb18bfd9e8b9f9c1acb805ec6dac08b4e3a56849d279',
+			'com.android.tools.layoutlib:layoutlib-api:26.1.2:layoutlib-api-26.1.2.jar:20220039fcc7d799f928153beff862e704457c0f55ab44258f3745ebeb662b4f',
+			'com.android.tools.lint:lint-api:26.1.2:lint-api-26.1.2.jar:e1d5b62b870a7c566e9877a6b96b27784a4d713f8caa07fdcb4705d47a40a1d9',
+			'com.android.tools.lint:lint-checks:26.1.2:lint-checks-26.1.2.jar:211e2afd58504372385d71b1e5be982c2b5121ab6fee1c04ddabeb75a8729e07',
+			'com.android.tools.lint:lint-gradle-api:26.1.2:lint-gradle-api-26.1.2.jar:71284f2a8b03c3e55c94511c9eb36f8184fbb85324325fc6b78abf5183f03d90',
+			'com.android.tools.lint:lint-gradle:26.1.2:lint-gradle-26.1.2.jar:855f0c82b7fc690df1b7319c0774f7517f7f8f5dd4eee1f6077dcf50e07c6240',
+			'com.android.tools.lint:lint-kotlin:26.1.2:lint-kotlin-26.1.2.jar:1e591f70bcbbc11569720a9bbcca2bc1f3d4f789f01f40f642848d920643d484',
+			'com.android.tools.lint:lint:26.1.2:lint-26.1.2.jar:93736c62e9f1976998c2b4aa716aea0734cdb162d05502f4af7292654aedb182',
+			'com.android.tools:annotations:26.1.2:annotations-26.1.2.jar:72773dcaf5c4ccca828e3c8467f1b78a8a00b3cc5f8ad1aab88fcf9379928018',
+			'com.android.tools:common:26.1.2:common-26.1.2.jar:ea4320f0c17dcbc4491896bb705c4d25ec08bd62ef02ab0579fe154e75e788e6',
+			'com.android.tools:dvlib:26.1.2:dvlib-26.1.2.jar:1187aa4fb666595c96c4deb6bc0e0f4b7e396bde9f6243330b49a232946130ea',
+			'com.android.tools:repository:26.1.2:repository-26.1.2.jar:8b86e512ad6d32bd76989451eefe2b271f5efce6d4d65ecb173afaf14606e01a',
+			'com.android.tools:sdk-common:26.1.2:sdk-common-26.1.2.jar:23584720a60a21cdcb5b1ec10269e3013789d6805d153cc696c39ec7ce251896',
+			'com.android.tools:sdklib:26.1.2:sdklib-26.1.2.jar:d3870fafc59ab8efa70d3f9649f40ee299c8ec5b58377b06e8853d7272a5bf4e',
+			'com.google.code.findbugs:jsr305:1.3.9:jsr305-1.3.9.jar:905721a0eea90a81534abb7ee6ef4ea2e5e645fa1def0a5cd88402df1b46c9ed',
+			'com.google.code.gson:gson:2.7:gson-2.7.jar:2d43eb5ea9e133d2ee2405cc14f5ee08951b8361302fdd93494a3a997b508d32',
 			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
 			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
 			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
+			'com.google.errorprone:error_prone_annotations:2.0.18:error_prone_annotations-2.0.18.jar:cb4cfad870bf563a07199f3ebea5763f0dec440fcda0b318640b1feaa788656b',
 			'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
+			'com.google.guava:guava:22.0:guava-22.0.jar:1158e94c7de4da480873f0b4ab4a1da14c0d23d4b1902cc94a58a6f0f9ab579e',
-			'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
+			'com.google.j2objc:j2objc-annotations:1.1:j2objc-annotations-1.1.jar:40ceb7157feb263949e0f503fe5f71689333a621021aa20ce0d0acee3badaa0f',
+			'com.google.jimfs:jimfs:1.1:jimfs-1.1.jar:c4828e28d7c0a930af9387510b3bada7daa5c04d7c25a75c7b8b081f1c257ddd',
+			'com.google.protobuf:protobuf-java:3.4.0:protobuf-java-3.4.0.jar:dce7e66b32456a1b1198da0caff3a8acb71548658391e798c79369241e6490a4',
+			'com.googlecode.json-simple:json-simple:1.1:json-simple-1.1.jar:2d9484f4c649f708f47f9a479465fc729770ee65617dca3011836602264f6439',
+			'com.squareup:javawriter:2.5.0:javawriter-2.5.0.jar:fcfb09fb0ea0aa97d3cfe7ea792398081348e468f126b3603cb3803f240197f0',
+			'com.sun.activation:javax.activation:1.2.0:javax.activation-1.2.0.jar:993302b16cd7056f21e779cc577d175a810bb4900ef73cd8fbf2b50f928ba9ce',
+			'com.sun.istack:istack-commons-runtime:2.21:istack-commons-runtime-2.21.jar:c33e67a0807095f02a0e2da139412dd7c4f9cc1a4c054b3e434f96831ba950f4',
+			'com.sun.xml.fastinfoset:FastInfoset:1.2.13:FastInfoset-1.2.13.jar:27a77db909f3c2833c0b1a37c55af1db06045118ad2eed96ce567b6632bce038',
+			'commons-codec:commons-codec:1.6:commons-codec-1.6.jar:54b34e941b8e1414bd3e40d736efd3481772dc26db3296f6aa45cec9f6203d86',
+			'commons-logging:commons-logging:1.1.1:commons-logging-1.1.1.jar:ce6f913cad1f0db3aad70186d65c5bc7ffcc9a99e3fe8e0b137312819f7c362f',
+			'it.unimi.dsi:fastutil:7.2.0:fastutil-7.2.0.jar:74fa208043740642f7e6eb09faba15965218ad2f50ce3020efb100136e4b591c',
 			'javax.annotation:jsr250-api:1.0:jsr250-api-1.0.jar:a1a922d0d9b6d183ed3800dfac01d1e1eb159f0e8c6f94736931c1def54a941f',
 			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
-			'net.i2p.crypto:eddsa:0.2.0:eddsa-0.2.0.jar:a7cb1b85c16e2f0730b9204106929a1d9aaae1df728adc7041a8b8b605692140',
+			'javax.xml.bind:jaxb-api:2.2.12-b140109.1041:jaxb-api-2.2.12-b140109.1041.jar:b5e60cd8b7b5ff01ce4a74c5dd008f4fbd14ced3495d0b47b85cfedc182211f2',
-			'org.bitlet:weupnp:0.1.4:weupnp-0.1.4.jar:88df7e6504929d00bdb832863761385c68ab92af945b04f0770b126270a444fb',
+			'net.sf.jopt-simple:jopt-simple:4.9:jopt-simple-4.9.jar:26c5856e954b5f864db76f13b86919b59c6eecf9fd930b96baa8884626baf2f5',
-			'org.jacoco:org.jacoco.agent:0.7.4.201502262128:org.jacoco.agent-0.7.4.201502262128-runtime.jar:e357a0f1d573c2f702a273992b1b6cb661734f66311854efb3778a888515c5b5',
+			'net.sf.kxml:kxml2:2.3.0:kxml2-2.3.0.jar:f264dd9f79a1fde10ce5ecc53221eff24be4c9331c830b7d52f2f08a7b633de2',
-			'org.jacoco:org.jacoco.agent:0.7.4.201502262128:org.jacoco.agent-0.7.4.201502262128.jar:47b4bec6df11a1118da3953da8b9fa1e7079d6fec857faa1a3cf912e53a6fd4e',
+			'org.apache.commons:commons-compress:1.12:commons-compress-1.12.jar:2c1542faf343185b7cab9c3d55c8ae5471d6d095d3887a4adefdbdf2984dc0b6',
-			'org.jacoco:org.jacoco.ant:0.7.4.201502262128:org.jacoco.ant-0.7.4.201502262128.jar:013ce2a68ba57a3c59215ae0dec4df3498c078062a38c3b94c841fc14450f283',
+			'org.apache.httpcomponents:httpclient:4.2.6:httpclient-4.2.6.jar:362e9324ee7c697e21279e20077b52737ddef3f1b2c1a7abe5ad34b465145550',
-			'org.jacoco:org.jacoco.core:0.7.4.201502262128:org.jacoco.core-0.7.4.201502262128.jar:ec4c74554312fac5116350164786f91b35c9e082fa4ea598bfa42b5db05d7abb',
+			'org.apache.httpcomponents:httpcore:4.2.5:httpcore-4.2.5.jar:e5e82da4cc66c8d917bbf743e3c0752efe8522735e7fc9dbddb65bccea81cfe9',
-			'org.jacoco:org.jacoco.report:0.7.4.201502262128:org.jacoco.report-0.7.4.201502262128.jar:7a3554c605e088e7e323b1084656243f0444fa353e2f2dee1f1a4204eb64ff09',
+			'org.apache.httpcomponents:httpmime:4.1:httpmime-4.1.jar:31629566148e8a47688ae43b420abc3ecd783ed15b33bebc00824bf24c9b15aa',
-			'org.ow2.asm:asm-debug-all:5.0.1:asm-debug-all-5.0.1.jar:4734de5b515a454b0096db6971fb068e5f70e6f10bbee2b3bd2fdfe5d978ed57',
+			'org.bouncycastle:bcpkix-jdk15on:1.56:bcpkix-jdk15on-1.56.jar:7043dee4e9e7175e93e0b36f45b1ec1ecb893c5f755667e8b916eb8dd201c6ca',
+			'org.bouncycastle:bcprov-jdk15on:1.56:bcprov-jdk15on-1.56.jar:963e1ee14f808ffb99897d848ddcdb28fa91ddda867eb18d303e82728f878349',
+			'org.codehaus.groovy:groovy-all:2.4.12:groovy-all-2.4.12.jar:6a56af4bd48903d56bec62821876cadefafd007360cc6bd0d8f7aa8d72b38be4',
+			'org.codehaus.mojo:animal-sniffer-annotations:1.14:animal-sniffer-annotations-1.14.jar:2068320bd6bad744c3673ab048f67e30bef8f518996fa380033556600669905d',
+			'org.glassfish.jaxb:jaxb-core:2.2.11:jaxb-core-2.2.11.jar:37bcaee8ebb04362c8352a5bf6221b86967ecdab5164c696b10b9a2bb587b2aa',
+			'org.glassfish.jaxb:jaxb-runtime:2.2.11:jaxb-runtime-2.2.11.jar:a874f2351cfba8e2946be3002d10c18a6da8f21b52ba2acf52f2b85d5520ed70',
+			'org.glassfish.jaxb:txw2:2.2.11:txw2-2.2.11.jar:272a3ccad45a4511351920cd2a8633c53cab8d5220c7a92954da5526bb5eafea',
+			'org.jetbrains.kotlin:kotlin-reflect:1.2.0:kotlin-reflect-1.2.0.jar:4f48a872bad6e4d9c053f4ad610d11e4012ad7e58dc19a03dd5eb811f36069dd',
+			'org.jetbrains.kotlin:kotlin-stdlib-jre7:1.2.0:kotlin-stdlib-jre7-1.2.0.jar:c7a20fb951d437797afe8980aff6c1e5a03f310c661ba58ba1d4fa90cb0f2926',
+			'org.jetbrains.kotlin:kotlin-stdlib-jre8:1.2.0:kotlin-stdlib-jre8-1.2.0.jar:633524eee6ef1941f7cb1dab7ee3927b0a221ceee9047aeb5515f4cbb990c82a',
+			'org.jetbrains.kotlin:kotlin-stdlib:1.2.0:kotlin-stdlib-1.2.0.jar:05cfd9f5ac0b41910703a8925f7211a495909b27a2ffdd1c5106f1689aeafcd4',
+			'org.jetbrains.trove4j:trove4j:20160824:trove4j-20160824.jar:1917871c8deb468307a584680c87a44572f5a8b0b98c6d397fc0f5f86596dbe7',
+			'org.jetbrains:annotations:13.0:annotations-13.0.jar:ace2a10dc8e2d5fd34925ecac03e4988b2c0f851650c94b8cef49ba1bd111478',
+			'org.jvnet.staxex:stax-ex:1.7.7:stax-ex-1.7.7.jar:a31ff7d77163c0deb09e7fee59ad35ae44c2cee2cc8552a116ccd1583d813fb4',
+			'org.ow2.asm:asm-analysis:5.1:asm-analysis-5.1.jar:a34658f5c5de4b573eef21131cc32cc25f7b66407944f312b28ec2e56abb1fa9',
+			'org.ow2.asm:asm-commons:5.1:asm-commons-5.1.jar:97b3786e1f55e74bddf8ad102bf50e33bbcbc1f6b7fd7b36f0bbbb25cd4981be',
+			'org.ow2.asm:asm-tree:5.1:asm-tree-5.1.jar:c0de2bbc4cb8297419659813ecd4ed1d077ed1dd5c1f5544cc5143e493e84c10',
+			'org.ow2.asm:asm-util:5.1:asm-util-5.1.jar:ee032c39ae5e3cd099148fbba9a2124f9ed613e5cb93e03ee0fa8808ce364040',
+			'org.ow2.asm:asm:5.1:asm-5.1.jar:d2da399a9967c69f0a21739256fa79d284222c223082cacadc17372244764b54',
 	]
 }
 

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPlugin.java

@@ -55,10 +55,12 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	// Non-null if the plugin started successfully
 	private volatile BluetoothAdapter adapter = null;
 
-	AndroidBluetoothPlugin(Executor ioExecutor, AndroidExecutor androidExecutor,
+	AndroidBluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
+			Executor ioExecutor, AndroidExecutor androidExecutor,
 			Context appContext, SecureRandom secureRandom, Backoff backoff,
 			DuplexPluginCallback callback, int maxLatency) {
-		super(ioExecutor, secureRandom, backoff, callback, maxLatency);
+		super(connectionLimiter, ioExecutor, secureRandom, backoff, callback,
+				maxLatency);
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 	}
@@ -154,7 +156,8 @@ class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
 	}
 
 	private DuplexTransportConnection wrapSocket(BluetoothSocket s) {
-		return new AndroidBluetoothTransportConnection(this, s);
+		return new AndroidBluetoothTransportConnection(this,
+				connectionLimiter, s);
 	}
 
 	@Override

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothPluginFactory.java

@@ -59,11 +59,13 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+		BluetoothConnectionLimiter connectionLimiter =
+				new BluetoothConnectionLimiterImpl();
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(ioExecutor,
+		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(
-				androidExecutor, appContext, secureRandom, backoff, callback,
+				connectionLimiter, ioExecutor, androidExecutor, appContext,
-				MAX_LATENCY);
+				secureRandom, backoff, callback, MAX_LATENCY);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-android/src/main/java/org/briarproject/bramble/plugin/bluetooth/AndroidBluetoothTransportConnection.java

@@ -14,10 +14,14 @@ import java.io.OutputStream;
 class AndroidBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
+	private final BluetoothConnectionLimiter connectionManager;
 	private final BluetoothSocket socket;
 
-	AndroidBluetoothTransportConnection(Plugin plugin, BluetoothSocket socket) {
+	AndroidBluetoothTransportConnection(Plugin plugin,
+			BluetoothConnectionLimiter connectionManager,
+			BluetoothSocket socket) {
 		super(plugin);
+		this.connectionManager = connectionManager;
 		this.socket = socket;
 	}
 
@@ -33,6 +37,10 @@ class AndroidBluetoothTransportConnection
 
 	@Override
 	protected void closeConnection(boolean exception) throws IOException {
-		socket.close();
+		try {
+			socket.close();
+		} finally {
+			connectionManager.connectionClosed(this);
+		}
 	}
 }

bramble-api/src/main/java/org/briarproject/bramble/api/client/ContactGroupFactory.java

@@ -12,19 +12,19 @@ public interface ContactGroupFactory {
 	/**
 	 * Creates a group that is not shared with any contacts.
 	 */
-	Group createLocalGroup(ClientId clientId, int clientVersion);
+	Group createLocalGroup(ClientId clientId, int majorVersion);
 
 	/**
 	 * Creates a group for the given client to share with the given contact.
 	 */
-	Group createContactGroup(ClientId clientId, int clientVersion,
+	Group createContactGroup(ClientId clientId, int majorVersion,
 			Contact contact);
 
 	/**
 	 * Creates a group for the given client to share between the given authors
 	 * identified by their AuthorIds.
 	 */
-	Group createContactGroup(ClientId clientId, int clientVersion,
+	Group createContactGroup(ClientId clientId, int majorVersion,
 			AuthorId authorId1, AuthorId authorId2);
 
 }

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactExchangeTask.java

@@ -13,9 +13,9 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 public interface ContactExchangeTask {
 
 	/**
-	 * The current version of the contact exchange protocol
+	 * The current version of the contact exchange protocol.
 	 */
-	int PROTOCOL_VERSION = 0;
+	byte PROTOCOL_VERSION = 1;
 
 	/**
 	 * Label for deriving Alice's header key from the master secret.

bramble-api/src/main/java/org/briarproject/bramble/api/contact/ContactManager.java

@@ -24,6 +24,8 @@ public interface ContactManager {
 	 * Stores a contact associated with the given local and remote pseudonyms,
 	 * derives and stores transport keys for each transport, and returns an ID
 	 * for the contact.
+	 *
+	 * @param alice true if the local party is Alice
 	 */
 	ContactId addContact(Transaction txn, Author remote, AuthorId local,
 			SecretKey master, long timestamp, boolean alice, boolean verified,
@@ -38,7 +40,10 @@ public interface ContactManager {
 
 	/**
 	 * Stores a contact associated with the given local and remote pseudonyms,
-	 * and returns an ID for the contact.
+	 * derives and stores transport keys for each transport, and returns an ID
+	 * for the contact.
+	 *
+	 * @param alice true if the local party is Alice
 	 */
 	ContactId addContact(Author remote, AuthorId local,
 			SecretKey master, long timestamp, boolean alice, boolean verified,

bramble-api/src/main/java/org/briarproject/bramble/api/contact/RecordTypes.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.contact;
+
+/**
+ * Record types for the contact exchange protocol.
+ */
+public interface RecordTypes {
+
+	byte CONTACT_INFO = 0;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/data/BdfDictionary.java

@@ -24,9 +24,9 @@ public class BdfDictionary extends TreeMap<String, Object> {
 	 * );
 	 * </pre>
 	 */
-	public static BdfDictionary of(Entry<String, Object>... entries) {
+	public static BdfDictionary of(Entry<String, ?>... entries) {
 		BdfDictionary d = new BdfDictionary();
-		for (Entry<String, Object> e : entries) d.put(e.getKey(), e.getValue());
+		for (Entry<String, ?> e : entries) d.put(e.getKey(), e.getValue());
 		return d;
 	}
 

bramble-api/src/main/java/org/briarproject/bramble/api/db/DatabaseComponent.java

@@ -136,8 +136,8 @@ public interface DatabaseComponent {
 
 	/**
 	 * Deletes the message with the given ID. Unlike
-	 * {@link #removeMessage(Transaction, MessageId)}, the message ID and any
+	 * {@link #removeMessage(Transaction, MessageId)}, the message ID,
-	 * other associated data are not deleted.
+	 * dependencies, metadata, and any other associated state are not deleted.
 	 */
 	void deleteMessage(Transaction txn, MessageId m) throws DbException;
 
@@ -241,7 +241,8 @@ public interface DatabaseComponent {
 	 * <p/>
 	 * Read-only.
 	 */
-	Collection<Group> getGroups(Transaction txn, ClientId c) throws DbException;
+	Collection<Group> getGroups(Transaction txn, ClientId c, int majorVersion)
+			throws DbException;
 
 	/**
 	 * Returns the given group's visibility to the given contact, or
@@ -266,6 +267,14 @@ public interface DatabaseComponent {
 	 */
 	Collection<LocalAuthor> getLocalAuthors(Transaction txn) throws DbException;
 
+	/**
+	 * Returns the IDs of all delivered messages in the given group.
+	 * <p/>
+	 * Read-only.
+	 */
+	Collection<MessageId> getMessageIds(Transaction txn, GroupId g)
+		throws DbException;
+
 	/**
 	 * Returns the IDs of any messages that need to be validated.
 	 * <p/>
@@ -310,9 +319,9 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Returns the metadata for any messages in the given group with metadata
+	 * Returns the metadata for any delivered messages in the given group with
-	 * that matches all entries in the given query. If the query is empty, the
+	 * metadata that matches all entries in the given query. If the query is
-	 * metadata for all messages is returned.
+	 * empty, the metadata for all delivered messages is returned.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -328,8 +337,8 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Returns the metadata for the given delivered and pending message.
+	 * Returns the metadata for the given delivered or pending message.
-	 * This is meant to be only used by the ValidationManager
+	 * This is only meant to be used by the ValidationManager.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -337,8 +346,8 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Returns the status of all messages in the given group with respect to
+	 * Returns the status of all delivered messages in the given group with
-	 * the given contact.
+	 * respect to the given contact.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -373,8 +382,8 @@ public interface DatabaseComponent {
 	State getMessageState(Transaction txn, MessageId m) throws DbException;
 
 	/**
-	 * Returns the status of the given message with respect to the given
+	 * Returns the status of the given delivered message with respect to the
-	 * contact.
+	 * given contact.
 	 * <p/>
 	 * Read-only.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/keyagreement/event/KeyAgreementStoppedListeningEvent.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.keyagreement.event;
+
+import org.briarproject.bramble.api.event.Event;
+
+/**
+ * An event that is broadcast when a BQP task stops listening.
+ */
+public class KeyAgreementStoppedListeningEvent extends Event {
+}

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/LifecycleManager.java

@@ -43,17 +43,20 @@ public interface LifecycleManager {
 	}
 
 	/**
-	 * Registers a {@link Service} to be started and stopped.
+	 * Registers a {@link Service} to be started and stopped. This method
+	 * should be called before {@link #startServices(String)}.
 	 */
 	void registerService(Service s);
 
 	/**
-	 * Registers a {@link Client} to be started.
+	 * Registers a {@link Client} to be started. This method should be called
+	 * before {@link #startServices(String)}.
 	 */
 	void registerClient(Client c);
 
 	/**
-	 * Registers an {@link ExecutorService} to be shut down.
+	 * Registers an {@link ExecutorService} to be shut down. This method
+	 * should be called before {@link #startServices(String)}.
 	 */
 	void registerForShutdown(ExecutorService e);
 

bramble-api/src/main/java/org/briarproject/bramble/api/properties/TransportPropertyManager.java

@@ -15,12 +15,17 @@ public interface TransportPropertyManager {
 	/**
 	 * The unique ID of the transport property client.
 	 */
-	ClientId CLIENT_ID = new ClientId("org.briarproject.briar.properties");
+	ClientId CLIENT_ID = new ClientId("org.briarproject.bramble.properties");
 
 	/**
-	 * The current version of the transport property client.
+	 * The current major version of the transport property client.
 	 */
-	int CLIENT_VERSION = 0;
+	int MAJOR_VERSION = 0;
+
+	/**
+	 * The current minor version of the transport property client.
+	 */
+	int MINOR_VERSION = 0;
 
 	/**
 	 * Stores the given properties received while adding a contact - they will
@@ -37,8 +42,8 @@ public interface TransportPropertyManager {
 
 	/**
 	 * Returns the local transport properties for all transports.
-	 * <br/>
+	 * <p/>
-	 * TODO: Transaction can be read-only when code is simplified
+	 * Read-only.
 	 */
 	Map<TransportId, TransportProperties> getLocalProperties(Transaction txn)
 			throws DbException;

bramble-api/src/main/java/org/briarproject/bramble/api/record/Record.java

@@ -0,0 +1,36 @@
+package org.briarproject.bramble.api.record;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class Record {
+
+	public static final int RECORD_HEADER_BYTES = 4;
+	public static final int MAX_RECORD_PAYLOAD_BYTES = 48 * 1024; // 48 KiB
+
+	private final byte protocolVersion, recordType;
+	private final byte[] payload;
+
+	public Record(byte protocolVersion, byte recordType, byte[] payload) {
+		if (payload.length > MAX_RECORD_PAYLOAD_BYTES)
+			throw new IllegalArgumentException();
+		this.protocolVersion = protocolVersion;
+		this.recordType = recordType;
+		this.payload = payload;
+	}
+
+	public byte getProtocolVersion() {
+		return protocolVersion;
+	}
+
+	public byte getRecordType() {
+		return recordType;
+	}
+
+	public byte[] getPayload() {
+		return payload;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/record/RecordReader.java

@@ -0,0 +1,20 @@
+package org.briarproject.bramble.api.record;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.io.EOFException;
+import java.io.IOException;
+
+@NotNullByDefault
+public interface RecordReader {
+
+	/**
+	 * Reads and returns the next record.
+	 *
+	 * @throws EOFException if the end of the stream is reached without reading
+	 * a complete record
+	 */
+	Record readRecord() throws IOException;
+
+	void close() throws IOException;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/record/RecordReaderFactory.java

@@ -0,0 +1,8 @@
+package org.briarproject.bramble.api.record;
+
+import java.io.InputStream;
+
+public interface RecordReaderFactory {
+
+	RecordReader createRecordReader(InputStream in);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/record/RecordWriter.java

@@ -0,0 +1,15 @@
+package org.briarproject.bramble.api.record;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.io.IOException;
+
+@NotNullByDefault
+public interface RecordWriter {
+
+	void writeRecord(Record r) throws IOException;
+
+	void flush() throws IOException;
+
+	void close() throws IOException;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/record/RecordWriterFactory.java

@@ -0,0 +1,8 @@
+package org.briarproject.bramble.api.record;
+
+import java.io.OutputStream;
+
+public interface RecordWriterFactory {
+
+	RecordWriter createRecordWriter(OutputStream out);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/sync/Group.java

@@ -5,9 +5,24 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPT
 public class Group {
 
 	public enum Visibility {
-		INVISIBLE, // The group is not visible
+
-		VISIBLE, // The group is visible but messages are not shared
+		INVISIBLE(0), // The group is not visible
-		SHARED // The group is visible and messages are shared
+		VISIBLE(1), // The group is visible, messages are accepted but not sent
+		SHARED(2); // The group is visible, messages are accepted and sent
+
+		private final int value;
+
+		Visibility(int value) {
+			this.value = value;
+		}
+
+		public int getValue() {
+			return value;
+		}
+
+		public static Visibility min(Visibility a, Visibility b) {
+			return a.getValue() < b.getValue() ? a : b;
+		}
 	}
 
 	/**
@@ -17,13 +32,16 @@ public class Group {
 
 	private final GroupId id;
 	private final ClientId clientId;
+	private final int majorVersion;
 	private final byte[] descriptor;
 
-	public Group(GroupId id, ClientId clientId, byte[] descriptor) {
+	public Group(GroupId id, ClientId clientId, int majorVersion,
+			byte[] descriptor) {
 		if (descriptor.length > MAX_GROUP_DESCRIPTOR_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;
 		this.clientId = clientId;
+		this.majorVersion = majorVersion;
 		this.descriptor = descriptor;
 	}
 
@@ -41,6 +59,13 @@ public class Group {
 		return clientId;
 	}
 
+	/**
+	 * Returns the major version of the client to which the group belongs.
+	 */
+	public int getMajorVersion() {
+		return majorVersion;
+	}
+
 	/**
 	 * Returns the group's descriptor.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/sync/GroupFactory.java

@@ -6,7 +6,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 public interface GroupFactory {
 
 	/**
-	 * Creates a group with the given client ID, client version and descriptor.
+	 * Creates a group with the given client ID, major version and descriptor.
 	 */
-	Group createGroup(ClientId c, int clientVersion, byte[] descriptor);
+	Group createGroup(ClientId c, int majorVersion, byte[] descriptor);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/MessageFactory.java

@@ -7,5 +7,7 @@ public interface MessageFactory {
 
 	Message createMessage(GroupId g, long timestamp, byte[] body);
 
+	Message createMessage(byte[] raw);
+
 	Message createMessage(MessageId m, byte[] raw);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncConstants.java

@@ -2,6 +2,8 @@ package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.UniqueId;
 
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
+
 public interface SyncConstants {
 
 	/**
@@ -10,16 +12,8 @@ public interface SyncConstants {
 	byte PROTOCOL_VERSION = 0;
 
 	/**
-	 * The length of the record header in bytes.
+	 * The maximum length of a group descriptor in bytes.
 	 */
-	int RECORD_HEADER_LENGTH = 4;
-
-	/**
-	 * The maximum length of the record payload in bytes.
-	 */
-	int MAX_RECORD_PAYLOAD_LENGTH = 48 * 1024; // 48 KiB
-
-	/** The maximum length of a group descriptor in bytes. */
 	int MAX_GROUP_DESCRIPTOR_LENGTH = 16 * 1024; // 16 KiB
 
 	/**
@@ -40,5 +34,5 @@ public interface SyncConstants {
 	/**
 	 * The maximum number of message IDs in an ack, offer or request record.
 	 */
-	int MAX_MESSAGE_IDS = MAX_RECORD_PAYLOAD_LENGTH / UniqueId.LENGTH;
+	int MAX_MESSAGE_IDS = MAX_RECORD_PAYLOAD_BYTES / UniqueId.LENGTH;
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncRecordReader.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import java.io.IOException;
 
 @NotNullByDefault
-public interface RecordReader {
+public interface SyncRecordReader {
 
 	boolean eof() throws IOException;
 

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncRecordReaderFactory.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import java.io.InputStream;
 
 @NotNullByDefault
-public interface RecordReaderFactory {
+public interface SyncRecordReaderFactory {
 
-	RecordReader createRecordReader(InputStream in);
+	SyncRecordReader createRecordReader(InputStream in);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncRecordWriter.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import java.io.IOException;
 
 @NotNullByDefault
-public interface RecordWriter {
+public interface SyncRecordWriter {
 
 	void writeAck(Ack a) throws IOException;
 

bramble-api/src/main/java/org/briarproject/bramble/api/sync/SyncRecordWriterFactory.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import java.io.OutputStream;
 
 @NotNullByDefault
-public interface RecordWriterFactory {
+public interface SyncRecordWriterFactory {
 
-	RecordWriter createRecordWriter(OutputStream out);
+	SyncRecordWriter createRecordWriter(OutputStream out);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/sync/ValidationManager.java

@@ -3,6 +3,7 @@ package org.briarproject.bramble.api.sync;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 /**
@@ -33,15 +34,20 @@ public interface ValidationManager {
 	}
 
 	/**
-	 * Sets the message validator for the given client.
+	 * Registers the message validator for the given client. This method
+	 * should be called before {@link LifecycleManager#startServices(String)}.
 	 */
-	void registerMessageValidator(ClientId c, MessageValidator v);
+	void registerMessageValidator(ClientId c, int majorVersion,
+			MessageValidator v);
 
 	/**
-	 * Sets the incoming message hook for the given client. The hook will be
+	 * Registers the incoming message hook for the given client. The hook will
-	 * called once for each incoming message that passes validation.
+	 * be called once for each incoming message that passes validation. This
+	 * method should be called before
+	 * {@link LifecycleManager#startServices(String)}.
 	 */
-	void registerIncomingMessageHook(ClientId c, IncomingMessageHook hook);
+	void registerIncomingMessageHook(ClientId c, int majorVersion,
+			IncomingMessageHook hook);
 
 	interface MessageValidator {
 

bramble-api/src/main/java/org/briarproject/bramble/api/transport/KeyManager.java

@@ -23,6 +23,8 @@ public interface KeyManager {
 	 * <p/>
 	 * {@link StreamContext StreamContexts} for the contact can be created
 	 * after this method has returned.
+	 *
+	 * @param alice true if the local party is Alice
 	 */
 	void addContact(Transaction txn, ContactId c, SecretKey master,
 			long timestamp, boolean alice) throws DbException;
@@ -33,6 +35,8 @@ public interface KeyManager {
 	 * <p/>
 	 * The keys must be bound before they can be used for incoming streams,
 	 * and also activated before they can be used for outgoing streams.
+	 *
+	 * @param alice true if the local party is Alice
 	 */
 	Map<TransportId, KeySetId> addUnboundKeys(Transaction txn, SecretKey master,
 			long timestamp, boolean alice) throws DbException;
@@ -55,7 +59,7 @@ public interface KeyManager {
 	 * the manager and the database.
 	 */
 	void removeKeys(Transaction txn, Map<TransportId, KeySetId> keys)
-		throws DbException;
+			throws DbException;
 
 	/**
 	 * Returns true if we have keys that can be used for outgoing streams to

bramble-api/src/main/java/org/briarproject/bramble/api/versioning/ClientMajorVersion.java

@@ -0,0 +1,50 @@
+package org.briarproject.bramble.api.versioning;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.ClientId;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class ClientMajorVersion implements Comparable<ClientMajorVersion> {
+
+	private final ClientId clientId;
+	private final int majorVersion;
+
+	public ClientMajorVersion(ClientId clientId, int majorVersion) {
+		this.clientId = clientId;
+		this.majorVersion = majorVersion;
+	}
+
+	public ClientId getClientId() {
+		return clientId;
+	}
+
+	public int getMajorVersion() {
+		return majorVersion;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (o instanceof ClientMajorVersion) {
+			ClientMajorVersion cv = (ClientMajorVersion) o;
+			return clientId.equals(cv.clientId)
+					&& majorVersion == cv.majorVersion;
+		}
+		return false;
+	}
+
+	@Override
+	public int hashCode() {
+		return (clientId.hashCode() << 16) + majorVersion;
+	}
+
+	@Override
+	public int compareTo(ClientMajorVersion cv) {
+		int compare = clientId.compareTo(cv.clientId);
+		if (compare != 0) return compare;
+		return majorVersion - cv.majorVersion;
+	}
+}
+

bramble-api/src/main/java/org/briarproject/bramble/api/versioning/ClientVersioningManager.java

@@ -0,0 +1,45 @@
+package org.briarproject.bramble.api.versioning;
+
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.ClientId;
+import org.briarproject.bramble.api.sync.Group.Visibility;
+
+@NotNullByDefault
+public interface ClientVersioningManager {
+
+	/**
+	 * The unique ID of the versioning client.
+	 */
+	ClientId CLIENT_ID = new ClientId("org.briarproject.bramble.versioning");
+
+	/**
+	 * The current major version of the versioning client.
+	 */
+	int MAJOR_VERSION = 0;
+
+	/**
+	 * Registers a client that will be advertised to contacts. The hook will
+	 * be called when the visibility of the client changes. This method should
+	 * be called before {@link LifecycleManager#startServices(String)}.
+	 */
+	void registerClient(ClientId clientId, int majorVersion, int minorVersion,
+			ClientVersioningHook hook);
+
+	/**
+	 * Returns the visibility of the given client with respect to the given
+	 * contact.
+	 */
+	Visibility getClientVisibility(Transaction txn, ContactId contactId,
+			ClientId clientId, int majorVersion) throws DbException;
+
+	interface ClientVersioningHook {
+
+		void onClientVisibilityChanging(Transaction txn, Contact c,
+				Visibility v) throws DbException;
+	}
+}

bramble-api/src/test/java/org/briarproject/bramble/test/TestUtils.java

@@ -117,15 +117,16 @@ public class TestUtils {
 		return new Author(id, FORMAT_VERSION, name, publicKey);
 	}
 
-	public static Group getGroup(ClientId clientId) {
+	public static Group getGroup(ClientId clientId, int majorVersion) {
 		int descriptorLength = 1 + random.nextInt(MAX_GROUP_DESCRIPTOR_LENGTH);
-		return getGroup(clientId, descriptorLength);
+		return getGroup(clientId, majorVersion, descriptorLength);
 	}
 
-	public static Group getGroup(ClientId clientId, int descriptorLength) {
+	public static Group getGroup(ClientId clientId, int majorVersion,
+			int descriptorLength) {
 		GroupId groupId = new GroupId(getRandomId());
 		byte[] descriptor = getRandomBytes(descriptorLength);
-		return new Group(groupId, clientId, descriptor);
+		return new Group(groupId, clientId, majorVersion, descriptor);
 	}
 
 	public static Message getMessage(GroupId groupId) {

bramble-core/build.gradle

@@ -31,7 +31,6 @@ dependencies {
 dependencyVerification {
 	verify = [
 			'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
 			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
 			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
 			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',

bramble-core/src/main/java/org/briarproject/bramble/BrambleCoreEagerSingletons.java

@@ -1,7 +1,7 @@
 package org.briarproject.bramble;
 
 import org.briarproject.bramble.contact.ContactModule;
-import org.briarproject.bramble.crypto.CryptoModule;
+import org.briarproject.bramble.crypto.CryptoExecutorModule;
 import org.briarproject.bramble.db.DatabaseExecutorModule;
 import org.briarproject.bramble.identity.IdentityModule;
 import org.briarproject.bramble.lifecycle.LifecycleModule;
@@ -10,12 +10,13 @@ import org.briarproject.bramble.properties.PropertiesModule;
 import org.briarproject.bramble.sync.SyncModule;
 import org.briarproject.bramble.system.SystemModule;
 import org.briarproject.bramble.transport.TransportModule;
+import org.briarproject.bramble.versioning.VersioningModule;
 
 public interface BrambleCoreEagerSingletons {
 
 	void inject(ContactModule.EagerSingletons init);
 
-	void inject(CryptoModule.EagerSingletons init);
+	void inject(CryptoExecutorModule.EagerSingletons init);
 
 	void inject(DatabaseExecutorModule.EagerSingletons init);
 
@@ -32,4 +33,6 @@ public interface BrambleCoreEagerSingletons {
 	void inject(SystemModule.EagerSingletons init);
 
 	void inject(TransportModule.EagerSingletons init);
+
+	void inject(VersioningModule.EagerSingletons init);
 }

bramble-core/src/main/java/org/briarproject/bramble/BrambleCoreModule.java

@@ -2,6 +2,7 @@ package org.briarproject.bramble;
 
 import org.briarproject.bramble.client.ClientModule;
 import org.briarproject.bramble.contact.ContactModule;
+import org.briarproject.bramble.crypto.CryptoExecutorModule;
 import org.briarproject.bramble.crypto.CryptoModule;
 import org.briarproject.bramble.data.DataModule;
 import org.briarproject.bramble.db.DatabaseExecutorModule;
@@ -12,6 +13,7 @@ import org.briarproject.bramble.keyagreement.KeyAgreementModule;
 import org.briarproject.bramble.lifecycle.LifecycleModule;
 import org.briarproject.bramble.plugin.PluginModule;
 import org.briarproject.bramble.properties.PropertiesModule;
+import org.briarproject.bramble.record.RecordModule;
 import org.briarproject.bramble.reliability.ReliabilityModule;
 import org.briarproject.bramble.reporting.ReportingModule;
 import org.briarproject.bramble.settings.SettingsModule;
@@ -19,6 +21,7 @@ import org.briarproject.bramble.socks.SocksModule;
 import org.briarproject.bramble.sync.SyncModule;
 import org.briarproject.bramble.system.SystemModule;
 import org.briarproject.bramble.transport.TransportModule;
+import org.briarproject.bramble.versioning.VersioningModule;
 
 import dagger.Module;
 
@@ -26,6 +29,7 @@ import dagger.Module;
 		ClientModule.class,
 		ContactModule.class,
 		CryptoModule.class,
+		CryptoExecutorModule.class,
 		DataModule.class,
 		DatabaseModule.class,
 		DatabaseExecutorModule.class,
@@ -35,19 +39,21 @@ import dagger.Module;
 		LifecycleModule.class,
 		PluginModule.class,
 		PropertiesModule.class,
+		RecordModule.class,
 		ReliabilityModule.class,
 		ReportingModule.class,
 		SettingsModule.class,
 		SocksModule.class,
 		SyncModule.class,
 		SystemModule.class,
-		TransportModule.class
+		TransportModule.class,
+		VersioningModule.class
 })
 public class BrambleCoreModule {
 
 	public static void initEagerSingletons(BrambleCoreEagerSingletons c) {
 		c.inject(new ContactModule.EagerSingletons());
-		c.inject(new CryptoModule.EagerSingletons());
+		c.inject(new CryptoExecutorModule.EagerSingletons());
 		c.inject(new DatabaseExecutorModule.EagerSingletons());
 		c.inject(new IdentityModule.EagerSingletons());
 		c.inject(new LifecycleModule.EagerSingletons());
@@ -56,5 +62,6 @@ public class BrambleCoreModule {
 		c.inject(new SyncModule.EagerSingletons());
 		c.inject(new SystemModule.EagerSingletons());
 		c.inject(new TransportModule.EagerSingletons());
+		c.inject(new VersioningModule.EagerSingletons());
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/client/ContactGroupFactoryImpl.java

@@ -32,25 +32,25 @@ class ContactGroupFactoryImpl implements ContactGroupFactory {
 	}
 
 	@Override
-	public Group createLocalGroup(ClientId clientId, int clientVersion) {
+	public Group createLocalGroup(ClientId clientId, int majorVersion) {
-		return groupFactory.createGroup(clientId, clientVersion,
+		return groupFactory.createGroup(clientId, majorVersion,
 				LOCAL_GROUP_DESCRIPTOR);
 	}
 
 	@Override
-	public Group createContactGroup(ClientId clientId, int clientVersion,
+	public Group createContactGroup(ClientId clientId, int majorVersion,
 			Contact contact) {
 		AuthorId local = contact.getLocalAuthorId();
 		AuthorId remote = contact.getAuthor().getId();
 		byte[] descriptor = createGroupDescriptor(local, remote);
-		return groupFactory.createGroup(clientId, clientVersion, descriptor);
+		return groupFactory.createGroup(clientId, majorVersion, descriptor);
 	}
 
 	@Override
-	public Group createContactGroup(ClientId clientId, int clientVersion,
+	public Group createContactGroup(ClientId clientId, int majorVersion,
 			AuthorId authorId1, AuthorId authorId2) {
 		byte[] descriptor = createGroupDescriptor(authorId1, authorId2);
-		return groupFactory.createGroup(clientId, clientVersion, descriptor);
+		return groupFactory.createGroup(clientId, majorVersion, descriptor);
 	}
 
 	private byte[] createGroupDescriptor(AuthorId local, AuthorId remote) {

bramble-core/src/main/java/org/briarproject/bramble/contact/ContactExchangeTaskImpl.java

@@ -1,23 +1,20 @@
 package org.briarproject.bramble.contact;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.client.ClientHelper;
 import org.briarproject.bramble.api.contact.ContactExchangeListener;
 import org.briarproject.bramble.api.contact.ContactExchangeTask;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.data.BdfDictionary;
 import org.briarproject.bramble.api.data.BdfList;
-import org.briarproject.bramble.api.data.BdfReader;
-import org.briarproject.bramble.api.data.BdfReaderFactory;
-import org.briarproject.bramble.api.data.BdfWriter;
-import org.briarproject.bramble.api.data.BdfWriterFactory;
 import org.briarproject.bramble.api.db.ContactExistsException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.bramble.api.identity.AuthorFactory;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
@@ -26,30 +23,30 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
 import org.briarproject.bramble.api.transport.StreamWriterFactory;
 
+import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.security.GeneralSecurityException;
-import java.util.HashMap;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
+import static org.briarproject.bramble.api.contact.RecordTypes.CONTACT_INFO;
-import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
-import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_SIGNATURE_LENGTH;
-import static org.briarproject.bramble.api.plugin.TransportId.MAX_TRANSPORT_ID_LENGTH;
+import static org.briarproject.bramble.util.ValidationUtils.checkLength;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTIES_PER_TRANSPORT;
+import static org.briarproject.bramble.util.ValidationUtils.checkSize;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -62,9 +59,9 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 			"org.briarproject.briar.contact/EXCHANGE";
 
 	private final DatabaseComponent db;
-	private final AuthorFactory authorFactory;
+	private final ClientHelper clientHelper;
-	private final BdfReaderFactory bdfReaderFactory;
+	private final RecordReaderFactory recordReaderFactory;
-	private final BdfWriterFactory bdfWriterFactory;
+	private final RecordWriterFactory recordWriterFactory;
 	private final Clock clock;
 	private final ConnectionManager connectionManager;
 	private final ContactManager contactManager;
@@ -81,17 +78,17 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 	private volatile boolean alice;
 
 	@Inject
-	ContactExchangeTaskImpl(DatabaseComponent db,
+	ContactExchangeTaskImpl(DatabaseComponent db, ClientHelper clientHelper,
-			AuthorFactory authorFactory, BdfReaderFactory bdfReaderFactory,
+			RecordReaderFactory recordReaderFactory,
-			BdfWriterFactory bdfWriterFactory, Clock clock,
+			RecordWriterFactory recordWriterFactory, Clock clock,
 			ConnectionManager connectionManager, ContactManager contactManager,
 			TransportPropertyManager transportPropertyManager,
 			CryptoComponent crypto, StreamReaderFactory streamReaderFactory,
 			StreamWriterFactory streamWriterFactory) {
 		this.db = db;
-		this.authorFactory = authorFactory;
+		this.clientHelper = clientHelper;
-		this.bdfReaderFactory = bdfReaderFactory;
+		this.recordReaderFactory = recordReaderFactory;
-		this.bdfWriterFactory = bdfWriterFactory;
+		this.recordWriterFactory = recordWriterFactory;
 		this.clock = clock;
 		this.connectionManager = connectionManager;
 		this.contactManager = contactManager;
@@ -126,18 +123,18 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 		} catch (IOException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			listener.contactExchangeFailed();
-			tryToClose(conn, true);
+			tryToClose(conn);
 			return;
 		}
 
 		// Get the local transport properties
-		Map<TransportId, TransportProperties> localProperties, remoteProperties;
+		Map<TransportId, TransportProperties> localProperties;
 		try {
 			localProperties = transportPropertyManager.getLocalProperties();
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			listener.contactExchangeFailed();
-			tryToClose(conn, true);
+			tryToClose(conn);
 			return;
 		}
 
@@ -151,159 +148,138 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 		InputStream streamReader =
 				streamReaderFactory.createContactExchangeStreamReader(in,
 						alice ? bobHeaderKey : aliceHeaderKey);
-		BdfReader r = bdfReaderFactory.createReader(streamReader);
+		RecordReader recordReader =
+				recordReaderFactory.createRecordReader(streamReader);
+
 		// Create the writers
 		OutputStream streamWriter =
 				streamWriterFactory.createContactExchangeStreamWriter(out,
 						alice ? aliceHeaderKey : bobHeaderKey);
-		BdfWriter w = bdfWriterFactory.createWriter(streamWriter);
+		RecordWriter recordWriter =
+				recordWriterFactory.createRecordWriter(streamWriter);
 
 		// Derive the nonces to be signed
 		byte[] aliceNonce = crypto.mac(ALICE_NONCE_LABEL, masterSecret,
 				new byte[] {PROTOCOL_VERSION});
 		byte[] bobNonce = crypto.mac(BOB_NONCE_LABEL, masterSecret,
 				new byte[] {PROTOCOL_VERSION});
+		byte[] localNonce = alice ? aliceNonce : bobNonce;
+		byte[] remoteNonce = alice ? bobNonce : aliceNonce;
 
-		// Exchange pseudonyms, signed nonces, and timestamps
+		// Sign the nonce
+		byte[] localSignature = sign(localAuthor, localNonce);
+
+		// Exchange contact info
 		long localTimestamp = clock.currentTimeMillis();
-		Author remoteAuthor;
+		ContactInfo remoteInfo;
-		long remoteTimestamp;
 		try {
 			if (alice) {
-				sendPseudonym(w, aliceNonce);
+				sendContactInfo(recordWriter, localAuthor, localProperties,
-				sendTimestamp(w, localTimestamp);
+						localSignature, localTimestamp);
-				sendTransportProperties(w, localProperties);
+				recordWriter.flush();
-				w.flush();
+				remoteInfo = receiveContactInfo(recordReader);
-				remoteAuthor = receivePseudonym(r, bobNonce);
-				remoteTimestamp = receiveTimestamp(r);
-				remoteProperties = receiveTransportProperties(r);
 			} else {
-				remoteAuthor = receivePseudonym(r, aliceNonce);
+				remoteInfo = receiveContactInfo(recordReader);
-				remoteTimestamp = receiveTimestamp(r);
+				sendContactInfo(recordWriter, localAuthor, localProperties,
-				remoteProperties = receiveTransportProperties(r);
+						localSignature, localTimestamp);
-				sendPseudonym(w, bobNonce);
+				recordWriter.flush();
-				sendTimestamp(w, localTimestamp);
-				sendTransportProperties(w, localProperties);
-				w.flush();
 			}
-			// Close the outgoing stream and expect EOF on the incoming stream
+			// Close the outgoing stream
-			w.close();
+			recordWriter.close();
-			if (!r.eof()) LOG.warning("Unexpected data at end of connection");
+			// Skip any remaining records from the incoming stream
-		} catch (GeneralSecurityException | IOException e) {
+			try {
+				while (true) recordReader.readRecord();
+			} catch (EOFException expected) {
+				LOG.info("End of stream");
+			}
+		} catch (IOException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			listener.contactExchangeFailed();
-			tryToClose(conn, true);
+			tryToClose(conn);
+			return;
+		}
+
+		// Verify the contact's signature
+		if (!verify(remoteInfo.author, remoteNonce, remoteInfo.signature)) {
+			LOG.warning("Invalid signature");
+			listener.contactExchangeFailed();
+			tryToClose(conn);
 			return;
 		}
 
 		// The agreed timestamp is the minimum of the peers' timestamps
-		long timestamp = Math.min(localTimestamp, remoteTimestamp);
+		long timestamp = Math.min(localTimestamp, remoteInfo.timestamp);
 
 		try {
 			// Add the contact
-			ContactId contactId = addContact(remoteAuthor, timestamp,
+			ContactId contactId = addContact(remoteInfo.author, timestamp,
-					remoteProperties);
+					remoteInfo.properties);
 			// Reuse the connection as a transport connection
 			connectionManager.manageOutgoingConnection(contactId, transportId,
 					conn);
 			// Pseudonym exchange succeeded
 			LOG.info("Pseudonym exchange succeeded");
-			listener.contactExchangeSucceeded(remoteAuthor);
+			listener.contactExchangeSucceeded(remoteInfo.author);
 		} catch (ContactExistsException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-			tryToClose(conn, true);
+			tryToClose(conn);
-			listener.duplicateContact(remoteAuthor);
+			listener.duplicateContact(remoteInfo.author);
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-			tryToClose(conn, true);
+			tryToClose(conn);
 			listener.contactExchangeFailed();
 		}
 	}
 
-	private void sendPseudonym(BdfWriter w, byte[] nonce)
+	private byte[] sign(LocalAuthor author, byte[] nonce) {
-			throws GeneralSecurityException, IOException {
+		try {
-		// Sign the nonce
+			return crypto.sign(SIGNING_LABEL_EXCHANGE, nonce,
-		byte[] privateKey = localAuthor.getPrivateKey();
+					author.getPrivateKey());
-		byte[] sig = crypto.sign(SIGNING_LABEL_EXCHANGE, nonce, privateKey);
+		} catch (GeneralSecurityException e) {
-
+			throw new AssertionError();
-		// Write the name, public key and signature
-		w.writeListStart();
-		w.writeLong(localAuthor.getFormatVersion());
-		w.writeString(localAuthor.getName());
-		w.writeRaw(localAuthor.getPublicKey());
-		w.writeRaw(sig);
-		w.writeListEnd();
-		LOG.info("Sent pseudonym");
-	}
-
-	private Author receivePseudonym(BdfReader r, byte[] nonce)
-			throws GeneralSecurityException, IOException {
-		// Read the format version, name, public key and signature
-		r.readListStart();
-		int formatVersion = (int) r.readLong();
-		if (formatVersion != FORMAT_VERSION) throw new FormatException();
-		String name = r.readString(MAX_AUTHOR_NAME_LENGTH);
-		if (name.isEmpty()) throw new FormatException();
-		byte[] publicKey = r.readRaw(MAX_PUBLIC_KEY_LENGTH);
-		if (publicKey.length == 0) throw new FormatException();
-		byte[] sig = r.readRaw(MAX_SIGNATURE_LENGTH);
-		if (sig.length == 0) throw new FormatException();
-		r.readListEnd();
-		LOG.info("Received pseudonym");
-		// Verify the signature
-		if (!crypto.verifySignature(sig, SIGNING_LABEL_EXCHANGE, nonce,
-				publicKey)) {
-			if (LOG.isLoggable(INFO))
-				LOG.info("Invalid signature");
-			throw new GeneralSecurityException();
 		}
-		return authorFactory.createAuthor(formatVersion, name, publicKey);
 	}
 
-	private void sendTimestamp(BdfWriter w, long timestamp)
+	private boolean verify(Author author, byte[] nonce, byte[] signature) {
+		try {
+			return crypto.verifySignature(signature, SIGNING_LABEL_EXCHANGE,
+					nonce, author.getPublicKey());
+		} catch (GeneralSecurityException e) {
+			return false;
+		}
+	}
+
+	private void sendContactInfo(RecordWriter recordWriter, Author author,
+			Map<TransportId, TransportProperties> properties, byte[] signature,
+			long timestamp) throws IOException {
+		BdfList authorList = clientHelper.toList(author);
+		BdfDictionary props = clientHelper.toDictionary(properties);
+		BdfList payload = BdfList.of(authorList, props, signature, timestamp);
+		recordWriter.writeRecord(new Record(PROTOCOL_VERSION, CONTACT_INFO,
+				clientHelper.toByteArray(payload)));
+		LOG.info("Sent contact info");
+	}
+
+	private ContactInfo receiveContactInfo(RecordReader recordReader)
 			throws IOException {
-		w.writeLong(timestamp);
+		Record record;
-		LOG.info("Sent timestamp");
+		do {
-	}
+			record = recordReader.readRecord();
-
+			if (record.getProtocolVersion() != PROTOCOL_VERSION)
-	private long receiveTimestamp(BdfReader r) throws IOException {
+				throw new FormatException();
-		long timestamp = r.readLong();
+		} while (record.getRecordType() != CONTACT_INFO);
+		LOG.info("Received contact info");
+		BdfList payload = clientHelper.toList(record.getPayload());
+		checkSize(payload, 4);
+		Author author = clientHelper.parseAndValidateAuthor(payload.getList(0));
+		BdfDictionary props = payload.getDictionary(1);
+		Map<TransportId, TransportProperties> properties =
+				clientHelper.parseAndValidateTransportPropertiesMap(props);
+		byte[] signature = payload.getRaw(2);
+		checkLength(signature, 1, MAX_SIGNATURE_LENGTH);
+		long timestamp = payload.getLong(3);
 		if (timestamp < 0) throw new FormatException();
-		LOG.info("Received timestamp");
+		return new ContactInfo(author, properties, signature, timestamp);
-		return timestamp;
-	}
-
-	private void sendTransportProperties(BdfWriter w,
-			Map<TransportId, TransportProperties> local) throws IOException {
-		w.writeListStart();
-		for (Entry<TransportId, TransportProperties> e : local.entrySet())
-			w.writeList(BdfList.of(e.getKey().getString(), e.getValue()));
-		w.writeListEnd();
-	}
-
-	private Map<TransportId, TransportProperties> receiveTransportProperties(
-			BdfReader r) throws IOException {
-		Map<TransportId, TransportProperties> remote = new HashMap<>();
-		r.readListStart();
-		while (!r.hasListEnd()) {
-			r.readListStart();
-			String id = r.readString(MAX_TRANSPORT_ID_LENGTH);
-			if (id.isEmpty()) throw new FormatException();
-			TransportProperties p = new TransportProperties();
-			r.readDictionaryStart();
-			while (!r.hasDictionaryEnd()) {
-				if (p.size() == MAX_PROPERTIES_PER_TRANSPORT)
-					throw new FormatException();
-				String key = r.readString(MAX_PROPERTY_LENGTH);
-				String value = r.readString(MAX_PROPERTY_LENGTH);
-				p.put(key, value);
-			}
-			r.readDictionaryEnd();
-			r.readListEnd();
-			remote.put(new TransportId(id), p);
-		}
-		r.readListEnd();
-		return remote;
 	}
 
 	private ContactId addContact(Author remoteAuthor, long timestamp,
@@ -324,13 +300,30 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 		return contactId;
 	}
 
-	private void tryToClose(DuplexTransportConnection conn, boolean exception) {
+	private void tryToClose(DuplexTransportConnection conn) {
 		try {
 			LOG.info("Closing connection");
-			conn.getReader().dispose(exception, true);
+			conn.getReader().dispose(true, true);
-			conn.getWriter().dispose(exception);
+			conn.getWriter().dispose(true);
 		} catch (IOException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 		}
 	}
+
+	private static class ContactInfo {
+
+		private final Author author;
+		private final Map<TransportId, TransportProperties> properties;
+		private final byte[] signature;
+		private final long timestamp;
+
+		private ContactInfo(Author author,
+				Map<TransportId, TransportProperties> properties,
+				byte[] signature, long timestamp) {
+			this.author = author;
+			this.properties = properties;
+			this.signature = signature;
+			this.timestamp = timestamp;
+		}
+	}
 }

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoExecutorModule.java

@@ -0,0 +1,67 @@
+package org.briarproject.bramble.crypto;
+
+import org.briarproject.bramble.TimeLoggingExecutor;
+import org.briarproject.bramble.api.crypto.CryptoExecutor;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ThreadPoolExecutor;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+import static java.util.concurrent.TimeUnit.SECONDS;
+
+@Module
+public class CryptoExecutorModule {
+
+	public static class EagerSingletons {
+		@Inject
+		@CryptoExecutor
+		ExecutorService cryptoExecutor;
+	}
+
+	/**
+	 * The maximum number of executor threads.
+	 * <p>
+	 * The number of available processors can change during the lifetime of the
+	 * JVM, so this is just a reasonable guess.
+	 */
+	private static final int MAX_EXECUTOR_THREADS =
+			Math.max(1, Runtime.getRuntime().availableProcessors() - 1);
+
+	private final ExecutorService cryptoExecutor;
+
+	public CryptoExecutorModule() {
+		// Use an unbounded queue
+		BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>();
+		// Discard tasks that are submitted during shutdown
+		RejectedExecutionHandler policy =
+				new ThreadPoolExecutor.DiscardPolicy();
+		// Create a limited # of threads and keep them in the pool for 60 secs
+		cryptoExecutor = new TimeLoggingExecutor("CryptoExecutor", 0,
+				MAX_EXECUTOR_THREADS, 60, SECONDS, queue, policy);
+	}
+
+	@Provides
+	@Singleton
+	@CryptoExecutor
+	ExecutorService provideCryptoExecutorService(
+			LifecycleManager lifecycleManager) {
+		lifecycleManager.registerForShutdown(cryptoExecutor);
+		return cryptoExecutor;
+	}
+
+	@Provides
+	@CryptoExecutor
+	Executor provideCryptoExecutor() {
+		return cryptoExecutor;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/crypto/CryptoModule.java

@@ -1,64 +1,24 @@
 package org.briarproject.bramble.crypto;
 
-import org.briarproject.bramble.TimeLoggingExecutor;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
-import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.crypto.KeyAgreementCrypto;
 import org.briarproject.bramble.api.crypto.PasswordStrengthEstimator;
 import org.briarproject.bramble.api.crypto.StreamDecrypterFactory;
 import org.briarproject.bramble.api.crypto.StreamEncrypterFactory;
 import org.briarproject.bramble.api.crypto.TransportCrypto;
-import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.system.SecureRandomProvider;
 
 import java.security.SecureRandom;
-import java.util.concurrent.BlockingQueue;
-import java.util.concurrent.Executor;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.LinkedBlockingQueue;
-import java.util.concurrent.RejectedExecutionHandler;
-import java.util.concurrent.ThreadPoolExecutor;
 
-import javax.inject.Inject;
 import javax.inject.Provider;
 import javax.inject.Singleton;
 
 import dagger.Module;
 import dagger.Provides;
 
-import static java.util.concurrent.TimeUnit.SECONDS;
-
 @Module
 public class CryptoModule {
 
-	public static class EagerSingletons {
-		@Inject
-		@CryptoExecutor
-		ExecutorService cryptoExecutor;
-	}
-
-	/**
-	 * The maximum number of executor threads.
-	 * <p>
-	 * The number of available processors can change during the lifetime of the
-	 * JVM, so this is just a reasonable guess.
-	 */
-	private static final int MAX_EXECUTOR_THREADS =
-			Math.max(1, Runtime.getRuntime().availableProcessors() - 1);
-
-	private final ExecutorService cryptoExecutor;
-
-	public CryptoModule() {
-		// Use an unbounded queue
-		BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>();
-		// Discard tasks that are submitted during shutdown
-		RejectedExecutionHandler policy =
-				new ThreadPoolExecutor.DiscardPolicy();
-		// Create a limited # of threads and keep them in the pool for 60 secs
-		cryptoExecutor = new TimeLoggingExecutor("CryptoExecutor", 0,
-				MAX_EXECUTOR_THREADS, 60, SECONDS, queue, policy);
-	}
-
 	@Provides
 	AuthenticatedCipher provideAuthenticatedCipher() {
 		return new XSalsa20Poly1305AuthenticatedCipher();
@@ -103,21 +63,6 @@ public class CryptoModule {
 		return keyAgreementCrypto;
 	}
 
-	@Provides
-	@Singleton
-	@CryptoExecutor
-	ExecutorService getCryptoExecutorService(
-			LifecycleManager lifecycleManager) {
-		lifecycleManager.registerForShutdown(cryptoExecutor);
-		return cryptoExecutor;
-	}
-
-	@Provides
-	@CryptoExecutor
-	Executor getCryptoExecutor() {
-		return cryptoExecutor;
-	}
-
 	@Provides
 	SecureRandom getSecureRandom(CryptoComponent crypto) {
 		return crypto.getSecureRandom();

bramble-core/src/main/java/org/briarproject/bramble/db/Database.java

@@ -266,7 +266,8 @@ interface Database<T> {
 	 * <p/>
 	 * Read-only.
 	 */
-	Collection<Group> getGroups(T txn, ClientId c) throws DbException;
+	Collection<Group> getGroups(T txn, ClientId c, int majorVersion)
+			throws DbException;
 
 	/**
 	 * Returns the given group's visibility to the given contact, or
@@ -321,16 +322,16 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns the IDs of all messages in the given group.
+	 * Returns the IDs of all delivered messages in the given group.
 	 * <p/>
 	 * Read-only.
 	 */
 	Collection<MessageId> getMessageIds(T txn, GroupId g) throws DbException;
 
 	/**
-	 * Returns the IDs of any messages in the given group with metadata
+	 * Returns the IDs of any delivered messages in the given group with
-	 * matching all entries in the given query. If the query is empty, the IDs
+	 * metadata that matches all entries in the given query. If the query is
-	 * of all messages are returned.
+	 * empty, the IDs of all delivered messages are returned.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -346,9 +347,9 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns the metadata for any messages in the given group with metadata
+	 * Returns the metadata for any delivered messages in the given group with
-	 * matching all entries in the given query. If the query is empty, the
+	 * metadata that matches all entries in the given query. If the query is
-	 * metadata for all messages is returned.
+	 * empty, the metadata for all delivered messages is returned.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -356,7 +357,8 @@ interface Database<T> {
 			Metadata query) throws DbException;
 
 	/**
-	 * Returns the metadata for the given delivered message.
+	 * Returns the metadata for the given delivered or pending message.
+	 * This is only meant to be used by the ValidationManager.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -364,7 +366,7 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns the metadata for the given message.
+	 * Returns the metadata for the given delivered message.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -378,8 +380,8 @@ interface Database<T> {
 	State getMessageState(T txn, MessageId m) throws DbException;
 
 	/**
-	 * Returns the status of all messages in the given group with respect
+	 * Returns the status of all delivered messages in the given group with
-	 * to the given contact.
+	 * respect to the given contact.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -387,11 +389,13 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns the status of the given message with respect to the given
+	 * Returns the status of the given delivered message with respect to the
+	 * given contact, or null if the message's group is invisible to the
 	 * contact.
 	 * <p/>
 	 * Read-only.
 	 */
+	@Nullable
 	MessageStatus getMessageStatus(T txn, ContactId c, MessageId m)
 			throws DbException;
 
@@ -654,7 +658,7 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Stores the given transport keys, deleting any keys they have replaced.
+	 * Updates the given transport keys following key rotation.
 	 */
-	void updateTransportKeys(T txn, Collection<KeySet> keys) throws DbException;
+	void updateTransportKeys(T txn, KeySet ks) throws DbException;
 }

bramble-core/src/main/java/org/briarproject/bramble/db/DatabaseComponentImpl.java

@@ -435,10 +435,10 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public Collection<Group> getGroups(Transaction transaction, ClientId c)
+	public Collection<Group> getGroups(Transaction transaction, ClientId c,
-			throws DbException {
+			int majorVersion) throws DbException {
 		T txn = unbox(transaction);
-		return db.getGroups(txn, c);
+		return db.getGroups(txn, c, majorVersion);
 	}
 
 	@Override
@@ -466,6 +466,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getLocalAuthors(txn);
 	}
 
+	@Override
+	public Collection<MessageId> getMessageIds(Transaction transaction,
+			GroupId g) throws DbException {
+		T txn = unbox(transaction);
+		if (!db.containsGroup(txn, g))
+			throw new NoSuchGroupException();
+		return db.getMessageIds(txn, g);
+	}
+
 	@Override
 	public Collection<MessageId> getMessagesToValidate(Transaction transaction)
 			throws DbException {
@@ -551,6 +560,13 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		if (!db.containsGroup(txn, g))
 			throw new NoSuchGroupException();
+		if (db.getGroupVisibility(txn, c, g) == INVISIBLE) {
+			// No status rows exist - return default statuses
+			Collection<MessageStatus> statuses = new ArrayList<>();
+			for (MessageId m : db.getMessageIds(txn, g))
+				statuses.add(new MessageStatus(m, c, false, false));
+			return statuses;
+		}
 		return db.getMessageStatus(txn, c, g);
 	}
 
@@ -562,7 +578,9 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		if (!db.containsMessage(txn, m))
 			throw new NoSuchMessageException();
-		return db.getMessageStatus(txn, c, m);
+		MessageStatus status = db.getMessageStatus(txn, c, m);
+		if (status == null) return new MessageStatus(m, c, false, false);
+		return status;
 	}
 
 	@Override
@@ -903,11 +921,9 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			Collection<KeySet> keys) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
-		Collection<KeySet> filtered = new ArrayList<>();
 		for (KeySet ks : keys) {
 			TransportId t = ks.getTransportKeys().getTransportId();
-			if (db.containsTransport(txn, t)) filtered.add(ks);
+			if (db.containsTransport(txn, t)) db.updateTransportKeys(txn, ks);
 		}
-		db.updateTransportKeys(txn, filtered);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/JdbcDatabase.java

@@ -74,7 +74,12 @@ import static org.briarproject.bramble.db.ExponentialBackoff.calculateExpiry;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 36;
+	static final int CODE_SCHEMA_VERSION = 38;
+
+	// Rotation period offsets for incoming transport keys
+	private static final int OFFSET_PREV = -1;
+	private static final int OFFSET_CURR = 0;
+	private static final int OFFSET_NEXT = 1;
 
 	private static final String CREATE_SETTINGS =
 			"CREATE TABLE settings"
@@ -112,6 +117,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE TABLE groups"
 					+ " (groupId _HASH NOT NULL,"
 					+ " clientId _STRING NOT NULL,"
+					+ " majorVersion INT NOT NULL,"
 					+ " descriptor _BINARY NOT NULL,"
 					+ " PRIMARY KEY (groupId))";
 
@@ -254,7 +260,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " headerKey _SECRET NOT NULL,"
 					+ " base BIGINT NOT NULL,"
 					+ " bitmap _BINARY NOT NULL,"
-					+ " PRIMARY KEY (transportId, keySetId, rotationPeriod),"
+					+ " periodOffset INT NOT NULL,"
+					+ " PRIMARY KEY (transportId, keySetId, periodOffset),"
 					+ " FOREIGN KEY (transportId)"
 					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE,"
@@ -269,9 +276,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE INDEX IF NOT EXISTS contactsByAuthorId"
 					+ " ON contacts (authorId)";
 
-	private static final String INDEX_GROUPS_BY_CLIENT_ID =
+	private static final String INDEX_GROUPS_BY_CLIENT_ID_MAJOR_VERSION =
-			"CREATE INDEX IF NOT EXISTS groupsByClientId"
+			"CREATE INDEX IF NOT EXISTS groupsByClientIdMajorVersion"
-					+ " ON groups (clientId)";
+					+ " ON groups (clientId, majorVersion)";
 
 	private static final String INDEX_MESSAGE_METADATA_BY_GROUP_ID_STATE =
 			"CREATE INDEX IF NOT EXISTS messageMetadataByGroupIdState"
@@ -438,7 +445,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			s = txn.createStatement();
 			s.executeUpdate(INDEX_CONTACTS_BY_AUTHOR_ID);
-			s.executeUpdate(INDEX_GROUPS_BY_CLIENT_ID);
+			s.executeUpdate(INDEX_GROUPS_BY_CLIENT_ID_MAJOR_VERSION);
 			s.executeUpdate(INDEX_MESSAGE_METADATA_BY_GROUP_ID_STATE);
 			s.executeUpdate(INDEX_MESSAGE_DEPENDENCIES_BY_DEPENDENCY_ID);
 			s.executeUpdate(INDEX_STATUSES_BY_CONTACT_ID_GROUP_ID);
@@ -606,12 +613,14 @@ abstract class JdbcDatabase implements Database<Connection> {
 	public void addGroup(Connection txn, Group g) throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql = "INSERT INTO groups (groupId, clientId, descriptor)"
+			String sql = "INSERT INTO groups"
-					+ " VALUES (?, ?, ?)";
+					+ " (groupId, clientId, majorVersion, descriptor)"
+					+ " VALUES (?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getId().getBytes());
 			ps.setString(2, g.getClientId().getString());
-			ps.setBytes(3, g.getDescriptor());
+			ps.setInt(3, g.getMajorVersion());
+			ps.setBytes(4, g.getDescriptor());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
@@ -908,8 +917,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.close();
 			// Store the incoming keys
 			sql = "INSERT INTO incomingKeys (keySetId, contactId, transportId,"
-					+ " rotationPeriod, tagKey, headerKey, base, bitmap)"
+					+ " rotationPeriod, tagKey, headerKey, base, bitmap,"
-					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
+					+ " periodOffset)"
+					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, keySetId.getInt());
 			if (c == null) ps.setNull(2, INTEGER);
@@ -922,6 +932,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setBytes(6, inPrev.getHeaderKey().getBytes());
 			ps.setLong(7, inPrev.getWindowBase());
 			ps.setBytes(8, inPrev.getWindowBitmap());
+			ps.setInt(9, OFFSET_PREV);
 			ps.addBatch();
 			// Current rotation period
 			IncomingKeys inCurr = k.getCurrentIncomingKeys();
@@ -930,6 +941,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setBytes(6, inCurr.getHeaderKey().getBytes());
 			ps.setLong(7, inCurr.getWindowBase());
 			ps.setBytes(8, inCurr.getWindowBitmap());
+			ps.setInt(9, OFFSET_CURR);
 			ps.addBatch();
 			// Next rotation period
 			IncomingKeys inNext = k.getNextIncomingKeys();
@@ -938,6 +950,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setBytes(6, inNext.getHeaderKey().getBytes());
 			ps.setLong(7, inNext.getWindowBase());
 			ps.setBytes(8, inNext.getWindowBitmap());
+			ps.setInt(9, OFFSET_NEXT);
 			ps.addBatch();
 			int[] batchAffected = ps.executeBatch();
 			if (batchAffected.length != 3) throw new DbStateException();
@@ -1336,17 +1349,18 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT clientId, descriptor FROM groups"
+			String sql = "SELECT clientId, majorVersion, descriptor"
-					+ " WHERE groupId = ?";
+					+ " FROM groups WHERE groupId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
 			rs = ps.executeQuery();
 			if (!rs.next()) throw new DbStateException();
 			ClientId clientId = new ClientId(rs.getString(1));
-			byte[] descriptor = rs.getBytes(2);
+			int majorVersion = rs.getInt(2);
+			byte[] descriptor = rs.getBytes(3);
 			rs.close();
 			ps.close();
-			return new Group(g, clientId, descriptor);
+			return new Group(g, clientId, majorVersion, descriptor);
 		} catch (SQLException e) {
 			tryToClose(rs);
 			tryToClose(ps);
@@ -1355,21 +1369,22 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public Collection<Group> getGroups(Connection txn, ClientId c)
+	public Collection<Group> getGroups(Connection txn, ClientId c,
-			throws DbException {
+			int majorVersion) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT groupId, descriptor FROM groups"
-					+ " WHERE clientId = ?";
+					+ " WHERE clientId = ? AND majorVersion = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, c.getString());
+			ps.setInt(2, majorVersion);
 			rs = ps.executeQuery();
 			List<Group> groups = new ArrayList<>();
 			while (rs.next()) {
 				GroupId id = new GroupId(rs.getBytes(1));
 				byte[] descriptor = rs.getBytes(2);
-				groups.add(new Group(id, c, descriptor));
+				groups.add(new Group(id, c, majorVersion, descriptor));
 			}
 			rs.close();
 			ps.close();
@@ -1501,32 +1516,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT messageId FROM messages WHERE groupId = ?";
+			String sql = "SELECT messageId FROM messages"
+					+ " WHERE groupId = ? AND state = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
-			rs = ps.executeQuery();
+			ps.setInt(2, DELIVERED.getValue());
-			List<MessageId> ids = new ArrayList<>();
-			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
-			rs.close();
-			ps.close();
-			return ids;
-		} catch (SQLException e) {
-			tryToClose(rs);
-			tryToClose(ps);
-			throw new DbException(e);
-		}
-	}
-
-	private Collection<MessageId> getMessageIds(Connection txn, GroupId g,
-			State state) throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT messageId FROM messages"
-					+ " WHERE state = ? AND groupId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, state.getValue());
-			ps.setBytes(2, g.getBytes());
 			rs = ps.executeQuery();
 			List<MessageId> ids = new ArrayList<>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
@@ -1544,7 +1538,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	public Collection<MessageId> getMessageIds(Connection txn, GroupId g,
 			Metadata query) throws DbException {
 		// If there are no query terms, return all delivered messages
-		if (query.isEmpty()) return getMessageIds(txn, g, DELIVERED);
+		if (query.isEmpty()) return getMessageIds(txn, g);
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -1703,10 +1697,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT messageId, txCount > 0, seen FROM statuses"
-					+ " WHERE groupId = ? AND contactId = ?";
+					+ " WHERE groupId = ? AND contactId = ? AND state = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
 			ps.setInt(2, c.getInt());
+			ps.setInt(3, DELIVERED.getValue());
 			rs = ps.executeQuery();
 			List<MessageStatus> statuses = new ArrayList<>();
 			while (rs.next()) {
@@ -1726,24 +1721,29 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
+	@Nullable
 	public MessageStatus getMessageStatus(Connection txn, ContactId c,
 			MessageId m) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
 			String sql = "SELECT txCount > 0, seen FROM statuses"
-					+ " WHERE messageId = ? AND contactId = ?";
+					+ " WHERE messageId = ? AND contactId = ? AND state = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			ps.setInt(2, c.getInt());
+			ps.setInt(3, DELIVERED.getValue());
 			rs = ps.executeQuery();
-			if (!rs.next()) throw new DbStateException();
+			MessageStatus status = null;
-			boolean sent = rs.getBoolean(1);
+			if (rs.next()) {
-			boolean seen = rs.getBoolean(2);
+				boolean sent = rs.getBoolean(1);
+				boolean seen = rs.getBoolean(2);
+				status = new MessageStatus(m, c, sent, seen);
+			}
 			if (rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
-			return new MessageStatus(m, c, sent, seen);
+			return status;
 		} catch (SQLException e) {
 			tryToClose(rs);
 			tryToClose(ps);
@@ -2141,7 +2141,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " base, bitmap"
 					+ " FROM incomingKeys"
 					+ " WHERE transportId = ?"
-					+ " ORDER BY keySetId, rotationPeriod";
+					+ " ORDER BY keySetId, periodOffset";
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, t.getString());
 			rs = ps.executeQuery();
@@ -2563,7 +2563,14 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if (affected != 1) throw new DbStateException();
 			ps.close();
 			// Remove status rows for the messages in the group
-			for (MessageId m : getMessageIds(txn, g)) removeStatus(txn, c, m);
+			sql = "DELETE FROM statuses"
+					+ " WHERE contactId = ? AND groupId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setBytes(2, g.getBytes());
+			affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
 		} catch (SQLException e) {
 			tryToClose(ps);
 			throw new DbException(e);
@@ -2647,24 +2654,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private void removeStatus(Connection txn, ContactId c, MessageId m)
-			throws DbException {
-		PreparedStatement ps = null;
-		try {
-			String sql = "DELETE FROM statuses"
-					+ " WHERE messageId = ? AND contactId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setInt(2, c.getInt());
-			int affected = ps.executeUpdate();
-			if (affected != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(ps);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	public void removeTransport(Connection txn, TransportId t)
 			throws DbException {
@@ -2944,12 +2933,69 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void updateTransportKeys(Connection txn, Collection<KeySet> keys)
+	public void updateTransportKeys(Connection txn, KeySet ks)
 			throws DbException {
-		for (KeySet ks : keys) {
+		PreparedStatement ps = null;
+		try {
+			// Update the outgoing keys
+			String sql = "UPDATE outgoingKeys SET rotationPeriod = ?,"
+					+ " tagKey = ?, headerKey = ?, stream = ?"
+					+ " WHERE transportId = ? AND keySetId = ?";
+			ps = txn.prepareStatement(sql);
 			TransportKeys k = ks.getTransportKeys();
-			removeTransportKeys(txn, k.getTransportId(), ks.getKeySetId());
+			OutgoingKeys outCurr = k.getCurrentOutgoingKeys();
-			addTransportKeys(txn, ks.getContactId(), k);
+			ps.setLong(1, outCurr.getRotationPeriod());
+			ps.setBytes(2, outCurr.getTagKey().getBytes());
+			ps.setBytes(3, outCurr.getHeaderKey().getBytes());
+			ps.setLong(4, outCurr.getStreamCounter());
+			ps.setString(5, k.getTransportId().getString());
+			ps.setInt(6, ks.getKeySetId().getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+			// Update the incoming keys
+			sql = "UPDATE incomingKeys SET rotationPeriod = ?,"
+					+ " tagKey = ?, headerKey = ?, base = ?, bitmap = ?"
+					+ " WHERE transportId = ? AND keySetId = ?"
+					+ " AND periodOffset = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setString(6, k.getTransportId().getString());
+			ps.setInt(7, ks.getKeySetId().getInt());
+			// Previous rotation period
+			IncomingKeys inPrev = k.getPreviousIncomingKeys();
+			ps.setLong(1, inPrev.getRotationPeriod());
+			ps.setBytes(2, inPrev.getTagKey().getBytes());
+			ps.setBytes(3, inPrev.getHeaderKey().getBytes());
+			ps.setLong(4, inPrev.getWindowBase());
+			ps.setBytes(5, inPrev.getWindowBitmap());
+			ps.setInt(8, OFFSET_PREV);
+			ps.addBatch();
+			// Current rotation period
+			IncomingKeys inCurr = k.getCurrentIncomingKeys();
+			ps.setLong(1, inCurr.getRotationPeriod());
+			ps.setBytes(2, inCurr.getTagKey().getBytes());
+			ps.setBytes(3, inCurr.getHeaderKey().getBytes());
+			ps.setLong(4, inCurr.getWindowBase());
+			ps.setBytes(5, inCurr.getWindowBitmap());
+			ps.setInt(8, OFFSET_CURR);
+			ps.addBatch();
+			// Next rotation period
+			IncomingKeys inNext = k.getNextIncomingKeys();
+			ps.setLong(1, inNext.getRotationPeriod());
+			ps.setBytes(2, inNext.getTagKey().getBytes());
+			ps.setBytes(3, inNext.getHeaderKey().getBytes());
+			ps.setLong(4, inNext.getWindowBase());
+			ps.setBytes(5, inNext.getWindowBitmap());
+			ps.setInt(8, OFFSET_NEXT);
+			ps.addBatch();
+			int[] batchAffected = ps.executeBatch();
+			if (batchAffected.length != 3) throw new DbStateException();
+			for (int rows : batchAffected)
+				if (rows < 0 || rows > 1) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps);
+			throw new DbException(e);
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementConnector.java

@@ -13,6 +13,8 @@ import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -44,6 +46,8 @@ class KeyAgreementConnector {
 	private final KeyAgreementCrypto keyAgreementCrypto;
 	private final PluginManager pluginManager;
 	private final ConnectionChooser connectionChooser;
+	private final RecordReaderFactory recordReaderFactory;
+	private final RecordWriterFactory recordWriterFactory;
 
 	private final List<KeyAgreementListener> listeners =
 			new CopyOnWriteArrayList<>();
@@ -54,11 +58,15 @@ class KeyAgreementConnector {
 
 	KeyAgreementConnector(Callbacks callbacks,
 			KeyAgreementCrypto keyAgreementCrypto, PluginManager pluginManager,
-			ConnectionChooser connectionChooser) {
+			ConnectionChooser connectionChooser,
+			RecordReaderFactory recordReaderFactory,
+			RecordWriterFactory recordWriterFactory) {
 		this.callbacks = callbacks;
 		this.keyAgreementCrypto = keyAgreementCrypto;
 		this.pluginManager = pluginManager;
 		this.connectionChooser = connectionChooser;
+		this.recordReaderFactory = recordReaderFactory;
+		this.recordWriterFactory = recordWriterFactory;
 	}
 
 	Payload listen(KeyPair localKeyPair) {
@@ -119,7 +127,8 @@ class KeyAgreementConnector {
 			KeyAgreementConnection chosen =
 					connectionChooser.poll(CONNECTION_TIMEOUT);
 			if (chosen == null) return null;
-			return new KeyAgreementTransport(chosen);
+			return new KeyAgreementTransport(recordReaderFactory,
+					recordWriterFactory, chosen);
 		} catch (InterruptedException e) {
 			LOG.info("Interrupted while waiting for connection");
 			Thread.currentThread().interrupt();

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementTaskImpl.java

@@ -14,10 +14,13 @@ import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFailedEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementFinishedEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStartedEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStoppedListeningEvent;
 import org.briarproject.bramble.api.keyagreement.event.KeyAgreementWaitingEvent;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
 
 import java.io.IOException;
 import java.util.logging.Logger;
@@ -48,14 +51,17 @@ class KeyAgreementTaskImpl extends Thread implements KeyAgreementTask,
 	KeyAgreementTaskImpl(CryptoComponent crypto,
 			KeyAgreementCrypto keyAgreementCrypto, EventBus eventBus,
 			PayloadEncoder payloadEncoder, PluginManager pluginManager,
-			ConnectionChooser connectionChooser) {
+			ConnectionChooser connectionChooser,
+			RecordReaderFactory recordReaderFactory,
+			RecordWriterFactory recordWriterFactory) {
 		this.crypto = crypto;
 		this.keyAgreementCrypto = keyAgreementCrypto;
 		this.eventBus = eventBus;
 		this.payloadEncoder = payloadEncoder;
 		localKeyPair = crypto.generateAgreementKeyPair();
 		connector = new KeyAgreementConnector(this, keyAgreementCrypto,
-				pluginManager, connectionChooser);
+				pluginManager, connectionChooser, recordReaderFactory,
+				recordWriterFactory);
 	}
 
 	@Override
@@ -71,6 +77,7 @@ class KeyAgreementTaskImpl extends Thread implements KeyAgreementTask,
 		if (localPayload != null) {
 			if (remotePayload == null) connector.stopListening();
 			else interrupt();
+			eventBus.broadcast(new KeyAgreementStoppedListeningEvent());
 		}
 	}
 

bramble-core/src/main/java/org/briarproject/bramble/keyagreement/KeyAgreementTransport.java

@@ -4,9 +4,12 @@ import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.util.ByteUtils;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
 
-import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -14,8 +17,6 @@ import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.RECORD_HEADER_LENGTH;
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.RECORD_HEADER_PAYLOAD_LENGTH_OFFSET;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.ABORT;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.CONFIRM;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.KEY;
@@ -30,14 +31,17 @@ class KeyAgreementTransport {
 			Logger.getLogger(KeyAgreementTransport.class.getName());
 
 	private final KeyAgreementConnection kac;
-	private final InputStream in;
+	private final RecordReader reader;
-	private final OutputStream out;
+	private final RecordWriter writer;
 
-	KeyAgreementTransport(KeyAgreementConnection kac)
+	KeyAgreementTransport(RecordReaderFactory recordReaderFactory,
+			RecordWriterFactory recordWriterFactory, KeyAgreementConnection kac)
 			throws IOException {
 		this.kac = kac;
-		in = kac.getConnection().getReader().getInputStream();
+		InputStream in = kac.getConnection().getReader().getInputStream();
-		out = kac.getConnection().getWriter().getOutputStream();
+		reader = recordReaderFactory.createRecordReader(in);
+		OutputStream out = kac.getConnection().getWriter().getOutputStream();
+		writer = recordWriterFactory.createRecordWriter(out);
 	}
 
 	public DuplexTransportConnection getConnection() {
@@ -74,9 +78,8 @@ class KeyAgreementTransport {
 		tryToClose(exception);
 	}
 
-	public void tryToClose(boolean exception) {
+	private void tryToClose(boolean exception) {
 		try {
-			LOG.info("Closing connection");
 			kac.getConnection().getReader().dispose(exception, true);
 			kac.getConnection().getWriter().dispose(exception);
 		} catch (IOException e) {
@@ -85,59 +88,27 @@ class KeyAgreementTransport {
 	}
 
 	private void writeRecord(byte type, byte[] payload) throws IOException {
-		byte[] recordHeader = new byte[RECORD_HEADER_LENGTH];
+		writer.writeRecord(new Record(PROTOCOL_VERSION, type, payload));
-		recordHeader[0] = PROTOCOL_VERSION;
+		writer.flush();
-		recordHeader[1] = type;
-		ByteUtils.writeUint16(payload.length, recordHeader,
-				RECORD_HEADER_PAYLOAD_LENGTH_OFFSET);
-		out.write(recordHeader);
-		out.write(payload);
-		out.flush();
 	}
 
 	private byte[] readRecord(byte expectedType) throws AbortException {
 		while (true) {
-			byte[] header = readHeader();
-			byte version = header[0], type = header[1];
-			int len = ByteUtils.readUint16(header,
-					RECORD_HEADER_PAYLOAD_LENGTH_OFFSET);
-			// Reject unrecognised protocol version
-			if (version != PROTOCOL_VERSION) throw new AbortException(false);
-			if (type == ABORT) throw new AbortException(true);
-			if (type == expectedType) {
-				try {
-					return readData(len);
-				} catch (IOException e) {
-					throw new AbortException(e);
-				}
-			}
-			// Reject recognised but unexpected record type
-			if (type == KEY || type == CONFIRM) throw new AbortException(false);
-			// Skip unrecognised record type
 			try {
-				readData(len);
+				Record record = reader.readRecord();
+				// Reject unrecognised protocol version
+				if (record.getProtocolVersion() != PROTOCOL_VERSION)
+					throw new AbortException(false);
+				byte type = record.getRecordType();
+				if (type == ABORT) throw new AbortException(true);
+				if (type == expectedType) return record.getPayload();
+				// Reject recognised but unexpected record type
+				if (type == KEY || type == CONFIRM)
+					throw new AbortException(false);
+				// Skip unrecognised record type
 			} catch (IOException e) {
 				throw new AbortException(e);
 			}
 		}
 	}
-
-	private byte[] readHeader() throws AbortException {
-		try {
-			return readData(RECORD_HEADER_LENGTH);
-		} catch (IOException e) {
-			throw new AbortException(e);
-		}
-	}
-
-	private byte[] readData(int len) throws IOException {
-		byte[] data = new byte[len];
-		int offset = 0;
-		while (offset < data.length) {
-			int read = in.read(data, offset, data.length - offset);
-			if (read == -1) throw new EOFException();
-			offset += read;
-		}
-		return data;
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/Poller.java

@@ -24,7 +24,9 @@ import org.briarproject.bramble.api.system.Scheduler;
 
 import java.security.SecureRandom;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
@@ -53,6 +55,7 @@ class Poller implements EventListener {
 	private final Clock clock;
 	private final Lock lock;
 	private final Map<TransportId, ScheduledPollTask> tasks; // Locking: lock
+	private final Set<TransportId> polling; // Locking: lock
 
 	@Inject
 	Poller(@IoExecutor Executor ioExecutor,
@@ -69,16 +72,19 @@ class Poller implements EventListener {
 		this.clock = clock;
 		lock = new ReentrantLock();
 		tasks = new HashMap<>();
+		polling = new HashSet<>();
 	}
 
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof ContactStatusChangedEvent) {
 			ContactStatusChangedEvent c = (ContactStatusChangedEvent) e;
+			/*
 			if (c.isActive()) {
 				// Connect to the newly activated contact
 				connectToContact(c.getContactId());
 			}
+			*/
 		} else if (e instanceof ConnectionClosedEvent) {
 			ConnectionClosedEvent c = (ConnectionClosedEvent) e;
 			// Reschedule polling, the polling interval may have decreased
@@ -215,20 +221,33 @@ class Poller implements EventListener {
 		@Override
 		@IoExecutor
 		public void run() {
+			TransportId t = plugin.getId();
+			boolean shouldPoll;
 			lock.lock();
 			try {
-				TransportId t = plugin.getId();
 				ScheduledPollTask scheduled = tasks.get(t);
 				if (scheduled != null && scheduled.task != this)
 					return; // Replaced by another task
 				tasks.remove(t);
+				// Don't poll again if last poll is still running
+				shouldPoll = polling.add(t);
 			} finally {
 				lock.unlock();
 			}
 			int delay = plugin.getPollingInterval();
 			if (randomiseNext) delay = (int) (delay * random.nextDouble());
 			schedule(plugin, delay, false);
-			poll(plugin);
+			if (shouldPoll) {
+				poll(plugin);
+			} else if (LOG.isLoggable(INFO)) {
+				LOG.info("Last poll for " + t + " is still running");
+			}
+			lock.lock();
+			try {
+				polling.remove(t);
+			} finally {
+				lock.unlock();
+			}
 		}
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothConnectionLimiter.java

@@ -0,0 +1,47 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+@NotNullByDefault
+interface BluetoothConnectionLimiter {
+
+	/**
+	 * Informs the limiter that key agreement has started.
+	 */
+	void keyAgreementStarted();
+
+	/**
+	 * Informs the limiter that key agreement has ended.
+	 */
+	void keyAgreementEnded();
+
+	/**
+	 * Returns true if a contact connection can be opened. This method does not
+	 * need to be called for key agreement connections.
+	 */
+	boolean canOpenContactConnection();
+
+	/**
+	 * Informs the limiter that a contact connection has been opened. The
+	 * limiter may close the new connection if key agreement is in progress.
+	 * <p/>
+	 * Returns false if the limiter has closed the new connection.
+	 */
+	boolean contactConnectionOpened(DuplexTransportConnection conn);
+
+	/**
+	 * Informs the limiter that a key agreement connection has been opened.
+	 */
+	void keyAgreementConnectionOpened(DuplexTransportConnection conn);
+
+	/**
+	 * Informs the limiter that the given connection has been closed.
+	 */
+	void connectionClosed(DuplexTransportConnection conn);
+
+	/**
+	 * Informs the limiter that all connections have been closed.
+	 */
+	void allConnectionsClosed();
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothConnectionLimiterImpl.java

@@ -0,0 +1,115 @@
+package org.briarproject.bramble.plugin.bluetooth;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+
+@NotNullByDefault
+@ThreadSafe
+class BluetoothConnectionLimiterImpl implements BluetoothConnectionLimiter {
+
+	private static final Logger LOG =
+			Logger.getLogger(BluetoothConnectionLimiterImpl.class.getName());
+
+	private final Object lock = new Object();
+	// The following are locking: lock
+	private final LinkedList<DuplexTransportConnection> connections =
+			new LinkedList<>();
+	private boolean keyAgreementInProgress = false;
+
+	@Override
+	public void keyAgreementStarted() {
+		List<DuplexTransportConnection> close;
+		synchronized (lock) {
+			keyAgreementInProgress = true;
+			close = new ArrayList<>(connections);
+			connections.clear();
+		}
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Key agreement started, closing " + close.size() +
+					" connections");
+		}
+		for (DuplexTransportConnection conn : close) tryToClose(conn);
+	}
+
+	@Override
+	public void keyAgreementEnded() {
+		synchronized (lock) {
+			keyAgreementInProgress = false;
+		}
+		LOG.info("Key agreement ended");
+	}
+
+	@Override
+	public boolean canOpenContactConnection() {
+		synchronized (lock) {
+			if (keyAgreementInProgress) {
+				LOG.info("Can't open contact connection during key agreement");
+				return false;
+			} else {
+				LOG.info("Can open contact connection");
+				return true;
+			}
+		}
+	}
+
+	@Override
+	public boolean contactConnectionOpened(DuplexTransportConnection conn) {
+		boolean accept = true;
+		synchronized (lock) {
+			if (keyAgreementInProgress) {
+				LOG.info("Refusing contact connection during key agreement");
+				accept = false;
+			} else {
+				LOG.info("Accepting contact connection");
+				connections.add(conn);
+			}
+		}
+		if (!accept) tryToClose(conn);
+		return accept;
+	}
+
+	@Override
+	public void keyAgreementConnectionOpened(DuplexTransportConnection conn) {
+		synchronized (lock) {
+			LOG.info("Accepting key agreement connection");
+			connections.add(conn);
+		}
+	}
+
+	private void tryToClose(DuplexTransportConnection conn) {
+		try {
+			conn.getWriter().dispose(false);
+			conn.getReader().dispose(false, false);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
+	@Override
+	public void connectionClosed(DuplexTransportConnection conn) {
+		synchronized (lock) {
+			connections.remove(conn);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connection closed, " + connections.size() + " open");
+		}
+	}
+
+	@Override
+	public void allConnectionsClosed() {
+		synchronized (lock) {
+			connections.clear();
+			LOG.info("All connections closed");
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/plugin/bluetooth/BluetoothPlugin.java

@@ -7,6 +7,8 @@ import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementListeningEvent;
+import org.briarproject.bramble.api.keyagreement.event.KeyAgreementStoppedListeningEvent;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
@@ -24,9 +26,11 @@ import org.briarproject.bramble.util.StringUtils;
 
 import java.io.IOException;
 import java.security.SecureRandom;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.UUID;
 import java.util.concurrent.Executor;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -51,6 +55,14 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	private static final Logger LOG =
 			Logger.getLogger(BluetoothPlugin.class.getName());
 
+	/**
+	 * How many milliseconds to pause between connection attempts when
+	 * polling, to avoid interfering with other Bluetooth or wifi connections.
+	 */
+	private static final int POLLING_PAUSE_MS = 3000;
+
+	final BluetoothConnectionLimiter connectionLimiter;
+
 	private final Executor ioExecutor;
 	private final SecureRandom secureRandom;
 	private final Backoff backoff;
@@ -91,8 +103,10 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	abstract DuplexTransportConnection connectTo(String address, String uuid)
 			throws IOException;
 
-	BluetoothPlugin(Executor ioExecutor, SecureRandom secureRandom,
+	BluetoothPlugin(BluetoothConnectionLimiter connectionLimiter,
+			Executor ioExecutor, SecureRandom secureRandom,
 			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
+		this.connectionLimiter = connectionLimiter;
 		this.ioExecutor = ioExecutor;
 		this.secureRandom = secureRandom;
 		this.backoff = backoff;
@@ -110,6 +124,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	void onAdapterDisabled() {
 		LOG.info("Bluetooth disabled");
 		tryToClose(socket);
+		connectionLimiter.allConnectionsClosed();
 		callback.transportDisabled();
 	}
 
@@ -213,7 +228,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				return;
 			}
 			backoff.reset();
-			callback.incomingConnectionCreated(conn);
+			if (connectionLimiter.contactConnectionOpened(conn))
+				callback.incomingConnectionCreated(conn);
 			if (!running) return;
 		}
 	}
@@ -245,25 +261,42 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	public void poll(Collection<ContactId> connected) {
 		if (!isRunning() || !shouldAllowContactConnections()) return;
 		backoff.increment();
-		// Try to connect to known devices in parallel
+		// Try to connect to known devices in a random order
 		Map<ContactId, TransportProperties> remote =
 				callback.getRemoteProperties();
-		for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
+		List<ContactId> keys = new ArrayList<>(remote.keySet());
-			ContactId c = e.getKey();
+		Collections.shuffle(keys);
-			if (connected.contains(c)) continue;
+		ioExecutor.execute(() -> {
-			String address = e.getValue().get(PROP_ADDRESS);
+			boolean first = true;
-			if (StringUtils.isNullOrEmpty(address)) continue;
+			for (ContactId c : keys) {
-			String uuid = e.getValue().get(PROP_UUID);
-			if (StringUtils.isNullOrEmpty(uuid)) continue;
-			ioExecutor.execute(() -> {
 				if (!isRunning() || !shouldAllowContactConnections()) return;
+				if (!connectionLimiter.canOpenContactConnection()) return;
+				if (connected.contains(c)) continue;
+				TransportProperties p = remote.get(c);
+				String address = p.get(PROP_ADDRESS);
+				if (StringUtils.isNullOrEmpty(address)) continue;
+				String uuid = p.get(PROP_UUID);
+				if (StringUtils.isNullOrEmpty(uuid)) continue;
+				// Pause between connection attempts
+				if (first) {
+					first = false;
+				} else {
+					try {
+						Thread.sleep(POLLING_PAUSE_MS);
+					} catch (InterruptedException ex) {
+						LOG.info("Interrupted while polling");
+						Thread.currentThread().interrupt();
+						return;
+					}
+				}
 				DuplexTransportConnection conn = connect(address, uuid);
 				if (conn != null) {
 					backoff.reset();
-					callback.outgoingConnectionCreated(c, conn);
+					if (connectionLimiter.contactConnectionOpened(conn))
+						callback.outgoingConnectionCreated(c, conn);
 				}
-			});
+			}
-		}
+		});
 	}
 
 	@Nullable
@@ -300,12 +333,16 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	@Override
 	public DuplexTransportConnection createConnection(ContactId c) {
 		if (!isRunning() || !shouldAllowContactConnections()) return null;
+		if (!connectionLimiter.canOpenContactConnection()) return null;
 		TransportProperties p = callback.getRemoteProperties(c);
 		String address = p.get(PROP_ADDRESS);
 		if (StringUtils.isNullOrEmpty(address)) return null;
 		String uuid = p.get(PROP_UUID);
 		if (StringUtils.isNullOrEmpty(uuid)) return null;
-		return connect(address, uuid);
+		DuplexTransportConnection conn = connect(address, uuid);
+		if (conn == null) return null;
+		// TODO: Why don't we reset the backoff here?
+		return connectionLimiter.contactConnectionOpened(conn) ? conn : null;
 	}
 
 	@Override
@@ -355,7 +392,9 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		String uuid = UUID.nameUUIDFromBytes(commitment).toString();
 		if (LOG.isLoggable(INFO))
 			LOG.info("Connecting to key agreement UUID " + uuid);
-		return connect(address, uuid);
+		DuplexTransportConnection conn = connect(address, uuid);
+		if (conn != null) connectionLimiter.keyAgreementConnectionOpened(conn);
+		return conn;
 	}
 
 	private String parseAddress(BdfList descriptor) throws FormatException {
@@ -376,6 +415,10 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
 			if (s.getNamespace().equals(ID.getString()))
 				ioExecutor.execute(this::onSettingsUpdated);
+		} else if (e instanceof KeyAgreementListeningEvent) {
+			ioExecutor.execute(connectionLimiter::keyAgreementStarted);
+		} else if (e instanceof KeyAgreementStoppedListeningEvent) {
+			ioExecutor.execute(connectionLimiter::keyAgreementEnded);
 		}
 	}
 
@@ -408,6 +451,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 		public KeyAgreementConnection accept() throws IOException {
 			DuplexTransportConnection conn = acceptConnection(ss);
 			if (LOG.isLoggable(INFO)) LOG.info(ID + ": Incoming connection");
+			connectionLimiter.keyAgreementConnectionOpened(conn);
 			return new KeyAgreementConnection(conn, ID);
 		}
 

bramble-core/src/main/java/org/briarproject/bramble/properties/PropertiesModule.java

@@ -7,6 +7,7 @@ import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.sync.ValidationManager;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -15,6 +16,8 @@ import dagger.Module;
 import dagger.Provides;
 
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_ID;
+import static org.briarproject.bramble.api.properties.TransportPropertyManager.MAJOR_VERSION;
+import static org.briarproject.bramble.api.properties.TransportPropertyManager.MINOR_VERSION;
 
 @Module
 public class PropertiesModule {
@@ -33,7 +36,8 @@ public class PropertiesModule {
 			Clock clock) {
 		TransportPropertyValidator validator = new TransportPropertyValidator(
 				clientHelper, metadataEncoder, clock);
-		validationManager.registerMessageValidator(CLIENT_ID, validator);
+		validationManager.registerMessageValidator(CLIENT_ID, MAJOR_VERSION,
+				validator);
 		return validator;
 	}
 
@@ -42,11 +46,14 @@ public class PropertiesModule {
 	TransportPropertyManager getTransportPropertyManager(
 			LifecycleManager lifecycleManager,
 			ValidationManager validationManager, ContactManager contactManager,
+			ClientVersioningManager clientVersioningManager,
 			TransportPropertyManagerImpl transportPropertyManager) {
 		lifecycleManager.registerClient(transportPropertyManager);
-		validationManager.registerIncomingMessageHook(CLIENT_ID,
+		validationManager.registerIncomingMessageHook(CLIENT_ID, MAJOR_VERSION,
 				transportPropertyManager);
 		contactManager.registerContactHook(transportPropertyManager);
+		clientVersioningManager.registerClient(CLIENT_ID, MAJOR_VERSION,
+				MINOR_VERSION, transportPropertyManager);
 		return transportPropertyManager;
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/properties/TransportPropertyManagerImpl.java

@@ -19,12 +19,15 @@ import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.properties.TransportPropertyManager;
 import org.briarproject.bramble.api.sync.Client;
 import org.briarproject.bramble.api.sync.Group;
+import org.briarproject.bramble.api.sync.Group.Visibility;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.InvalidMessageException;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.ValidationManager.IncomingMessageHook;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -34,15 +37,14 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
-
 @Immutable
 @NotNullByDefault
 class TransportPropertyManagerImpl implements TransportPropertyManager,
-		Client, ContactHook, IncomingMessageHook {
+		Client, ContactHook, ClientVersioningHook, IncomingMessageHook {
 
 	private final DatabaseComponent db;
 	private final ClientHelper clientHelper;
+	private final ClientVersioningManager clientVersioningManager;
 	private final MetadataParser metadataParser;
 	private final ContactGroupFactory contactGroupFactory;
 	private final Clock clock;
@@ -50,22 +52,25 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 
 	@Inject
 	TransportPropertyManagerImpl(DatabaseComponent db,
-			ClientHelper clientHelper, MetadataParser metadataParser,
+			ClientHelper clientHelper,
+			ClientVersioningManager clientVersioningManager,
+			MetadataParser metadataParser,
 			ContactGroupFactory contactGroupFactory, Clock clock) {
 		this.db = db;
 		this.clientHelper = clientHelper;
+		this.clientVersioningManager = clientVersioningManager;
 		this.metadataParser = metadataParser;
 		this.contactGroupFactory = contactGroupFactory;
 		this.clock = clock;
 		localGroup = contactGroupFactory.createLocalGroup(CLIENT_ID,
-				CLIENT_VERSION);
+				MAJOR_VERSION);
 	}
 
 	@Override
 	public void createLocalState(Transaction txn) throws DbException {
 		if (db.containsGroup(txn, localGroup.getId())) return;
 		db.addGroup(txn, localGroup);
-		// Ensure we've set things up for any pre-existing contacts
+		// Set things up for any pre-existing contacts
 		for (Contact c : db.getContacts(txn)) addingContact(txn, c);
 	}
 
@@ -73,11 +78,11 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 	public void addingContact(Transaction txn, Contact c) throws DbException {
 		// Create a group to share with the contact
 		Group g = getContactGroup(c);
-		// Return if we've already set things up for this contact
-		if (db.containsGroup(txn, g.getId())) return;
-		// Store the group and share it with the contact
 		db.addGroup(txn, g);
-		db.setGroupVisibility(txn, c.getId(), g.getId(), SHARED);
+		// Apply the client's visibility to the contact group
+		Visibility client = clientVersioningManager.getClientVisibility(txn,
+				c.getId(), CLIENT_ID, MAJOR_VERSION);
+		db.setGroupVisibility(txn, c.getId(), g.getId(), client);
 		// Copy the latest local properties into the group
 		Map<TransportId, TransportProperties> local = getLocalProperties(txn);
 		for (Entry<TransportId, TransportProperties> e : local.entrySet()) {
@@ -91,6 +96,14 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 		db.removeGroup(txn, getContactGroup(c));
 	}
 
+	@Override
+	public void onClientVisibilityChanging(Transaction txn, Contact c,
+			Visibility v) throws DbException {
+		// Apply the client's visibility to the contact group
+		Group g = getContactGroup(c);
+		db.setGroupVisibility(txn, c.getId(), g.getId(), v);
+	}
+
 	@Override
 	public boolean incomingMessage(Transaction txn, Message m, Metadata meta)
 			throws DbException, InvalidMessageException {
@@ -289,7 +302,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 
 	private Group getContactGroup(Contact c) {
 		return contactGroupFactory.createContactGroup(CLIENT_ID,
-				CLIENT_VERSION, c);
+				MAJOR_VERSION, c);
 	}
 
 	private void storeMessage(Transaction txn, GroupId g, TransportId t,

bramble-core/src/main/java/org/briarproject/bramble/record/RecordModule.java

@@ -0,0 +1,21 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class RecordModule {
+
+	@Provides
+	RecordReaderFactory provideRecordReaderFactory() {
+		return new RecordReaderFactoryImpl();
+	}
+
+	@Provides
+	RecordWriterFactory provideRecordWriterFactory() {
+		return new RecordWriterFactoryImpl();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/record/RecordReaderFactoryImpl.java

@@ -0,0 +1,14 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+
+import java.io.InputStream;
+
+class RecordReaderFactoryImpl implements RecordReaderFactory {
+
+	@Override
+	public RecordReader createRecordReader(InputStream in) {
+		return new RecordReaderImpl(in);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/record/RecordReaderImpl.java

@@ -0,0 +1,46 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.util.ByteUtils;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
+import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
+
+@NotThreadSafe
+@NotNullByDefault
+class RecordReaderImpl implements RecordReader {
+
+	private final DataInputStream in;
+	private final byte[] header = new byte[RECORD_HEADER_BYTES];
+
+	RecordReaderImpl(InputStream in) {
+		this.in = new DataInputStream(in);
+	}
+
+	@Override
+	public Record readRecord() throws IOException {
+		in.readFully(header);
+		byte protocolVersion = header[0];
+		byte recordType = header[1];
+		int payloadLength = ByteUtils.readUint16(header, 2);
+		if (payloadLength < 0 || payloadLength > MAX_RECORD_PAYLOAD_BYTES)
+			throw new FormatException();
+		byte[] payload = new byte[payloadLength];
+		in.readFully(payload);
+		return new Record(protocolVersion, recordType, payload);
+	}
+
+	@Override
+	public void close() throws IOException {
+		in.close();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/record/RecordWriterFactoryImpl.java

@@ -0,0 +1,14 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
+
+import java.io.OutputStream;
+
+class RecordWriterFactoryImpl implements RecordWriterFactory {
+
+	@Override
+	public RecordWriter createRecordWriter(OutputStream out) {
+		return new RecordWriterImpl(out);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/record/RecordWriterImpl.java

@@ -0,0 +1,45 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.util.ByteUtils;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
+
+@NotThreadSafe
+@NotNullByDefault
+class RecordWriterImpl implements RecordWriter {
+
+	private final OutputStream out;
+	private final byte[] header = new byte[RECORD_HEADER_BYTES];
+
+	RecordWriterImpl(OutputStream out) {
+		this.out = out;
+	}
+
+	@Override
+	public void writeRecord(Record r) throws IOException {
+		byte[] payload = r.getPayload();
+		header[0] = r.getProtocolVersion();
+		header[1] = r.getRecordType();
+		ByteUtils.writeUint16(payload.length, header, 2);
+		out.write(header);
+		out.write(payload);
+	}
+
+	@Override
+	public void flush() throws IOException {
+		out.flush();
+	}
+
+	@Override
+	public void close() throws IOException {
+		out.close();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/DuplexOutgoingSession.java

@@ -14,8 +14,8 @@ import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.RecordWriter;
 import org.briarproject.bramble.api.sync.Request;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.sync.SyncSession;
 import org.briarproject.bramble.api.sync.event.GroupVisibilityUpdatedEvent;
 import org.briarproject.bramble.api.sync.event.MessageRequestedEvent;
@@ -39,8 +39,8 @@ import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_RECORD_PAYLOAD_LENGTH;
 
 /**
  * An outgoing {@link SyncSession} suitable for duplex transports. The session
@@ -67,7 +67,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private final Clock clock;
 	private final ContactId contactId;
 	private final int maxLatency, maxIdleTime;
-	private final RecordWriter recordWriter;
+	private final SyncRecordWriter recordWriter;
 	private final BlockingQueue<ThrowingRunnable<IOException>> writerTasks;
 
 	private final AtomicBoolean generateAckQueued = new AtomicBoolean(false);
@@ -81,7 +81,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 
 	DuplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
 			EventBus eventBus, Clock clock, ContactId contactId, int maxLatency,
-			int maxIdleTime, RecordWriter recordWriter) {
+			int maxIdleTime, SyncRecordWriter recordWriter) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
@@ -273,7 +273,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 				Transaction txn = db.startTransaction(false);
 				try {
 					b = db.generateRequestedBatch(txn, contactId,
-							MAX_RECORD_PAYLOAD_LENGTH, maxLatency);
+							MAX_RECORD_PAYLOAD_BYTES, maxLatency);
 					setNextSendTime(db.getNextSendTime(txn, contactId));
 					db.commitTransaction(txn);
 				} finally {

bramble-core/src/main/java/org/briarproject/bramble/sync/GroupFactoryImpl.java

@@ -20,6 +20,9 @@ import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
 @NotNullByDefault
 class GroupFactoryImpl implements GroupFactory {
 
+	private static final byte[] FORMAT_VERSION_BYTES =
+			new byte[] {FORMAT_VERSION};
+
 	private final CryptoComponent crypto;
 
 	@Inject
@@ -28,12 +31,12 @@ class GroupFactoryImpl implements GroupFactory {
 	}
 
 	@Override
-	public Group createGroup(ClientId c, int clientVersion, byte[] descriptor) {
+	public Group createGroup(ClientId c, int majorVersion, byte[] descriptor) {
-		byte[] clientVersionBytes = new byte[INT_32_BYTES];
+		byte[] majorVersionBytes = new byte[INT_32_BYTES];
-		ByteUtils.writeUint32(clientVersion, clientVersionBytes, 0);
+		ByteUtils.writeUint32(majorVersion, majorVersionBytes, 0);
-		byte[] hash = crypto.hash(LABEL, new byte[] {FORMAT_VERSION},
+		byte[] hash = crypto.hash(LABEL, FORMAT_VERSION_BYTES,
-				StringUtils.toUtf8(c.getString()), clientVersionBytes,
+				StringUtils.toUtf8(c.getString()), majorVersionBytes,
 				descriptor);
-		return new Group(new GroupId(hash), c, descriptor);
+		return new Group(new GroupId(hash), c, majorVersion, descriptor);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/IncomingSession.java

@@ -16,8 +16,8 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.RecordReader;
 import org.briarproject.bramble.api.sync.Request;
+import org.briarproject.bramble.api.sync.SyncRecordReader;
 import org.briarproject.bramble.api.sync.SyncSession;
 
 import java.io.IOException;
@@ -43,13 +43,13 @@ class IncomingSession implements SyncSession, EventListener {
 	private final Executor dbExecutor;
 	private final EventBus eventBus;
 	private final ContactId contactId;
-	private final RecordReader recordReader;
+	private final SyncRecordReader recordReader;
 
 	private volatile boolean interrupted = false;
 
 	IncomingSession(DatabaseComponent db, Executor dbExecutor,
 			EventBus eventBus, ContactId contactId,
-			RecordReader recordReader) {
+			SyncRecordReader recordReader) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;

bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java

@@ -16,6 +16,7 @@ import static org.briarproject.bramble.api.sync.Message.FORMAT_VERSION;
 import static org.briarproject.bramble.api.sync.MessageId.BLOCK_LABEL;
 import static org.briarproject.bramble.api.sync.MessageId.ID_LABEL;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
+import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 
@@ -23,6 +24,9 @@ import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 @NotNullByDefault
 class MessageFactoryImpl implements MessageFactory {
 
+	private static final byte[] FORMAT_VERSION_BYTES =
+			new byte[] {FORMAT_VERSION};
+
 	private final CryptoComponent crypto;
 
 	@Inject
@@ -34,14 +38,7 @@ class MessageFactoryImpl implements MessageFactory {
 	public Message createMessage(GroupId g, long timestamp, byte[] body) {
 		if (body.length > MAX_MESSAGE_BODY_LENGTH)
 			throw new IllegalArgumentException();
-		byte[] versionBytes = new byte[] {FORMAT_VERSION};
+		MessageId id = getMessageId(g, timestamp, body);
-		// There's only one block, so the root hash is the hash of the block
-		byte[] rootHash = crypto.hash(BLOCK_LABEL, versionBytes, body);
-		byte[] timeBytes = new byte[INT_64_BYTES];
-		ByteUtils.writeUint64(timestamp, timeBytes, 0);
-		byte[] idHash = crypto.hash(ID_LABEL, versionBytes, g.getBytes(),
-				timeBytes, rootHash);
-		MessageId id = new MessageId(idHash);
 		byte[] raw = new byte[MESSAGE_HEADER_LENGTH + body.length];
 		System.arraycopy(g.getBytes(), 0, raw, 0, UniqueId.LENGTH);
 		ByteUtils.writeUint64(timestamp, raw, UniqueId.LENGTH);
@@ -49,10 +46,38 @@ class MessageFactoryImpl implements MessageFactory {
 		return new Message(id, g, timestamp, raw);
 	}
 
+	private MessageId getMessageId(GroupId g, long timestamp, byte[] body) {
+		// There's only one block, so the root hash is the hash of the block
+		byte[] rootHash = crypto.hash(BLOCK_LABEL, FORMAT_VERSION_BYTES, body);
+		byte[] timeBytes = new byte[INT_64_BYTES];
+		ByteUtils.writeUint64(timestamp, timeBytes, 0);
+		byte[] idHash = crypto.hash(ID_LABEL, FORMAT_VERSION_BYTES,
+				g.getBytes(), timeBytes, rootHash);
+		return new MessageId(idHash);
+	}
+
+	@Override
+	public Message createMessage(byte[] raw) {
+		if (raw.length < MESSAGE_HEADER_LENGTH)
+			throw new IllegalArgumentException();
+		if (raw.length > MAX_MESSAGE_LENGTH)
+			throw new IllegalArgumentException();
+		byte[] groupId = new byte[UniqueId.LENGTH];
+		System.arraycopy(raw, 0, groupId, 0, UniqueId.LENGTH);
+		GroupId g = new GroupId(groupId);
+		long timestamp = ByteUtils.readUint64(raw, UniqueId.LENGTH);
+		byte[] body = new byte[raw.length - MESSAGE_HEADER_LENGTH];
+		System.arraycopy(raw, MESSAGE_HEADER_LENGTH, body, 0, body.length);
+		MessageId id = getMessageId(g, timestamp, body);
+		return new Message(id, g, timestamp, raw);
+	}
+
 	@Override
 	public Message createMessage(MessageId m, byte[] raw) {
 		if (raw.length < MESSAGE_HEADER_LENGTH)
 			throw new IllegalArgumentException();
+		if (raw.length > MAX_MESSAGE_LENGTH)
+			throw new IllegalArgumentException();
 		byte[] groupId = new byte[UniqueId.LENGTH];
 		System.arraycopy(raw, 0, groupId, 0, UniqueId.LENGTH);
 		long timestamp = ByteUtils.readUint64(raw, UniqueId.LENGTH);

bramble-core/src/main/java/org/briarproject/bramble/sync/RecordReaderFactoryImpl.java

@@ -1,28 +0,0 @@
-package org.briarproject.bramble.sync;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.MessageFactory;
-import org.briarproject.bramble.api.sync.RecordReader;
-import org.briarproject.bramble.api.sync.RecordReaderFactory;
-
-import java.io.InputStream;
-
-import javax.annotation.concurrent.Immutable;
-import javax.inject.Inject;
-
-@Immutable
-@NotNullByDefault
-class RecordReaderFactoryImpl implements RecordReaderFactory {
-
-	private final MessageFactory messageFactory;
-
-	@Inject
-	RecordReaderFactoryImpl(MessageFactory messageFactory) {
-		this.messageFactory = messageFactory;
-	}
-
-	@Override
-	public RecordReader createRecordReader(InputStream in) {
-		return new RecordReaderImpl(messageFactory, in);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/sync/RecordWriterFactoryImpl.java

@@ -1,16 +0,0 @@
-package org.briarproject.bramble.sync;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.RecordWriter;
-import org.briarproject.bramble.api.sync.RecordWriterFactory;
-
-import java.io.OutputStream;
-
-@NotNullByDefault
-class RecordWriterFactoryImpl implements RecordWriterFactory {
-
-	@Override
-	public RecordWriter createRecordWriter(OutputStream out) {
-		return new RecordWriterImpl(out);
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/sync/SimplexOutgoingSession.java

@@ -13,7 +13,7 @@ import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Ack;
-import org.briarproject.bramble.api.sync.RecordWriter;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.api.sync.SyncSession;
 
 import java.io.IOException;
@@ -29,8 +29,8 @@ import javax.annotation.concurrent.ThreadSafe;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_RECORD_PAYLOAD_LENGTH;
 
 /**
  * An outgoing {@link SyncSession} suitable for simplex transports. The session
@@ -51,7 +51,7 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 	private final EventBus eventBus;
 	private final ContactId contactId;
 	private final int maxLatency;
-	private final RecordWriter recordWriter;
+	private final SyncRecordWriter recordWriter;
 	private final AtomicInteger outstandingQueries;
 	private final BlockingQueue<ThrowingRunnable<IOException>> writerTasks;
 
@@ -59,7 +59,7 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 
 	SimplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
 			EventBus eventBus, ContactId contactId,
-			int maxLatency, RecordWriter recordWriter) {
+			int maxLatency, SyncRecordWriter recordWriter) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
@@ -171,7 +171,7 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 				Transaction txn = db.startTransaction(false);
 				try {
 					b = db.generateBatch(txn, contactId,
-							MAX_RECORD_PAYLOAD_LENGTH, maxLatency);
+							MAX_RECORD_PAYLOAD_BYTES, maxLatency);
 					db.commitTransaction(txn);
 				} finally {
 					db.endTransaction(txn);

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncModule.java

@@ -9,8 +9,8 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.sync.GroupFactory;
 import org.briarproject.bramble.api.sync.MessageFactory;
-import org.briarproject.bramble.api.sync.RecordReaderFactory;
+import org.briarproject.bramble.api.sync.SyncRecordReaderFactory;
-import org.briarproject.bramble.api.sync.RecordWriterFactory;
+import org.briarproject.bramble.api.sync.SyncRecordWriterFactory;
 import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.sync.ValidationManager;
 import org.briarproject.bramble.api.system.Clock;
@@ -52,22 +52,23 @@ public class SyncModule {
 	}
 
 	@Provides
-	RecordReaderFactory provideRecordReaderFactory(
+	SyncRecordReaderFactory provideRecordReaderFactory(
-			RecordReaderFactoryImpl recordReaderFactory) {
+			SyncRecordReaderFactoryImpl recordReaderFactory) {
 		return recordReaderFactory;
 	}
 
 	@Provides
-	RecordWriterFactory provideRecordWriterFactory() {
+	SyncRecordWriterFactory provideRecordWriterFactory(
-		return new RecordWriterFactoryImpl();
+			SyncRecordWriterFactoryImpl recordWriterFactory) {
+		return recordWriterFactory;
 	}
 
 	@Provides
 	@Singleton
 	SyncSessionFactory provideSyncSessionFactory(DatabaseComponent db,
 			@DatabaseExecutor Executor dbExecutor, EventBus eventBus,
-			Clock clock, RecordReaderFactory recordReaderFactory,
+			Clock clock, SyncRecordReaderFactory recordReaderFactory,
-			RecordWriterFactory recordWriterFactory) {
+			SyncRecordWriterFactory recordWriterFactory) {
 		return new SyncSessionFactoryImpl(db, dbExecutor, eventBus, clock,
 				recordReaderFactory, recordWriterFactory);
 	}

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordReaderFactoryImpl.java

@@ -0,0 +1,34 @@
+package org.briarproject.bramble.sync;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.sync.MessageFactory;
+import org.briarproject.bramble.api.sync.SyncRecordReader;
+import org.briarproject.bramble.api.sync.SyncRecordReaderFactory;
+
+import java.io.InputStream;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+@Immutable
+@NotNullByDefault
+class SyncRecordReaderFactoryImpl implements SyncRecordReaderFactory {
+
+	private final MessageFactory messageFactory;
+	private final RecordReaderFactory recordReaderFactory;
+
+	@Inject
+	SyncRecordReaderFactoryImpl(MessageFactory messageFactory,
+			RecordReaderFactory recordReaderFactory) {
+		this.messageFactory = messageFactory;
+		this.recordReaderFactory = recordReaderFactory;
+	}
+
+	@Override
+	public SyncRecordReader createRecordReader(InputStream in) {
+		RecordReader reader = recordReaderFactory.createRecordReader(in);
+		return new SyncRecordReaderImpl(messageFactory, reader);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordReaderImpl.java

@@ -3,82 +3,56 @@ package org.briarproject.bramble.sync;
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.UniqueId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
 import org.briarproject.bramble.api.sync.Ack;
-import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.RecordReader;
 import org.briarproject.bramble.api.sync.Request;
+import org.briarproject.bramble.api.sync.SyncRecordReader;
 import org.briarproject.bramble.util.ByteUtils;
 
+import java.io.EOFException;
 import java.io.IOException;
-import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.List;
 
+import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
 import static org.briarproject.bramble.api.sync.RecordTypes.MESSAGE;
 import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
 import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_RECORD_PAYLOAD_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.api.sync.SyncConstants.RECORD_HEADER_LENGTH;
 
 @NotThreadSafe
 @NotNullByDefault
-class RecordReaderImpl implements RecordReader {
+class SyncRecordReaderImpl implements SyncRecordReader {
-
-	private enum State {BUFFER_EMPTY, BUFFER_FULL, EOF}
 
 	private final MessageFactory messageFactory;
-	private final InputStream in;
+	private final RecordReader reader;
-	private final byte[] header, payload;
 
-	private State state = State.BUFFER_EMPTY;
+	@Nullable
-	private int payloadLength = 0;
+	private Record nextRecord = null;
+	private boolean eof = false;
 
-	RecordReaderImpl(MessageFactory messageFactory, InputStream in) {
+	SyncRecordReaderImpl(MessageFactory messageFactory, RecordReader reader) {
 		this.messageFactory = messageFactory;
-		this.in = in;
+		this.reader = reader;
-		header = new byte[RECORD_HEADER_LENGTH];
-		payload = new byte[MAX_RECORD_PAYLOAD_LENGTH];
 	}
 
 	private void readRecord() throws IOException {
-		if (state != State.BUFFER_EMPTY) throw new IllegalStateException();
+		assert nextRecord == null;
 		while (true) {
-			// Read the header
+			nextRecord = reader.readRecord();
-			int offset = 0;
-			while (offset < RECORD_HEADER_LENGTH) {
-				int read =
-						in.read(header, offset, RECORD_HEADER_LENGTH - offset);
-				if (read == -1) {
-					if (offset > 0) throw new FormatException();
-					state = State.EOF;
-					return;
-				}
-				offset += read;
-			}
-			byte version = header[0], type = header[1];
-			payloadLength = ByteUtils.readUint16(header, 2);
 			// Check the protocol version
+			byte version = nextRecord.getProtocolVersion();
 			if (version != PROTOCOL_VERSION) throw new FormatException();
-			// Check the payload length
+			byte type = nextRecord.getRecordType();
-			if (payloadLength > MAX_RECORD_PAYLOAD_LENGTH)
-				throw new FormatException();
-			// Read the payload
-			offset = 0;
-			while (offset < payloadLength) {
-				int read = in.read(payload, offset, payloadLength - offset);
-				if (read == -1) throw new FormatException();
-				offset += read;
-			}
-			state = State.BUFFER_FULL;
 			// Return if this is a known record type, otherwise continue
 			if (type == ACK || type == MESSAGE || type == OFFER ||
 					type == REQUEST) {
@@ -87,6 +61,11 @@ class RecordReaderImpl implements RecordReader {
 		}
 	}
 
+	private byte getNextRecordType() {
+		assert nextRecord != null;
+		return nextRecord.getRecordType();
+	}
+
 	/**
 	 * Returns true if there's another record available or false if we've
 	 * reached the end of the input stream.
@@ -97,14 +76,21 @@ class RecordReaderImpl implements RecordReader {
 	 */
 	@Override
 	public boolean eof() throws IOException {
-		if (state == State.BUFFER_EMPTY) readRecord();
+		if (nextRecord != null) return false;
-		if (state == State.BUFFER_EMPTY) throw new IllegalStateException();
+		if (eof) return true;
-		return state == State.EOF;
+		try {
+			readRecord();
+			return false;
+		} catch (EOFException e) {
+			nextRecord = null;
+			eof = true;
+			return true;
+		}
 	}
 
 	@Override
 	public boolean hasAck() throws IOException {
-		return !eof() && header[1] == ACK;
+		return !eof() && getNextRecordType() == ACK;
 	}
 
 	@Override
@@ -114,45 +100,41 @@ class RecordReaderImpl implements RecordReader {
 	}
 
 	private List<MessageId> readMessageIds() throws IOException {
-		if (payloadLength == 0) throw new FormatException();
+		assert nextRecord != null;
-		if (payloadLength % UniqueId.LENGTH != 0) throw new FormatException();
+		byte[] payload = nextRecord.getPayload();
-		List<MessageId> ids = new ArrayList<>();
+		if (payload.length == 0) throw new FormatException();
-		for (int off = 0; off < payloadLength; off += UniqueId.LENGTH) {
+		if (payload.length % UniqueId.LENGTH != 0) throw new FormatException();
+		List<MessageId> ids = new ArrayList<>(payload.length / UniqueId.LENGTH);
+		for (int off = 0; off < payload.length; off += UniqueId.LENGTH) {
 			byte[] id = new byte[UniqueId.LENGTH];
 			System.arraycopy(payload, off, id, 0, UniqueId.LENGTH);
 			ids.add(new MessageId(id));
 		}
-		state = State.BUFFER_EMPTY;
+		nextRecord = null;
 		return ids;
 	}
 
 	@Override
 	public boolean hasMessage() throws IOException {
-		return !eof() && header[1] == MESSAGE;
+		return !eof() && getNextRecordType() == MESSAGE;
 	}
 
 	@Override
 	public Message readMessage() throws IOException {
 		if (!hasMessage()) throw new FormatException();
-		if (payloadLength <= MESSAGE_HEADER_LENGTH) throw new FormatException();
+		assert nextRecord != null;
-		// Group ID
+		byte[] payload = nextRecord.getPayload();
-		byte[] id = new byte[UniqueId.LENGTH];
+		if (payload.length < MESSAGE_HEADER_LENGTH) throw new FormatException();
-		System.arraycopy(payload, 0, id, 0, UniqueId.LENGTH);
+		// Validate timestamp
-		GroupId groupId = new GroupId(id);
-		// Timestamp
 		long timestamp = ByteUtils.readUint64(payload, UniqueId.LENGTH);
 		if (timestamp < 0) throw new FormatException();
-		// Body
+		nextRecord = null;
-		byte[] body = new byte[payloadLength - MESSAGE_HEADER_LENGTH];
+		return messageFactory.createMessage(payload);
-		System.arraycopy(payload, MESSAGE_HEADER_LENGTH, body, 0,
-				payloadLength - MESSAGE_HEADER_LENGTH);
-		state = State.BUFFER_EMPTY;
-		return messageFactory.createMessage(groupId, timestamp, body);
 	}
 
 	@Override
 	public boolean hasOffer() throws IOException {
-		return !eof() && header[1] == OFFER;
+		return !eof() && getNextRecordType() == OFFER;
 	}
 
 	@Override
@@ -163,7 +145,7 @@ class RecordReaderImpl implements RecordReader {
 
 	@Override
 	public boolean hasRequest() throws IOException {
-		return !eof() && header[1] == REQUEST;
+		return !eof() && getNextRecordType() == REQUEST;
 	}
 
 	@Override

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordWriterFactoryImpl.java

@@ -0,0 +1,28 @@
+package org.briarproject.bramble.sync;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
+import org.briarproject.bramble.api.sync.SyncRecordWriterFactory;
+
+import java.io.OutputStream;
+
+import javax.inject.Inject;
+
+@NotNullByDefault
+class SyncRecordWriterFactoryImpl implements SyncRecordWriterFactory {
+
+	private final RecordWriterFactory recordWriterFactory;
+
+	@Inject
+	SyncRecordWriterFactoryImpl(RecordWriterFactory recordWriterFactory) {
+		this.recordWriterFactory = recordWriterFactory;
+	}
+
+	@Override
+	public SyncRecordWriter createRecordWriter(OutputStream out) {
+		RecordWriter writer = recordWriterFactory.createRecordWriter(out);
+		return new SyncRecordWriterImpl(writer);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncRecordWriterImpl.java

@@ -1,81 +1,67 @@
 package org.briarproject.bramble.sync;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordWriter;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.RecordTypes;
-import org.briarproject.bramble.api.sync.RecordWriter;
 import org.briarproject.bramble.api.sync.Request;
-import org.briarproject.bramble.util.ByteUtils;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.OutputStream;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
 import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
+import static org.briarproject.bramble.api.sync.RecordTypes.MESSAGE;
 import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
 import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_RECORD_PAYLOAD_LENGTH;
-import static org.briarproject.bramble.api.sync.SyncConstants.RECORD_HEADER_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
 
 @NotThreadSafe
 @NotNullByDefault
-class RecordWriterImpl implements RecordWriter {
+class SyncRecordWriterImpl implements SyncRecordWriter {
 
-	private final OutputStream out;
+	private final RecordWriter writer;
-	private final byte[] header;
+	private final ByteArrayOutputStream payload = new ByteArrayOutputStream();
-	private final ByteArrayOutputStream payload;
 
-	RecordWriterImpl(OutputStream out) {
+	SyncRecordWriterImpl(RecordWriter writer) {
-		this.out = out;
+		this.writer = writer;
-		header = new byte[RECORD_HEADER_LENGTH];
-		header[0] = PROTOCOL_VERSION;
-		payload = new ByteArrayOutputStream(MAX_RECORD_PAYLOAD_LENGTH);
 	}
 
 	private void writeRecord(byte recordType) throws IOException {
-		header[1] = recordType;
+		writer.writeRecord(new Record(PROTOCOL_VERSION, recordType,
-		ByteUtils.writeUint16(payload.size(), header, 2);
+				payload.toByteArray()));
-		out.write(header);
-		payload.writeTo(out);
 		payload.reset();
 	}
 
 	@Override
 	public void writeAck(Ack a) throws IOException {
-		if (payload.size() != 0) throw new IllegalStateException();
 		for (MessageId m : a.getMessageIds()) payload.write(m.getBytes());
 		writeRecord(ACK);
 	}
 
 	@Override
 	public void writeMessage(byte[] raw) throws IOException {
-		header[1] = RecordTypes.MESSAGE;
+		writer.writeRecord(new Record(PROTOCOL_VERSION, MESSAGE, raw));
-		ByteUtils.writeUint16(raw.length, header, 2);
-		out.write(header);
-		out.write(raw);
 	}
 
 	@Override
 	public void writeOffer(Offer o) throws IOException {
-		if (payload.size() != 0) throw new IllegalStateException();
 		for (MessageId m : o.getMessageIds()) payload.write(m.getBytes());
 		writeRecord(OFFER);
 	}
 
 	@Override
 	public void writeRequest(Request r) throws IOException {
-		if (payload.size() != 0) throw new IllegalStateException();
 		for (MessageId m : r.getMessageIds()) payload.write(m.getBytes());
 		writeRecord(REQUEST);
 	}
 
 	@Override
 	public void flush() throws IOException {
-		out.flush();
+		writer.flush();
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/sync/SyncSessionFactoryImpl.java

@@ -5,10 +5,10 @@ import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.sync.RecordReader;
+import org.briarproject.bramble.api.sync.SyncRecordReader;
-import org.briarproject.bramble.api.sync.RecordReaderFactory;
+import org.briarproject.bramble.api.sync.SyncRecordReaderFactory;
-import org.briarproject.bramble.api.sync.RecordWriter;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
-import org.briarproject.bramble.api.sync.RecordWriterFactory;
+import org.briarproject.bramble.api.sync.SyncRecordWriterFactory;
 import org.briarproject.bramble.api.sync.SyncSession;
 import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.system.Clock;
@@ -28,14 +28,14 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 	private final Executor dbExecutor;
 	private final EventBus eventBus;
 	private final Clock clock;
-	private final RecordReaderFactory recordReaderFactory;
+	private final SyncRecordReaderFactory recordReaderFactory;
-	private final RecordWriterFactory recordWriterFactory;
+	private final SyncRecordWriterFactory recordWriterFactory;
 
 	@Inject
 	SyncSessionFactoryImpl(DatabaseComponent db,
 			@DatabaseExecutor Executor dbExecutor, EventBus eventBus,
-			Clock clock, RecordReaderFactory recordReaderFactory,
+			Clock clock, SyncRecordReaderFactory recordReaderFactory,
-			RecordWriterFactory recordWriterFactory) {
+			SyncRecordWriterFactory recordWriterFactory) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
@@ -46,14 +46,16 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 
 	@Override
 	public SyncSession createIncomingSession(ContactId c, InputStream in) {
-		RecordReader recordReader = recordReaderFactory.createRecordReader(in);
+		SyncRecordReader recordReader =
+				recordReaderFactory.createRecordReader(in);
 		return new IncomingSession(db, dbExecutor, eventBus, c, recordReader);
 	}
 
 	@Override
 	public SyncSession createSimplexOutgoingSession(ContactId c,
 			int maxLatency, OutputStream out) {
-		RecordWriter recordWriter = recordWriterFactory.createRecordWriter(out);
+		SyncRecordWriter recordWriter =
+				recordWriterFactory.createRecordWriter(out);
 		return new SimplexOutgoingSession(db, dbExecutor, eventBus, c,
 				maxLatency, recordWriter);
 	}
@@ -61,7 +63,8 @@ class SyncSessionFactoryImpl implements SyncSessionFactory {
 	@Override
 	public SyncSession createDuplexOutgoingSession(ContactId c, int maxLatency,
 			int maxIdleTime, OutputStream out) {
-		RecordWriter recordWriter = recordWriterFactory.createRecordWriter(out);
+		SyncRecordWriter recordWriter =
+				recordWriterFactory.createRecordWriter(out);
 		return new DuplexOutgoingSession(db, dbExecutor, eventBus, clock, c,
 				maxLatency, maxIdleTime, recordWriter);
 	}

bramble-core/src/main/java/org/briarproject/bramble/sync/ValidationManagerImpl.java

@@ -20,6 +20,7 @@ import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.ValidationManager;
 import org.briarproject.bramble.api.sync.event.MessageAddedEvent;
+import org.briarproject.bramble.api.versioning.ClientMajorVersion;
 
 import java.util.Collection;
 import java.util.LinkedList;
@@ -51,8 +52,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	private final DatabaseComponent db;
 	private final Executor dbExecutor, validationExecutor;
 	private final MessageFactory messageFactory;
-	private final Map<ClientId, MessageValidator> validators;
+	private final Map<ClientMajorVersion, MessageValidator> validators;
-	private final Map<ClientId, IncomingMessageHook> hooks;
+	private final Map<ClientMajorVersion, IncomingMessageHook> hooks;
 	private final AtomicBoolean used = new AtomicBoolean(false);
 
 	@Inject
@@ -81,14 +82,15 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	}
 
 	@Override
-	public void registerMessageValidator(ClientId c, MessageValidator v) {
+	public void registerMessageValidator(ClientId c, int majorVersion,
-		validators.put(c, v);
+			MessageValidator v) {
+		validators.put(new ClientMajorVersion(c, majorVersion), v);
 	}
 
 	@Override
-	public void registerIncomingMessageHook(ClientId c,
+	public void registerIncomingMessageHook(ClientId c, int majorVersion,
 			IncomingMessageHook hook) {
-		hooks.put(c, hook);
+		hooks.put(new ClientMajorVersion(c, majorVersion), hook);
 	}
 
 	private void validateOutstandingMessagesAsync() {
@@ -199,9 +201,11 @@ class ValidationManagerImpl implements ValidationManager, Service,
 						Message m = messageFactory.createMessage(id, raw);
 						Group g = db.getGroup(txn, m.getGroupId());
 						ClientId c = g.getClientId();
+						int majorVersion = g.getMajorVersion();
 						Metadata meta =
 								db.getMessageMetadataForValidator(txn, id);
-						DeliveryResult result = deliverMessage(txn, m, c, meta);
+						DeliveryResult result =
+								deliverMessage(txn, m, c, majorVersion, meta);
 						if (result.valid) {
 							pending.addAll(getPendingDependents(txn, id));
 							if (result.share) {
@@ -237,14 +241,16 @@ class ValidationManagerImpl implements ValidationManager, Service,
 
 	@ValidationExecutor
 	private void validateMessage(Message m, Group g) {
-		MessageValidator v = validators.get(g.getClientId());
+		ClientMajorVersion cv =
+				new ClientMajorVersion(g.getClientId(), g.getMajorVersion());
+		MessageValidator v = validators.get(cv);
 		if (v == null) {
-			if (LOG.isLoggable(WARNING))
+			if (LOG.isLoggable(WARNING)) LOG.warning("No validator for " + cv);
-				LOG.warning("No validator for " + g.getClientId().getString());
 		} else {
 			try {
 				MessageContext context = v.validateMessage(m, g);
-				storeMessageContextAsync(m, g.getClientId(), context);
+				storeMessageContextAsync(m, g.getClientId(),
+						g.getMajorVersion(), context);
 			} catch (InvalidMessageException e) {
 				if (LOG.isLoggable(INFO))
 					LOG.log(INFO, e.toString(), e);
@@ -256,12 +262,13 @@ class ValidationManagerImpl implements ValidationManager, Service,
 	}
 
 	private void storeMessageContextAsync(Message m, ClientId c,
-			MessageContext result) {
+			int majorVersion, MessageContext result) {
-		dbExecutor.execute(() -> storeMessageContext(m, c, result));
+		dbExecutor.execute(() ->
+				storeMessageContext(m, c, majorVersion, result));
 	}
 
 	@DatabaseExecutor
-	private void storeMessageContext(Message m, ClientId c,
+	private void storeMessageContext(Message m, ClientId c, int majorVersion,
 			MessageContext context) {
 		try {
 			MessageId id = m.getId();
@@ -292,7 +299,8 @@ class ValidationManagerImpl implements ValidationManager, Service,
 					Metadata meta = context.getMetadata();
 					db.mergeMessageMetadata(txn, id, meta);
 					if (allDelivered) {
-						DeliveryResult result = deliverMessage(txn, m, c, meta);
+						DeliveryResult result =
+								deliverMessage(txn, m, c, majorVersion, meta);
 						if (result.valid) {
 							pending = getPendingDependents(txn, id);
 							if (result.share) {
@@ -324,10 +332,11 @@ class ValidationManagerImpl implements ValidationManager, Service,
 
 	@DatabaseExecutor
 	private DeliveryResult deliverMessage(Transaction txn, Message m,
-			ClientId c, Metadata meta) throws DbException {
+			ClientId c, int majorVersion, Metadata meta) throws DbException {
 		// Deliver the message to the client if it's registered a hook
 		boolean shareMsg = false;
-		IncomingMessageHook hook = hooks.get(c);
+		ClientMajorVersion cv = new ClientMajorVersion(c, majorVersion);
+		IncomingMessageHook hook = hooks.get(cv);
 		if (hook != null) {
 			try {
 				shareMsg = hook.incomingMessage(txn, m, meta);

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningConstants.java

@@ -0,0 +1,10 @@
+package org.briarproject.bramble.versioning;
+
+interface ClientVersioningConstants {
+
+	// Metadata keys
+	String MSG_KEY_UPDATE_VERSION = "version";
+	String MSG_KEY_LOCAL = "local";
+	String GROUP_KEY_CONTACT_ID = "contactId";
+}
+

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningManagerImpl.java

@@ -0,0 +1,622 @@
+package org.briarproject.bramble.versioning;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.client.ClientHelper;
+import org.briarproject.bramble.api.client.ContactGroupFactory;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.contact.ContactManager.ContactHook;
+import org.briarproject.bramble.api.data.BdfDictionary;
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Metadata;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.lifecycle.Service;
+import org.briarproject.bramble.api.lifecycle.ServiceException;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.Client;
+import org.briarproject.bramble.api.sync.ClientId;
+import org.briarproject.bramble.api.sync.Group;
+import org.briarproject.bramble.api.sync.Group.Visibility;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.InvalidMessageException;
+import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.ValidationManager.IncomingMessageHook;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.versioning.ClientMajorVersion;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import javax.annotation.Nullable;
+import javax.inject.Inject;
+
+import static java.util.Collections.emptyList;
+import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
+import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
+import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.GROUP_KEY_CONTACT_ID;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
+
+@NotNullByDefault
+class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
+		Service, ContactHook, IncomingMessageHook {
+
+	private final DatabaseComponent db;
+	private final ClientHelper clientHelper;
+	private final ContactGroupFactory contactGroupFactory;
+	private final Clock clock;
+	private final Group localGroup;
+
+	private final List<ClientVersion> clients = new CopyOnWriteArrayList<>();
+	private final Map<ClientMajorVersion, ClientVersioningHook> hooks =
+			new ConcurrentHashMap<>();
+
+	@Inject
+	ClientVersioningManagerImpl(DatabaseComponent db, ClientHelper clientHelper,
+			ContactGroupFactory contactGroupFactory, Clock clock) {
+		this.db = db;
+		this.clientHelper = clientHelper;
+		this.contactGroupFactory = contactGroupFactory;
+		this.clock = clock;
+		localGroup = contactGroupFactory.createLocalGroup(CLIENT_ID,
+				MAJOR_VERSION);
+	}
+
+	@Override
+	public void registerClient(ClientId clientId, int majorVersion,
+			int minorVersion, ClientVersioningHook hook) {
+		ClientMajorVersion cv = new ClientMajorVersion(clientId, majorVersion);
+		clients.add(new ClientVersion(cv, minorVersion));
+		hooks.put(cv, hook);
+	}
+
+	@Override
+	public Visibility getClientVisibility(Transaction txn, ContactId contactId,
+			ClientId clientId, int majorVersion) throws DbException {
+		try {
+			Contact contact = db.getContact(txn, contactId);
+			Group g = getContactGroup(contact);
+			// Contact may be in the process of being added or removed, so
+			// contact group may not exist
+			if (!db.containsGroup(txn, g.getId())) return INVISIBLE;
+			LatestUpdates latest = findLatestUpdates(txn, g.getId());
+			if (latest.local == null) throw new DbException();
+			if (latest.remote == null) return INVISIBLE;
+			Update localUpdate = loadUpdate(txn, latest.local.messageId);
+			Update remoteUpdate = loadUpdate(txn, latest.remote.messageId);
+			Map<ClientMajorVersion, Visibility> visibilities =
+					getVisibilities(localUpdate.states, remoteUpdate.states);
+			ClientMajorVersion cv =
+					new ClientMajorVersion(clientId, majorVersion);
+			Visibility v = visibilities.get(cv);
+			return v == null ? INVISIBLE : v;
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
+	@Override
+	public void createLocalState(Transaction txn) throws DbException {
+		if (db.containsGroup(txn, localGroup.getId())) return;
+		db.addGroup(txn, localGroup);
+		// Set things up for any pre-existing contacts
+		for (Contact c : db.getContacts(txn)) addingContact(txn, c);
+	}
+
+	@Override
+	public void startService() throws ServiceException {
+		List<ClientVersion> versions = new ArrayList<>(clients);
+		Collections.sort(versions);
+		try {
+			Transaction txn = db.startTransaction(false);
+			try {
+				if (updateClientVersions(txn, versions)) {
+					for (Contact c : db.getContacts(txn))
+						clientVersionsUpdated(txn, c, versions);
+				}
+				db.commitTransaction(txn);
+			} finally {
+				db.endTransaction(txn);
+			}
+		} catch (DbException e) {
+			throw new ServiceException(e);
+		}
+	}
+
+	@Override
+	public void stopService() throws ServiceException {
+	}
+
+	@Override
+	public void addingContact(Transaction txn, Contact c) throws DbException {
+		// Create a group and share it with the contact
+		Group g = getContactGroup(c);
+		db.addGroup(txn, g);
+		db.setGroupVisibility(txn, c.getId(), g.getId(), SHARED);
+		// Attach the contact ID to the group
+		BdfDictionary meta = new BdfDictionary();
+		meta.put(GROUP_KEY_CONTACT_ID, c.getId().getInt());
+		try {
+			clientHelper.mergeGroupMetadata(txn, g.getId(), meta);
+		} catch (FormatException e) {
+			throw new AssertionError(e);
+		}
+		// Create and store the first local update
+		List<ClientVersion> versions = new ArrayList<>(clients);
+		Collections.sort(versions);
+		storeFirstUpdate(txn, g.getId(), versions);
+	}
+
+	@Override
+	public void removingContact(Transaction txn, Contact c) throws DbException {
+		db.removeGroup(txn, getContactGroup(c));
+	}
+
+	@Override
+	public boolean incomingMessage(Transaction txn, Message m, Metadata meta)
+			throws DbException, InvalidMessageException {
+		try {
+			// Parse the new remote update
+			Update newRemoteUpdate = parseUpdate(clientHelper.toList(m));
+			List<ClientState> newRemoteStates = newRemoteUpdate.states;
+			long newRemoteUpdateVersion = newRemoteUpdate.updateVersion;
+			// Find the latest local and remote updates, if any
+			LatestUpdates latest = findLatestUpdates(txn, m.getGroupId());
+			// If this update is obsolete, delete it and return
+			if (latest.remote != null
+					&& latest.remote.updateVersion > newRemoteUpdateVersion) {
+				db.deleteMessage(txn, m.getId());
+				db.deleteMessageMetadata(txn, m.getId());
+				return false;
+			}
+			// Load and parse the latest local update
+			if (latest.local == null) throw new DbException();
+			Update oldLocalUpdate = loadUpdate(txn, latest.local.messageId);
+			List<ClientState> oldLocalStates = oldLocalUpdate.states;
+			long oldLocalUpdateVersion = oldLocalUpdate.updateVersion;
+			// Load and parse the previous remote update, if any
+			List<ClientState> oldRemoteStates;
+			if (latest.remote == null) {
+				oldRemoteStates = emptyList();
+			} else {
+				oldRemoteStates =
+						loadUpdate(txn, latest.remote.messageId).states;
+				// Delete the previous remote update
+				db.deleteMessage(txn, latest.remote.messageId);
+				db.deleteMessageMetadata(txn, latest.remote.messageId);
+			}
+			// Update the local states from the remote states if necessary
+			List<ClientState> newLocalStates = updateStatesFromRemoteStates(
+					oldLocalStates, newRemoteStates);
+			if (!oldLocalStates.equals(newLocalStates)) {
+				// Delete the latest local update
+				db.deleteMessage(txn, latest.local.messageId);
+				db.deleteMessageMetadata(txn, latest.local.messageId);
+				// Store a new local update
+				storeUpdate(txn, m.getGroupId(), newLocalStates,
+						oldLocalUpdateVersion + 1);
+			}
+			// Calculate the old and new client visibilities
+			Map<ClientMajorVersion, Visibility> before =
+					getVisibilities(oldLocalStates, oldRemoteStates);
+			Map<ClientMajorVersion, Visibility> after =
+					getVisibilities(newLocalStates, newRemoteStates);
+			// Call hooks for any visibilities that have changed
+			if (!before.equals(after)) {
+				Contact c = getContact(txn, m.getGroupId());
+				callVisibilityHooks(txn, c, before, after);
+			}
+		} catch (FormatException e) {
+			throw new InvalidMessageException(e);
+		}
+		return false;
+	}
+
+	private void storeClientVersions(Transaction txn,
+			List<ClientVersion> versions) throws DbException {
+		long now = clock.currentTimeMillis();
+		BdfList body = encodeClientVersions(versions);
+		try {
+			Message m = clientHelper.createMessage(localGroup.getId(), now,
+					body);
+			db.addLocalMessage(txn, m, new Metadata(), false);
+		} catch (FormatException e) {
+			throw new AssertionError(e);
+		}
+	}
+
+	private BdfList encodeClientVersions(List<ClientVersion> versions) {
+		BdfList encoded = new BdfList();
+		for (ClientVersion cv : versions) encoded.add(encodeClientVersion(cv));
+		return encoded;
+	}
+
+	private BdfList encodeClientVersion(ClientVersion cv) {
+		return BdfList.of(cv.majorVersion.getClientId().getString(),
+				cv.majorVersion.getMajorVersion(), cv.minorVersion);
+	}
+
+	/**
+	 * Stores the local client versions and returns true if an update needs to
+	 * be sent to contacts.
+	 */
+	private boolean updateClientVersions(Transaction txn,
+			List<ClientVersion> newVersions) throws DbException {
+		Collection<MessageId> ids = db.getMessageIds(txn, localGroup.getId());
+		if (ids.isEmpty()) {
+			storeClientVersions(txn, newVersions);
+			return true;
+		}
+		if (ids.size() != 1) throw new DbException();
+		MessageId m = ids.iterator().next();
+		List<ClientVersion> oldVersions = loadClientVersions(txn, m);
+		if (oldVersions.equals(newVersions)) return false;
+		db.removeMessage(txn, m);
+		storeClientVersions(txn, newVersions);
+		return true;
+	}
+
+	private List<ClientVersion> loadClientVersions(Transaction txn,
+			MessageId m) throws DbException {
+		try {
+			BdfList body = clientHelper.getMessageAsList(txn, m);
+			if (body == null) throw new DbException();
+			return parseClientVersions(body);
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
+	private List<ClientVersion> parseClientVersions(BdfList body)
+			throws FormatException {
+		int size = body.size();
+		List<ClientVersion> parsed = new ArrayList<>(size);
+		for (int i = 0; i < size; i++) {
+			BdfList cv = body.getList(i);
+			ClientId clientId = new ClientId(cv.getString(0));
+			int majorVersion = cv.getLong(1).intValue();
+			int minorVersion = cv.getLong(2).intValue();
+			parsed.add(new ClientVersion(clientId, majorVersion,
+					minorVersion));
+		}
+		return parsed;
+	}
+
+	private void clientVersionsUpdated(Transaction txn, Contact c,
+			List<ClientVersion> versions) throws DbException {
+		try {
+			// Find the latest local and remote updates
+			Group g = getContactGroup(c);
+			LatestUpdates latest = findLatestUpdates(txn, g.getId());
+			// Load and parse the latest local update
+			if (latest.local == null) throw new DbException();
+			Update oldLocalUpdate = loadUpdate(txn, latest.local.messageId);
+			List<ClientState> oldLocalStates = oldLocalUpdate.states;
+			long oldLocalUpdateVersion = oldLocalUpdate.updateVersion;
+			// Load and parse the latest remote update, if any
+			List<ClientState> remoteStates;
+			if (latest.remote == null) remoteStates = emptyList();
+			else remoteStates = loadUpdate(txn, latest.remote.messageId).states;
+			// Update the local states if necessary
+			List<ClientState> newLocalStates =
+					updateStatesFromLocalVersions(oldLocalStates, versions);
+			newLocalStates = updateStatesFromRemoteStates(newLocalStates,
+					remoteStates);
+			if (!oldLocalStates.equals(newLocalStates)) {
+				// Delete the latest local update
+				db.deleteMessage(txn, latest.local.messageId);
+				db.deleteMessageMetadata(txn, latest.local.messageId);
+				// Store a new local update
+				storeUpdate(txn, g.getId(), newLocalStates,
+						oldLocalUpdateVersion + 1);
+			}
+			// Calculate the old and new client visibilities
+			Map<ClientMajorVersion, Visibility> before =
+					getVisibilities(oldLocalStates, remoteStates);
+			Map<ClientMajorVersion, Visibility> after =
+					getVisibilities(newLocalStates, remoteStates);
+			// Call hooks for any visibilities that have changed
+			callVisibilityHooks(txn, c, before, after);
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
+	private Group getContactGroup(Contact c) {
+		return contactGroupFactory.createContactGroup(CLIENT_ID,
+				MAJOR_VERSION, c);
+	}
+
+	private LatestUpdates findLatestUpdates(Transaction txn, GroupId g)
+			throws DbException, FormatException {
+		Map<MessageId, BdfDictionary> metadata =
+				clientHelper.getMessageMetadataAsDictionary(txn, g);
+		LatestUpdate local = null, remote = null;
+		for (Entry<MessageId, BdfDictionary> e : metadata.entrySet()) {
+			BdfDictionary meta = e.getValue();
+			long updateVersion = meta.getLong(MSG_KEY_UPDATE_VERSION);
+			if (meta.getBoolean(MSG_KEY_LOCAL))
+				local = new LatestUpdate(e.getKey(), updateVersion);
+			else remote = new LatestUpdate(e.getKey(), updateVersion);
+		}
+		return new LatestUpdates(local, remote);
+	}
+
+	private Update loadUpdate(Transaction txn, MessageId m) throws DbException {
+		try {
+			BdfList body = clientHelper.getMessageAsList(txn, m);
+			if (body == null) throw new DbException();
+			return parseUpdate(body);
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
+	private Update parseUpdate(BdfList body) throws FormatException {
+		List<ClientState> states = parseClientStates(body);
+		long updateVersion = parseUpdateVersion(body);
+		return new Update(states, updateVersion);
+	}
+
+	private List<ClientState> parseClientStates(BdfList body)
+			throws FormatException {
+		// Client states, update version
+		BdfList states = body.getList(0);
+		int size = states.size();
+		List<ClientState> parsed = new ArrayList<>(size);
+		for (int i = 0; i < size; i++)
+			parsed.add(parseClientState(states.getList(i)));
+		return parsed;
+	}
+
+	private ClientState parseClientState(BdfList clientState)
+			throws FormatException {
+		// Client ID, major version, minor version, active
+		ClientId clientId = new ClientId(clientState.getString(0));
+		int majorVersion = clientState.getLong(1).intValue();
+		int minorVersion = clientState.getLong(2).intValue();
+		boolean active = clientState.getBoolean(3);
+		return new ClientState(clientId, majorVersion, minorVersion, active);
+	}
+
+	private long parseUpdateVersion(BdfList body) throws FormatException {
+		// Client states, update version
+		return body.getLong(1);
+	}
+
+	private List<ClientState> updateStatesFromLocalVersions(
+			List<ClientState> oldStates, List<ClientVersion> newVersions) {
+		Map<ClientMajorVersion, ClientState> oldMap = new HashMap<>();
+		for (ClientState cs : oldStates) oldMap.put(cs.majorVersion, cs);
+		List<ClientState> newStates = new ArrayList<>(newVersions.size());
+		for (ClientVersion newVersion : newVersions) {
+			ClientState oldState = oldMap.get(newVersion.majorVersion);
+			boolean active = oldState != null && oldState.active;
+			newStates.add(new ClientState(newVersion.majorVersion,
+					newVersion.minorVersion, active));
+		}
+		return newStates;
+	}
+
+	private void storeUpdate(Transaction txn, GroupId g,
+			List<ClientState> states, long updateVersion) throws DbException {
+		try {
+			BdfList body = encodeUpdate(states, updateVersion);
+			long now = clock.currentTimeMillis();
+			Message m = clientHelper.createMessage(g, now, body);
+			BdfDictionary meta = new BdfDictionary();
+			meta.put(MSG_KEY_UPDATE_VERSION, updateVersion);
+			meta.put(MSG_KEY_LOCAL, true);
+			clientHelper.addLocalMessage(txn, m, meta, true);
+		} catch (FormatException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	private BdfList encodeUpdate(List<ClientState> states, long updateVersion) {
+		BdfList encoded = new BdfList();
+		for (ClientState cs : states) encoded.add(encodeClientState(cs));
+		return BdfList.of(encoded, updateVersion);
+	}
+
+	private BdfList encodeClientState(ClientState cs) {
+		return BdfList.of(cs.majorVersion.getClientId().getString(),
+				cs.majorVersion.getMajorVersion(), cs.minorVersion, cs.active);
+	}
+
+	private Map<ClientMajorVersion, Visibility> getVisibilities(
+			List<ClientState> localStates, List<ClientState> remoteStates) {
+		Map<ClientMajorVersion, ClientState> remoteMap = new HashMap<>();
+		for (ClientState cs : remoteStates) remoteMap.put(cs.majorVersion, cs);
+		Map<ClientMajorVersion, Visibility> visibilities = new HashMap<>();
+		for (ClientState local : localStates) {
+			ClientState remote = remoteMap.get(local.majorVersion);
+			if (remote == null) visibilities.put(local.majorVersion, INVISIBLE);
+			else if (remote.active)
+				visibilities.put(local.majorVersion, SHARED);
+			else visibilities.put(local.majorVersion, VISIBLE);
+		}
+		return visibilities;
+	}
+
+	private void callVisibilityHooks(Transaction txn, Contact c,
+			Map<ClientMajorVersion, Visibility> before,
+			Map<ClientMajorVersion, Visibility> after) throws DbException {
+		Set<ClientMajorVersion> keys = new TreeSet<>();
+		keys.addAll(before.keySet());
+		keys.addAll(after.keySet());
+		for (ClientMajorVersion cv : keys) {
+			Visibility vBefore = before.get(cv), vAfter = after.get(cv);
+			if (vAfter == null) {
+				callVisibilityHook(txn, cv, c, INVISIBLE);
+			} else if (vBefore == null || !vBefore.equals(vAfter)) {
+				callVisibilityHook(txn, cv, c, vAfter);
+			}
+		}
+	}
+
+	private void callVisibilityHook(Transaction txn, ClientMajorVersion cv,
+			Contact c, Visibility v) throws DbException {
+		ClientVersioningHook hook = hooks.get(cv);
+		if (hook != null) hook.onClientVisibilityChanging(txn, c, v);
+	}
+
+	private void storeFirstUpdate(Transaction txn, GroupId g,
+			List<ClientVersion> versions) throws DbException {
+		List<ClientState> states = new ArrayList<>(versions.size());
+		for (ClientVersion cv : versions) {
+			states.add(new ClientState(cv.majorVersion, cv.minorVersion,
+					false));
+		}
+		storeUpdate(txn, g, states, 1);
+	}
+
+	private Contact getContact(Transaction txn, GroupId g) throws DbException {
+		try {
+			BdfDictionary meta =
+					clientHelper.getGroupMetadataAsDictionary(txn, g);
+			int id = meta.getLong(GROUP_KEY_CONTACT_ID).intValue();
+			return db.getContact(txn, new ContactId(id));
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
+	private List<ClientState> updateStatesFromRemoteStates(
+			List<ClientState> oldLocalStates, List<ClientState> remoteStates) {
+		Set<ClientMajorVersion> remoteSet = new HashSet<>();
+		for (ClientState cs : remoteStates) remoteSet.add(cs.majorVersion);
+		List<ClientState> newLocalStates =
+				new ArrayList<>(oldLocalStates.size());
+		for (ClientState oldState : oldLocalStates) {
+			boolean active = remoteSet.contains(oldState.majorVersion);
+			newLocalStates.add(new ClientState(oldState.majorVersion,
+					oldState.minorVersion, active));
+		}
+		return newLocalStates;
+	}
+
+	private static class Update {
+
+		private final List<ClientState> states;
+		private final long updateVersion;
+
+		private Update(List<ClientState> states, long updateVersion) {
+			this.states = states;
+			this.updateVersion = updateVersion;
+		}
+	}
+
+	private static class LatestUpdate {
+
+		private final MessageId messageId;
+		private final long updateVersion;
+
+		private LatestUpdate(MessageId messageId, long updateVersion) {
+			this.messageId = messageId;
+			this.updateVersion = updateVersion;
+		}
+	}
+
+	private static class LatestUpdates {
+
+		@Nullable
+		private final LatestUpdate local, remote;
+
+		private LatestUpdates(@Nullable LatestUpdate local,
+				@Nullable LatestUpdate remote) {
+			this.local = local;
+			this.remote = remote;
+		}
+	}
+
+	private static class ClientVersion implements Comparable<ClientVersion> {
+
+		private final ClientMajorVersion majorVersion;
+		private final int minorVersion;
+
+		private ClientVersion(ClientMajorVersion majorVersion,
+				int minorVersion) {
+			this.majorVersion = majorVersion;
+			this.minorVersion = minorVersion;
+		}
+
+		private ClientVersion(ClientId clientId, int majorVersion,
+				int minorVersion) {
+			this(new ClientMajorVersion(clientId, majorVersion), minorVersion);
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (o instanceof ClientVersion) {
+				ClientVersion cv = (ClientVersion) o;
+				return majorVersion.equals(cv.majorVersion)
+						&& minorVersion == cv.minorVersion;
+			}
+			return false;
+		}
+
+		@Override
+		public int hashCode() {
+			return majorVersion.hashCode();
+		}
+
+		@Override
+		public int compareTo(ClientVersion cv) {
+			int compare = majorVersion.compareTo(cv.majorVersion);
+			if (compare != 0) return compare;
+			return minorVersion - cv.minorVersion;
+		}
+	}
+
+	private static class ClientState {
+
+		private final ClientMajorVersion majorVersion;
+		private final int minorVersion;
+		private final boolean active;
+
+		private ClientState(ClientMajorVersion majorVersion, int minorVersion,
+				boolean active) {
+			this.majorVersion = majorVersion;
+			this.minorVersion = minorVersion;
+			this.active = active;
+		}
+
+		private ClientState(ClientId clientId, int majorVersion,
+				int minorVersion, boolean active) {
+			this(new ClientMajorVersion(clientId, majorVersion), minorVersion,
+					active);
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (o instanceof ClientState) {
+				ClientState cs = (ClientState) o;
+				return majorVersion.equals(cs.majorVersion)
+						&& minorVersion == cs.minorVersion
+						&& active == cs.active;
+			}
+			return false;
+		}
+
+		@Override
+		public int hashCode() {
+			return majorVersion.hashCode();
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningValidator.java

@@ -0,0 +1,61 @@
+package org.briarproject.bramble.versioning;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.client.BdfMessageContext;
+import org.briarproject.bramble.api.client.BdfMessageValidator;
+import org.briarproject.bramble.api.client.ClientHelper;
+import org.briarproject.bramble.api.data.BdfDictionary;
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.data.MetadataEncoder;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.Group;
+import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.system.Clock;
+
+import javax.annotation.concurrent.Immutable;
+
+import static org.briarproject.bramble.api.sync.ClientId.MAX_CLIENT_ID_LENGTH;
+import static org.briarproject.bramble.util.ValidationUtils.checkLength;
+import static org.briarproject.bramble.util.ValidationUtils.checkSize;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
+
+@Immutable
+@NotNullByDefault
+class ClientVersioningValidator extends BdfMessageValidator {
+
+	ClientVersioningValidator(ClientHelper clientHelper,
+			MetadataEncoder metadataEncoder, Clock clock) {
+		super(clientHelper, metadataEncoder, clock);
+	}
+
+	@Override
+	protected BdfMessageContext validateMessage(Message m, Group g,
+			BdfList body) throws FormatException {
+		// Client states, update version
+		checkSize(body, 2);
+		// Client states
+		BdfList states = body.getList(0);
+		int size = states.size();
+		for (int i = 0; i < size; i++) {
+			BdfList clientState = states.getList(i);
+			// Client ID, major version, minor version, active
+			checkSize(clientState, 4);
+			String clientId = clientState.getString(0);
+			checkLength(clientId, 1, MAX_CLIENT_ID_LENGTH);
+			int majorVersion = clientState.getLong(1).intValue();
+			if (majorVersion < 0) throw new FormatException();
+			int minorVersion = clientState.getLong(2).intValue();
+			if (minorVersion < 0) throw new FormatException();
+			clientState.getBoolean(3);
+		}
+		// Update version
+		long updateVersion = body.getLong(1);
+		if (updateVersion < 0) throw new FormatException();
+		// Return the metadata
+		BdfDictionary meta = new BdfDictionary();
+		meta.put(MSG_KEY_UPDATE_VERSION, updateVersion);
+		meta.put(MSG_KEY_LOCAL, false);
+		return new BdfMessageContext(meta);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/versioning/VersioningModule.java

@@ -0,0 +1,56 @@
+package org.briarproject.bramble.versioning;
+
+import org.briarproject.bramble.api.client.ClientHelper;
+import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.data.MetadataEncoder;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.sync.ValidationManager;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+import static org.briarproject.bramble.api.versioning.ClientVersioningManager.CLIENT_ID;
+import static org.briarproject.bramble.api.versioning.ClientVersioningManager.MAJOR_VERSION;
+
+@Module
+public class VersioningModule {
+
+	public static class EagerSingletons {
+		@Inject
+		ClientVersioningManager clientVersioningManager;
+		@Inject
+		ClientVersioningValidator clientVersioningValidator;
+	}
+
+
+	@Provides
+	@Singleton
+	ClientVersioningManager provideClientVersioningManager(
+			ClientVersioningManagerImpl clientVersioningManager,
+			LifecycleManager lifecycleManager, ContactManager contactManager,
+			ValidationManager validationManager) {
+		lifecycleManager.registerClient(clientVersioningManager);
+		lifecycleManager.registerService(clientVersioningManager);
+		contactManager.registerContactHook(clientVersioningManager);
+		validationManager.registerIncomingMessageHook(CLIENT_ID, MAJOR_VERSION,
+				clientVersioningManager);
+		return clientVersioningManager;
+	}
+
+	@Provides
+	@Singleton
+	ClientVersioningValidator provideClientVersioningValidator(
+			ClientHelper clientHelper, MetadataEncoder metadataEncoder,
+			Clock clock, ValidationManager validationManager) {
+		ClientVersioningValidator validator = new ClientVersioningValidator(
+				clientHelper, metadataEncoder, clock);
+		validationManager.registerMessageValidator(CLIENT_ID, MAJOR_VERSION,
+				validator);
+		return validator;
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/db/DatabaseComponentImplTest.java

@@ -30,6 +30,7 @@ import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.sync.MessageStatus;
 import org.briarproject.bramble.api.sync.Offer;
 import org.briarproject.bramble.api.sync.Request;
 import org.briarproject.bramble.api.sync.event.GroupAddedEvent;
@@ -77,6 +78,7 @@ import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
 public class DatabaseComponentImplTest extends BrambleMockTestCase {
@@ -89,6 +91,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 	private final Object txn = new Object();
 	private final ClientId clientId;
+	private final int majorVersion;
 	private final GroupId groupId;
 	private final Group group;
 	private final Author author;
@@ -106,7 +109,8 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 
 	public DatabaseComponentImplTest() {
 		clientId = getClientId();
-		group = getGroup(clientId);
+		majorVersion = 123;
+		group = getGroup(clientId, majorVersion);
 		groupId = group.getId();
 		author = getAuthor();
 		localAuthor = getLocalAuthor();
@@ -175,7 +179,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).containsGroup(txn, groupId);
 			will(returnValue(true));
 			// getGroups()
-			oneOf(database).getGroups(txn, clientId);
+			oneOf(database).getGroups(txn, clientId, majorVersion);
 			will(returnValue(singletonList(group)));
 			// removeGroup()
 			oneOf(database).containsGroup(txn, groupId);
@@ -215,7 +219,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			db.addGroup(transaction, group); // First time - listeners called
 			db.addGroup(transaction, group); // Second time - not called
 			assertEquals(singletonList(group),
-					db.getGroups(transaction, clientId));
+					db.getGroups(transaction, clientId, majorVersion));
 			db.removeGroup(transaction, group);
 			db.removeContact(transaction, contactId);
 			db.removeLocalAuthor(transaction, localAuthor.getId());
@@ -1315,8 +1319,9 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 	@Test
 	public void testTransportKeys() throws Exception {
 		TransportKeys transportKeys = createTransportKeys();
-		Collection<KeySet> keys =
+		KeySet ks = new KeySet(keySetId, contactId, transportKeys);
-				singletonList(new KeySet(keySetId, contactId, transportKeys));
+		Collection<KeySet> keys = singletonList(ks);
+
 		context.checking(new Expectations() {{
 			// startTransaction()
 			oneOf(database).startTransaction();
@@ -1324,7 +1329,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// updateTransportKeys()
 			oneOf(database).containsTransport(txn, transportId);
 			will(returnValue(true));
-			oneOf(database).updateTransportKeys(txn, keys);
+			oneOf(database).updateTransportKeys(txn, ks);
 			// getTransportKeys()
 			oneOf(database).containsTransport(txn, transportId);
 			will(returnValue(true));
@@ -1346,6 +1351,114 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 	}
 
+	@Test
+	public void testGetMessageStatusByGroupId() throws Exception {
+		MessageStatus status =
+				new MessageStatus(messageId, contactId, true, true);
+
+		context.checking(new Expectations() {{
+			// startTransaction()
+			oneOf(database).startTransaction();
+			will(returnValue(txn));
+			// getMessageStatus()
+			oneOf(database).containsContact(txn, contactId);
+			will(returnValue(true));
+			oneOf(database).containsGroup(txn, groupId);
+			will(returnValue(true));
+			oneOf(database).getGroupVisibility(txn, contactId, groupId);
+			will(returnValue(VISIBLE));
+			oneOf(database).getMessageStatus(txn, contactId, groupId);
+			will(returnValue(singletonList(status)));
+			// getMessageStatus() again
+			oneOf(database).containsContact(txn, contactId);
+			will(returnValue(true));
+			oneOf(database).containsGroup(txn, groupId);
+			will(returnValue(true));
+			oneOf(database).getGroupVisibility(txn, contactId, groupId);
+			will(returnValue(INVISIBLE));
+			oneOf(database).getMessageIds(txn, groupId);
+			will(returnValue(singletonList(messageId)));
+			// endTransaction()
+			oneOf(database).commitTransaction(txn);
+		}});
+		DatabaseComponent db = createDatabaseComponent(database, eventBus,
+				shutdown);
+
+		Transaction transaction = db.startTransaction(true);
+		try {
+			// With visible group - return stored status
+			Collection<MessageStatus> statuses =
+					db.getMessageStatus(transaction, contactId, groupId);
+			assertEquals(1, statuses.size());
+			MessageStatus s = statuses.iterator().next();
+			assertEquals(messageId, s.getMessageId());
+			assertEquals(contactId, s.getContactId());
+			assertTrue(s.isSent());
+			assertTrue(s.isSeen());
+			// With invisible group - return default status
+			statuses = db.getMessageStatus(transaction, contactId, groupId);
+			assertEquals(1, statuses.size());
+			s = statuses.iterator().next();
+			assertEquals(messageId, s.getMessageId());
+			assertEquals(contactId, s.getContactId());
+			assertFalse(s.isSent());
+			assertFalse(s.isSeen());
+			db.commitTransaction(transaction);
+		} finally {
+			db.endTransaction(transaction);
+		}
+	}
+
+	@Test
+	public void testGetMessageStatusByMessageId() throws Exception {
+		MessageStatus status =
+				new MessageStatus(messageId, contactId, true, true);
+
+		context.checking(new Expectations() {{
+			// startTransaction()
+			oneOf(database).startTransaction();
+			will(returnValue(txn));
+			// getMessageStatus()
+			oneOf(database).containsContact(txn, contactId);
+			will(returnValue(true));
+			oneOf(database).containsMessage(txn, messageId);
+			will(returnValue(true));
+			oneOf(database).getMessageStatus(txn, contactId, messageId);
+			will(returnValue(status));
+			// getMessageStatus() again
+			oneOf(database).containsContact(txn, contactId);
+			will(returnValue(true));
+			oneOf(database).containsMessage(txn, messageId);
+			will(returnValue(true));
+			oneOf(database).getMessageStatus(txn, contactId, messageId);
+			will(returnValue(null));
+			// endTransaction()
+			oneOf(database).commitTransaction(txn);
+		}});
+		DatabaseComponent db = createDatabaseComponent(database, eventBus,
+				shutdown);
+
+		Transaction transaction = db.startTransaction(true);
+		try {
+			// With visible group - return stored status
+			MessageStatus s =
+					db.getMessageStatus(transaction, contactId, messageId);
+			assertEquals(messageId, s.getMessageId());
+			assertEquals(contactId, s.getContactId());
+			assertTrue(s.isSent());
+			assertTrue(s.isSeen());
+			// With invisible group - return default status
+			s = db.getMessageStatus(transaction, contactId, messageId);
+			assertEquals(messageId, s.getMessageId());
+			assertEquals(contactId, s.getContactId());
+			assertFalse(s.isSent());
+			assertFalse(s.isSeen());
+			db.commitTransaction(transaction);
+		} finally {
+			db.endTransaction(transaction);
+		}
+	}
+
 	private TransportKeys createTransportKeys() {
 		SecretKey inPrevTagKey = getSecretKey();
 		SecretKey inPrevHeaderKey = getSecretKey();

bramble-core/src/test/java/org/briarproject/bramble/db/DatabasePerformanceTest.java

@@ -267,7 +267,7 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 		String name = "getGroups(T, ClientId)";
 		benchmark(name, db -> {
 			Connection txn = db.startTransaction();
-			db.getGroups(txn, pickRandom(clientIds));
+			db.getGroups(txn, pickRandom(clientIds), 123);
 			db.commitTransaction(txn);
 		});
 	}
@@ -550,7 +550,7 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 			contacts.add(db.getContact(txn, c));
 			contactGroups.put(c, new ArrayList<>());
 			for (int j = 0; j < GROUPS_PER_CONTACT; j++) {
-				Group g = getGroup(clientIds.get(j % CLIENTS));
+				Group g = getGroup(clientIds.get(j % CLIENTS), 123);
 				groups.add(g);
 				messageMeta.put(g.getId(), new ArrayList<>());
 				contactGroups.get(c).add(g);
@@ -584,7 +584,7 @@ public abstract class DatabasePerformanceTest extends BrambleTestCase {
 			}
 		}
 		for (int i = 0; i < LOCAL_GROUPS; i++) {
-			Group g = getGroup(clientIds.get(i % CLIENTS));
+			Group g = getGroup(clientIds.get(i % CLIENTS), 123);
 			groups.add(g);
 			messageMeta.put(g.getId(), new ArrayList<>());
 			groupMessages.put(g.getId(), new ArrayList<>());

bramble-core/src/test/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

@@ -82,6 +82,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 	private final File testDir = TestUtils.getTestDirectory();
 	private final GroupId groupId;
 	private final ClientId clientId;
+	private final int majorVersion;
 	private final Group group;
 	private final Author author;
 	private final LocalAuthor localAuthor;
@@ -96,7 +97,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 	JdbcDatabaseTest() throws Exception {
 		clientId = getClientId();
-		group = getGroup(clientId);
+		majorVersion = 123;
+		group = getGroup(clientId, majorVersion);
 		groupId = group.getId();
 		author = getAuthor();
 		localAuthor = getLocalAuthor();
@@ -667,8 +669,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 	@Test
 	public void testTransportKeys() throws Exception {
-		TransportKeys keys = createTransportKeys();
+		long rotationPeriod = 123, rotationPeriod1 = 234;
-		TransportKeys keys1 = createTransportKeys();
+		TransportKeys keys = createTransportKeys(rotationPeriod);
+		TransportKeys keys1 = createTransportKeys(rotationPeriod1);
 
 		Database<Connection> db = open(false);
 		Connection txn = db.startTransaction();
@@ -697,6 +700,25 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 			}
 		}
 
+		// Rotate the transport keys
+		TransportKeys rotated = createTransportKeys(rotationPeriod + 1);
+		TransportKeys rotated1 = createTransportKeys(rotationPeriod1 + 1);
+		db.updateTransportKeys(txn, new KeySet(keySetId, contactId, rotated));
+		db.updateTransportKeys(txn, new KeySet(keySetId1, contactId, rotated1));
+
+		// Retrieve the transport keys again
+		allKeys = db.getTransportKeys(txn, transportId);
+		assertEquals(2, allKeys.size());
+		for (KeySet ks : allKeys) {
+			assertEquals(contactId, ks.getContactId());
+			if (ks.getKeySetId().equals(keySetId)) {
+				assertKeysEquals(rotated, ks.getTransportKeys());
+			} else {
+				assertEquals(keySetId1, ks.getKeySetId());
+				assertKeysEquals(rotated1, ks.getTransportKeys());
+			}
+		}
+
 		// Removing the contact should remove the transport keys
 		db.removeContact(txn, contactId);
 		assertEquals(emptyList(), db.getTransportKeys(txn, transportId));
@@ -707,8 +729,9 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 	@Test
 	public void testUnboundTransportKeys() throws Exception {
-		TransportKeys keys = createTransportKeys();
+		long rotationPeriod = 123, rotationPeriod1 = 234;
-		TransportKeys keys1 = createTransportKeys();
+		TransportKeys keys = createTransportKeys(rotationPeriod);
+		TransportKeys keys1 = createTransportKeys(rotationPeriod1);
 
 		Database<Connection> db = open(false);
 		Connection txn = db.startTransaction();
@@ -754,6 +777,26 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 			}
 		}
 
+		// Rotate the transport keys
+		TransportKeys rotated = createTransportKeys(rotationPeriod + 1);
+		TransportKeys rotated1 = createTransportKeys(rotationPeriod1 + 1);
+		db.updateTransportKeys(txn, new KeySet(keySetId, contactId, rotated));
+		db.updateTransportKeys(txn, new KeySet(keySetId1, null, rotated1));
+
+		// Retrieve the transport keys again
+		allKeys = db.getTransportKeys(txn, transportId);
+		assertEquals(2, allKeys.size());
+		for (KeySet ks : allKeys) {
+			if (ks.getKeySetId().equals(keySetId)) {
+				assertEquals(contactId, ks.getContactId());
+				assertKeysEquals(rotated, ks.getTransportKeys());
+			} else {
+				assertEquals(keySetId1, ks.getKeySetId());
+				assertNull(ks.getContactId());
+				assertKeysEquals(rotated1, ks.getTransportKeys());
+			}
+		}
+
 		// Remove the unbound transport keys
 		db.removeTransportKeys(txn, transportId, keySetId1);
 
@@ -763,7 +806,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		KeySet ks = allKeys.iterator().next();
 		assertEquals(keySetId, ks.getKeySetId());
 		assertEquals(contactId, ks.getContactId());
-		assertKeysEquals(keys, ks.getTransportKeys());
+		assertKeysEquals(rotated, ks.getTransportKeys());
 
 		// Removing the transport should remove the remaining transport keys
 		db.removeTransport(txn, transportId);
@@ -809,8 +852,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 	@Test
 	public void testIncrementStreamCounter() throws Exception {
-		TransportKeys keys = createTransportKeys();
+		long rotationPeriod = 123;
-		long rotationPeriod = keys.getCurrentOutgoingKeys().getRotationPeriod();
+		TransportKeys keys = createTransportKeys(rotationPeriod);
 		long streamCounter = keys.getCurrentOutgoingKeys().getStreamCounter();
 
 		Database<Connection> db = open(false);
@@ -821,8 +864,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(contactId, db.addContact(txn, author, localAuthor.getId(),
 				true, true));
 		db.addTransport(txn, transportId, 123);
-		db.updateTransportKeys(txn,
+		assertEquals(keySetId, db.addTransportKeys(txn, contactId, keys));
-				singletonList(new KeySet(keySetId, contactId, keys)));
 
 		// Increment the stream counter twice and retrieve the transport keys
 		db.incrementStreamCounter(txn, transportId, keySetId);
@@ -838,14 +880,21 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(rotationPeriod, outCurr.getRotationPeriod());
 		assertEquals(streamCounter + 2, outCurr.getStreamCounter());
 
+		// The rest of the keys should be unaffected
+		assertKeysEquals(keys.getPreviousIncomingKeys(),
+				k.getPreviousIncomingKeys());
+		assertKeysEquals(keys.getCurrentIncomingKeys(),
+				k.getCurrentIncomingKeys());
+		assertKeysEquals(keys.getNextIncomingKeys(), k.getNextIncomingKeys());
+
 		db.commitTransaction(txn);
 		db.close();
 	}
 
 	@Test
 	public void testSetReorderingWindow() throws Exception {
-		TransportKeys keys = createTransportKeys();
+		long rotationPeriod = 123;
-		long rotationPeriod = keys.getCurrentIncomingKeys().getRotationPeriod();
+		TransportKeys keys = createTransportKeys(rotationPeriod);
 		long base = keys.getCurrentIncomingKeys().getWindowBase();
 		byte[] bitmap = keys.getCurrentIncomingKeys().getWindowBitmap();
 
@@ -857,8 +906,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(contactId, db.addContact(txn, author, localAuthor.getId(),
 				true, true));
 		db.addTransport(txn, transportId, 123);
-		db.updateTransportKeys(txn,
+		assertEquals(keySetId, db.addTransportKeys(txn, contactId, keys));
-				singletonList(new KeySet(keySetId, contactId, keys)));
 
 		// Update the reordering window and retrieve the transport keys
 		new Random().nextBytes(bitmap);
@@ -876,6 +924,13 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(base + 1, inCurr.getWindowBase());
 		assertArrayEquals(bitmap, inCurr.getWindowBitmap());
 
+		// The rest of the keys should be unaffected
+		assertKeysEquals(keys.getPreviousIncomingKeys(),
+				k.getPreviousIncomingKeys());
+		assertKeysEquals(keys.getNextIncomingKeys(), k.getNextIncomingKeys());
+		assertKeysEquals(keys.getCurrentOutgoingKeys(),
+				k.getCurrentOutgoingKeys());
+
 		db.commitTransaction(txn);
 		db.close();
 	}
@@ -973,8 +1028,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Attach some metadata to the group
 		Metadata metadata = new Metadata();
-		metadata.put("foo", new byte[]{'b', 'a', 'r'});
+		metadata.put("foo", new byte[] {'b', 'a', 'r'});
-		metadata.put("baz", new byte[]{'b', 'a', 'm'});
+		metadata.put("baz", new byte[] {'b', 'a', 'm'});
 		db.mergeGroupMetadata(txn, groupId, metadata);
 
 		// Retrieve the metadata for the group
@@ -1012,8 +1067,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Attach some metadata to the message
 		Metadata metadata = new Metadata();
-		metadata.put("foo", new byte[]{'b', 'a', 'r'});
+		metadata.put("foo", new byte[] {'b', 'a', 'r'});
-		metadata.put("baz", new byte[]{'b', 'a', 'm'});
+		metadata.put("baz", new byte[] {'b', 'a', 'm'});
 		db.mergeMessageMetadata(txn, messageId, metadata);
 
 		// Retrieve the metadata for the message
@@ -1083,8 +1138,8 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Attach some metadata to the message
 		Metadata metadata = new Metadata();
-		metadata.put("foo", new byte[]{'b', 'a', 'r'});
+		metadata.put("foo", new byte[] {'b', 'a', 'r'});
-		metadata.put("baz", new byte[]{'b', 'a', 'm'});
+		metadata.put("baz", new byte[] {'b', 'a', 'm'});
 		db.mergeMessageMetadata(txn, messageId, metadata);
 
 		// Retrieve the metadata for the message
@@ -1145,11 +1200,11 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Attach some metadata to the messages
 		Metadata metadata = new Metadata();
-		metadata.put("foo", new byte[]{'b', 'a', 'r'});
+		metadata.put("foo", new byte[] {'b', 'a', 'r'});
-		metadata.put("baz", new byte[]{'b', 'a', 'm'});
+		metadata.put("baz", new byte[] {'b', 'a', 'm'});
 		db.mergeMessageMetadata(txn, messageId, metadata);
 		Metadata metadata1 = new Metadata();
-		metadata1.put("foo", new byte[]{'q', 'u', 'x'});
+		metadata1.put("foo", new byte[] {'q', 'u', 'x'});
 		db.mergeMessageMetadata(txn, messageId1, metadata1);
 
 		// Retrieve all the metadata for the group
@@ -1249,11 +1304,11 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// Attach some metadata to the messages
 		Metadata metadata = new Metadata();
-		metadata.put("foo", new byte[]{'b', 'a', 'r'});
+		metadata.put("foo", new byte[] {'b', 'a', 'r'});
-		metadata.put("baz", new byte[]{'b', 'a', 'm'});
+		metadata.put("baz", new byte[] {'b', 'a', 'm'});
 		db.mergeMessageMetadata(txn, messageId, metadata);
 		Metadata metadata1 = new Metadata();
-		metadata1.put("foo", new byte[]{'b', 'a', 'r'});
+		metadata1.put("foo", new byte[] {'b', 'a', 'r'});
 		db.mergeMessageMetadata(txn, messageId1, metadata1);
 
 		for (int i = 0; i < 2; i++) {
@@ -1264,7 +1319,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 			} else {
 				// Query for foo
 				query = new Metadata();
-				query.put("foo", new byte[]{'b', 'a', 'r'});
+				query.put("foo", new byte[] {'b', 'a', 'r'});
 			}
 
 			db.setMessageState(txn, messageId, DELIVERED);
@@ -1407,7 +1462,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.addMessage(txn, message, PENDING, true, contactId);
 
 		// Add a second group
-		Group group1 = getGroup(clientId);
+		Group group1 = getGroup(clientId, 123);
 		GroupId groupId1 = group1.getId();
 		db.addGroup(txn, group1);
 
@@ -1541,6 +1596,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The message should not be sent or seen
 		MessageStatus status = db.getMessageStatus(txn, contactId, messageId);
+		assertNotNull(status);
 		assertEquals(messageId, status.getMessageId());
 		assertEquals(contactId, status.getContactId());
 		assertFalse(status.isSent());
@@ -1561,6 +1617,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The message should be sent but not seen
 		status = db.getMessageStatus(txn, contactId, messageId);
+		assertNotNull(status);
 		assertEquals(messageId, status.getMessageId());
 		assertEquals(contactId, status.getContactId());
 		assertTrue(status.isSent());
@@ -1580,6 +1637,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The message should be sent and seen
 		status = db.getMessageStatus(txn, contactId, messageId);
+		assertNotNull(status);
 		assertEquals(messageId, status.getMessageId());
 		assertEquals(contactId, status.getContactId());
 		assertTrue(status.isSent());
@@ -1594,6 +1652,36 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertTrue(status.isSent());
 		assertTrue(status.isSeen());
 
+		// Make the group invisible to the contact
+		db.removeGroupVisibility(txn, contactId, groupId);
+
+		// Null should be returned when querying by message
+		assertNull(db.getMessageStatus(txn, contactId, messageId));
+
+		// No statuses should be returned when querying by group
+		statuses = db.getMessageStatus(txn, contactId, groupId);
+		assertEquals(0, statuses.size());
+
+		// Make the group visible to the contact again
+		db.addGroupVisibility(txn, contactId, groupId, false);
+
+		// The default status should be returned when querying by message
+		status = db.getMessageStatus(txn, contactId, messageId);
+		assertNotNull(status);
+		assertEquals(messageId, status.getMessageId());
+		assertEquals(contactId, status.getContactId());
+		assertFalse(status.isSent());
+		assertFalse(status.isSeen());
+
+		// The default status should be returned when querying by group
+		statuses = db.getMessageStatus(txn, contactId, groupId);
+		assertEquals(1, statuses.size());
+		status = statuses.iterator().next();
+		assertEquals(messageId, status.getMessageId());
+		assertEquals(contactId, status.getContactId());
+		assertFalse(status.isSent());
+		assertFalse(status.isSeen());
+
 		db.commitTransaction(txn);
 		db.close();
 	}
@@ -1775,6 +1863,22 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
+	@Test
+	public void testGetGroups() throws Exception {
+		Database<Connection> db = open(false);
+		Connection txn = db.startTransaction();
+
+		assertEquals(emptyList(), db.getGroups(txn, clientId, majorVersion));
+		db.addGroup(txn, group);
+		assertEquals(singletonList(group),
+				db.getGroups(txn, clientId, majorVersion));
+		db.removeGroup(txn, groupId);
+		assertEquals(emptyList(), db.getGroups(txn, clientId, majorVersion));
+
+		db.commitTransaction(txn);
+		db.close();
+	}
+
 	@Test
 	public void testExceptionHandling() throws Exception {
 		Database<Connection> db = open(false);
@@ -1804,23 +1908,23 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		return db;
 	}
 
-	private TransportKeys createTransportKeys() {
+	private TransportKeys createTransportKeys(long rotationPeriod) {
 		SecretKey inPrevTagKey = getSecretKey();
 		SecretKey inPrevHeaderKey = getSecretKey();
 		IncomingKeys inPrev = new IncomingKeys(inPrevTagKey, inPrevHeaderKey,
-				1, 123, new byte[4]);
+				rotationPeriod - 1, 123, new byte[4]);
 		SecretKey inCurrTagKey = getSecretKey();
 		SecretKey inCurrHeaderKey = getSecretKey();
 		IncomingKeys inCurr = new IncomingKeys(inCurrTagKey, inCurrHeaderKey,
-				2, 234, new byte[4]);
+				rotationPeriod, 234, new byte[4]);
 		SecretKey inNextTagKey = getSecretKey();
 		SecretKey inNextHeaderKey = getSecretKey();
 		IncomingKeys inNext = new IncomingKeys(inNextTagKey, inNextHeaderKey,
-				3, 345, new byte[4]);
+				rotationPeriod + 1, 345, new byte[4]);
 		SecretKey outCurrTagKey = getSecretKey();
 		SecretKey outCurrHeaderKey = getSecretKey();
 		OutgoingKeys outCurr = new OutgoingKeys(outCurrTagKey, outCurrHeaderKey,
-				2, 456, true);
+				rotationPeriod, 456, true);
 		return new TransportKeys(transportId, inPrev, inCurr, inNext, outCurr);
 	}
 

bramble-core/src/test/java/org/briarproject/bramble/keyagreement/KeyAgreementTransportTest.java

@@ -5,23 +5,31 @@ import org.briarproject.bramble.api.plugin.TransportConnectionReader;
 import org.briarproject.bramble.api.plugin.TransportConnectionWriter;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.record.RecordReaderFactory;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.api.record.RecordWriterFactory;
 import org.briarproject.bramble.test.BrambleMockTestCase;
-import org.briarproject.bramble.test.TestUtils;
+import org.briarproject.bramble.test.CaptureArgumentAction;
-import org.briarproject.bramble.util.ByteUtils;
 import org.jmock.Expectations;
+import org.jmock.lib.legacy.ClassImposteriser;
 import org.junit.Test;
 
-import java.io.ByteArrayInputStream;
+import java.io.EOFException;
-import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.RECORD_HEADER_LENGTH;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.ABORT;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.CONFIRM;
 import static org.briarproject.bramble.api.keyagreement.RecordTypes.KEY;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 
 public class KeyAgreementTransportTest extends BrambleMockTestCase {
 
@@ -31,222 +39,268 @@ public class KeyAgreementTransportTest extends BrambleMockTestCase {
 			context.mock(TransportConnectionReader.class);
 	private final TransportConnectionWriter transportConnectionWriter =
 			context.mock(TransportConnectionWriter.class);
+	private final RecordReaderFactory recordReaderFactory =
+			context.mock(RecordReaderFactory.class);
+	private final RecordWriterFactory recordWriterFactory =
+			context.mock(RecordWriterFactory.class);
+	private final RecordReader recordReader = context.mock(RecordReader.class);
+	private final RecordWriter recordWriter = context.mock(RecordWriter.class);
 
 	private final TransportId transportId = getTransportId();
 	private final KeyAgreementConnection keyAgreementConnection =
 			new KeyAgreementConnection(duplexTransportConnection, transportId);
 
-	private ByteArrayInputStream inputStream;
+	private final InputStream inputStream;
-	private ByteArrayOutputStream outputStream;
+	private final OutputStream outputStream;
+
 	private KeyAgreementTransport kat;
 
+	public KeyAgreementTransportTest() {
+		context.setImposteriser(ClassImposteriser.INSTANCE);
+		inputStream = context.mock(InputStream.class);
+		outputStream = context.mock(OutputStream.class);
+	}
+
 	@Test
 	public void testSendKey() throws Exception {
-		setup(new byte[0]);
+		byte[] key = getRandomBytes(123);
-		byte[] key = TestUtils.getRandomBytes(123);
+
+		setup();
+		AtomicReference<Record> written = expectWriteRecord();
+
 		kat.sendKey(key);
-		assertRecordSent(KEY, key);
+		assertNotNull(written.get());
+		assertRecordEquals(PROTOCOL_VERSION, KEY, key, written.get());
 	}
 
 	@Test
 	public void testSendConfirm() throws Exception {
-		setup(new byte[0]);
+		byte[] confirm = getRandomBytes(123);
-		byte[] confirm = TestUtils.getRandomBytes(123);
+
+		setup();
+		AtomicReference<Record> written = expectWriteRecord();
+
 		kat.sendConfirm(confirm);
-		assertRecordSent(CONFIRM, confirm);
+		assertNotNull(written.get());
+		assertRecordEquals(PROTOCOL_VERSION, CONFIRM, confirm, written.get());
 	}
 
 	@Test
 	public void testSendAbortWithException() throws Exception {
-		setup(new byte[0]);
+		setup();
+		AtomicReference<Record> written = expectWriteRecord();
 		context.checking(new Expectations() {{
 			oneOf(transportConnectionReader).dispose(true, true);
 			oneOf(transportConnectionWriter).dispose(true);
 		}});
+
 		kat.sendAbort(true);
-		assertRecordSent(ABORT, new byte[0]);
+		assertNotNull(written.get());
+		assertRecordEquals(PROTOCOL_VERSION, ABORT, new byte[0], written.get());
 	}
 
 	@Test
 	public void testSendAbortWithoutException() throws Exception {
-		setup(new byte[0]);
+		setup();
+		AtomicReference<Record> written = expectWriteRecord();
 		context.checking(new Expectations() {{
 			oneOf(transportConnectionReader).dispose(false, true);
 			oneOf(transportConnectionWriter).dispose(false);
 		}});
+
 		kat.sendAbort(false);
-		assertRecordSent(ABORT, new byte[0]);
+		assertNotNull(written.get());
+		assertRecordEquals(PROTOCOL_VERSION, ABORT, new byte[0], written.get());
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveKeyThrowsExceptionIfAtEndOfStream()
 			throws Exception {
-		setup(new byte[0]);
+		setup();
-		kat.receiveKey();
+		context.checking(new Expectations() {{
-	}
+			oneOf(recordReader).readRecord();
+			will(throwException(new EOFException()));
+		}});
 
-	@Test(expected = AbortException.class)
-	public void testReceiveKeyThrowsExceptionIfHeaderIsTooShort()
-			throws Exception {
-		byte[] input = new byte[RECORD_HEADER_LENGTH - 1];
-		input[0] = PROTOCOL_VERSION;
-		input[1] = KEY;
-		setup(input);
-		kat.receiveKey();
-	}
-
-	@Test(expected = AbortException.class)
-	public void testReceiveKeyThrowsExceptionIfPayloadIsTooShort()
-			throws Exception {
-		int payloadLength = 123;
-		byte[] input = new byte[RECORD_HEADER_LENGTH + payloadLength - 1];
-		input[0] = PROTOCOL_VERSION;
-		input[1] = KEY;
-		ByteUtils.writeUint16(payloadLength, input, 2);
-		setup(input);
 		kat.receiveKey();
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveKeyThrowsExceptionIfProtocolVersionIsUnrecognised()
 			throws Exception {
-		setup(createRecord((byte) (PROTOCOL_VERSION + 1), KEY, new byte[123]));
+		byte unknownVersion = (byte) (PROTOCOL_VERSION + 1);
+		byte[] key = getRandomBytes(123);
+
+		setup();
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(new Record(unknownVersion, KEY, key)));
+		}});
+
 		kat.receiveKey();
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveKeyThrowsExceptionIfAbortIsReceived()
 			throws Exception {
-		setup(createRecord(PROTOCOL_VERSION, ABORT, new byte[0]));
+		setup();
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(new Record(PROTOCOL_VERSION, ABORT, new byte[0])));
+		}});
+
 		kat.receiveKey();
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveKeyThrowsExceptionIfConfirmIsReceived()
 			throws Exception {
-		setup(createRecord(PROTOCOL_VERSION, CONFIRM, new byte[123]));
+		byte[] confirm = getRandomBytes(123);
+
+		setup();
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(new Record(PROTOCOL_VERSION, CONFIRM, confirm)));
+		}});
+
 		kat.receiveKey();
 	}
 
 	@Test
 	public void testReceiveKeySkipsUnrecognisedRecordTypes() throws Exception {
-		byte[] skip1 = createRecord(PROTOCOL_VERSION, (byte) (ABORT + 1),
+		byte type1 = (byte) (ABORT + 1);
-				new byte[123]);
+		byte[] payload1 = getRandomBytes(123);
-		byte[] skip2 = createRecord(PROTOCOL_VERSION, (byte) (ABORT + 2),
+		Record unknownRecord1 = new Record(PROTOCOL_VERSION, type1, payload1);
-				new byte[0]);
+		byte type2 = (byte) (ABORT + 2);
-		byte[] payload = TestUtils.getRandomBytes(123);
+		byte[] payload2 = new byte[0];
-		byte[] key = createRecord(PROTOCOL_VERSION, KEY, payload);
+		Record unknownRecord2 = new Record(PROTOCOL_VERSION, type2, payload2);
-		ByteArrayOutputStream input = new ByteArrayOutputStream();
+		byte[] key = getRandomBytes(123);
-		input.write(skip1);
+		Record keyRecord = new Record(PROTOCOL_VERSION, KEY, key);
-		input.write(skip2);
+
-		input.write(key);
+		setup();
-		setup(input.toByteArray());
+		context.checking(new Expectations() {{
-		assertArrayEquals(payload, kat.receiveKey());
+			oneOf(recordReader).readRecord();
+			will(returnValue(unknownRecord1));
+			oneOf(recordReader).readRecord();
+			will(returnValue(unknownRecord2));
+			oneOf(recordReader).readRecord();
+			will(returnValue(keyRecord));
+		}});
+
+		assertArrayEquals(key, kat.receiveKey());
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveConfirmThrowsExceptionIfAtEndOfStream()
 			throws Exception {
-		setup(new byte[0]);
+		setup();
-		kat.receiveConfirm();
+		context.checking(new Expectations() {{
-	}
+			oneOf(recordReader).readRecord();
+			will(throwException(new EOFException()));
+		}});
 
-	@Test(expected = AbortException.class)
-	public void testReceiveConfirmThrowsExceptionIfHeaderIsTooShort()
-			throws Exception {
-		byte[] input = new byte[RECORD_HEADER_LENGTH - 1];
-		input[0] = PROTOCOL_VERSION;
-		input[1] = CONFIRM;
-		setup(input);
-		kat.receiveConfirm();
-	}
-
-	@Test(expected = AbortException.class)
-	public void testReceiveConfirmThrowsExceptionIfPayloadIsTooShort()
-			throws Exception {
-		int payloadLength = 123;
-		byte[] input = new byte[RECORD_HEADER_LENGTH + payloadLength - 1];
-		input[0] = PROTOCOL_VERSION;
-		input[1] = CONFIRM;
-		ByteUtils.writeUint16(payloadLength, input, 2);
-		setup(input);
 		kat.receiveConfirm();
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveConfirmThrowsExceptionIfProtocolVersionIsUnrecognised()
 			throws Exception {
-		setup(createRecord((byte) (PROTOCOL_VERSION + 1), CONFIRM,
+		byte unknownVersion = (byte) (PROTOCOL_VERSION + 1);
-				new byte[123]));
+		byte[] confirm = getRandomBytes(123);
+
+		setup();
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(new Record(unknownVersion, CONFIRM, confirm)));
+		}});
+
 		kat.receiveConfirm();
 	}
 
 	@Test(expected = AbortException.class)
 	public void testReceiveConfirmThrowsExceptionIfAbortIsReceived()
 			throws Exception {
-		setup(createRecord(PROTOCOL_VERSION, ABORT, new byte[0]));
+		setup();
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(new Record(PROTOCOL_VERSION, ABORT, new byte[0])));
+		}});
+
 		kat.receiveConfirm();
 	}
 
 	@Test(expected = AbortException.class)
-	public void testReceiveKeyThrowsExceptionIfKeyIsReceived()
+	public void testReceiveConfirmThrowsExceptionIfKeyIsReceived()
 			throws Exception {
-		setup(createRecord(PROTOCOL_VERSION, KEY, new byte[123]));
+		byte[] key = getRandomBytes(123);
+
+		setup();
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(new Record(PROTOCOL_VERSION, KEY, key)));
+		}});
+
 		kat.receiveConfirm();
 	}
 
 	@Test
 	public void testReceiveConfirmSkipsUnrecognisedRecordTypes()
 			throws Exception {
-		byte[] skip1 = createRecord(PROTOCOL_VERSION, (byte) (ABORT + 1),
+		byte type1 = (byte) (ABORT + 1);
-				new byte[123]);
+		byte[] payload1 = getRandomBytes(123);
-		byte[] skip2 = createRecord(PROTOCOL_VERSION, (byte) (ABORT + 2),
+		Record unknownRecord1 = new Record(PROTOCOL_VERSION, type1, payload1);
-				new byte[0]);
+		byte type2 = (byte) (ABORT + 2);
-		byte[] payload = TestUtils.getRandomBytes(123);
+		byte[] payload2 = new byte[0];
-		byte[] confirm = createRecord(PROTOCOL_VERSION, CONFIRM, payload);
+		Record unknownRecord2 = new Record(PROTOCOL_VERSION, type2, payload2);
-		ByteArrayOutputStream input = new ByteArrayOutputStream();
+		byte[] confirm = getRandomBytes(123);
-		input.write(skip1);
+		Record confirmRecord = new Record(PROTOCOL_VERSION, CONFIRM, confirm);
-		input.write(skip2);
+
-		input.write(confirm);
+		setup();
-		setup(input.toByteArray());
+		context.checking(new Expectations() {{
-		assertArrayEquals(payload, kat.receiveConfirm());
+			oneOf(recordReader).readRecord();
+			will(returnValue(unknownRecord1));
+			oneOf(recordReader).readRecord();
+			will(returnValue(unknownRecord2));
+			oneOf(recordReader).readRecord();
+			will(returnValue(confirmRecord));
+		}});
+
+		assertArrayEquals(confirm, kat.receiveConfirm());
 	}
 
-	private void setup(byte[] input) throws Exception {
+	private void setup() throws Exception {
-		inputStream = new ByteArrayInputStream(input);
-		outputStream = new ByteArrayOutputStream();
 		context.checking(new Expectations() {{
 			allowing(duplexTransportConnection).getReader();
 			will(returnValue(transportConnectionReader));
 			allowing(transportConnectionReader).getInputStream();
 			will(returnValue(inputStream));
+			oneOf(recordReaderFactory).createRecordReader(inputStream);
+			will(returnValue(recordReader));
 			allowing(duplexTransportConnection).getWriter();
 			will(returnValue(transportConnectionWriter));
 			allowing(transportConnectionWriter).getOutputStream();
 			will(returnValue(outputStream));
+			oneOf(recordWriterFactory).createRecordWriter(outputStream);
+			will(returnValue(recordWriter));
 		}});
-		kat = new KeyAgreementTransport(keyAgreementConnection);
+		kat = new KeyAgreementTransport(recordReaderFactory,
+				recordWriterFactory, keyAgreementConnection);
 	}
 
-	private void assertRecordSent(byte expectedType, byte[] expectedPayload) {
+	private AtomicReference<Record> expectWriteRecord() throws Exception {
-		byte[] output = outputStream.toByteArray();
+		AtomicReference<Record> captured = new AtomicReference<>();
-		assertEquals(RECORD_HEADER_LENGTH + expectedPayload.length,
+		context.checking(new Expectations() {{
-				output.length);
+			oneOf(recordWriter).writeRecord(with(any(Record.class)));
-		assertEquals(PROTOCOL_VERSION, output[0]);
+			will(new CaptureArgumentAction<>(captured, Record.class, 0));
-		assertEquals(expectedType, output[1]);
+			oneOf(recordWriter).flush();
-		assertEquals(expectedPayload.length, ByteUtils.readUint16(output, 2));
+		}});
-		byte[] payload = new byte[output.length - RECORD_HEADER_LENGTH];
+		return captured;
-		System.arraycopy(output, RECORD_HEADER_LENGTH, payload, 0,
-				payload.length);
-		assertArrayEquals(expectedPayload, payload);
 	}
 
-	private byte[] createRecord(byte version, byte type, byte[] payload) {
+	private void assertRecordEquals(byte expectedVersion, byte expectedType,
-		byte[] b = new byte[RECORD_HEADER_LENGTH + payload.length];
+			byte[] expectedPayload, Record actual) {
-		b[0] = version;
+		assertEquals(expectedVersion, actual.getProtocolVersion());
-		b[1] = type;
+		assertEquals(expectedType, actual.getRecordType());
-		ByteUtils.writeUint16(payload.length, b, 2);
+		assertArrayEquals(expectedPayload, actual.getPayload());
-		System.arraycopy(payload, 0, b, RECORD_HEADER_LENGTH, payload.length);
-		return b;
 	}
 }

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyManagerImplTest.java

@@ -19,6 +19,7 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.jmock.Expectations;
 import org.junit.Test;
@@ -29,8 +30,9 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 
+import static java.util.Collections.singletonList;
 import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_ID;
-import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_VERSION;
+import static org.briarproject.bramble.api.properties.TransportPropertyManager.MAJOR_VERSION;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.bramble.test.TestUtils.getAuthor;
@@ -45,13 +47,15 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 
 	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
 	private final ClientHelper clientHelper = context.mock(ClientHelper.class);
+	private final ClientVersioningManager clientVersioningManager =
+			context.mock(ClientVersioningManager.class);
 	private final MetadataParser metadataParser =
 			context.mock(MetadataParser.class);
 	private final ContactGroupFactory contactGroupFactory =
 			context.mock(ContactGroupFactory.class);
 	private final Clock clock = context.mock(Clock.class);
 
-	private final Group localGroup = getGroup(CLIENT_ID);
+	private final Group localGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 	private final LocalAuthor localAuthor = getLocalAuthor();
 	private final BdfDictionary fooPropertiesDict = BdfDictionary.of(
 			new BdfEntry("fooKey1", "fooValue1"),
@@ -77,49 +81,41 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	private TransportPropertyManagerImpl createInstance() {
 		context.checking(new Expectations() {{
 			oneOf(contactGroupFactory).createLocalGroup(CLIENT_ID,
-					CLIENT_VERSION);
+					MAJOR_VERSION);
 			will(returnValue(localGroup));
 		}});
 		return new TransportPropertyManagerImpl(db, clientHelper,
-				metadataParser, contactGroupFactory, clock);
+				clientVersioningManager, metadataParser, contactGroupFactory,
+				clock);
 	}
 
 	@Test
 	public void testCreatesGroupsAtStartup() throws Exception {
 		Transaction txn = new Transaction(null, false);
-		Contact contact1 = getContact(true);
+		Contact contact = getContact(true);
-		Contact contact2 = getContact(true);
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
-		List<Contact> contacts = Arrays.asList(contact1, contact2);
-		Group contactGroup1 = getGroup(CLIENT_ID);
-		Group contactGroup2 = getGroup(CLIENT_ID);
 
 		context.checking(new Expectations() {{
 			oneOf(db).containsGroup(txn, localGroup.getId());
 			will(returnValue(false));
 			oneOf(db).addGroup(txn, localGroup);
 			oneOf(db).getContacts(txn);
-			will(returnValue(contacts));
+			will(returnValue(singletonList(contact)));
-			// The first contact's group has already been set up
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact1);
+					MAJOR_VERSION, contact);
-			will(returnValue(contactGroup1));
+			will(returnValue(contactGroup));
-			oneOf(db).containsGroup(txn, contactGroup1.getId());
+			oneOf(db).addGroup(txn, contactGroup);
-			will(returnValue(true));
+			oneOf(clientVersioningManager).getClientVisibility(txn,
-			// The second contact's group hasn't been set up
+					contact.getId(), CLIENT_ID, MAJOR_VERSION);
-			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+			will(returnValue(SHARED));
-					CLIENT_VERSION, contact2);
+			oneOf(db).setGroupVisibility(txn, contact.getId(),
-			will(returnValue(contactGroup2));
+					contactGroup.getId(), SHARED);
-			oneOf(db).containsGroup(txn, contactGroup2.getId());
-			will(returnValue(false));
-			oneOf(db).addGroup(txn, contactGroup2);
-			oneOf(db).setGroupVisibility(txn, contact2.getId(),
-					contactGroup2.getId(), SHARED);
 		}});
 		// Copy the latest local properties into the group
 		expectGetLocalProperties(txn);
-		expectStoreMessage(txn, contactGroup2.getId(), "foo", fooPropertiesDict,
+		expectStoreMessage(txn, contactGroup.getId(), "foo", fooPropertiesDict,
 				1, true, true);
-		expectStoreMessage(txn, contactGroup2.getId(), "bar", barPropertiesDict,
+		expectStoreMessage(txn, contactGroup.getId(), "bar", barPropertiesDict,
 				1, true, true);
 
 		TransportPropertyManagerImpl t = createInstance();
@@ -144,16 +140,17 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testCreatesContactGroupWhenAddingContact() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup(CLIENT_ID);
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 
 		context.checking(new Expectations() {{
 			// Create the group and share it with the contact
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact);
+					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
-			oneOf(db).containsGroup(txn, contactGroup.getId());
-			will(returnValue(false));
 			oneOf(db).addGroup(txn, contactGroup);
+			oneOf(clientVersioningManager).getClientVisibility(txn,
+					contact.getId(), CLIENT_ID, MAJOR_VERSION);
+			will(returnValue(SHARED));
 			oneOf(db).setGroupVisibility(txn, contact.getId(),
 					contactGroup.getId(), SHARED);
 		}});
@@ -172,11 +169,11 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testRemovesGroupWhenRemovingContact() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup(CLIENT_ID);
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 
 		context.checking(new Expectations() {{
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact);
+					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 			oneOf(db).removeGroup(txn, contactGroup);
 		}});
@@ -307,7 +304,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	@Test
 	public void testStoresRemotePropertiesWithVersion0() throws Exception {
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup(CLIENT_ID);
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 		Transaction txn = new Transaction(null, false);
 		Map<TransportId, TransportProperties> properties =
 				new LinkedHashMap<>();
@@ -318,7 +315,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).getContact(txn, contact.getId());
 			will(returnValue(contact));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact);
+					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 		}});
 		expectStoreMessage(txn, contactGroup.getId(), "foo", fooPropertiesDict,
@@ -421,8 +418,8 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 		Contact contact3 = getContact(true);
 		List<Contact> contacts =
 				Arrays.asList(contact1, contact2, contact3);
-		Group contactGroup2 = getGroup(CLIENT_ID);
+		Group contactGroup2 = getGroup(CLIENT_ID, MAJOR_VERSION);
-		Group contactGroup3 = getGroup(CLIENT_ID);
+		Group contactGroup3 = getGroup(CLIENT_ID, MAJOR_VERSION);
 		Map<MessageId, BdfDictionary> messageMetadata3 =
 				new LinkedHashMap<>();
 		// A remote update for another transport should be ignored
@@ -456,14 +453,14 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			// First contact: skipped because not active
 			// Second contact: no updates
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact2);
+					MAJOR_VERSION, contact2);
 			will(returnValue(contactGroup2));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup2.getId());
 			will(returnValue(Collections.emptyMap()));
 			// Third contact: returns an update
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact3);
+					MAJOR_VERSION, contact3);
 			will(returnValue(contactGroup3));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup3.getId());
@@ -524,7 +521,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testMergingNewPropertiesCreatesUpdate() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup(CLIENT_ID);
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 
 		context.checking(new Expectations() {{
 			oneOf(db).startTransaction(false);
@@ -538,9 +535,9 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 					fooPropertiesDict, 1, true, false);
 			// Store the new properties in each contact's group, version 1
 			oneOf(db).getContacts(txn);
-			will(returnValue(Collections.singletonList(contact)));
+			will(returnValue(singletonList(contact)));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact);
+					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());
@@ -559,7 +556,7 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 	public void testMergingUpdatedPropertiesCreatesUpdate() throws Exception {
 		Transaction txn = new Transaction(null, false);
 		Contact contact = getContact(true);
-		Group contactGroup = getGroup(CLIENT_ID);
+		Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
 		BdfDictionary oldMetadata = BdfDictionary.of(
 				new BdfEntry("transportId", "foo"),
 				new BdfEntry("version", 1),
@@ -597,9 +594,9 @@ public class TransportPropertyManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).removeMessage(txn, localGroupUpdateId);
 			// Store the merged properties in each contact's group, version 2
 			oneOf(db).getContacts(txn);
-			will(returnValue(Collections.singletonList(contact)));
+			will(returnValue(singletonList(contact)));
 			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
-					CLIENT_VERSION, contact);
+					MAJOR_VERSION, contact);
 			will(returnValue(contactGroup));
 			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
 					contactGroup.getId());

bramble-core/src/test/java/org/briarproject/bramble/properties/TransportPropertyValidatorTest.java

@@ -18,7 +18,8 @@ import org.junit.Test;
 import java.io.IOException;
 
 import static org.briarproject.bramble.api.plugin.TransportId.MAX_TRANSPORT_ID_LENGTH;
-import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.api.properties.TransportPropertyManager.CLIENT_ID;
+import static org.briarproject.bramble.api.properties.TransportPropertyManager.MAJOR_VERSION;
 import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getTransportId;
@@ -42,7 +43,7 @@ public class TransportPropertyValidatorTest extends BrambleMockTestCase {
 		transportProperties = new TransportProperties();
 		transportProperties.put("foo", "bar");
 
-		group = getGroup(getClientId());
+		group = getGroup(CLIENT_ID, MAJOR_VERSION);
 		message = getMessage(group.getId());
 
 		MetadataEncoder metadataEncoder = context.mock(MetadataEncoder.class);

bramble-core/src/test/java/org/briarproject/bramble/record/RecordReaderImplTest.java

@@ -0,0 +1,102 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.briarproject.bramble.util.ByteUtils;
+import org.junit.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.EOFException;
+
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
+import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+public class RecordReaderImplTest extends BrambleTestCase {
+
+	@Test
+	public void testAcceptsEmptyPayload() throws Exception {
+		// Version 1, type 2, payload length 0
+		byte[] header = new byte[] {1, 2, 0, 0};
+		ByteArrayInputStream in = new ByteArrayInputStream(header);
+		RecordReader reader = new RecordReaderImpl(in);
+		Record record = reader.readRecord();
+		assertEquals(1, record.getProtocolVersion());
+		assertEquals(2, record.getRecordType());
+		assertArrayEquals(new byte[0], record.getPayload());
+	}
+
+	@Test
+	public void testAcceptsMaxLengthPayload() throws Exception {
+		byte[] record =
+				new byte[RECORD_HEADER_BYTES + MAX_RECORD_PAYLOAD_BYTES];
+		// Version 1, type 2, payload length MAX_RECORD_PAYLOAD_BYTES
+		record[0] = 1;
+		record[1] = 2;
+		ByteUtils.writeUint16(MAX_RECORD_PAYLOAD_BYTES, record, 2);
+		ByteArrayInputStream in = new ByteArrayInputStream(record);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = FormatException.class)
+	public void testFormatExceptionIfPayloadLengthIsNegative()
+			throws Exception {
+		// Version 1, type 2, payload length -1
+		byte[] header = new byte[] {1, 2, (byte) 0xFF, (byte) 0xFF};
+		ByteArrayInputStream in = new ByteArrayInputStream(header);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = FormatException.class)
+	public void testFormatExceptionIfPayloadLengthIsTooLarge()
+			throws Exception {
+		// Version 1, type 2, payload length MAX_RECORD_PAYLOAD_BYTES + 1
+		byte[] header = new byte[] {1, 2, 0, 0};
+		ByteUtils.writeUint16(MAX_RECORD_PAYLOAD_BYTES + 1, header, 2);
+		ByteArrayInputStream in = new ByteArrayInputStream(header);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = EOFException.class)
+	public void testEofExceptionIfProtocolVersionIsMissing() throws Exception {
+		ByteArrayInputStream in = new ByteArrayInputStream(new byte[0]);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = EOFException.class)
+	public void testEofExceptionIfRecordTypeIsMissing() throws Exception {
+		ByteArrayInputStream in = new ByteArrayInputStream(new byte[1]);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = EOFException.class)
+	public void testEofExceptionIfPayloadLengthIsMissing() throws Exception {
+		ByteArrayInputStream in = new ByteArrayInputStream(new byte[2]);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = EOFException.class)
+	public void testEofExceptionIfPayloadLengthIsTruncated() throws Exception {
+		ByteArrayInputStream in = new ByteArrayInputStream(new byte[3]);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+
+	@Test(expected = EOFException.class)
+	public void testEofExceptionIfPayloadIsTruncated() throws Exception {
+		// Version 0, type 0, payload length 1
+		byte[] header = new byte[] {0, 0, 0, 1};
+		ByteArrayInputStream in = new ByteArrayInputStream(header);
+		RecordReader reader = new RecordReaderImpl(in);
+		reader.readRecord();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/record/RecordWriterImplTest.java

@@ -0,0 +1,49 @@
+package org.briarproject.bramble.record;
+
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordWriter;
+import org.briarproject.bramble.test.BrambleTestCase;
+import org.briarproject.bramble.util.ByteUtils;
+import org.junit.Test;
+
+import java.io.ByteArrayOutputStream;
+
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
+import static org.briarproject.bramble.api.record.Record.RECORD_HEADER_BYTES;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+public class RecordWriterImplTest extends BrambleTestCase {
+
+	@Test
+	public void testWritesEmptyRecord() throws Exception {
+		testWritesRecord(0);
+	}
+
+	@Test
+	public void testWritesMaxLengthRecord() throws Exception {
+		testWritesRecord(MAX_RECORD_PAYLOAD_BYTES);
+	}
+
+	private void testWritesRecord(int payloadLength) throws Exception {
+		byte protocolVersion = 123;
+		byte recordType = 45;
+		byte[] payload = getRandomBytes(payloadLength);
+
+		ByteArrayOutputStream out = new ByteArrayOutputStream();
+		RecordWriter writer = new RecordWriterImpl(out);
+		writer.writeRecord(new Record(protocolVersion, recordType, payload));
+		writer.flush();
+		byte[] written = out.toByteArray();
+
+		assertEquals(RECORD_HEADER_BYTES + payloadLength, written.length);
+		assertEquals(protocolVersion, written[0]);
+		assertEquals(recordType, written[1]);
+		assertEquals(payloadLength, ByteUtils.readUint16(written, 2));
+		byte[] writtenPayload = new byte[payloadLength];
+		System.arraycopy(written, RECORD_HEADER_BYTES, writtenPayload, 0,
+				payloadLength);
+		assertArrayEquals(payload, writtenPayload);
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/sync/RecordReaderImplTest.java

@@ -1,219 +0,0 @@
-package org.briarproject.bramble.sync;
-
-import org.briarproject.bramble.api.FormatException;
-import org.briarproject.bramble.api.UniqueId;
-import org.briarproject.bramble.api.sync.Ack;
-import org.briarproject.bramble.api.sync.MessageFactory;
-import org.briarproject.bramble.test.BrambleMockTestCase;
-import org.briarproject.bramble.test.TestUtils;
-import org.briarproject.bramble.util.ByteUtils;
-import org.junit.Test;
-
-import java.io.ByteArrayInputStream;
-import java.io.ByteArrayOutputStream;
-
-import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
-import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
-import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
-import static org.briarproject.bramble.api.sync.SyncConstants.MAX_RECORD_PAYLOAD_LENGTH;
-import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
-import static org.briarproject.bramble.api.sync.SyncConstants.RECORD_HEADER_LENGTH;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
-
-public class RecordReaderImplTest extends BrambleMockTestCase {
-
-	private final MessageFactory messageFactory =
-			context.mock(MessageFactory.class);
-
-	@Test(expected = FormatException.class)
-	public void testFormatExceptionIfAckIsTooLarge() throws Exception {
-		byte[] b = createAck(true);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readAck();
-	}
-
-	@Test
-	public void testNoFormatExceptionIfAckIsMaximumSize() throws Exception {
-		byte[] b = createAck(false);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readAck();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testFormatExceptionIfAckIsEmpty() throws Exception {
-		byte[] b = createEmptyAck();
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readAck();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testFormatExceptionIfOfferIsTooLarge() throws Exception {
-		byte[] b = createOffer(true);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readOffer();
-	}
-
-	@Test
-	public void testNoFormatExceptionIfOfferIsMaximumSize() throws Exception {
-		byte[] b = createOffer(false);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readOffer();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testFormatExceptionIfOfferIsEmpty() throws Exception {
-		byte[] b = createEmptyOffer();
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readOffer();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testFormatExceptionIfRequestIsTooLarge() throws Exception {
-		byte[] b = createRequest(true);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readRequest();
-	}
-
-	@Test
-	public void testNoFormatExceptionIfRequestIsMaximumSize() throws Exception {
-		byte[] b = createRequest(false);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readRequest();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testFormatExceptionIfRequestIsEmpty() throws Exception {
-		byte[] b = createEmptyRequest();
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.readRequest();
-	}
-
-	@Test
-	public void testEofReturnsTrueWhenAtEndOfStream() throws Exception {
-		ByteArrayInputStream in = new ByteArrayInputStream(new byte[0]);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		assertTrue(reader.eof());
-	}
-
-	@Test
-	public void testEofReturnsFalseWhenNotAtEndOfStream() throws Exception {
-		byte[] b = createAck(false);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		assertFalse(reader.eof());
-	}
-
-	@Test(expected = FormatException.class)
-	public void testThrowsExceptionIfHeaderIsTooShort() throws Exception {
-		byte[] b = new byte[RECORD_HEADER_LENGTH - 1];
-		b[0] = PROTOCOL_VERSION;
-		b[1] = ACK;
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.eof();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testThrowsExceptionIfPayloadIsTooShort() throws Exception {
-		int payloadLength = 123;
-		byte[] b = new byte[RECORD_HEADER_LENGTH + payloadLength - 1];
-		b[0] = PROTOCOL_VERSION;
-		b[1] = ACK;
-		ByteUtils.writeUint16(payloadLength, b, 2);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.eof();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testThrowsExceptionIfProtocolVersionIsUnrecognised()
-			throws Exception {
-		byte version = (byte) (PROTOCOL_VERSION + 1);
-		byte[] b = createRecord(version, ACK, new byte[0]);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.eof();
-	}
-
-	@Test(expected = FormatException.class)
-	public void testThrowsExceptionIfPayloadIsTooLong() throws Exception {
-		byte[] payload = new byte[MAX_RECORD_PAYLOAD_LENGTH + 1];
-		byte[] b = createRecord(PROTOCOL_VERSION, ACK, payload);
-		ByteArrayInputStream in = new ByteArrayInputStream(b);
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		reader.eof();
-	}
-
-	@Test
-	public void testSkipsUnrecognisedRecordTypes() throws Exception {
-		byte[] skip1 = createRecord(PROTOCOL_VERSION, (byte) (REQUEST + 1),
-				new byte[123]);
-		byte[] skip2 = createRecord(PROTOCOL_VERSION, (byte) (REQUEST + 2),
-				new byte[0]);
-		byte[] ack = createAck(false);
-		ByteArrayOutputStream input = new ByteArrayOutputStream();
-		input.write(skip1);
-		input.write(skip2);
-		input.write(ack);
-		ByteArrayInputStream in = new ByteArrayInputStream(input.toByteArray());
-		RecordReaderImpl reader = new RecordReaderImpl(messageFactory, in);
-		assertTrue(reader.hasAck());
-		Ack a = reader.readAck();
-		assertEquals(MAX_MESSAGE_IDS, a.getMessageIds().size());
-	}
-
-	private byte[] createAck(boolean tooBig) throws Exception {
-		return createRecord(PROTOCOL_VERSION, ACK, createPayload(tooBig));
-	}
-
-	private byte[] createEmptyAck() throws Exception {
-		return createRecord(PROTOCOL_VERSION, ACK, new byte[0]);
-	}
-
-	private byte[] createOffer(boolean tooBig) throws Exception {
-		return createRecord(PROTOCOL_VERSION, OFFER, createPayload(tooBig));
-	}
-
-	private byte[] createEmptyOffer() throws Exception {
-		return createRecord(PROTOCOL_VERSION, OFFER, new byte[0]);
-	}
-
-	private byte[] createRequest(boolean tooBig) throws Exception {
-		return createRecord(PROTOCOL_VERSION, REQUEST, createPayload(tooBig));
-	}
-
-	private byte[] createEmptyRequest() throws Exception {
-		return createRecord(PROTOCOL_VERSION, REQUEST, new byte[0]);
-	}
-
-	private byte[] createRecord(byte version, byte type, byte[] payload) {
-		byte[] b = new byte[RECORD_HEADER_LENGTH + payload.length];
-		b[0] = version;
-		b[1] = type;
-		ByteUtils.writeUint16(payload.length, b, 2);
-		System.arraycopy(payload, 0, b, RECORD_HEADER_LENGTH, payload.length);
-		return b;
-	}
-
-	private byte[] createPayload(boolean tooBig) throws Exception {
-		ByteArrayOutputStream payload = new ByteArrayOutputStream();
-		while (payload.size() + UniqueId.LENGTH <= MAX_RECORD_PAYLOAD_LENGTH) {
-			payload.write(TestUtils.getRandomId());
-		}
-		if (tooBig) payload.write(TestUtils.getRandomId());
-		assertEquals(tooBig, payload.size() > MAX_RECORD_PAYLOAD_LENGTH);
-		return payload.toByteArray();
-	}
-}

bramble-core/src/test/java/org/briarproject/bramble/sync/SimplexOutgoingSessionTest.java

@@ -6,7 +6,7 @@ import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.sync.Ack;
 import org.briarproject.bramble.api.sync.MessageId;
-import org.briarproject.bramble.api.sync.RecordWriter;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
 import org.briarproject.bramble.test.BrambleTestCase;
 import org.briarproject.bramble.test.ImmediateExecutor;
 import org.briarproject.bramble.test.TestUtils;
@@ -29,14 +29,14 @@ public class SimplexOutgoingSessionTest extends BrambleTestCase {
 	private final ContactId contactId;
 	private final MessageId messageId;
 	private final int maxLatency;
-	private final RecordWriter recordWriter;
+	private final SyncRecordWriter recordWriter;
 
 	public SimplexOutgoingSessionTest() {
 		context = new Mockery();
 		db = context.mock(DatabaseComponent.class);
 		dbExecutor = new ImmediateExecutor();
 		eventBus = context.mock(EventBus.class);
-		recordWriter = context.mock(RecordWriter.class);
+		recordWriter = context.mock(SyncRecordWriter.class);
 		contactId = new ContactId(234);
 		messageId = new MessageId(TestUtils.getRandomId());
 		maxLatency = Integer.MAX_VALUE;

bramble-core/src/test/java/org/briarproject/bramble/sync/SyncIntegrationTest.java

@@ -12,11 +12,11 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.Offer;
-import org.briarproject.bramble.api.sync.RecordReader;
-import org.briarproject.bramble.api.sync.RecordReaderFactory;
-import org.briarproject.bramble.api.sync.RecordWriter;
-import org.briarproject.bramble.api.sync.RecordWriterFactory;
 import org.briarproject.bramble.api.sync.Request;
+import org.briarproject.bramble.api.sync.SyncRecordReader;
+import org.briarproject.bramble.api.sync.SyncRecordReaderFactory;
+import org.briarproject.bramble.api.sync.SyncRecordWriter;
+import org.briarproject.bramble.api.sync.SyncRecordWriterFactory;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
 import org.briarproject.bramble.api.transport.StreamWriterFactory;
@@ -54,9 +54,9 @@ public class SyncIntegrationTest extends BrambleTestCase {
 	@Inject
 	StreamWriterFactory streamWriterFactory;
 	@Inject
-	RecordReaderFactory recordReaderFactory;
+	SyncRecordReaderFactory recordReaderFactory;
 	@Inject
-	RecordWriterFactory recordWriterFactory;
+	SyncRecordWriterFactory recordWriterFactory;
 	@Inject
 	TransportCrypto transportCrypto;
 
@@ -81,9 +81,9 @@ public class SyncIntegrationTest extends BrambleTestCase {
 		streamNumber = 123;
 		// Create a group
 		ClientId clientId = getClientId();
-		int clientVersion = 1234567890;
+		int majorVersion = 1234567890;
 		byte[] descriptor = new byte[MAX_GROUP_DESCRIPTOR_LENGTH];
-		Group group = groupFactory.createGroup(clientId, clientVersion,
+		Group group = groupFactory.createGroup(clientId, majorVersion,
 				descriptor);
 		// Add two messages to the group
 		long timestamp = System.currentTimeMillis();
@@ -104,7 +104,7 @@ public class SyncIntegrationTest extends BrambleTestCase {
 				headerKey, streamNumber);
 		OutputStream streamWriter = streamWriterFactory.createStreamWriter(out,
 				ctx);
-		RecordWriter recordWriter = recordWriterFactory.createRecordWriter(
+		SyncRecordWriter recordWriter = recordWriterFactory.createRecordWriter(
 				streamWriter);
 
 		recordWriter.writeAck(new Ack(messageIds));
@@ -112,8 +112,8 @@ public class SyncIntegrationTest extends BrambleTestCase {
 		recordWriter.writeMessage(message1.getRaw());
 		recordWriter.writeOffer(new Offer(messageIds));
 		recordWriter.writeRequest(new Request(messageIds));
+		recordWriter.flush();
 
-		streamWriter.flush();
 		return out.toByteArray();
 	}
 
@@ -134,7 +134,7 @@ public class SyncIntegrationTest extends BrambleTestCase {
 				headerKey, streamNumber);
 		InputStream streamReader = streamReaderFactory.createStreamReader(in,
 				ctx);
-		RecordReader recordReader = recordReaderFactory.createRecordReader(
+		SyncRecordReader recordReader = recordReaderFactory.createRecordReader(
 				streamReader);
 
 		// Read the ack

bramble-core/src/test/java/org/briarproject/bramble/sync/SyncIntegrationTestComponent.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.sync;
 
 import org.briarproject.bramble.crypto.CryptoModule;
+import org.briarproject.bramble.record.RecordModule;
 import org.briarproject.bramble.system.SystemModule;
 import org.briarproject.bramble.test.TestSecureRandomModule;
 import org.briarproject.bramble.transport.TransportModule;
@@ -13,6 +14,7 @@ import dagger.Component;
 @Component(modules = {
 		TestSecureRandomModule.class,
 		CryptoModule.class,
+		RecordModule.class,
 		SyncModule.class,
 		SystemModule.class,
 		TransportModule.class

bramble-core/src/test/java/org/briarproject/bramble/sync/SyncRecordReaderImplTest.java

@@ -0,0 +1,195 @@
+package org.briarproject.bramble.sync;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.UniqueId;
+import org.briarproject.bramble.api.record.Record;
+import org.briarproject.bramble.api.record.RecordReader;
+import org.briarproject.bramble.api.sync.Ack;
+import org.briarproject.bramble.api.sync.MessageFactory;
+import org.briarproject.bramble.api.sync.Offer;
+import org.briarproject.bramble.api.sync.Request;
+import org.briarproject.bramble.api.sync.SyncRecordReader;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.jmock.Expectations;
+import org.junit.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.io.EOFException;
+
+import static org.briarproject.bramble.api.record.Record.MAX_RECORD_PAYLOAD_BYTES;
+import static org.briarproject.bramble.api.sync.RecordTypes.ACK;
+import static org.briarproject.bramble.api.sync.RecordTypes.OFFER;
+import static org.briarproject.bramble.api.sync.RecordTypes.REQUEST;
+import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_IDS;
+import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class SyncRecordReaderImplTest extends BrambleMockTestCase {
+
+	private final MessageFactory messageFactory =
+			context.mock(MessageFactory.class);
+	private final RecordReader recordReader = context.mock(RecordReader.class);
+
+	@Test
+	public void testNoFormatExceptionIfAckIsMaximumSize() throws Exception {
+		expectReadRecord(createAck());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		Ack ack = reader.readAck();
+		assertEquals(MAX_MESSAGE_IDS, ack.getMessageIds().size());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testFormatExceptionIfAckIsEmpty() throws Exception {
+		expectReadRecord(createEmptyAck());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		reader.readAck();
+	}
+
+	@Test
+	public void testNoFormatExceptionIfOfferIsMaximumSize() throws Exception {
+		expectReadRecord(createOffer());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		Offer offer = reader.readOffer();
+		assertEquals(MAX_MESSAGE_IDS, offer.getMessageIds().size());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testFormatExceptionIfOfferIsEmpty() throws Exception {
+		expectReadRecord(createEmptyOffer());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		reader.readOffer();
+	}
+
+	@Test
+	public void testNoFormatExceptionIfRequestIsMaximumSize() throws Exception {
+		expectReadRecord(createRequest());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		Request request = reader.readRequest();
+		assertEquals(MAX_MESSAGE_IDS, request.getMessageIds().size());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testFormatExceptionIfRequestIsEmpty() throws Exception {
+		expectReadRecord(createEmptyRequest());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		reader.readRequest();
+	}
+
+	@Test
+	public void testEofReturnsTrueWhenAtEndOfStream() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(throwException(new EOFException()));
+		}});
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		assertTrue(reader.eof());
+		assertTrue(reader.eof());
+	}
+
+	@Test
+	public void testEofReturnsFalseWhenNotAtEndOfStream() throws Exception {
+		expectReadRecord(createAck());
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		assertFalse(reader.eof());
+		assertFalse(reader.eof());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testThrowsExceptionIfProtocolVersionIsUnrecognised()
+			throws Exception {
+		byte version = (byte) (PROTOCOL_VERSION + 1);
+		byte[] payload = getRandomId();
+
+		expectReadRecord(new Record(version, ACK, payload));
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		reader.eof();
+	}
+
+	@Test
+	public void testSkipsUnrecognisedRecordTypes() throws Exception {
+		byte type1 = (byte) (REQUEST + 1);
+		byte[] payload1 = getRandomBytes(123);
+		Record unknownRecord1 = new Record(PROTOCOL_VERSION, type1, payload1);
+		byte type2 = (byte) (REQUEST + 2);
+		byte[] payload2 = new byte[0];
+		Record unknownRecord2 = new Record(PROTOCOL_VERSION, type2, payload2);
+		Record ackRecord = createAck();
+
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(unknownRecord1));
+			oneOf(recordReader).readRecord();
+			will(returnValue(unknownRecord2));
+			oneOf(recordReader).readRecord();
+			will(returnValue(ackRecord));
+
+		}});
+
+		SyncRecordReader reader =
+				new SyncRecordReaderImpl(messageFactory, recordReader);
+		assertTrue(reader.hasAck());
+		Ack a = reader.readAck();
+		assertEquals(MAX_MESSAGE_IDS, a.getMessageIds().size());
+	}
+
+	private void expectReadRecord(Record record) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(recordReader).readRecord();
+			will(returnValue(record));
+		}});
+	}
+
+	private Record createAck() throws Exception {
+		return new Record(PROTOCOL_VERSION, ACK, createPayload());
+	}
+
+	private Record createEmptyAck() throws Exception {
+		return new Record(PROTOCOL_VERSION, ACK, new byte[0]);
+	}
+
+	private Record createOffer() throws Exception {
+		return new Record(PROTOCOL_VERSION, OFFER, createPayload());
+	}
+
+	private Record createEmptyOffer() throws Exception {
+		return new Record(PROTOCOL_VERSION, OFFER, new byte[0]);
+	}
+
+	private Record createRequest() throws Exception {
+		return new Record(PROTOCOL_VERSION, REQUEST, createPayload());
+	}
+
+	private Record createEmptyRequest() throws Exception {
+		return new Record(PROTOCOL_VERSION, REQUEST, new byte[0]);
+	}
+
+	private byte[] createPayload() throws Exception {
+		ByteArrayOutputStream payload = new ByteArrayOutputStream();
+		while (payload.size() + UniqueId.LENGTH <= MAX_RECORD_PAYLOAD_BYTES) {
+			payload.write(getRandomId());
+		}
+		return payload.toByteArray();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/sync/ValidationManagerImplTest.java

@@ -53,10 +53,11 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 	private final Executor dbExecutor = new ImmediateExecutor();
 	private final Executor validationExecutor = new ImmediateExecutor();
 	private final ClientId clientId = getClientId();
+	private final int majorVersion = 123;
 	private final MessageId messageId = new MessageId(getRandomId());
 	private final MessageId messageId1 = new MessageId(getRandomId());
 	private final MessageId messageId2 = new MessageId(getRandomId());
-	private final Group group = getGroup(clientId);
+	private final Group group = getGroup(clientId, majorVersion);
 	private final GroupId groupId = group.getId();
 	private final long timestamp = System.currentTimeMillis();
 	private final byte[] raw = new byte[123];
@@ -85,8 +86,8 @@ public class ValidationManagerImplTest extends BrambleMockTestCase {
 	public void setUp() {
 		vm = new ValidationManagerImpl(db, dbExecutor, validationExecutor,
 				messageFactory);
-		vm.registerMessageValidator(clientId, validator);
+		vm.registerMessageValidator(clientId, majorVersion, validator);
-		vm.registerIncomingMessageHook(clientId, hook);
+		vm.registerIncomingMessageHook(clientId, majorVersion, hook);
 	}
 
 	@Test

bramble-core/src/test/java/org/briarproject/bramble/test/TestCryptoExecutorModule.java

@@ -0,0 +1,21 @@
+package org.briarproject.bramble.test;
+
+import org.briarproject.bramble.api.crypto.CryptoExecutor;
+
+import java.util.concurrent.Executor;
+
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class TestCryptoExecutorModule {
+
+	@Provides
+	@Singleton
+	@CryptoExecutor
+	Executor provideCryptoExecutor() {
+		return new ImmediateExecutor();
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/test/UTestTest.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.test;
 
+import org.junit.Ignore;
 import org.junit.Test;
 
 import java.util.ArrayList;
@@ -11,6 +12,7 @@ import static org.briarproject.bramble.test.UTest.Result.LARGER;
 import static org.briarproject.bramble.test.UTest.Result.SMALLER;
 import static org.junit.Assert.assertEquals;
 
+@Ignore
 public class UTestTest extends BrambleTestCase {
 
 	private final Random random = new Random();

bramble-core/src/test/java/org/briarproject/bramble/test/ValidatorTestCase.java

@@ -24,7 +24,7 @@ public abstract class ValidatorTestCase extends BrambleMockTestCase {
 			context.mock(MetadataEncoder.class);
 	protected final Clock clock = context.mock(Clock.class);
 
-	protected final Group group = getGroup(getClientId());
+	protected final Group group = getGroup(getClientId(), 123);
 	protected final GroupId groupId = group.getId();
 	protected final byte[] descriptor = group.getDescriptor();
 	protected final Message message = getMessage(groupId);

bramble-core/src/test/java/org/briarproject/bramble/versioning/ClientVersioningManagerImplTest.java

@@ -0,0 +1,669 @@
+package org.briarproject.bramble.versioning;
+
+import org.briarproject.bramble.api.client.ClientHelper;
+import org.briarproject.bramble.api.client.ContactGroupFactory;
+import org.briarproject.bramble.api.contact.Contact;
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.data.BdfDictionary;
+import org.briarproject.bramble.api.data.BdfEntry;
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.Metadata;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.sync.ClientId;
+import org.briarproject.bramble.api.sync.Group;
+import org.briarproject.bramble.api.sync.Group.Visibility;
+import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.sync.MessageId;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.versioning.ClientVersioningManager.ClientVersioningHook;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.jmock.Expectations;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static java.util.Collections.singletonMap;
+import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
+import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
+import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
+import static org.briarproject.bramble.api.versioning.ClientVersioningManager.CLIENT_ID;
+import static org.briarproject.bramble.api.versioning.ClientVersioningManager.MAJOR_VERSION;
+import static org.briarproject.bramble.test.TestUtils.getAuthor;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
+import static org.briarproject.bramble.test.TestUtils.getLocalAuthor;
+import static org.briarproject.bramble.test.TestUtils.getMessage;
+import static org.briarproject.bramble.test.TestUtils.getRandomId;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.GROUP_KEY_CONTACT_ID;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
+import static org.junit.Assert.assertFalse;
+
+public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
+
+	private final DatabaseComponent db = context.mock(DatabaseComponent.class);
+	private final ClientHelper clientHelper = context.mock(ClientHelper.class);
+	private final ContactGroupFactory contactGroupFactory =
+			context.mock(ContactGroupFactory.class);
+	private final Clock clock = context.mock(Clock.class);
+	private final ClientVersioningHook hook =
+			context.mock(ClientVersioningHook.class);
+
+	private final Group localGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
+	private final Group contactGroup = getGroup(CLIENT_ID, MAJOR_VERSION);
+	private final Contact contact = new Contact(new ContactId(123),
+			getAuthor(), getLocalAuthor().getId(), true, true);
+	private final ClientId clientId = getClientId();
+	private final long now = System.currentTimeMillis();
+	private final Transaction txn = new Transaction(null, false);
+
+	private ClientVersioningManagerImpl createInstance() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(contactGroupFactory).createLocalGroup(CLIENT_ID,
+					MAJOR_VERSION);
+			will(returnValue(localGroup));
+		}});
+		return new ClientVersioningManagerImpl(db, clientHelper,
+				contactGroupFactory, clock);
+	}
+
+	@Test
+	public void testCreatesGroupsAtStartup() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(db).containsGroup(txn, localGroup.getId());
+			will(returnValue(false));
+			oneOf(db).addGroup(txn, localGroup);
+			oneOf(db).getContacts(txn);
+			will(returnValue(singletonList(contact)));
+		}});
+		expectAddingContact();
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.createLocalState(txn);
+	}
+
+	@Test
+	public void testDoesNotCreateGroupsAtStartupIfAlreadyCreated()
+			throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(db).containsGroup(txn, localGroup.getId());
+			will(returnValue(true));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.createLocalState(txn);
+	}
+
+	@Test
+	public void testCreatesContactGroupWhenAddingContact() throws Exception {
+		expectAddingContact();
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.addingContact(txn, contact);
+	}
+
+	private void expectAddingContact() throws Exception {
+		BdfDictionary groupMeta = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_CONTACT_ID, contact.getId().getInt()));
+		long now = System.currentTimeMillis();
+		BdfList localUpdateBody = BdfList.of(new BdfList(), 1L);
+		Message localUpdate = getMessage(contactGroup.getId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+
+		context.checking(new Expectations() {{
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(db).addGroup(txn, contactGroup);
+			oneOf(db).setGroupVisibility(txn, contact.getId(),
+					contactGroup.getId(), SHARED);
+			oneOf(clientHelper).mergeGroupMetadata(txn, contactGroup.getId(),
+					groupMeta);
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(contactGroup.getId(), now,
+					localUpdateBody);
+			will(returnValue(localUpdate));
+			oneOf(clientHelper).addLocalMessage(txn, localUpdate,
+					localUpdateMeta, true);
+		}});
+	}
+
+	@Test
+	public void testRemovesGroupWhenRemovingContact() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(db).removeGroup(txn, contactGroup);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.removingContact(txn, contact);
+	}
+
+	@Test
+	public void testStoresClientVersionsAtFirstStartup() throws Exception {
+		BdfList localVersionsBody =
+				BdfList.of(BdfList.of(clientId.getString(), 123, 234));
+		Message localVersions = getMessage(localGroup.getId());
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		BdfList localUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+
+		context.checking(new Expectations() {{
+			oneOf(db).startTransaction(false);
+			will(returnValue(txn));
+			// No client versions have been stored yet
+			oneOf(db).getMessageIds(txn, localGroup.getId());
+			will(returnValue(emptyList()));
+			// Store the client versions
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(localGroup.getId(), now,
+					localVersionsBody);
+			will(returnValue(localVersions));
+			oneOf(db).addLocalMessage(txn, localVersions, new Metadata(),
+					false);
+			// Inform contacts that client versions have changed
+			oneOf(db).getContacts(txn);
+			will(returnValue(singletonList(contact)));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			// Find the latest local and remote updates (no remote update)
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(singletonMap(localUpdateId, localUpdateMeta)));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			will(returnValue(localUpdateBody));
+			// Latest local update is up-to-date, no visibilities have changed
+			oneOf(db).commitTransaction(txn);
+			oneOf(db).endTransaction(txn);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		c.startService();
+	}
+
+	@Test
+	public void testComparesClientVersionsAtSubsequentStartup()
+			throws Exception {
+		MessageId localVersionsId = new MessageId(getRandomId());
+		BdfList localVersionsBody =
+				BdfList.of(BdfList.of(clientId.getString(), 123, 234));
+
+		context.checking(new Expectations() {{
+			oneOf(db).startTransaction(false);
+			will(returnValue(txn));
+			// Load the old client versions
+			oneOf(db).getMessageIds(txn, localGroup.getId());
+			will(returnValue(singletonList(localVersionsId)));
+			oneOf(clientHelper).getMessageAsList(txn, localVersionsId);
+			will(returnValue(localVersionsBody));
+			// Client versions are up-to-date
+			oneOf(db).commitTransaction(txn);
+			oneOf(db).endTransaction(txn);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		c.startService();
+	}
+
+	@Test
+	public void testStoresClientVersionsAtSubsequentStartupIfChanged()
+			throws Exception {
+		// The client had minor version 234 in the old client versions
+		BdfList oldLocalVersionsBody =
+				BdfList.of(BdfList.of(clientId.getString(), 123, 234));
+		// The client has minor version 345 in the new client versions
+		BdfList newLocalVersionsBody =
+				BdfList.of(BdfList.of(clientId.getString(), 123, 345));
+		// The client had minor version 234 in the old local update
+		BdfList oldLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+		// The client has minor version 345 in the new local update
+		BdfList newLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 345, false)), 2L);
+
+		MessageId oldLocalVersionsId = new MessageId(getRandomId());
+		Message newLocalVersions = getMessage(localGroup.getId());
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		Message newLocalUpdate = getMessage(contactGroup.getId());
+		BdfDictionary newLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+
+		context.checking(new Expectations() {{
+			oneOf(db).startTransaction(false);
+			will(returnValue(txn));
+			// Load the old client versions
+			oneOf(db).getMessageIds(txn, localGroup.getId());
+			will(returnValue(singletonList(oldLocalVersionsId)));
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalVersionsId);
+			will(returnValue(oldLocalVersionsBody));
+			// Delete the old client versions
+			oneOf(db).removeMessage(txn, oldLocalVersionsId);
+			// Store the new client versions
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(localGroup.getId(), now,
+					newLocalVersionsBody);
+			will(returnValue(newLocalVersions));
+			oneOf(db).addLocalMessage(txn, newLocalVersions, new Metadata(),
+					false);
+			// Inform contacts that client versions have changed
+			oneOf(db).getContacts(txn);
+			will(returnValue(singletonList(contact)));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			// Find the latest local and remote updates (no remote update)
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(singletonMap(oldLocalUpdateId,
+					oldLocalUpdateMeta)));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			will(returnValue(oldLocalUpdateBody));
+			// Delete the latest local update
+			oneOf(db).deleteMessage(txn, oldLocalUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldLocalUpdateId);
+			// Store the new local update
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(contactGroup.getId(), now,
+					newLocalUpdateBody);
+			will(returnValue(newLocalUpdate));
+			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
+					newLocalUpdateMeta, true);
+			// No visibilities have changed
+			oneOf(db).commitTransaction(txn);
+			oneOf(db).endTransaction(txn);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 345, hook);
+		c.startService();
+	}
+
+	@Test
+	public void testActivatesNewClientAtStartupIfAlreadyAdvertisedByContact()
+			throws Exception {
+		testActivatesNewClientAtStartup(false, VISIBLE);
+	}
+
+	@Test
+	public void testActivatesNewClientAtStartupIfAlreadyActivatedByContact()
+			throws Exception {
+		testActivatesNewClientAtStartup(true, SHARED);
+	}
+
+	private void testActivatesNewClientAtStartup(boolean remoteActive,
+			Visibility visibility) throws Exception {
+		// The client was missing from the old client versions
+		BdfList oldLocalVersionsBody = new BdfList();
+		// The client is included in the new client versions
+		BdfList newLocalVersionsBody =
+				BdfList.of(BdfList.of(clientId.getString(), 123, 234));
+		// The client was missing from the old local update
+		BdfList oldLocalUpdateBody = BdfList.of(new BdfList(), 1L);
+		// The client was included in the old remote update
+		BdfList oldRemoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 345, remoteActive)), 1L);
+		// The client is active in the new local update
+		BdfList newLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 2L);
+
+		MessageId oldLocalVersionsId = new MessageId(getRandomId());
+		Message newLocalVersions = getMessage(localGroup.getId());
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId oldRemoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldRemoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(oldLocalUpdateId, oldLocalUpdateMeta);
+		messageMetadata.put(oldRemoteUpdateId, oldRemoteUpdateMeta);
+		Message newLocalUpdate = getMessage(localGroup.getId());
+		BdfDictionary newLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+
+		context.checking(new Expectations() {{
+			oneOf(db).startTransaction(false);
+			will(returnValue(txn));
+			// Load the old client versions
+			oneOf(db).getMessageIds(txn, localGroup.getId());
+			will(returnValue(singletonList(oldLocalVersionsId)));
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalVersionsId);
+			will(returnValue(oldLocalVersionsBody));
+			// Delete the old client versions
+			oneOf(db).removeMessage(txn, oldLocalVersionsId);
+			// Store the new client versions
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(localGroup.getId(), now,
+					newLocalVersionsBody);
+			will(returnValue(newLocalVersions));
+			oneOf(db).addLocalMessage(txn, newLocalVersions, new Metadata(),
+					false);
+			// Inform contacts that client versions have changed
+			oneOf(db).getContacts(txn);
+			will(returnValue(singletonList(contact)));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			// Find the latest local and remote updates
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			will(returnValue(oldLocalUpdateBody));
+			// Load the latest remote update
+			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			will(returnValue(oldRemoteUpdateBody));
+			// Delete the latest local update
+			oneOf(db).deleteMessage(txn, oldLocalUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldLocalUpdateId);
+			// Store the new local update
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(contactGroup.getId(), now,
+					newLocalUpdateBody);
+			will(returnValue(newLocalUpdate));
+			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
+					newLocalUpdateMeta, true);
+			// The client's visibility has changed
+			oneOf(hook).onClientVisibilityChanging(txn, contact, visibility);
+			oneOf(db).commitTransaction(txn);
+			oneOf(db).endTransaction(txn);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		c.startService();
+	}
+
+	@Test
+	public void testDeletesObsoleteRemoteUpdate() throws Exception {
+		Message newRemoteUpdate = getMessage(contactGroup.getId());
+		BdfList newRemoteUpdateBody = BdfList.of(new BdfList(), 1L);
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId oldRemoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldRemoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(oldLocalUpdateId, oldLocalUpdateMeta);
+		messageMetadata.put(oldRemoteUpdateId, oldRemoteUpdateMeta);
+
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).toList(newRemoteUpdate);
+			will(returnValue(newRemoteUpdateBody));
+			// Find the latest local and remote updates
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			// Delete the new remote update, which is obsolete
+			oneOf(db).deleteMessage(txn, newRemoteUpdate.getId());
+			oneOf(db).deleteMessageMetadata(txn, newRemoteUpdate.getId());
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		assertFalse(c.incomingMessage(txn, newRemoteUpdate, new Metadata()));
+	}
+
+	@Test
+	public void testDeletesPreviousRemoteUpdate() throws Exception {
+		Message newRemoteUpdate = getMessage(contactGroup.getId());
+		BdfList newRemoteUpdateBody = BdfList.of(new BdfList(), 2L);
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId oldRemoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldRemoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(oldLocalUpdateId, oldLocalUpdateMeta);
+		messageMetadata.put(oldRemoteUpdateId, oldRemoteUpdateMeta);
+		BdfList oldLocalUpdateBody = BdfList.of(new BdfList(), 1L);
+		BdfList oldRemoteUpdateBody = BdfList.of(new BdfList(), 1L);
+
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).toList(newRemoteUpdate);
+			will(returnValue(newRemoteUpdateBody));
+			// Find the latest local and remote updates
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			will(returnValue(oldLocalUpdateBody));
+			// Load the latest remote update
+			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			will(returnValue(oldRemoteUpdateBody));
+			// Delete the old remote update
+			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldRemoteUpdateId);
+			// No states or visibilities have changed
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		assertFalse(c.incomingMessage(txn, newRemoteUpdate, new Metadata()));
+	}
+
+	@Test
+	public void testAcceptsFirstRemoteUpdate() throws Exception {
+		Message newRemoteUpdate = getMessage(contactGroup.getId());
+		BdfList newRemoteUpdateBody = BdfList.of(new BdfList(), 1L);
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		BdfList oldLocalUpdateBody = BdfList.of(new BdfList(), 1L);
+
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).toList(newRemoteUpdate);
+			will(returnValue(newRemoteUpdateBody));
+			// Find the latest local and remote updates (no remote update)
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(singletonMap(oldLocalUpdateId,
+					oldLocalUpdateMeta)));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			will(returnValue(oldLocalUpdateBody));
+			// No states or visibilities have changed
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		assertFalse(c.incomingMessage(txn, newRemoteUpdate, new Metadata()));
+	}
+
+	@Test
+	public void testActivatesClientOnIncomingMessageWhenAdvertisedByContact()
+			throws Exception {
+		testActivatesClientOnIncomingMessage(false, VISIBLE);
+	}
+
+	@Test
+	public void testActivatesClientOnIncomingMessageWhenActivatedByContact()
+			throws Exception {
+		testActivatesClientOnIncomingMessage(true, SHARED);
+	}
+
+	private void testActivatesClientOnIncomingMessage(boolean remoteActive,
+			Visibility visibility) throws Exception {
+		// The client was missing from the old remote update
+		BdfList oldRemoteUpdateBody = BdfList.of(new BdfList(), 1L);
+		// The client was inactive in the old local update
+		BdfList oldLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+		// The client is included in the new remote update
+		BdfList newRemoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, remoteActive)), 2L);
+		// The client is active in the new local update
+		BdfList newLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 2L);
+
+		Message newRemoteUpdate = getMessage(contactGroup.getId());
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId oldRemoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldRemoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(oldLocalUpdateId, oldLocalUpdateMeta);
+		messageMetadata.put(oldRemoteUpdateId, oldRemoteUpdateMeta);
+		Message newLocalUpdate = getMessage(contactGroup.getId());
+		BdfDictionary newLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		BdfDictionary groupMeta = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_CONTACT_ID, contact.getId().getInt()));
+
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).toList(newRemoteUpdate);
+			will(returnValue(newRemoteUpdateBody));
+			// Find the latest local and remote updates
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			will(returnValue(oldLocalUpdateBody));
+			// Load the latest remote update
+			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			will(returnValue(oldRemoteUpdateBody));
+			// Delete the old remote update
+			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldRemoteUpdateId);
+			// Delete the old local update
+			oneOf(db).deleteMessage(txn, oldLocalUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldLocalUpdateId);
+			// Store the new local update
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(contactGroup.getId(), now,
+					newLocalUpdateBody);
+			will(returnValue(newLocalUpdate));
+			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
+					newLocalUpdateMeta, true);
+			// The client's visibility has changed
+			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(groupMeta));
+			oneOf(db).getContact(txn, contact.getId());
+			will(returnValue(contact));
+			oneOf(hook).onClientVisibilityChanging(txn, contact, visibility);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		assertFalse(c.incomingMessage(txn, newRemoteUpdate, new Metadata()));
+	}
+
+	@Test
+	public void testDeactivatesClientOnIncomingMessage() throws Exception {
+		// The client was active in the old local and remote updates
+		BdfList oldLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 1L);
+		BdfList oldRemoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 1L);
+		// The client is missing from the new remote update
+		BdfList newRemoteUpdateBody = BdfList.of(new BdfList(), 2L);
+		// The client is inactive in the new local update
+		BdfList newLocalUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 2L);
+
+		Message newRemoteUpdate = getMessage(contactGroup.getId());
+		MessageId oldLocalUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId oldRemoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary oldRemoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(oldLocalUpdateId, oldLocalUpdateMeta);
+		messageMetadata.put(oldRemoteUpdateId, oldRemoteUpdateMeta);
+		Message newLocalUpdate = getMessage(contactGroup.getId());
+		BdfDictionary newLocalUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		BdfDictionary groupMeta = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_CONTACT_ID, contact.getId().getInt()));
+
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).toList(newRemoteUpdate);
+			will(returnValue(newRemoteUpdateBody));
+			// Find the latest local and remote updates
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			// Load the latest local update
+			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
+			will(returnValue(oldLocalUpdateBody));
+			// Load the latest remote update
+			oneOf(clientHelper).getMessageAsList(txn, oldRemoteUpdateId);
+			will(returnValue(oldRemoteUpdateBody));
+			// Delete the old remote update
+			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldRemoteUpdateId);
+			// Delete the old local update
+			oneOf(db).deleteMessage(txn, oldLocalUpdateId);
+			oneOf(db).deleteMessageMetadata(txn, oldLocalUpdateId);
+			// Store the new local update
+			oneOf(clock).currentTimeMillis();
+			will(returnValue(now));
+			oneOf(clientHelper).createMessage(contactGroup.getId(), now,
+					newLocalUpdateBody);
+			will(returnValue(newLocalUpdate));
+			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
+					newLocalUpdateMeta, true);
+			// The client's visibility has changed
+			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(groupMeta));
+			oneOf(db).getContact(txn, contact.getId());
+			will(returnValue(contact));
+			oneOf(hook).onClientVisibilityChanging(txn, contact, INVISIBLE);
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.registerClient(clientId, 123, 234, hook);
+		assertFalse(c.incomingMessage(txn, newRemoteUpdate, new Metadata()));
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/versioning/ClientVersioningValidatorTest.java

@@ -0,0 +1,274 @@
+package org.briarproject.bramble.versioning;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.client.BdfMessageContext;
+import org.briarproject.bramble.api.client.ClientHelper;
+import org.briarproject.bramble.api.data.BdfDictionary;
+import org.briarproject.bramble.api.data.BdfEntry;
+import org.briarproject.bramble.api.data.BdfList;
+import org.briarproject.bramble.api.data.MetadataEncoder;
+import org.briarproject.bramble.api.sync.ClientId;
+import org.briarproject.bramble.api.sync.Group;
+import org.briarproject.bramble.api.sync.Message;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.junit.Test;
+
+import static java.util.Collections.emptyList;
+import static org.briarproject.bramble.api.sync.ClientId.MAX_CLIENT_ID_LENGTH;
+import static org.briarproject.bramble.api.versioning.ClientVersioningManager.CLIENT_ID;
+import static org.briarproject.bramble.api.versioning.ClientVersioningManager.MAJOR_VERSION;
+import static org.briarproject.bramble.test.TestUtils.getClientId;
+import static org.briarproject.bramble.test.TestUtils.getGroup;
+import static org.briarproject.bramble.test.TestUtils.getMessage;
+import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.util.StringUtils.getRandomString;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
+import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
+import static org.junit.Assert.assertEquals;
+
+public class ClientVersioningValidatorTest extends BrambleMockTestCase {
+
+	private final ClientHelper clientHelper = context.mock(ClientHelper.class);
+	private final MetadataEncoder metadataEncoder =
+			context.mock(MetadataEncoder.class);
+	private final Clock clock = context.mock(Clock.class);
+	private final ClientVersioningValidator validator =
+			new ClientVersioningValidator(clientHelper, metadataEncoder, clock);
+
+	private final Group group = getGroup(CLIENT_ID, MAJOR_VERSION);
+	private final Message message = getMessage(group.getId());
+	private final ClientId clientId = getClientId();
+
+	@Test(expected = FormatException.class)
+	public void testRejectsTooShortBody() throws Exception {
+		BdfList body = BdfList.of(new BdfList());
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsTooLongBody() throws Exception {
+		BdfList body = BdfList.of(new BdfList(), 123, null);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNullStatesList() throws Exception {
+		BdfList body = BdfList.of(null, 123);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNonListStatesList() throws Exception {
+		BdfList body = BdfList.of("", 123);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsEmptyStatesList() throws Exception {
+		BdfList body = BdfList.of(new BdfList(), 123);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 123L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNullUpdateVersion() throws Exception {
+		BdfList body = BdfList.of(new BdfList(), null);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNonLongUpdateVersion() throws Exception {
+		BdfList body = BdfList.of(new BdfList(), "123");
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNegativeUpdateVersion() throws Exception {
+		BdfList body = BdfList.of(new BdfList(), -1);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsZeroUpdateVersion() throws Exception {
+		BdfList body = BdfList.of(new BdfList(), 0);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 0L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsTooShortClientState() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, 234);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsTooLongClientState() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, 234, true, null);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNullClientId() throws Exception {
+		BdfList state = BdfList.of(null, 123, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNonStringClientId() throws Exception {
+		byte[] id = getRandomBytes(MAX_CLIENT_ID_LENGTH);
+		BdfList state = BdfList.of(id, 123, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsTooShortClientId() throws Exception {
+		BdfList state = BdfList.of("", 123, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsMinLengthClientId() throws Exception {
+		BdfList state = BdfList.of(getRandomString(1), 123, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 345L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsTooLongClientId() throws Exception {
+		String id = getRandomString(MAX_CLIENT_ID_LENGTH + 1);
+		BdfList state = BdfList.of(id, 123, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsMaxLengthClientId() throws Exception {
+		String id = getRandomString(MAX_CLIENT_ID_LENGTH);
+		BdfList state = BdfList.of(id, 123, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 345L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNullMajorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), null, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNonLongMajorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), "123", 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNegativeMajorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), -1, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsZeroMajorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 0, 234, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 345L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNullMinorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, null, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNonLongMinorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, "234", true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNegativeMinorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, -1, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsZeroMinorVersion() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, 0, true);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 345L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNullActiveFlag() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, 234, null);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test(expected = FormatException.class)
+	public void testRejectsNonBooleanActiveFlag() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, 234, "true");
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		validator.validateMessage(message, group, body);
+	}
+
+	@Test
+	public void testAcceptsNegativeActiveFlag() throws Exception {
+		BdfList state = BdfList.of(clientId.getString(), 123, 234, false);
+		BdfList body = BdfList.of(BdfList.of(state), 345);
+		BdfMessageContext context =
+				validator.validateMessage(message, group, body);
+		assertEquals(emptyList(), context.getDependencies());
+		BdfDictionary expectedMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 345L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		assertEquals(expectedMeta, context.getDictionary());
+	}
+}

bramble-j2se/build.gradle

@@ -27,22 +27,17 @@ dependencies {
 dependencyVerification {
 	verify = [
 			'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
 			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
 			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
 			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
 			'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
-			'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
 			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
 			'junit:junit:4.12:junit-4.12.jar:59721f0805e223d84b90677887d9ff567dc534d7c502ca903c0c2b17f05c116a',
-			'net.i2p.crypto:eddsa:0.2.0:eddsa-0.2.0.jar:a7cb1b85c16e2f0730b9204106929a1d9aaae1df728adc7041a8b8b605692140',
 			'net.java.dev.jna:jna-platform:4.4.0:jna-platform-4.4.0.jar:e9dda9e884fc107eb6367710540789a12dfa8ad28be9326b22ca6e352e325499',
 			'net.java.dev.jna:jna:4.4.0:jna-4.4.0.jar:c4dadeeecaa90c8847902082aee5eb107fcf59c5d0e63a17fcaf273c0e2d2bd1',
 			'org.apache.ant:ant-launcher:1.9.4:ant-launcher-1.9.4.jar:7bccea20b41801ca17bcbc909a78c835d0f443f12d639c77bd6ae3d05861608d',
 			'org.apache.ant:ant:1.9.4:ant-1.9.4.jar:649ae0730251de07b8913f49286d46bba7b92d47c5f332610aa426c4f02161d8',
 			'org.beanshell:bsh:1.3.0:bsh-1.3.0.jar:9b04edc75d19db54f1b4e8b5355e9364384c6cf71eb0a1b9724c159d779879f8',
-			'org.bitlet:weupnp:0.1.4:weupnp-0.1.4.jar:88df7e6504929d00bdb832863761385c68ab92af945b04f0770b126270a444fb',
 			'org.hamcrest:hamcrest-core:1.3:hamcrest-core-1.3.jar:66fdef91e9739348df7a096aa384a5685f4e875584cce89386a7a47251c4d8e9',
 			'org.hamcrest:hamcrest-library:1.3:hamcrest-library-1.3.jar:711d64522f9ec410983bd310934296da134be4254a125080a0416ec178dfad1c',
 			'org.jmock:jmock-junit4:2.8.2:jmock-junit4-2.8.2.jar:f7ee4df4f7bd7b7f1cafad3b99eb74d579f109d5992ff625347352edb55e674c',

bramble-j2se/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPlugin.java

@@ -31,9 +31,11 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	// Non-null if the plugin started successfully
 	private volatile LocalDevice localDevice = null;
 
-	JavaBluetoothPlugin(Executor ioExecutor, SecureRandom secureRandom,
+	JavaBluetoothPlugin(BluetoothConnectionLimiter connectionManager,
+			Executor ioExecutor, SecureRandom secureRandom,
 			Backoff backoff, DuplexPluginCallback callback, int maxLatency) {
-		super(ioExecutor, secureRandom, backoff, callback, maxLatency);
+		super(connectionManager, ioExecutor, secureRandom, backoff, callback,
+				maxLatency);
 	}
 
 	@Override
@@ -110,6 +112,6 @@ class JavaBluetoothPlugin extends BluetoothPlugin<StreamConnectionNotifier> {
 	}
 
 	private DuplexTransportConnection wrapSocket(StreamConnection s) {
-		return new JavaBluetoothTransportConnection(this, s);
+		return new JavaBluetoothTransportConnection(this, connectionLimiter, s);
 	}
 }

bramble-j2se/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothPluginFactory.java

@@ -51,10 +51,12 @@ public class JavaBluetoothPluginFactory implements DuplexPluginFactory {
 
 	@Override
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
+		BluetoothConnectionLimiter connectionLimiter =
+				new BluetoothConnectionLimiterImpl();
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		JavaBluetoothPlugin plugin = new JavaBluetoothPlugin(ioExecutor,
+		JavaBluetoothPlugin plugin = new JavaBluetoothPlugin(connectionLimiter,
-				secureRandom, backoff, callback, MAX_LATENCY);
+				ioExecutor, secureRandom, backoff, callback, MAX_LATENCY);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

bramble-j2se/src/main/java/org/briarproject/bramble/plugin/bluetooth/JavaBluetoothTransportConnection.java

@@ -14,11 +14,15 @@ import javax.microedition.io.StreamConnection;
 class JavaBluetoothTransportConnection
 		extends AbstractDuplexTransportConnection {
 
+	private final BluetoothConnectionLimiter connectionManager;
 	private final StreamConnection stream;
 
-	JavaBluetoothTransportConnection(Plugin plugin, StreamConnection stream) {
+	JavaBluetoothTransportConnection(Plugin plugin,
+			BluetoothConnectionLimiter connectionManager,
+			StreamConnection stream) {
 		super(plugin);
 		this.stream = stream;
+		this.connectionManager = connectionManager;
 	}
 
 	@Override
@@ -33,6 +37,10 @@ class JavaBluetoothTransportConnection
 
 	@Override
 	protected void closeConnection(boolean exception) throws IOException {
-		stream.close();
+		try {
+			stream.close();
+		} finally {
+			connectionManager.connectionClosed(this);
+		}
 	}
 }