Bump version numbers for 1.0.3 release.

Clear the UI when memory is critically low

See merge request akwizgran/briar!786

.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

@@ -1,19 +1,21 @@
 import de.undercouch.gradle.tasks.download.Download
 import de.undercouch.gradle.tasks.download.Verify
 
+import java.security.NoSuchAlgorithmException
+
 apply plugin: 'com.android.library'
 apply plugin: 'witness'
 apply plugin: 'de.undercouch.download'
 
 android {
 	compileSdkVersion 27
-	buildToolsVersion '26.0.2'
+	buildToolsVersion '27.0.3'
 
 	defaultConfig {
 		minSdkVersion 14
 		targetSdkVersion 26
-		versionCode 1700
+		versionCode 10003
-		versionName "0.17.0"
+		versionName "1.0.3"
 		consumerProguardFiles 'proguard-rules.txt'
 	}
 
@@ -34,23 +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',
 	]
 }
 
@@ -67,30 +125,68 @@ def torBinaries = [
 		"geoip"      : '8239b98374493529a29096e45fc5877d4d6fdad0146ad8380b291f90d61484ea'
 ]
 
-def downloadBinary(name) {
+def verifyOrDeleteBinary(name, chksum, alreadyVerified) {
-	return tasks.create("downloadBinary${name}", Download) {
+	return tasks.create("verifyOrDeleteBinary${name}", VerifyOrDelete) {
+		src "${torBinaryDir}/${name}.zip"
+		algorithm 'SHA-256'
+		checksum chksum
+		result alreadyVerified
+		onlyIf {
+			src.exists()
+		}
+	}
+}
+
+def downloadBinary(name, chksum, alreadyVerified) {
+	return tasks.create([
+			name: "downloadBinary${name}",
+			type: Download,
+			dependsOn: verifyOrDeleteBinary(name, chksum, alreadyVerified)]) {
 		src "${torDownloadUrl}${name}.zip"
 				.replace('tor_', "tor-${torVersion}-")
 				.replace('geoip', "geoip-${geoipVersion}")
 				.replaceAll('_', '-')
 		dest "${torBinaryDir}/${name}.zip"
-		onlyIfNewer true
+		onlyIf {
+			!dest.exists()
+		}
 	}
 }
 
 def verifyBinary(name, chksum) {
+	boolean[] alreadyVerified = [false]
 	return tasks.create([
 			name     : "verifyBinary${name}",
 			type     : Verify,
-			dependsOn: downloadBinary(name)]) {
+			dependsOn: downloadBinary(name, chksum, alreadyVerified)]) {
 		src "${torBinaryDir}/${name}.zip"
 		algorithm 'SHA-256'
 		checksum chksum
+		onlyIf {
+			!alreadyVerified[0]
+		}
 	}
 }
 
 project.afterEvaluate {
-	torBinaries.every { key, value ->
+	torBinaries.every { name, checksum ->
-		preBuild.dependsOn.add(verifyBinary(key, value))
+		preBuild.dependsOn.add(verifyBinary(name, checksum))
+	}
+}
+
+class VerifyOrDelete extends Verify {
+
+	boolean[] result
+
+	@TaskAction
+	@Override
+	void verify() throws IOException, NoSuchAlgorithmException {
+		try {
+			super.verify()
+			result[0] = true
+		} catch (Exception e) {
+			println "${src} failed verification - deleting"
+			src.delete()
+		}
 	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/AndroidPluginModule.java

@@ -48,7 +48,7 @@ public class AndroidPluginModule {
 				appContext, locationUtils, reporter, eventBus,
 				torSocketFactory, backoffFactory);
 		DuplexPluginFactory lan = new AndroidLanTcpPluginFactory(ioExecutor,
-				backoffFactory, appContext);
+				scheduler, backoffFactory, appContext);
 		Collection<DuplexPluginFactory> duplex =
 				Arrays.asList(bluetooth, tor, lan);
 		@NotNullByDefault

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-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPlugin.java

@@ -5,37 +5,84 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.net.ConnectivityManager;
+import android.net.Network;
 import android.net.NetworkInfo;
+import android.net.wifi.WifiInfo;
+import android.net.wifi.WifiManager;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.Socket;
+import java.net.UnknownHostException;
+import java.util.Collection;
 import java.util.concurrent.Executor;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
+import javax.net.SocketFactory;
 
 import static android.content.Context.CONNECTIVITY_SERVICE;
+import static android.content.Context.WIFI_SERVICE;
 import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
 import static android.net.ConnectivityManager.TYPE_WIFI;
+import static android.net.wifi.WifiManager.EXTRA_WIFI_STATE;
+import static android.os.Build.VERSION.SDK_INT;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.singletonList;
+import static java.util.concurrent.TimeUnit.SECONDS;
 
 @NotNullByDefault
 class AndroidLanTcpPlugin extends LanTcpPlugin {
 
+	// See android.net.wifi.WifiManager
+	private static final String WIFI_AP_STATE_CHANGED_ACTION =
+			"android.net.wifi.WIFI_AP_STATE_CHANGED";
+	private static final int WIFI_AP_STATE_ENABLED = 13;
+
+	private static final byte[] WIFI_AP_ADDRESS_BYTES =
+			{(byte) 192, (byte) 168, 43, 1};
+	private static final InetAddress WIFI_AP_ADDRESS;
+
 	private static final Logger LOG =
 			Logger.getLogger(AndroidLanTcpPlugin.class.getName());
 
+	static {
+		try {
+			WIFI_AP_ADDRESS = InetAddress.getByAddress(WIFI_AP_ADDRESS_BYTES);
+		} catch (UnknownHostException e) {
+			// Should only be thrown if the address has an illegal length
+			throw new AssertionError(e);
+		}
+	}
+
+	private final ScheduledExecutorService scheduler;
 	private final Context appContext;
+	private final ConnectivityManager connectivityManager;
+	@Nullable
+	private final WifiManager wifiManager;
 
 	@Nullable
 	private volatile BroadcastReceiver networkStateReceiver = null;
+	private volatile SocketFactory socketFactory;
 
-	AndroidLanTcpPlugin(Executor ioExecutor, Backoff backoff,
+	AndroidLanTcpPlugin(Executor ioExecutor, ScheduledExecutorService scheduler,
-			Context appContext, DuplexPluginCallback callback, int maxLatency,
+			Backoff backoff, Context appContext, DuplexPluginCallback callback,
-			int maxIdleTime) {
+			int maxLatency, int maxIdleTime) {
 		super(ioExecutor, backoff, callback, maxLatency, maxIdleTime);
+		this.scheduler = scheduler;
 		this.appContext = appContext;
+		ConnectivityManager connectivityManager = (ConnectivityManager)
+				appContext.getSystemService(CONNECTIVITY_SERVICE);
+		if (connectivityManager == null) throw new AssertionError();
+		this.connectivityManager = connectivityManager;
+		wifiManager = (WifiManager) appContext.getApplicationContext()
+				.getSystemService(WIFI_SERVICE);
+		socketFactory = SocketFactory.getDefault();
 	}
 
 	@Override
@@ -44,7 +91,9 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		running = true;
 		// Register to receive network status events
 		networkStateReceiver = new NetworkStateReceiver();
-		IntentFilter filter = new IntentFilter(CONNECTIVITY_ACTION);
+		IntentFilter filter = new IntentFilter();
+		filter.addAction(CONNECTIVITY_ACTION);
+		filter.addAction(WIFI_AP_STATE_CHANGED_ACTION);
 		appContext.registerReceiver(networkStateReceiver, filter);
 	}
 
@@ -56,21 +105,92 @@ class AndroidLanTcpPlugin extends LanTcpPlugin {
 		tryToClose(socket);
 	}
 
+	@Override
+	protected Socket createSocket() throws IOException {
+		return socketFactory.createSocket();
+	}
+
+	@Override
+	protected Collection<InetAddress> getLocalIpAddresses() {
+		// If the device doesn't have wifi, don't open any sockets
+		if (wifiManager == null) return emptyList();
+		// If we're connected to a wifi network, use that network
+		WifiInfo info = wifiManager.getConnectionInfo();
+		if (info != null && info.getIpAddress() != 0)
+			return singletonList(intToInetAddress(info.getIpAddress()));
+		// If we're running an access point, return its address
+		if (super.getLocalIpAddresses().contains(WIFI_AP_ADDRESS))
+				return singletonList(WIFI_AP_ADDRESS);
+		// No suitable addresses
+		return emptyList();
+	}
+
+	private InetAddress intToInetAddress(int ip) {
+		byte[] ipBytes = new byte[4];
+		ipBytes[0] = (byte) (ip & 0xFF);
+		ipBytes[1] = (byte) ((ip >> 8) & 0xFF);
+		ipBytes[2] = (byte) ((ip >> 16) & 0xFF);
+		ipBytes[3] = (byte) ((ip >> 24) & 0xFF);
+		try {
+			return InetAddress.getByAddress(ipBytes);
+		} catch (UnknownHostException e) {
+			// Should only be thrown if address has illegal length
+			throw new AssertionError(e);
+		}
+	}
+
+	// On API 21 and later, a socket that is not created with the wifi
+	// network's socket factory may try to connect via another network
+	private SocketFactory getSocketFactory() {
+		if (SDK_INT < 21) return SocketFactory.getDefault();
+		for (Network net : connectivityManager.getAllNetworks()) {
+			NetworkInfo info = connectivityManager.getNetworkInfo(net);
+			if (info != null && info.getType() == TYPE_WIFI)
+				return net.getSocketFactory();
+		}
+		LOG.warning("Could not find suitable socket factory");
+		return SocketFactory.getDefault();
+	}
+
 	private class NetworkStateReceiver extends BroadcastReceiver {
 
 		@Override
 		public void onReceive(Context ctx, Intent i) {
 			if (!running) return;
-			Object o = ctx.getSystemService(CONNECTIVITY_SERVICE);
+			if (isApEnabledEvent(i)) {
-			ConnectivityManager cm = (ConnectivityManager) o;
+				// The state change may be broadcast before the AP address is
-			NetworkInfo net = cm.getActiveNetworkInfo();
+				// visible, so delay handling the event
-			if (net != null && net.getType() == TYPE_WIFI && net.isConnected()) {
+				scheduler.schedule(this::handleConnectivityChange, 1, SECONDS);
-				LOG.info("Connected to Wi-Fi");
-				if (socket == null || socket.isClosed()) bind();
 			} else {
-				LOG.info("Not connected to Wi-Fi");
+				handleConnectivityChange();
-				tryToClose(socket);
 			}
 		}
+
+		private void handleConnectivityChange() {
+			if (!running) return;
+			Collection<InetAddress> addrs = getLocalIpAddresses();
+			if (addrs.contains(WIFI_AP_ADDRESS)) {
+				LOG.info("Providing wifi hotspot");
+				// There's no corresponding Network object and thus no way
+				// to get a suitable socket factory, so we won't be able to
+				// make outgoing connections on API 21+ if another network
+				// has internet access
+				socketFactory = SocketFactory.getDefault();
+				if (socket == null || socket.isClosed()) bind();
+			} else if (addrs.isEmpty()) {
+				LOG.info("Not connected to wifi");
+				socketFactory = SocketFactory.getDefault();
+				tryToClose(socket);
+			} else {
+				LOG.info("Connected to wifi");
+				socketFactory = getSocketFactory();
+				if (socket == null || socket.isClosed()) bind();
+			}
+		}
+
+		private boolean isApEnabledEvent(Intent i) {
+			return WIFI_AP_STATE_CHANGED_ACTION.equals(i.getAction()) &&
+					i.getIntExtra(EXTRA_WIFI_STATE, 0) == WIFI_AP_STATE_ENABLED;
+		}
 	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/tcp/AndroidLanTcpPluginFactory.java

@@ -11,6 +11,7 @@ import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginFactory;
 
 import java.util.concurrent.Executor;
+import java.util.concurrent.ScheduledExecutorService;
 
 import javax.annotation.concurrent.Immutable;
 
@@ -27,12 +28,15 @@ public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
+	private final ScheduledExecutorService scheduler;
 	private final BackoffFactory backoffFactory;
 	private final Context appContext;
 
 	public AndroidLanTcpPluginFactory(Executor ioExecutor,
-			BackoffFactory backoffFactory, Context appContext) {
+			ScheduledExecutorService scheduler, BackoffFactory backoffFactory,
+			Context appContext) {
 		this.ioExecutor = ioExecutor;
+		this.scheduler = scheduler;
 		this.backoffFactory = backoffFactory;
 		this.appContext = appContext;
 	}
@@ -51,7 +55,7 @@ public class AndroidLanTcpPluginFactory implements DuplexPluginFactory {
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		return new AndroidLanTcpPlugin(ioExecutor, backoff, appContext,
+		return new AndroidLanTcpPlugin(ioExecutor, scheduler, backoff,
-				callback, MAX_LATENCY, MAX_IDLE_TIME);
+				appContext, callback, MAX_LATENCY, MAX_IDLE_TIME);
 	}
 }

bramble-android/src/main/java/org/briarproject/bramble/plugin/tor/TorPlugin.java

@@ -16,6 +16,7 @@ import android.os.PowerManager;
 import net.freehaven.tor.control.EventHandler;
 import net.freehaven.tor.control.TorControlConnection;
 
+import org.briarproject.bramble.PoliteExecutor;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
@@ -63,8 +64,6 @@ import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
-import java.util.concurrent.locks.Lock;
-import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
 import java.util.regex.Pattern;
 import java.util.zip.ZipInputStream;
@@ -111,7 +110,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private static final Logger LOG =
 			Logger.getLogger(TorPlugin.class.getName());
 
-	private final Executor ioExecutor;
+	private final Executor ioExecutor, connectionStatusExecutor;
 	private final ScheduledExecutorService scheduler;
 	private final Context appContext;
 	private final LocationUtils locationUtils;
@@ -125,7 +124,6 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private final File torDirectory, torFile, geoIpFile, configFile;
 	private final File doneFile, cookieFile;
 	private final PowerManager.WakeLock wakeLock;
-	private final Lock connectionStatusLock;
 	private final AtomicReference<Future<?>> connectivityCheck =
 			new AtomicReference<>();
 	private final AtomicBoolean used = new AtomicBoolean(false);
@@ -167,7 +165,9 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		// This tag will prevent Huawei's powermanager from killing us.
 		wakeLock = pm.newWakeLock(PARTIAL_WAKE_LOCK, "LocationManagerService");
 		wakeLock.setReferenceCounted(false);
-		connectionStatusLock = new ReentrantLock();
+		// Don't execute more than one connection status check at a time
+		connectionStatusExecutor = new PoliteExecutor("TorPlugin",
+				ioExecutor, 1);
 	}
 
 	@Override
@@ -697,56 +697,46 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void updateConnectionStatus() {
-		ioExecutor.execute(() -> {
+		connectionStatusExecutor.execute(() -> {
 			if (!running) return;
+			Object o = appContext.getSystemService(CONNECTIVITY_SERVICE);
+			ConnectivityManager cm = (ConnectivityManager) o;
+			NetworkInfo net = cm.getActiveNetworkInfo();
+			boolean online = net != null && net.isConnected();
+			boolean wifi = online && net.getType() == TYPE_WIFI;
+			String country = locationUtils.getCurrentCountry();
+			boolean blocked = TorNetworkMetadata.isTorProbablyBlocked(
+					country);
+			Settings s = callback.getSettings();
+			int network = s.getInt(PREF_TOR_NETWORK, PREF_TOR_NETWORK_ALWAYS);
+
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Online: " + online + ", wifi: " + wifi);
+				if ("".equals(country)) LOG.info("Country code unknown");
+				else LOG.info("Country code: " + country);
+			}
+
 			try {
-				connectionStatusLock.lock();
+				if (!online) {
-				updateConnectionStatusLocked();
+					LOG.info("Disabling network, device is offline");
-			} finally {
+					enableNetwork(false);
-				connectionStatusLock.unlock();
+				} else if (blocked) {
+					LOG.info("Disabling network, country is blocked");
+					enableNetwork(false);
+				} else if (network == PREF_TOR_NETWORK_NEVER
+						|| (network == PREF_TOR_NETWORK_WIFI && !wifi)) {
+					LOG.info("Disabling network due to data setting");
+					enableNetwork(false);
+				} else {
+					LOG.info("Enabling network");
+					enableNetwork(true);
+				}
+			} catch (IOException e) {
+				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			}
 		});
 	}
 
-	// Locking: connectionStatusLock
-	private void updateConnectionStatusLocked() {
-		Object o = appContext.getSystemService(CONNECTIVITY_SERVICE);
-		ConnectivityManager cm = (ConnectivityManager) o;
-		NetworkInfo net = cm.getActiveNetworkInfo();
-		boolean online = net != null && net.isConnected();
-		boolean wifi = online && net.getType() == TYPE_WIFI;
-		String country = locationUtils.getCurrentCountry();
-		boolean blocked = TorNetworkMetadata.isTorProbablyBlocked(
-				country);
-		Settings s = callback.getSettings();
-		int network = s.getInt(PREF_TOR_NETWORK, PREF_TOR_NETWORK_ALWAYS);
-
-		if (LOG.isLoggable(INFO)) {
-			LOG.info("Online: " + online + ", wifi: " + wifi);
-			if ("".equals(country)) LOG.info("Country code unknown");
-			else LOG.info("Country code: " + country);
-		}
-
-		try {
-			if (!online) {
-				LOG.info("Disabling network, device is offline");
-				enableNetwork(false);
-			} else if (blocked) {
-				LOG.info("Disabling network, country is blocked");
-				enableNetwork(false);
-			} else if (network == PREF_TOR_NETWORK_NEVER
-					|| (network == PREF_TOR_NETWORK_WIFI && !wifi)) {
-				LOG.info("Disabling network due to data setting");
-				enableNetwork(false);
-			} else {
-				LOG.info("Enabling network");
-				enableNetwork(true);
-			}
-		} catch (IOException e) {
-			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-		}
-	}
-
 	private void scheduleConnectionStatusUpdate() {
 		Future<?> newConnectivityCheck =
 				scheduler.schedule(this::updateConnectionStatus, 1, MINUTES);
@@ -788,7 +778,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 		private synchronized void enableNetwork(boolean enable) {
 			networkEnabled = enable;
-			circuitBuilt = false;
+			if (!enable) circuitBuilt = false;
 		}
 
 		private synchronized boolean isConnected() {

bramble-android/src/main/java/org/briarproject/bramble/util/AndroidUtils.java

@@ -1,20 +1,29 @@
 package org.briarproject.bramble.util;
 
+import android.annotation.SuppressLint;
 import android.bluetooth.BluetoothAdapter;
 import android.content.Context;
+import android.content.SharedPreferences;
 import android.os.Build;
 import android.provider.Settings;
 
 import java.io.File;
+import java.io.FileNotFoundException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.Scanner;
+import java.util.logging.Logger;
 
 import static android.content.Context.MODE_PRIVATE;
+import static java.util.logging.Level.INFO;
 
 public class AndroidUtils {
 
+	private static final Logger LOG =
+			Logger.getLogger(AndroidUtils.class.getName());
+
 	// Fake Bluetooth address returned by BluetoothAdapter on API 23 and later
 	private static final String FAKE_BLUETOOTH_ADDRESS = "02:00:00:00:00:00";
 
@@ -35,6 +44,7 @@ public class AndroidUtils {
 	public static String getBluetoothAddress(Context ctx,
 			BluetoothAdapter adapter) {
 		// Return the adapter's address if it's valid and not fake
+		@SuppressLint("HardwareIds")
 		String address = adapter.getAddress();
 		if (isValidBluetoothAddress(address)) return address;
 		// Return the address from settings if it's valid and not fake
@@ -51,17 +61,77 @@ public class AndroidUtils {
 				&& !address.equals(FAKE_BLUETOOTH_ADDRESS);
 	}
 
-	public static void deleteAppData(Context ctx) {
+	public static void logDataDirContents(Context ctx) {
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Contents of data directory:");
+			logFileOrDir(new File(ctx.getApplicationInfo().dataDir));
+		}
+	}
+
+	private static void logFileOrDir(File f) {
+		LOG.info(f.getAbsolutePath() + " " + f.length());
+		if (f.isDirectory()) {
+			File[] children = f.listFiles();
+			if (children == null) {
+				LOG.info("Could not list files in " + f.getAbsolutePath());
+			} else {
+				for (File child : children) logFileOrDir(child);
+			}
+		}
+	}
+
+	public static File getSharedPrefsFile(Context ctx, String name) {
 		File dataDir = new File(ctx.getApplicationInfo().dataDir);
+		File prefsDir = new File(dataDir, "shared_prefs");
+		return new File(prefsDir, name + ".xml");
+	}
+
+	public static void logFileContents(File f) {
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Contents of " + f.getAbsolutePath() + ":");
+			try {
+				Scanner s = new Scanner(f);
+				while (s.hasNextLine()) LOG.info(s.nextLine());
+				s.close();
+			} catch (FileNotFoundException e) {
+				LOG.info(f.getAbsolutePath() + " not found");
+			}
+		}
+	}
+
+	@SuppressLint("ApplySharedPref")
+	public static void deleteAppData(Context ctx, SharedPreferences... clear) {
+		// Clear and commit shared preferences
+		for (SharedPreferences prefs : clear) {
+			boolean cleared = prefs.edit().clear().commit();
+			if (LOG.isLoggable(INFO)) {
+				if (cleared) LOG.info("Cleared shared preferences");
+				else LOG.info("Could not clear shared preferences");
+			}
+		}
+		// Delete files, except lib and shared_prefs directories
+		File dataDir = new File(ctx.getApplicationInfo().dataDir);
+		if (LOG.isLoggable(INFO))
+			LOG.info("Deleting app data from " + dataDir.getAbsolutePath());
 		File[] children = dataDir.listFiles();
 		if (children != null) {
 			for (File child : children) {
-				if (!child.getName().equals("lib"))
+				String name = child.getName();
+				if (!name.equals("lib") && !name.equals("shared_prefs")) {
+					if (LOG.isLoggable(INFO))
+						LOG.info("Deleting " + child.getAbsolutePath());
 					IoUtils.deleteFileOrDir(child);
+				}
 			}
+		} else if (LOG.isLoggable(INFO)) {
+			LOG.info("Could not list files in " + dataDir.getAbsolutePath());
 		}
 		// Recreate the cache dir as some OpenGL drivers expect it to exist
-		new File(dataDir, "cache").mkdir();
+		boolean recreated = new File(dataDir, "cache").mkdir();
+		if (LOG.isLoggable(INFO)) {
+			if (recreated) LOG.info("Recreated cache dir");
+			else LOG.info("Could not recreate cache dir");
+		}
 	}
 
 	public static File getReportDir(Context ctx) {

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

@@ -7,6 +7,8 @@ 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.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
@@ -88,6 +90,10 @@ public interface ClientHelper {
 	BdfDictionary toDictionary(byte[] b, int off, int len)
 			throws FormatException;
 
+	BdfDictionary toDictionary(TransportProperties transportProperties);
+
+	BdfDictionary toDictionary(Map<TransportId, TransportProperties> map);
+
 	BdfList toList(byte[] b, int off, int len) throws FormatException;
 
 	BdfList toList(byte[] b) throws FormatException;
@@ -99,8 +105,15 @@ public interface ClientHelper {
 	byte[] sign(String label, BdfList toSign, byte[] privateKey)
 			throws FormatException, GeneralSecurityException;
 
-	void verifySignature(String label, byte[] sig, byte[] publicKey,
+	void verifySignature(byte[] signature, String label, BdfList signed,
-			BdfList signed) throws FormatException, GeneralSecurityException;
+			byte[] publicKey) throws FormatException, GeneralSecurityException;
 
 	Author parseAndValidateAuthor(BdfList author) throws FormatException;
+
+	TransportProperties parseAndValidateTransportProperties(
+			BdfDictionary properties) throws FormatException;
+
+	Map<TransportId, TransportProperties> parseAndValidateTransportPropertiesMap(
+			BdfDictionary properties) throws FormatException;
+
 }

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/ContactId.java

@@ -6,7 +6,7 @@ import javax.annotation.concurrent.Immutable;
 
 /**
  * Type-safe wrapper for an integer that uniquely identifies a contact within
- * the scope of a single node.
+ * the scope of the local device.
  */
 @Immutable
 @NotNullByDefault

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

@@ -5,6 +5,7 @@ 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.AuthorId;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.util.Collection;
@@ -13,27 +14,37 @@ import java.util.Collection;
 public interface ContactManager {
 
 	/**
-	 * Registers a hook to be called whenever a contact is added.
+	 * Registers a hook to be called whenever a contact is added or removed.
+	 * This method should be called before
+	 * {@link LifecycleManager#startServices(String)}.
 	 */
-	void registerAddContactHook(AddContactHook hook);
+	void registerContactHook(ContactHook hook);
 
 	/**
-	 * Registers a hook to be called whenever a contact is removed.
+	 * Stores a contact associated with the given local and remote pseudonyms,
-	 */
+	 * derives and stores transport keys for each transport, and returns an ID
-	void registerRemoveContactHook(RemoveContactHook hook);
+	 * for the contact.
-
+	 *
-	/**
+	 * @param alice true if the local party is Alice
-	 * Stores a contact within the given transaction associated with the given
-	 * local and remote pseudonyms, and returns an ID for the contact.
 	 */
 	ContactId addContact(Transaction txn, Author remote, AuthorId local,
 			SecretKey master, long timestamp, boolean alice, boolean verified,
 			boolean active) throws DbException;
 
 	/**
-	 * Stores a contact associated with the given local and remote pseudonyms,
+	 * Stores a contact associated with the given local and remote pseudonyms
 	 * and returns an ID for the contact.
 	 */
+	ContactId addContact(Transaction txn, Author remote, AuthorId local,
+			boolean verified, boolean active) throws DbException;
+
+	/**
+	 * 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(Author remote, AuthorId local,
 			SecretKey master, long timestamp, boolean alice, boolean verified,
 			boolean active) throws DbException;
@@ -94,11 +105,10 @@ public interface ContactManager {
 	boolean contactExists(AuthorId remoteAuthorId, AuthorId localAuthorId)
 			throws DbException;
 
-	interface AddContactHook {
+	interface ContactHook {
-		void addingContact(Transaction txn, Contact c) throws DbException;
+
-	}
+		void addingContact(Transaction txn, Contact c) throws DbException;
 
-	interface RemoveContactHook {
 		void removingContact(Transaction txn, Contact c) throws DbException;
 	}
 }

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/crypto/CryptoComponent.java

@@ -67,8 +67,8 @@ public interface CryptoComponent {
 	 * signature created for another purpose
 	 * @return true if the signature was valid, false otherwise.
 	 */
-	boolean verify(String label, byte[] signedData, byte[] publicKey,
+	boolean verifySignature(byte[] signature, String label, byte[] signed,
-			byte[] signature) throws GeneralSecurityException;
+			byte[] publicKey) throws GeneralSecurityException;
 
 	/**
 	 * Returns the hash of the given inputs. The inputs are unambiguously
@@ -91,6 +91,18 @@ public interface CryptoComponent {
 	 */
 	byte[] mac(String label, SecretKey macKey, byte[]... inputs);
 
+	/**
+	 * Verifies that the given message authentication code is valid for the
+	 * given secret key and inputs.
+	 *
+	 * @param label a namespaced label indicating the purpose of this MAC, to
+	 * prevent it from being repurposed or colliding with a MAC created for
+	 * another purpose
+	 * @return true if the MAC was valid, false otherwise.
+	 */
+	boolean verifyMac(byte[] mac, String label, SecretKey macKey,
+			byte[]... inputs);
+
 	/**
 	 * Encrypts and authenticates the given plaintext so it can be written to
 	 * storage. The encryption and authentication keys are derived from the

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/CryptoConstants.java

@@ -16,4 +16,10 @@ public interface CryptoConstants {
 	 * The maximum length of a signature in bytes.
 	 */
 	int MAX_SIGNATURE_BYTES = 64;
+
+	/**
+	 * The length of a MAC in bytes.
+	 */
+	int MAC_BYTES = SecretKey.LENGTH;
+
 }

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/KeyPair.java

@@ -5,7 +5,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import javax.annotation.concurrent.Immutable;
 
 /**
- * A key pair consisting of a {@link PublicKey} and a {@link PrivateKey).
+ * A key pair consisting of a {@link PublicKey} and a {@link PrivateKey}.
  */
 @Immutable
 @NotNullByDefault

bramble-api/src/main/java/org/briarproject/bramble/api/crypto/TransportCrypto.java

@@ -14,9 +14,10 @@ public interface TransportCrypto {
 	 * rotation period from the given master secret.
 	 *
 	 * @param alice whether the keys are for use by Alice or Bob.
+	 * @param active whether the keys are usable for outgoing streams.
 	 */
 	TransportKeys deriveTransportKeys(TransportId t, SecretKey master,
-			long rotationPeriod, boolean alice);
+			long rotationPeriod, boolean alice, boolean active);
 
 	/**
 	 * Rotates the given transport keys to the given rotation period. If the

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;
 	}
 
@@ -34,7 +34,7 @@ public class BdfDictionary extends TreeMap<String, Object> {
 		super();
 	}
 
-	public BdfDictionary(Map<String, Object> m) {
+	public BdfDictionary(Map<String, ?> m) {
 		super(m);
 	}
 

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

@@ -18,7 +18,8 @@ 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.ValidationManager;
+import org.briarproject.bramble.api.transport.KeySet;
+import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.TransportKeys;
 
 import java.util.Collection;
@@ -103,10 +104,17 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Stores transport keys for a newly added contact.
+	 * Stores the given transport keys, optionally binding them to the given
+	 * contact, and returns a key set ID.
 	 */
-	void addTransportKeys(Transaction txn, ContactId c, TransportKeys k)
+	KeySetId addTransportKeys(Transaction txn, @Nullable ContactId c,
-			throws DbException;
+			TransportKeys k) throws DbException;
+
+	/**
+	 * Binds the given keys for the given transport to the given contact.
+	 */
+	void bindTransportKeys(Transaction txn, ContactId c, TransportId t,
+			KeySetId k) throws DbException;
 
 	/**
 	 * Returns true if the database contains the given contact for the given
@@ -128,8 +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;
 
@@ -233,7 +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
@@ -258,6 +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/>
@@ -302,9 +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.
 	 */
@@ -320,8 +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.
 	 */
@@ -329,8 +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.
 	 */
@@ -339,12 +356,8 @@ public interface DatabaseComponent {
 
 	/**
 	 * Returns the IDs and states of all dependencies of the given message.
-	 * Missing dependencies have the state
+	 * For missing dependencies and dependencies in other groups, the state
-	 * {@link ValidationManager.State UNKNOWN}.
+	 * {@link State UNKNOWN} is returned.
-	 * Dependencies in other groups have the state
-	 * {@link ValidationManager.State INVALID}.
-	 * Note that these states are not set on the dependencies themselves; the
-	 * returned states should only be taken in the context of the given message.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -352,9 +365,9 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Returns all IDs of messages that depend on the given message.
+	 * Returns the IDs and states of all dependents of the given message.
-	 * Messages in other groups that declare a dependency on the given message
+	 * Dependents in other groups are not returned. If the given message is
-	 * will be returned even though such dependencies are invalid.
+	 * missing, no dependents are returned.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -369,8 +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.
 	 */
@@ -399,15 +412,14 @@ public interface DatabaseComponent {
 	 * <p/>
 	 * Read-only.
 	 */
-	Map<ContactId, TransportKeys> getTransportKeys(Transaction txn,
+	Collection<KeySet> getTransportKeys(Transaction txn, TransportId t)
-			TransportId t) throws DbException;
+			throws DbException;
 
 	/**
-	 * Increments the outgoing stream counter for the given contact and
+	 * Increments the outgoing stream counter for the given transport keys.
-	 * transport in the given rotation period .
 	 */
-	void incrementStreamCounter(Transaction txn, ContactId c, TransportId t,
+	void incrementStreamCounter(Transaction txn, TransportId t, KeySetId k)
-			long rotationPeriod) throws DbException;
+			throws DbException;
 
 	/**
 	 * Merges the given metadata with the existing metadata for the given
@@ -477,6 +489,12 @@ public interface DatabaseComponent {
 	 */
 	void removeTransport(Transaction txn, TransportId t) throws DbException;
 
+	/**
+	 * Removes the given transport keys from the database.
+	 */
+	void removeTransportKeys(Transaction txn, TransportId t, KeySetId k)
+		throws DbException;
+
 	/**
 	 * Marks the given contact as verified.
 	 */
@@ -512,15 +530,21 @@ public interface DatabaseComponent {
 			Collection<MessageId> dependencies) throws DbException;
 
 	/**
-	 * Sets the reordering window for the given contact and transport in the
+	 * Sets the reordering window for the given key set and transport in the
 	 * given rotation period.
 	 */
-	void setReorderingWindow(Transaction txn, ContactId c, TransportId t,
+	void setReorderingWindow(Transaction txn, KeySetId k, TransportId t,
 			long rotationPeriod, long base, byte[] bitmap) throws DbException;
 
+	/**
+	 * Marks the given transport keys as usable for outgoing streams.
+	 */
+	void setTransportKeysActive(Transaction txn, TransportId t, KeySetId k)
+		throws DbException;
+
 	/**
 	 * Stores the given transport keys, deleting any keys they have replaced.
 	 */
-	void updateTransportKeys(Transaction txn,
+	void updateTransportKeys(Transaction txn, Collection<KeySet> keys)
-			Map<ContactId, TransportKeys> keys) throws DbException;
+			throws DbException;
 }

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/plugin/TransportId.java

@@ -1,22 +1,23 @@
 package org.briarproject.bramble.api.plugin;
 
-import java.nio.charset.Charset;
+import org.briarproject.bramble.util.StringUtils;
 
 /**
- * Type-safe wrapper for a string that uniquely identifies a transport plugin.
+ * Type-safe wrapper for a namespaced string that uniquely identifies a
+ * transport plugin.
  */
 public class TransportId {
 
 	/**
-	 * The maximum length of transport identifier in UTF-8 bytes.
+	 * The maximum length of a transport identifier in UTF-8 bytes.
 	 */
-	public static int MAX_TRANSPORT_ID_LENGTH = 64;
+	public static int MAX_TRANSPORT_ID_LENGTH = 100;
 
 	private final String id;
 
 	public TransportId(String id) {
-		byte[] b = id.getBytes(Charset.forName("UTF-8"));
+		int length = StringUtils.toUtf8(id).length;
-		if (b.length == 0 || b.length > MAX_TRANSPORT_ID_LENGTH)
+		if (length == 0 || length > MAX_TRANSPORT_ID_LENGTH)
 			throw new IllegalArgumentException();
 		this.id = id;
 	}

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/ClientId.java

@@ -1,19 +1,29 @@
 package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.StringUtils;
 
 import javax.annotation.concurrent.Immutable;
 
 /**
- * Wrapper for a name-spaced string that uniquely identifies a sync client.
+ * Type-safe wrapper for a namespaced string that uniquely identifies a sync
+ * client.
  */
 @Immutable
 @NotNullByDefault
 public class ClientId implements Comparable<ClientId> {
 
+	/**
+	 * The maximum length of a client identifier in UTF-8 bytes.
+	 */
+	public static int MAX_CLIENT_ID_LENGTH = 100;
+
 	private final String id;
 
 	public ClientId(String id) {
+		int length = StringUtils.toUtf8(id).length;
+		if (length == 0 || length > MAX_CLIENT_ID_LENGTH)
+			throw new IllegalArgumentException();
 		this.id = id;
 	}
 

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

@@ -5,20 +5,43 @@ 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;
+		}
 	}
 
+	/**
+	 * The current version of the group format.
+	 */
+	public static final int FORMAT_VERSION = 1;
+
 	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;
 	}
 
@@ -36,6 +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/Message.java

@@ -5,6 +5,11 @@ import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LEN
 
 public class Message {
 
+	/**
+	 * The current version of the message format.
+	 */
+	public static final int FORMAT_VERSION = 1;
+
 	private final MessageId id;
 	private final GroupId groupId;
 	private final long timestamp;

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/MessageId.java

@@ -16,7 +16,13 @@ public class MessageId extends UniqueId {
 	/**
 	 * Label for hashing messages to calculate their identifiers.
 	 */
-	public static final String LABEL = "org.briarproject.bramble/MESSAGE_ID";
+	public static final String ID_LABEL = "org.briarproject.bramble/MESSAGE_ID";
+
+	/**
+	 * Label for hashing blocks of messages.
+	 */
+	public static final String BLOCK_LABEL =
+			"org.briarproject.bramble/MESSAGE_BLOCK";
 
 	public MessageId(byte[] id) {
 		super(id);

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/SyncSessionFactory.java

@@ -2,9 +2,9 @@ package org.briarproject.bramble.api.sync;
 
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.transport.StreamWriter;
 
 import java.io.InputStream;
-import java.io.OutputStream;
 
 @NotNullByDefault
 public interface SyncSessionFactory {
@@ -12,8 +12,8 @@ public interface SyncSessionFactory {
 	SyncSession createIncomingSession(ContactId c, InputStream in);
 
 	SyncSession createSimplexOutgoingSession(ContactId c, int maxLatency,
-			OutputStream out);
+			StreamWriter streamWriter);
 
 	SyncSession createDuplexOutgoingSession(ContactId c, int maxLatency,
-			int maxIdleTime, OutputStream out);
+			int maxIdleTime, StreamWriter streamWriter);
 }

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/system/Clock.java

@@ -7,12 +7,12 @@ package org.briarproject.bramble.api.system;
 public interface Clock {
 
 	/**
-	 * @see {@link System#currentTimeMillis()}
+	 * @see System#currentTimeMillis()
 	 */
 	long currentTimeMillis();
 
 	/**
-	 * @see {@link Thread#sleep(long)}
+	 * @see Thread#sleep(long)
 	 */
 	void sleep(long milliseconds) throws InterruptedException;
 }

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

@@ -6,6 +6,8 @@ import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.plugin.TransportId;
 
+import java.util.Map;
+
 import javax.annotation.Nullable;
 
 /**
@@ -16,13 +18,55 @@ public interface KeyManager {
 
 	/**
 	 * Informs the key manager that a new contact has been added. Derives and
-	 * stores transport keys for communicating with the contact.
+	 * stores a set of transport keys for communicating with the contact over
+	 * each transport.
+	 * <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;
 
+	/**
+	 * Derives and stores a set of unbound transport keys for each transport
+	 * and returns the key set IDs.
+	 * <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;
+
+	/**
+	 * Binds the given transport keys to the given contact.
+	 */
+	void bindKeys(Transaction txn, ContactId c, Map<TransportId, KeySetId> keys)
+			throws DbException;
+
+	/**
+	 * Marks the given transport keys as usable for outgoing streams. Keys must
+	 * be bound before they are activated.
+	 */
+	void activateKeys(Transaction txn, Map<TransportId, KeySetId> keys)
+			throws DbException;
+
+	/**
+	 * Removes the given transport keys, which must not have been bound, from
+	 * the manager and the database.
+	 */
+	void removeKeys(Transaction txn, Map<TransportId, KeySetId> keys)
+			throws DbException;
+
+	/**
+	 * Returns true if we have keys that can be used for outgoing streams to
+	 * the given contact over the given transport.
+	 */
+	boolean canSendOutgoingStreams(ContactId c, TransportId t);
+
 	/**
 	 * Returns a {@link StreamContext} for sending a stream to the given
 	 * contact over the given transport, or null if an error occurs or the

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

@@ -0,0 +1,51 @@
+package org.briarproject.bramble.api.transport;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A set of transport keys for communicating with a contact. If the keys have
+ * not yet been bound to a contact, {@link #getContactId()}} returns null.
+ */
+@Immutable
+@NotNullByDefault
+public class KeySet {
+
+	private final KeySetId keySetId;
+	@Nullable
+	private final ContactId contactId;
+	private final TransportKeys transportKeys;
+
+	public KeySet(KeySetId keySetId, @Nullable ContactId contactId,
+			TransportKeys transportKeys) {
+		this.keySetId = keySetId;
+		this.contactId = contactId;
+		this.transportKeys = transportKeys;
+	}
+
+	public KeySetId getKeySetId() {
+		return keySetId;
+	}
+
+	@Nullable
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	public TransportKeys getTransportKeys() {
+		return transportKeys;
+	}
+
+	@Override
+	public int hashCode() {
+		return keySetId.hashCode();
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof KeySet && keySetId.equals(((KeySet) o).keySetId);
+	}
+}

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

@@ -0,0 +1,36 @@
+package org.briarproject.bramble.api.transport;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Type-safe wrapper for an integer that uniquely identifies a set of transport
+ * keys within the scope of the local device.
+ * <p/>
+ * Key sets created on a given device must have increasing identifiers.
+ */
+@Immutable
+@NotNullByDefault
+public class KeySetId {
+
+	private final int id;
+
+	public KeySetId(int id) {
+		this.id = id;
+	}
+
+	public int getInt() {
+		return id;
+	}
+
+	@Override
+	public int hashCode() {
+		return id;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof KeySetId && id == ((KeySetId) o).id;
+	}
+}

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

@@ -10,18 +10,20 @@ public class OutgoingKeys {
 
 	private final SecretKey tagKey, headerKey;
 	private final long rotationPeriod, streamCounter;
+	private final boolean active;
 
 	public OutgoingKeys(SecretKey tagKey, SecretKey headerKey,
-			long rotationPeriod) {
+			long rotationPeriod, boolean active) {
-		this(tagKey, headerKey, rotationPeriod, 0);
+		this(tagKey, headerKey, rotationPeriod, 0, active);
 	}
 
 	public OutgoingKeys(SecretKey tagKey, SecretKey headerKey,
-			long rotationPeriod, long streamCounter) {
+			long rotationPeriod, long streamCounter, boolean active) {
 		this.tagKey = tagKey;
 		this.headerKey = headerKey;
 		this.rotationPeriod = rotationPeriod;
 		this.streamCounter = streamCounter;
+		this.active = active;
 	}
 
 	public SecretKey getTagKey() {
@@ -39,4 +41,8 @@ public class OutgoingKeys {
 	public long getStreamCounter() {
 		return streamCounter;
 	}
+
+	public boolean isActive() {
+		return active;
+	}
 }

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

@@ -0,0 +1,19 @@
+package org.briarproject.bramble.api.transport;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * An interface for writing data to a transport connection. Data will be
+ * encrypted and authenticated before being written to the connection.
+ */
+public interface StreamWriter {
+
+	OutputStream getOutputStream();
+
+	/**
+	 * Sends the end of stream marker, informing the recipient that no more
+	 * data will be sent. The connection is flushed but not closed.
+	 */
+	void sendEndOfStream() throws IOException;
+}

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

@@ -12,12 +12,12 @@ public interface StreamWriterFactory {
 	 * Creates an {@link OutputStream OutputStream} for writing to a
 	 * transport stream
 	 */
-	OutputStream createStreamWriter(OutputStream out, StreamContext ctx);
+	StreamWriter createStreamWriter(OutputStream out, StreamContext ctx);
 
 	/**
 	 * Creates an {@link OutputStream OutputStream} for writing to a contact
 	 * exchange stream.
 	 */
-	OutputStream createContactExchangeStreamWriter(OutputStream out,
+	StreamWriter createContactExchangeStreamWriter(OutputStream out,
 			SecretKey headerKey);
 }

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/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -9,25 +9,37 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.Socket;
+import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
+import static java.util.logging.Level.INFO;
+
 @NotNullByDefault
 public class IoUtils {
 
+	private static final Logger LOG = Logger.getLogger(IoUtils.class.getName());
+
 	public static void deleteFileOrDir(File f) {
 		if (f.isFile()) {
-			f.delete();
+			delete(f);
 		} else if (f.isDirectory()) {
 			File[] children = f.listFiles();
 			if (children != null)
 				for (File child : children) deleteFileOrDir(child);
-			f.delete();
+			delete(f);
 		}
 	}
 
-	public static void copyAndClose(InputStream in, OutputStream out)
+	private static void delete(File f) {
-			throws IOException {
+		boolean deleted = f.delete();
+		if (LOG.isLoggable(INFO)) {
+			if (deleted) LOG.info("Deleted " + f.getAbsolutePath());
+			else LOG.info("Could not delete " + f.getAbsolutePath());
+		}
+	}
+
+	public static void copyAndClose(InputStream in, OutputStream out) {
 		byte[] buf = new byte[4096];
 		try {
 			while (true) {

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

@@ -5,6 +5,8 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.LocalAuthor;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.sync.ClientId;
 import org.briarproject.bramble.api.sync.Group;
 import org.briarproject.bramble.api.sync.GroupId;
@@ -16,13 +18,18 @@ import java.io.File;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 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.plugin.TransportId.MAX_TRANSPORT_ID_LENGTH;
+import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
+import static org.briarproject.bramble.api.sync.ClientId.MAX_CLIENT_ID_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_GROUP_DESCRIPTOR_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
@@ -54,6 +61,33 @@ public class TestUtils {
 		return getRandomBytes(UniqueId.LENGTH);
 	}
 
+	public static ClientId getClientId() {
+		return new ClientId(getRandomString(MAX_CLIENT_ID_LENGTH));
+	}
+
+	public static TransportId getTransportId() {
+		return new TransportId(getRandomString(MAX_TRANSPORT_ID_LENGTH));
+	}
+
+	public static TransportProperties getTransportProperties(int number) {
+		TransportProperties tp = new TransportProperties();
+		for (int i = 0; i < number; i++) {
+			tp.put(getRandomString(1 + random.nextInt(MAX_PROPERTY_LENGTH)),
+					getRandomString(1 + random.nextInt(MAX_PROPERTY_LENGTH))
+			);
+		}
+		return tp;
+	}
+
+	public static Map<TransportId, TransportProperties> getTransportPropertiesMap(
+			int number) {
+		Map<TransportId, TransportProperties> map = new HashMap<>();
+		for (int i = 0; i < number; i++) {
+			map.put(getTransportId(), getTransportProperties(number));
+		}
+		return map;
+	}
+
 	public static SecretKey getSecretKey() {
 		return new SecretKey(getRandomBytes(SecretKey.LENGTH));
 	}
@@ -83,15 +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/ClientHelperImpl.java

@@ -18,6 +18,8 @@ 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.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.TransportId;
+import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageFactory;
@@ -37,6 +39,8 @@ import javax.inject.Inject;
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 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.properties.TransportPropertyConstants.MAX_PROPERTIES_PER_TRANSPORT;
+import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
 import static org.briarproject.bramble.util.ValidationUtils.checkLength;
 import static org.briarproject.bramble.util.ValidationUtils.checkSize;
@@ -324,6 +328,20 @@ class ClientHelperImpl implements ClientHelper {
 		}
 	}
 
+	@Override
+	public BdfDictionary toDictionary(TransportProperties transportProperties) {
+		return new BdfDictionary(transportProperties);
+	}
+
+	@Override
+	public BdfDictionary toDictionary(
+			Map<TransportId, TransportProperties> map) {
+		BdfDictionary d = new BdfDictionary();
+		for (Entry<TransportId, TransportProperties> e : map.entrySet())
+			d.put(e.getKey().getString(), new BdfDictionary(e.getValue()));
+		return d;
+	}
+
 	@Override
 	public BdfList toList(byte[] b, int off, int len) throws FormatException {
 		ByteArrayInputStream in = new ByteArrayInputStream(b, off, len);
@@ -363,9 +381,10 @@ class ClientHelperImpl implements ClientHelper {
 	}
 
 	@Override
-	public void verifySignature(String label, byte[] sig, byte[] publicKey,
+	public void verifySignature(byte[] signature, String label, BdfList signed,
-			BdfList signed) throws FormatException, GeneralSecurityException {
+			byte[] publicKey) throws FormatException, GeneralSecurityException {
-		if (!crypto.verify(label, toByteArray(signed), publicKey, sig)) {
+		if (!crypto.verifySignature(signature, label, toByteArray(signed),
+				publicKey)) {
 			throw new GeneralSecurityException("Invalid signature");
 		}
 	}
@@ -382,4 +401,33 @@ class ClientHelperImpl implements ClientHelper {
 		checkLength(publicKey, 1, MAX_PUBLIC_KEY_LENGTH);
 		return authorFactory.createAuthor(formatVersion, name, publicKey);
 	}
+
+	@Override
+	public TransportProperties parseAndValidateTransportProperties(
+			BdfDictionary properties) throws FormatException {
+		checkSize(properties, 0, MAX_PROPERTIES_PER_TRANSPORT);
+		TransportProperties p = new TransportProperties();
+		for (String key : properties.keySet()) {
+			checkLength(key, 1, MAX_PROPERTY_LENGTH);
+			String value = properties.getString(key);
+			checkLength(value, 1, MAX_PROPERTY_LENGTH);
+			p.put(key, value);
+		}
+		return p;
+	}
+
+	@Override
+	public Map<TransportId, TransportProperties> parseAndValidateTransportPropertiesMap(
+			BdfDictionary properties) throws FormatException {
+		Map<TransportId, TransportProperties> tpMap = new HashMap<>();
+		for (String key : properties.keySet()) {
+			TransportId transportId = new TransportId(key);
+			TransportProperties transportProperties =
+					parseAndValidateTransportProperties(
+							properties.getDictionary(key));
+			tpMap.put(transportId, transportProperties);
+		}
+		return tpMap;
+	}
+
 }

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 +23,31 @@ 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.StreamWriter;
 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 +60,9 @@ 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 +79,17 @@ 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 +124,18 @@ 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;
 		}
 
@@ -151,158 +149,138 @@ 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 =
+		StreamWriter streamWriter =
 				streamWriterFactory.createContactExchangeStreamWriter(out,
 						alice ? aliceHeaderKey : bobHeaderKey);
-		BdfWriter w = bdfWriterFactory.createWriter(streamWriter);
+		RecordWriter recordWriter =
+				recordWriterFactory.createRecordWriter(streamWriter.getOutputStream());
 
 		// 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
+			// Send EOF on the outgoing stream
-			w.close();
+			streamWriter.sendEndOfStream();
-			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.verify(SIGNING_LABEL_EXCHANGE, nonce, publicKey, sig)) {
-			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,
@@ -323,13 +301,30 @@ 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/contact/ContactManagerImpl.java

@@ -27,36 +27,37 @@ class ContactManagerImpl implements ContactManager {
 
 	private final DatabaseComponent db;
 	private final KeyManager keyManager;
-	private final List<AddContactHook> addHooks;
+	private final List<ContactHook> hooks;
-	private final List<RemoveContactHook> removeHooks;
 
 	@Inject
 	ContactManagerImpl(DatabaseComponent db, KeyManager keyManager) {
 		this.db = db;
 		this.keyManager = keyManager;
-		addHooks = new CopyOnWriteArrayList<>();
+		hooks = new CopyOnWriteArrayList<>();
-		removeHooks = new CopyOnWriteArrayList<>();
 	}
 
 	@Override
-	public void registerAddContactHook(AddContactHook hook) {
+	public void registerContactHook(ContactHook hook) {
-		addHooks.add(hook);
+		hooks.add(hook);
-	}
-
-	@Override
-	public void registerRemoveContactHook(RemoveContactHook hook) {
-		removeHooks.add(hook);
 	}
 
 	@Override
 	public ContactId addContact(Transaction txn, Author remote, AuthorId local,
-			SecretKey master,long timestamp, boolean alice, boolean verified,
+			SecretKey master, long timestamp, boolean alice, boolean verified,
 			boolean active) throws DbException {
 		ContactId c = db.addContact(txn, remote, local, verified, active);
 		keyManager.addContact(txn, c, master, timestamp, alice);
 		Contact contact = db.getContact(txn, c);
-		for (AddContactHook hook : addHooks)
+		for (ContactHook hook : hooks) hook.addingContact(txn, contact);
-			hook.addingContact(txn, contact);
+		return c;
+	}
+
+	@Override
+	public ContactId addContact(Transaction txn, Author remote, AuthorId local,
+			boolean verified, boolean active) throws DbException {
+		ContactId c = db.addContact(txn, remote, local, verified, active);
+		Contact contact = db.getContact(txn, c);
+		for (ContactHook hook : hooks) hook.addingContact(txn, contact);
 		return c;
 	}
 
@@ -156,7 +157,7 @@ class ContactManagerImpl implements ContactManager {
 	@Override
 	public boolean contactExists(AuthorId remoteAuthorId,
 			AuthorId localAuthorId) throws DbException {
-		boolean exists = false;
+		boolean exists;
 		Transaction txn = db.startTransaction(true);
 		try {
 			exists = contactExists(txn, remoteAuthorId, localAuthorId);
@@ -171,8 +172,7 @@ class ContactManagerImpl implements ContactManager {
 	public void removeContact(Transaction txn, ContactId c)
 			throws DbException {
 		Contact contact = db.getContact(txn, c);
-		for (RemoveContactHook hook : removeHooks)
+		for (ContactHook hook : hooks) hook.removingContact(txn, contact);
-			hook.removingContact(txn, contact);
 		db.removeContact(txn, c);
 	}
 

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

@@ -205,12 +205,12 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
-	public boolean verify(String label, byte[] signedData, byte[] publicKey,
+	public boolean verifySignature(byte[] signature, String label,
-			byte[] signature) throws GeneralSecurityException {
+			byte[] signed, byte[] publicKey) throws GeneralSecurityException {
 		PublicKey key = signatureKeyParser.parsePublicKey(publicKey);
 		Signature sig = new EdSignature();
 		sig.initVerify(key);
-		updateSignature(sig, label, signedData);
+		updateSignature(sig, label, signed);
 		return sig.verify(signature);
 	}
 
@@ -262,6 +262,17 @@ class CryptoComponentImpl implements CryptoComponent {
 		return output;
 	}
 
+	@Override
+	public boolean verifyMac(byte[] mac, String label, SecretKey macKey,
+			byte[]... inputs) {
+		byte[] expected = mac(label, macKey, inputs);
+		if (mac.length != expected.length) return false;
+		// Constant-time comparison
+		int cmp = 0;
+		for (int i = 0; i < mac.length; i++) cmp |= mac[i] ^ expected[i];
+		return cmp == 0;
+	}
+
 	@Override
 	public byte[] encryptWithPassword(byte[] input, String password) {
 		AuthenticatedCipher cipher = new XSalsa20Poly1305AuthenticatedCipher();

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/crypto/Signature.java

@@ -10,37 +10,37 @@ import java.security.GeneralSecurityException;
 interface Signature {
 
 	/**
-	 * @see {@link java.security.Signature#initSign(java.security.PrivateKey)}
+	 * @see java.security.Signature#initSign(java.security.PrivateKey)
 	 */
 	void initSign(PrivateKey k) throws GeneralSecurityException;
 
 	/**
-	 * @see {@link java.security.Signature#initVerify(java.security.PublicKey)}
+	 * @see java.security.Signature#initVerify(java.security.PublicKey)
 	 */
 	void initVerify(PublicKey k) throws GeneralSecurityException;
 
 	/**
-	 * @see {@link java.security.Signature#update(byte)}
+	 * @see java.security.Signature#update(byte)
 	 */
 	void update(byte b) throws GeneralSecurityException;
 
 	/**
-	 * @see {@link java.security.Signature#update(byte[])}
+	 * @see java.security.Signature#update(byte[])
 	 */
 	void update(byte[] b) throws GeneralSecurityException;
 
 	/**
-	 * @see {@link java.security.Signature#update(byte[], int, int)}
+	 * @see java.security.Signature#update(byte[], int, int)
 	 */
 	void update(byte[] b, int off, int len) throws GeneralSecurityException;
 
 	/**
-	 * @see {@link java.security.Signature#sign()}
+	 * @see java.security.Signature#sign()}
 	 */
 	byte[] sign() throws GeneralSecurityException;
 
 	/**
-	 * @see {@link java.security.Signature#verify(byte[])}
+	 * @see java.security.Signature#verify(byte[])
 	 */
 	boolean verify(byte[] signature) throws GeneralSecurityException;
 }

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

@@ -36,7 +36,8 @@ class TransportCryptoImpl implements TransportCrypto {
 
 	@Override
 	public TransportKeys deriveTransportKeys(TransportId t,
-			SecretKey master, long rotationPeriod, boolean alice) {
+			SecretKey master, long rotationPeriod, boolean alice,
+			boolean active) {
 		// Keys for the previous period are derived from the master secret
 		SecretKey inTagPrev = deriveTagKey(master, t, !alice);
 		SecretKey inHeaderPrev = deriveHeaderKey(master, t, !alice);
@@ -57,7 +58,7 @@ class TransportCryptoImpl implements TransportCrypto {
 		IncomingKeys inNext = new IncomingKeys(inTagNext, inHeaderNext,
 				rotationPeriod + 1);
 		OutgoingKeys outCurr = new OutgoingKeys(outTagCurr, outHeaderCurr,
-				rotationPeriod);
+				rotationPeriod, active);
 		// Collect and return the keys
 		return new TransportKeys(t, inPrev, inCurr, inNext, outCurr);
 	}
@@ -71,6 +72,7 @@ class TransportCryptoImpl implements TransportCrypto {
 		IncomingKeys inNext = k.getNextIncomingKeys();
 		OutgoingKeys outCurr = k.getCurrentOutgoingKeys();
 		long startPeriod = outCurr.getRotationPeriod();
+		boolean active = outCurr.isActive();
 		// Rotate the keys
 		for (long p = startPeriod + 1; p <= rotationPeriod; p++) {
 			inPrev = inCurr;
@@ -80,7 +82,7 @@ class TransportCryptoImpl implements TransportCrypto {
 			inNext = new IncomingKeys(inNextTag, inNextHeader, p + 1);
 			SecretKey outCurrTag = rotateKey(outCurr.getTagKey(), p);
 			SecretKey outCurrHeader = rotateKey(outCurr.getHeaderKey(), p);
-			outCurr = new OutgoingKeys(outCurrTag, outCurrHeader, p);
+			outCurr = new OutgoingKeys(outCurrTag, outCurrHeader, p, active);
 		}
 		// Collect and return the keys
 		return new TransportKeys(k.getTransportId(), inPrev, inCurr, inNext,

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

@@ -21,6 +21,8 @@ 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.ValidationManager.State;
+import org.briarproject.bramble.api.transport.KeySet;
+import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.TransportKeys;
 
 import java.util.Collection;
@@ -32,8 +34,8 @@ import javax.annotation.Nullable;
  * A low-level interface to the database (DatabaseComponent provides a
  * high-level interface). Most operations take a transaction argument, which is
  * obtained by calling {@link #startTransaction()}. Every transaction must be
- * terminated by calling either {@link #abortTransaction(T)} or
+ * terminated by calling either {@link #abortTransaction(Object) abortTransaction(T)} or
- * {@link #commitTransaction(T)}, even if an exception is thrown.
+ * {@link #commitTransaction(Object) commitTransaction(T)}, even if an exception is thrown.
  */
 @NotNullByDefault
 interface Database<T> {
@@ -105,10 +107,11 @@ interface Database<T> {
 			@Nullable ContactId sender) throws DbException;
 
 	/**
-	 * Adds a dependency between two messages in the given group.
+	 * Adds a dependency between two messages, where the dependent message is
+	 * in the given state.
 	 */
-	void addMessageDependency(T txn, GroupId g, MessageId dependent,
+	void addMessageDependency(T txn, Message dependent, MessageId dependency,
-			MessageId dependency) throws DbException;
+			State dependentState) throws DbException;
 
 	/**
 	 * Records that a message has been offered by the given contact.
@@ -122,9 +125,16 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Stores transport keys for a newly added contact.
+	 * Stores the given transport keys, optionally binding them to the given
+	 * contact, and returns a key set ID.
 	 */
-	void addTransportKeys(T txn, ContactId c, TransportKeys k)
+	KeySetId addTransportKeys(T txn, @Nullable ContactId c, TransportKeys k)
+			throws DbException;
+
+	/**
+	 * Binds the given keys for the given transport to the given contact.
+	 */
+	void bindTransportKeys(T txn, ContactId c, TransportId t, KeySetId k)
 			throws DbException;
 
 	/**
@@ -256,7 +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
@@ -292,10 +303,8 @@ interface Database<T> {
 
 	/**
 	 * Returns the IDs and states of all dependencies of the given message.
-	 * Missing dependencies have the state {@link State UNKNOWN}.
+	 * For missing dependencies and dependencies in other groups, the state
-	 * Dependencies in other groups have the state {@link State INVALID}.
+	 * {@link State UNKNOWN} is returned.
-	 * Note that these states are not set on the dependencies themselves; the
-	 * returned states should only be taken in the context of the given message.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -303,9 +312,9 @@ interface Database<T> {
 			throws DbException;
 
 	/**
-	 * Returns all IDs and states of all dependents of the given message.
+	 * Returns the IDs and states of all dependents of the given message.
-	 * Messages in other groups that declare a dependency on the given message
+	 * Dependents in other groups are not returned. If the given message is
-	 * will be returned even though such dependencies are invalid.
+	 * missing, no dependents are returned.
 	 * <p/>
 	 * Read-only.
 	 */
@@ -313,16 +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.
 	 */
@@ -338,9 +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.
 	 */
@@ -348,7 +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.
 	 */
@@ -356,7 +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.
 	 */
@@ -370,8 +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.
 	 */
@@ -379,11 +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;
 
@@ -487,15 +499,14 @@ interface Database<T> {
 	 * <p/>
 	 * Read-only.
 	 */
-	Map<ContactId, TransportKeys> getTransportKeys(T txn, TransportId t)
+	Collection<KeySet> getTransportKeys(T txn, TransportId t)
 			throws DbException;
 
 	/**
-	 * Increments the outgoing stream counter for the given contact and
+	 * Increments the outgoing stream counter for the given transport keys.
-	 * transport in the given rotation period.
 	 */
-	void incrementStreamCounter(T txn, ContactId c, TransportId t,
+	void incrementStreamCounter(T txn, TransportId t, KeySetId k)
-			long rotationPeriod) throws DbException;
+			throws DbException;
 
 	/**
 	 * Marks the given messages as not needing to be acknowledged to the
@@ -585,6 +596,12 @@ interface Database<T> {
 	 */
 	void removeTransport(T txn, TransportId t) throws DbException;
 
+	/**
+	 * Removes the given transport keys from the database.
+	 */
+	void removeTransportKeys(T txn, TransportId t, KeySetId k)
+			throws DbException;
+
 	/**
 	 * Resets the transmission count and expiry time of the given message with
 	 * respect to the given contact.
@@ -620,12 +637,18 @@ interface Database<T> {
 	void setMessageState(T txn, MessageId m, State state) throws DbException;
 
 	/**
-	 * Sets the reordering window for the given contact and transport in the
+	 * Sets the reordering window for the given key set and transport in the
 	 * given rotation period.
 	 */
-	void setReorderingWindow(T txn, ContactId c, TransportId t,
+	void setReorderingWindow(T txn, KeySetId k, TransportId t,
 			long rotationPeriod, long base, byte[] bitmap) throws DbException;
 
+	/**
+	 * Marks the given transport keys as usable for outgoing streams.
+	 */
+	void setTransportKeysActive(T txn, TransportId t, KeySetId k)
+		throws DbException;
+
 	/**
 	 * Updates the transmission count and expiry time of the given message
 	 * with respect to the given contact, using the latency of the transport
@@ -635,8 +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, Map<ContactId, TransportKeys> keys)
+	void updateTransportKeys(T txn, KeySet ks) throws DbException;
-			throws DbException;
 }

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

@@ -51,15 +51,15 @@ import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
 import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
+import org.briarproject.bramble.api.transport.KeySet;
+import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.TransportKeys;
 
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.logging.Logger;
@@ -234,15 +234,27 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public void addTransportKeys(Transaction transaction, ContactId c,
+	public KeySetId addTransportKeys(Transaction transaction,
-			TransportKeys k) throws DbException {
+			@Nullable ContactId c, TransportKeys k) throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (c != null && !db.containsContact(txn, c))
+			throw new NoSuchContactException();
+		if (!db.containsTransport(txn, k.getTransportId()))
+			throw new NoSuchTransportException();
+		return db.addTransportKeys(txn, c, k);
+	}
+
+	@Override
+	public void bindTransportKeys(Transaction transaction, ContactId c,
+			TransportId t, KeySetId k) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		if (!db.containsTransport(txn, k.getTransportId()))
+		if (!db.containsTransport(txn, t))
 			throw new NoSuchTransportException();
-		db.addTransportKeys(txn, c, k);
+		db.bindTransportKeys(txn, c, t, k);
 	}
 
 	@Override
@@ -423,10 +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
@@ -454,6 +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 {
@@ -539,6 +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);
 	}
 
@@ -550,7 +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
@@ -586,8 +616,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public Map<ContactId, TransportKeys> getTransportKeys(
+	public Collection<KeySet> getTransportKeys(Transaction transaction,
-			Transaction transaction, TransportId t) throws DbException {
+			TransportId t) throws DbException {
 		T txn = unbox(transaction);
 		if (!db.containsTransport(txn, t))
 			throw new NoSuchTransportException();
@@ -595,15 +625,13 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public void incrementStreamCounter(Transaction transaction, ContactId c,
+	public void incrementStreamCounter(Transaction transaction, TransportId t,
-			TransportId t, long rotationPeriod) throws DbException {
+			KeySetId k) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
-		if (!db.containsContact(txn, c))
-			throw new NoSuchContactException();
 		if (!db.containsTransport(txn, t))
 			throw new NoSuchTransportException();
-		db.incrementStreamCounter(txn, c, t, rotationPeriod);
+		db.incrementStreamCounter(txn, t, k);
 	}
 
 	@Override
@@ -765,6 +793,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsMessage(txn, m))
 			throw new NoSuchMessageException();
+		// TODO: Don't allow messages with dependents to be removed
 		db.removeMessage(txn, m);
 	}
 
@@ -778,6 +807,16 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		db.removeTransport(txn, t);
 	}
 
+	@Override
+	public void removeTransportKeys(Transaction transaction,
+			TransportId t, KeySetId k) throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (!db.containsTransport(txn, t))
+			throw new NoSuchTransportException();
+		db.removeTransportKeys(txn, t, k);
+	}
+
 	@Override
 	public void setContactVerified(Transaction transaction, ContactId c)
 			throws DbException {
@@ -850,39 +889,41 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsMessage(txn, dependent.getId()))
 			throw new NoSuchMessageException();
+		State dependentState = db.getMessageState(txn, dependent.getId());
 		for (MessageId dependency : dependencies) {
-			db.addMessageDependency(txn, dependent.getGroupId(),
+			db.addMessageDependency(txn, dependent, dependency, dependentState);
-					dependent.getId(), dependency);
 		}
 	}
 
 	@Override
-	public void setReorderingWindow(Transaction transaction, ContactId c,
+	public void setReorderingWindow(Transaction transaction, KeySetId k,
 			TransportId t, long rotationPeriod, long base, byte[] bitmap)
 			throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
-		if (!db.containsContact(txn, c))
-			throw new NoSuchContactException();
 		if (!db.containsTransport(txn, t))
 			throw new NoSuchTransportException();
-		db.setReorderingWindow(txn, c, t, rotationPeriod, base, bitmap);
+		db.setReorderingWindow(txn, k, t, rotationPeriod, base, bitmap);
+	}
+
+	@Override
+	public void setTransportKeysActive(Transaction transaction, TransportId t,
+			KeySetId k) throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (!db.containsTransport(txn, t))
+			throw new NoSuchTransportException();
+		db.setTransportKeysActive(txn, t, k);
 	}
 
 	@Override
 	public void updateTransportKeys(Transaction transaction,
-			Map<ContactId, TransportKeys> keys) throws DbException {
+			Collection<KeySet> keys) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
-		Map<ContactId, TransportKeys> filtered = new HashMap<>();
+		for (KeySet ks : keys) {
-		for (Entry<ContactId, TransportKeys> e : keys.entrySet()) {
+			TransportId t = ks.getTransportKeys().getTransportId();
-			ContactId c = e.getKey();
+			if (db.containsTransport(txn, t)) db.updateTransportKeys(txn, ks);
-			TransportKeys k = e.getValue();
-			if (db.containsContact(txn, c)
-					&& db.containsTransport(txn, k.getTransportId())) {
-				filtered.put(c, k);
-			}
 		}
-		db.updateTransportKeys(txn, filtered);
 	}
 }

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

@@ -25,6 +25,8 @@ import org.briarproject.bramble.api.sync.MessageStatus;
 import org.briarproject.bramble.api.sync.ValidationManager.State;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.transport.IncomingKeys;
+import org.briarproject.bramble.api.transport.KeySet;
+import org.briarproject.bramble.api.transport.KeySetId;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
 
@@ -50,6 +52,7 @@ import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
+import static java.sql.Types.INTEGER;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
@@ -57,7 +60,6 @@ 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.sync.ValidationManager.State.DELIVERED;
-import static org.briarproject.bramble.api.sync.ValidationManager.State.INVALID;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.PENDING;
 import static org.briarproject.bramble.api.sync.ValidationManager.State.UNKNOWN;
 import static org.briarproject.bramble.db.DatabaseConstants.DB_SETTINGS_NAMESPACE;
@@ -72,7 +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 = 35;
+	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"
@@ -110,6 +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))";
 
@@ -170,6 +178,10 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " (groupId _HASH NOT NULL,"
 					+ " messageId _HASH NOT NULL,"
 					+ " dependencyId _HASH NOT NULL," // Not a foreign key
+					+ " messageState INT NOT NULL," // Denormalised
+					// Denormalised, null if dependency is missing or in a
+					// different group
+					+ " dependencyState INT,"
 					+ " FOREIGN KEY (groupId)"
 					+ " REFERENCES groups (groupId)"
 					+ " ON DELETE CASCADE,"
@@ -219,51 +231,63 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " maxLatency INT NOT NULL,"
 					+ " PRIMARY KEY (transportId))";
 
+	private static final String CREATE_OUTGOING_KEYS =
+			"CREATE TABLE outgoingKeys"
+					+ " (transportId _STRING NOT NULL,"
+					+ " keySetId _COUNTER,"
+					+ " rotationPeriod BIGINT NOT NULL,"
+					+ " contactId INT," // Null if keys are not bound
+					+ " tagKey _SECRET NOT NULL,"
+					+ " headerKey _SECRET NOT NULL,"
+					+ " stream BIGINT NOT NULL,"
+					+ " active BOOLEAN NOT NULL,"
+					+ " PRIMARY KEY (transportId, keySetId),"
+					+ " FOREIGN KEY (transportId)"
+					+ " REFERENCES transports (transportId)"
+					+ " ON DELETE CASCADE,"
+					+ " UNIQUE (keySetId),"
+					+ " FOREIGN KEY (contactId)"
+					+ " REFERENCES contacts (contactId)"
+					+ " ON DELETE CASCADE)";
+
 	private static final String CREATE_INCOMING_KEYS =
 			"CREATE TABLE incomingKeys"
-					+ " (contactId INT NOT NULL,"
+					+ " (transportId _STRING NOT NULL,"
-					+ " transportId _STRING NOT NULL,"
+					+ " keySetId INT NOT NULL,"
 					+ " rotationPeriod BIGINT NOT NULL,"
+					+ " contactId INT," // Null if keys are not bound
 					+ " tagKey _SECRET NOT NULL,"
 					+ " headerKey _SECRET NOT NULL,"
 					+ " base BIGINT NOT NULL,"
 					+ " bitmap _BINARY NOT NULL,"
-					+ " PRIMARY KEY (contactId, transportId, rotationPeriod),"
+					+ " periodOffset INT NOT NULL,"
-					+ " FOREIGN KEY (contactId)"
+					+ " PRIMARY KEY (transportId, keySetId, periodOffset),"
-					+ " REFERENCES contacts (contactId)"
-					+ " ON DELETE CASCADE,"
 					+ " FOREIGN KEY (transportId)"
 					+ " REFERENCES transports (transportId)"
-					+ " ON DELETE CASCADE)";
+					+ " ON DELETE CASCADE,"
-
+					+ " FOREIGN KEY (keySetId)"
-	private static final String CREATE_OUTGOING_KEYS =
+					+ " REFERENCES outgoingKeys (keySetId)"
-			"CREATE TABLE outgoingKeys"
+					+ " ON DELETE CASCADE,"
-					+ " (contactId INT NOT NULL,"
-					+ " transportId _STRING NOT NULL,"
-					+ " rotationPeriod BIGINT NOT NULL,"
-					+ " tagKey _SECRET NOT NULL,"
-					+ " headerKey _SECRET NOT NULL,"
-					+ " stream BIGINT NOT NULL,"
-					+ " PRIMARY KEY (contactId, transportId),"
 					+ " FOREIGN KEY (contactId)"
 					+ " REFERENCES contacts (contactId)"
-					+ " ON DELETE CASCADE,"
-					+ " FOREIGN KEY (transportId)"
-					+ " REFERENCES transports (transportId)"
 					+ " ON DELETE CASCADE)";
 
 	private static final String INDEX_CONTACTS_BY_AUTHOR_ID =
 			"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"
 					+ " ON messageMetadata (groupId, state)";
 
+	private static final String INDEX_MESSAGE_DEPENDENCIES_BY_DEPENDENCY_ID =
+			"CREATE INDEX IF NOT EXISTS messageDependenciesByDependencyId"
+					+ " ON messageDependencies (dependencyId)";
+
 	private static final String INDEX_STATUSES_BY_CONTACT_ID_GROUP_ID =
 			"CREATE INDEX IF NOT EXISTS statusesByContactIdGroupId"
 					+ " ON statuses (contactId, groupId)";
@@ -407,8 +431,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 			s.executeUpdate(insertTypeNames(CREATE_OFFERS));
 			s.executeUpdate(insertTypeNames(CREATE_STATUSES));
 			s.executeUpdate(insertTypeNames(CREATE_TRANSPORTS));
-			s.executeUpdate(insertTypeNames(CREATE_INCOMING_KEYS));
 			s.executeUpdate(insertTypeNames(CREATE_OUTGOING_KEYS));
+			s.executeUpdate(insertTypeNames(CREATE_INCOMING_KEYS));
 			s.close();
 		} catch (SQLException e) {
 			tryToClose(s);
@@ -421,8 +445,9 @@ 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);
 			s.executeUpdate(INDEX_STATUSES_BY_CONTACT_ID_TIMESTAMP);
 			s.close();
@@ -588,12 +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();
@@ -715,6 +742,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 						m.getLength(), state, e.getValue(), messageShared,
 						false, seen);
 			}
+			// Update denormalised column in messageDependencies if dependency
+			// is in same group as dependent
+			sql = "UPDATE messageDependencies SET dependencyState = ?"
+					+ " WHERE groupId = ? AND dependencyId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, state.getValue());
+			ps.setBytes(2, m.getGroupId().getBytes());
+			ps.setBytes(3, m.getId().getBytes());
+			affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
 		} catch (SQLException e) {
 			tryToClose(ps);
 			throw new DbException(e);
@@ -784,21 +822,42 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void addMessageDependency(Connection txn, GroupId g,
+	public void addMessageDependency(Connection txn, Message dependent,
-			MessageId dependent, MessageId dependency) throws DbException {
+			MessageId dependency, State dependentState) throws DbException {
 		PreparedStatement ps = null;
+		ResultSet rs = null;
 		try {
-			String sql = "INSERT INTO messageDependencies"
+			// Get state of dependency if present and in same group as dependent
-					+ " (groupId, messageId, dependencyId)"
+			String sql = "SELECT state FROM messages"
-					+ " VALUES (?, ?, ?)";
+					+ " WHERE messageId = ? AND groupId = ?";
 			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, g.getBytes());
+			ps.setBytes(1, dependency.getBytes());
-			ps.setBytes(2, dependent.getBytes());
+			ps.setBytes(2, dependent.getGroupId().getBytes());
+			rs = ps.executeQuery();
+			State dependencyState = null;
+			if (rs.next()) {
+				dependencyState = State.fromValue(rs.getInt(1));
+				if (rs.next()) throw new DbStateException();
+			}
+			rs.close();
+			ps.close();
+			// Create messageDependencies row
+			sql = "INSERT INTO messageDependencies"
+					+ " (groupId, messageId, dependencyId, messageState,"
+					+ " dependencyState)"
+					+ " VALUES (?, ?, ?, ? ,?)";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, dependent.getGroupId().getBytes());
+			ps.setBytes(2, dependent.getId().getBytes());
 			ps.setBytes(3, dependency.getBytes());
+			ps.setInt(4, dependentState.getValue());
+			if (dependencyState == null) ps.setNull(5, INTEGER);
+			else ps.setInt(5, dependencyState.getValue());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
 		} catch (SQLException e) {
+			tryToClose(rs);
 			tryToClose(ps);
 			throw new DbException(e);
 		}
@@ -824,61 +883,109 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void addTransportKeys(Connection txn, ContactId c, TransportKeys k)
+	public KeySetId addTransportKeys(Connection txn, @Nullable ContactId c,
-			throws DbException {
+			TransportKeys k) throws DbException {
 		PreparedStatement ps = null;
+		ResultSet rs = null;
 		try {
-			// Store the incoming keys
+			// Store the outgoing keys
-			String sql = "INSERT INTO incomingKeys (contactId, transportId,"
+			String sql = "INSERT INTO outgoingKeys (contactId, transportId,"
-					+ " rotationPeriod, tagKey, headerKey, base, bitmap)"
+					+ " rotationPeriod, tagKey, headerKey, stream, active)"
 					+ " VALUES (?, ?, ?, ?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
+			if (c == null) ps.setNull(1, INTEGER);
-			ps.setString(2, k.getTransportId().getString());
+			else ps.setInt(1, c.getInt());
-			// Previous rotation period
-			IncomingKeys inPrev = k.getPreviousIncomingKeys();
-			ps.setLong(3, inPrev.getRotationPeriod());
-			ps.setBytes(4, inPrev.getTagKey().getBytes());
-			ps.setBytes(5, inPrev.getHeaderKey().getBytes());
-			ps.setLong(6, inPrev.getWindowBase());
-			ps.setBytes(7, inPrev.getWindowBitmap());
-			ps.addBatch();
-			// Current rotation period
-			IncomingKeys inCurr = k.getCurrentIncomingKeys();
-			ps.setLong(3, inCurr.getRotationPeriod());
-			ps.setBytes(4, inCurr.getTagKey().getBytes());
-			ps.setBytes(5, inCurr.getHeaderKey().getBytes());
-			ps.setLong(6, inCurr.getWindowBase());
-			ps.setBytes(7, inCurr.getWindowBitmap());
-			ps.addBatch();
-			// Next rotation period
-			IncomingKeys inNext = k.getNextIncomingKeys();
-			ps.setLong(3, inNext.getRotationPeriod());
-			ps.setBytes(4, inNext.getTagKey().getBytes());
-			ps.setBytes(5, inNext.getHeaderKey().getBytes());
-			ps.setLong(6, inNext.getWindowBase());
-			ps.setBytes(7, inNext.getWindowBitmap());
-			ps.addBatch();
-			int[] batchAffected = ps.executeBatch();
-			if (batchAffected.length != 3) throw new DbStateException();
-			for (int rows : batchAffected)
-				if (rows != 1) throw new DbStateException();
-			ps.close();
-			// Store the outgoing keys
-			sql = "INSERT INTO outgoingKeys (contactId, transportId,"
-					+ " rotationPeriod, tagKey, headerKey, stream)"
-					+ " VALUES (?, ?, ?, ?, ?, ?)";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
 			ps.setString(2, k.getTransportId().getString());
 			OutgoingKeys outCurr = k.getCurrentOutgoingKeys();
 			ps.setLong(3, outCurr.getRotationPeriod());
 			ps.setBytes(4, outCurr.getTagKey().getBytes());
 			ps.setBytes(5, outCurr.getHeaderKey().getBytes());
 			ps.setLong(6, outCurr.getStreamCounter());
+			ps.setBoolean(7, outCurr.isActive());
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
+			// Get the new (highest) key set ID
+			sql = "SELECT keySetId FROM outgoingKeys"
+					+ " ORDER BY keySetId DESC LIMIT 1";
+			ps = txn.prepareStatement(sql);
+			rs = ps.executeQuery();
+			if (!rs.next()) throw new DbStateException();
+			KeySetId keySetId = new KeySetId(rs.getInt(1));
+			if (rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
+			// Store the incoming keys
+			sql = "INSERT INTO incomingKeys (keySetId, contactId, transportId,"
+					+ " rotationPeriod, tagKey, headerKey, base, bitmap,"
+					+ " periodOffset)"
+					+ " VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, keySetId.getInt());
+			if (c == null) ps.setNull(2, INTEGER);
+			else ps.setInt(2, c.getInt());
+			ps.setString(3, k.getTransportId().getString());
+			// Previous rotation period
+			IncomingKeys inPrev = k.getPreviousIncomingKeys();
+			ps.setLong(4, inPrev.getRotationPeriod());
+			ps.setBytes(5, inPrev.getTagKey().getBytes());
+			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();
+			ps.setLong(4, inCurr.getRotationPeriod());
+			ps.setBytes(5, inCurr.getTagKey().getBytes());
+			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();
+			ps.setLong(4, inNext.getRotationPeriod());
+			ps.setBytes(5, inNext.getTagKey().getBytes());
+			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();
+			for (int rows : batchAffected)
+				if (rows != 1) throw new DbStateException();
+			ps.close();
+			return keySetId;
+		} catch (SQLException e) {
+			tryToClose(rs);
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
+	@Override
+	public void bindTransportKeys(Connection txn, ContactId c, TransportId t,
+			KeySetId k) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE outgoingKeys SET contactId = ?"
+					+ " WHERE keySetId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, k.getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
+			sql = "UPDATE incomingKeys SET contactId = ?"
+					+ " WHERE keySetId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, k.getInt());
+			affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
 		} catch (SQLException e) {
 			tryToClose(ps);
 			throw new DbException(e);
@@ -1242,17 +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);
@@ -1261,21 +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();
@@ -1407,32 +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)));
@@ -1450,7 +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 {
@@ -1609,10 +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()) {
@@ -1632,24 +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);
@@ -1663,11 +1757,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT d.dependencyId, m.state, d.groupId, m.groupId"
+			String sql = "SELECT dependencyId, dependencyState"
-					+ " FROM messageDependencies AS d"
+					+ " FROM messageDependencies"
-					+ " LEFT OUTER JOIN messages AS m"
+					+ " WHERE messageId = ?";
-					+ " ON d.dependencyId = m.messageId"
-					+ " WHERE d.messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			rs = ps.executeQuery();
@@ -1675,14 +1767,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 			while (rs.next()) {
 				MessageId dependency = new MessageId(rs.getBytes(1));
 				State state = State.fromValue(rs.getInt(2));
-				if (rs.wasNull()) {
+				if (rs.wasNull())
-					state = UNKNOWN; // Missing dependency
+					state = UNKNOWN; // Missing or in a different group
-				} else {
-					GroupId dependentGroupId = new GroupId(rs.getBytes(3));
-					GroupId dependencyGroupId = new GroupId(rs.getBytes(4));
-					if (!dependentGroupId.equals(dependencyGroupId))
-						state = INVALID; // Dependency in another group
-				}
 				dependencies.put(dependency, state);
 			}
 			rs.close();
@@ -1701,11 +1787,12 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT d.messageId, m.state"
+			// Exclude dependencies that are missing or in a different group
-					+ " FROM messageDependencies AS d"
+			// from the dependent
-					+ " JOIN messages AS m"
+			String sql = "SELECT messageId, messageState"
-					+ " ON d.messageId = m.messageId"
+					+ " FROM messageDependencies"
-					+ " WHERE dependencyId = ?";
+					+ " WHERE dependencyId = ?"
+					+ " AND dependencyState IS NOT NULL";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			rs = ps.executeQuery();
@@ -2044,8 +2131,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public Map<ContactId, TransportKeys> getTransportKeys(Connection txn,
+	public Collection<KeySet> getTransportKeys(Connection txn, TransportId t)
-			TransportId t) throws DbException {
+			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -2054,7 +2141,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " base, bitmap"
 					+ " FROM incomingKeys"
 					+ " WHERE transportId = ?"
-					+ " ORDER BY contactId, rotationPeriod";
+					+ " ORDER BY keySetId, periodOffset";
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, t.getString());
 			rs = ps.executeQuery();
@@ -2071,29 +2158,34 @@ abstract class JdbcDatabase implements Database<Connection> {
 			rs.close();
 			ps.close();
 			// Retrieve the outgoing keys in the same order
-			sql = "SELECT contactId, rotationPeriod, tagKey, headerKey, stream"
+			sql = "SELECT keySetId, contactId, rotationPeriod,"
+					+ " tagKey, headerKey, stream, active"
 					+ " FROM outgoingKeys"
 					+ " WHERE transportId = ?"
-					+ " ORDER BY contactId, rotationPeriod";
+					+ " ORDER BY keySetId";
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, t.getString());
 			rs = ps.executeQuery();
-			Map<ContactId, TransportKeys> keys = new HashMap<>();
+			Collection<KeySet> keys = new ArrayList<>();
 			for (int i = 0; rs.next(); i++) {
 				// There should be three times as many incoming keys
 				if (inKeys.size() < (i + 1) * 3) throw new DbStateException();
-				ContactId contactId = new ContactId(rs.getInt(1));
+				KeySetId keySetId = new KeySetId(rs.getInt(1));
-				long rotationPeriod = rs.getLong(2);
+				ContactId contactId = new ContactId(rs.getInt(2));
-				SecretKey tagKey = new SecretKey(rs.getBytes(3));
+				if (rs.wasNull()) contactId = null;
-				SecretKey headerKey = new SecretKey(rs.getBytes(4));
+				long rotationPeriod = rs.getLong(3);
-				long streamCounter = rs.getLong(5);
+				SecretKey tagKey = new SecretKey(rs.getBytes(4));
+				SecretKey headerKey = new SecretKey(rs.getBytes(5));
+				long streamCounter = rs.getLong(6);
+				boolean active = rs.getBoolean(7);
 				OutgoingKeys outCurr = new OutgoingKeys(tagKey, headerKey,
-						rotationPeriod, streamCounter);
+						rotationPeriod, streamCounter, active);
 				IncomingKeys inPrev = inKeys.get(i * 3);
 				IncomingKeys inCurr = inKeys.get(i * 3 + 1);
 				IncomingKeys inNext = inKeys.get(i * 3 + 2);
-				keys.put(contactId, new TransportKeys(t, inPrev, inCurr,
+				TransportKeys transportKeys = new TransportKeys(t, inPrev,
-						inNext, outCurr));
+						inCurr, inNext, outCurr);
+				keys.add(new KeySet(keySetId, contactId, transportKeys));
 			}
 			rs.close();
 			ps.close();
@@ -2106,17 +2198,15 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void incrementStreamCounter(Connection txn, ContactId c,
+	public void incrementStreamCounter(Connection txn, TransportId t,
-			TransportId t, long rotationPeriod) throws DbException {
+			KeySetId k) throws DbException {
 		PreparedStatement ps = null;
 		try {
 			String sql = "UPDATE outgoingKeys SET stream = stream + 1"
-					+ " WHERE contactId = ? AND transportId = ?"
+					+ " WHERE transportId = ? AND keySetId = ?";
-					+ " AND rotationPeriod = ?";
 			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
+			ps.setString(1, t.getString());
-			ps.setString(2, t.getString());
+			ps.setInt(2, k.getInt());
-			ps.setLong(3, rotationPeriod);
 			int affected = ps.executeUpdate();
 			if (affected != 1) throw new DbStateException();
 			ps.close();
@@ -2473,7 +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);
@@ -2557,24 +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 {
@@ -2592,6 +2671,27 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public void removeTransportKeys(Connection txn, TransportId t, KeySetId k)
+			throws DbException {
+		PreparedStatement ps = null;
+		try {
+			// Delete any existing outgoing keys - this will also remove any
+			// incoming keys with the same key set ID
+			String sql = "DELETE FROM outgoingKeys"
+					+ " WHERE transportId = ? AND keySetId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setString(1, t.getString());
+			ps.setInt(2, k.getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void resetExpiryTime(Connection txn, ContactId c, MessageId m)
 			throws DbException {
@@ -2731,6 +2831,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 			affected = ps.executeUpdate();
 			if (affected < 0) throw new DbStateException();
 			ps.close();
+			// Update denormalised column in messageDependencies
+			sql = "UPDATE messageDependencies SET messageState = ?"
+					+ " WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, state.getValue());
+			ps.setBytes(2, m.getBytes());
+			affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
+			// Update denormalised column in messageDependencies if dependency
+			// is present and in same group as dependent
+			sql = "UPDATE messageDependencies SET dependencyState = ?"
+					+ " WHERE dependencyId = ? AND dependencyState IS NOT NULL";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, state.getValue());
+			ps.setBytes(2, m.getBytes());
+			affected = ps.executeUpdate();
+			if (affected < 0) throw new DbStateException();
+			ps.close();
 		} catch (SQLException e) {
 			tryToClose(ps);
 			throw new DbException(e);
@@ -2738,18 +2857,18 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void setReorderingWindow(Connection txn, ContactId c, TransportId t,
+	public void setReorderingWindow(Connection txn, KeySetId k, TransportId t,
 			long rotationPeriod, long base, byte[] bitmap) throws DbException {
 		PreparedStatement ps = null;
 		try {
 			String sql = "UPDATE incomingKeys SET base = ?, bitmap = ?"
-					+ " WHERE contactId = ? AND transportId = ?"
+					+ " WHERE transportId = ? AND keySetId = ?"
 					+ " AND rotationPeriod = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setLong(1, base);
 			ps.setBytes(2, bitmap);
-			ps.setInt(3, c.getInt());
+			ps.setString(3, t.getString());
-			ps.setString(4, t.getString());
+			ps.setInt(4, k.getInt());
 			ps.setLong(5, rotationPeriod);
 			int affected = ps.executeUpdate();
 			if (affected < 0 || affected > 1) throw new DbStateException();
@@ -2760,6 +2879,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public void setTransportKeysActive(Connection txn, TransportId t,
+			KeySetId k) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE outgoingKeys SET active = true"
+					+ " WHERE transportId = ? AND keySetId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setString(1, t.getString());
+			ps.setInt(2, k.getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void updateExpiryTime(Connection txn, ContactId c, MessageId m,
 			int maxLatency) throws DbException {
@@ -2795,45 +2933,69 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void updateTransportKeys(Connection txn,
+	public void updateTransportKeys(Connection txn, KeySet ks)
-			Map<ContactId, TransportKeys> keys) throws DbException {
+			throws DbException {
 		PreparedStatement ps = null;
 		try {
-			// Delete any existing incoming keys
+			// Update the outgoing keys
-			String sql = "DELETE FROM incomingKeys"
+			String sql = "UPDATE outgoingKeys SET rotationPeriod = ?,"
-					+ " WHERE contactId = ?"
+					+ " tagKey = ?, headerKey = ?, stream = ?"
-					+ " AND transportId = ?";
+					+ " WHERE transportId = ? AND keySetId = ?";
 			ps = txn.prepareStatement(sql);
-			for (Entry<ContactId, TransportKeys> e : keys.entrySet()) {
+			TransportKeys k = ks.getTransportKeys();
-				ps.setInt(1, e.getKey().getInt());
+			OutgoingKeys outCurr = k.getCurrentOutgoingKeys();
-				ps.setString(2, e.getValue().getTransportId().getString());
+			ps.setLong(1, outCurr.getRotationPeriod());
-				ps.addBatch();
+			ps.setBytes(2, outCurr.getTagKey().getBytes());
-			}
+			ps.setBytes(3, outCurr.getHeaderKey().getBytes());
-			int[] batchAffected = ps.executeBatch();
+			ps.setLong(4, outCurr.getStreamCounter());
-			if (batchAffected.length != keys.size())
+			ps.setString(5, k.getTransportId().getString());
-				throw new DbStateException();
+			ps.setInt(6, ks.getKeySetId().getInt());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
 			ps.close();
-			// Delete any existing outgoing keys
+			// Update the incoming keys
-			sql = "DELETE FROM outgoingKeys"
+			sql = "UPDATE incomingKeys SET rotationPeriod = ?,"
-					+ " WHERE contactId = ?"
+					+ " tagKey = ?, headerKey = ?, base = ?, bitmap = ?"
-					+ " AND transportId = ?";
+					+ " WHERE transportId = ? AND keySetId = ?"
+					+ " AND periodOffset = ?";
 			ps = txn.prepareStatement(sql);
-			for (Entry<ContactId, TransportKeys> e : keys.entrySet()) {
+			ps.setString(6, k.getTransportId().getString());
-				ps.setInt(1, e.getKey().getInt());
+			ps.setInt(7, ks.getKeySetId().getInt());
-				ps.setString(2, e.getValue().getTransportId().getString());
+			// Previous rotation period
-				ps.addBatch();
+			IncomingKeys inPrev = k.getPreviousIncomingKeys();
-			}
+			ps.setLong(1, inPrev.getRotationPeriod());
-			batchAffected = ps.executeBatch();
+			ps.setBytes(2, inPrev.getTagKey().getBytes());
-			if (batchAffected.length != keys.size())
+			ps.setBytes(3, inPrev.getHeaderKey().getBytes());
-				throw new DbStateException();
+			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);
 		}
-		// Store the new keys
-		for (Entry<ContactId, TransportKeys> e : keys.entrySet()) {
-			addTransportKeys(txn, e.getKey(), e.getValue());
-		}
 	}
 }

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/ConnectionManagerImpl.java

@@ -14,12 +14,12 @@ import org.briarproject.bramble.api.sync.SyncSessionFactory;
 import org.briarproject.bramble.api.transport.KeyManager;
 import org.briarproject.bramble.api.transport.StreamContext;
 import org.briarproject.bramble.api.transport.StreamReaderFactory;
+import org.briarproject.bramble.api.transport.StreamWriter;
 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.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -101,7 +101,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 
 	private SyncSession createSimplexOutgoingSession(StreamContext ctx,
 			TransportConnectionWriter w) throws IOException {
-		OutputStream streamWriter = streamWriterFactory.createStreamWriter(
+		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
 				w.getOutputStream(), ctx);
 		return syncSessionFactory.createSimplexOutgoingSession(
 				ctx.getContactId(), w.getMaxLatency(), streamWriter);
@@ -109,7 +109,7 @@ class ConnectionManagerImpl implements ConnectionManager {
 
 	private SyncSession createDuplexOutgoingSession(StreamContext ctx,
 			TransportConnectionWriter w) throws IOException {
-		OutputStream streamWriter = streamWriterFactory.createStreamWriter(
+		StreamWriter streamWriter = streamWriterFactory.createStreamWriter(
 				w.getOutputStream(), ctx);
 		return syncSessionFactory.createDuplexOutgoingSession(
 				ctx.getContactId(), w.getMaxLatency(), w.getMaxIdleTime(),
@@ -300,8 +300,8 @@ class ConnectionManagerImpl implements ConnectionManager {
 		}
 
 		private void disposeReader(boolean exception, boolean recognised) {
-			if (exception && outgoingSession != null)
+			// Interrupt the outgoing session so it finishes cleanly
-				outgoingSession.interrupt();
+			if (outgoingSession != null) outgoingSession.interrupt();
 			try {
 				reader.dispose(exception, recognised);
 			} catch (IOException e) {
@@ -310,6 +310,8 @@ class ConnectionManagerImpl implements ConnectionManager {
 		}
 
 		private void disposeWriter(boolean exception) {
+			// Interrupt the incoming session if an exception occurred,
+			// otherwise wait for the end of stream marker
 			if (exception && incomingSession != null)
 				incomingSession.interrupt();
 			try {
@@ -407,8 +409,8 @@ class ConnectionManagerImpl implements ConnectionManager {
 		}
 
 		private void disposeReader(boolean exception, boolean recognised) {
-			if (exception && outgoingSession != null)
+			// Interrupt the outgoing session so it finishes cleanly
-				outgoingSession.interrupt();
+			if (outgoingSession != null) outgoingSession.interrupt();
 			try {
 				reader.dispose(exception, recognised);
 			} catch (IOException e) {
@@ -417,6 +419,8 @@ class ConnectionManagerImpl implements ConnectionManager {
 		}
 
 		private void disposeWriter(boolean exception) {
+			// Interrupt the incoming session if an exception occurred,
+			// otherwise wait for the end of stream marker
 			if (exception && incomingSession != null)
 				incomingSession.interrupt();
 			try {

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

@@ -106,7 +106,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 			if (m == null) return Collections.emptyList();
 			List<ContactId> ids = new ArrayList<>(m.keySet());
 			if (LOG.isLoggable(INFO))
-				LOG.info(ids.size() + " contacts connected");
+				LOG.info(ids.size() + " contacts connected: " + t);
 			return ids;
 		} 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;
@@ -51,6 +53,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	private static final Logger LOG =
 			Logger.getLogger(BluetoothPlugin.class.getName());
 
+	final BluetoothConnectionLimiter connectionLimiter;
+
 	private final Executor ioExecutor;
 	private final SecureRandom secureRandom;
 	private final Backoff backoff;
@@ -91,8 +95,10 @@ 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 +116,7 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 	void onAdapterDisabled() {
 		LOG.info("Bluetooth disabled");
 		tryToClose(socket);
+		connectionLimiter.allConnectionsClosed();
 		callback.transportDisabled();
 	}
 
@@ -213,7 +220,8 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 				return;
 			}
 			backoff.reset();
-			callback.incomingConnectionCreated(conn);
+			if (connectionLimiter.contactConnectionOpened(conn))
+				callback.incomingConnectionCreated(conn);
 			if (!running) return;
 		}
 	}
@@ -257,10 +265,12 @@ abstract class BluetoothPlugin<SS> implements DuplexPlugin, EventListener {
 			if (StringUtils.isNullOrEmpty(uuid)) continue;
 			ioExecutor.execute(() -> {
 				if (!isRunning() || !shouldAllowContactConnections()) return;
+				if (!connectionLimiter.canOpenContactConnection()) return;
 				DuplexTransportConnection conn = connect(address, uuid);
 				if (conn != null) {
 					backoff.reset();
-					callback.outgoingConnectionCreated(c, conn);
+					if (connectionLimiter.contactConnectionOpened(conn))
+						callback.outgoingConnectionCreated(c, conn);
 				}
 			});
 		}
@@ -300,12 +310,16 @@ 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 +369,9 @@ 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 +392,10 @@ 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 +428,7 @@ 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/plugin/tcp/LanTcpPlugin.java

@@ -241,10 +241,11 @@ class LanTcpPlugin extends TcpPlugin {
 			}
 			return null;
 		}
-		Socket s = new Socket();
 		try {
 			if (LOG.isLoggable(INFO))
 				LOG.info("Connecting to " + scrubSocketAddress(remote));
+			Socket s = createSocket();
+			s.bind(new InetSocketAddress(socket.getInetAddress(), 0));
 			s.connect(remote);
 			s.setSoTimeout(socketTimeout);
 			if (LOG.isLoggable(INFO))

bramble-core/src/main/java/org/briarproject/bramble/plugin/tcp/TcpPlugin.java

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.plugin.tcp;
 
+import org.briarproject.bramble.PoliteExecutor;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
@@ -47,7 +48,7 @@ abstract class TcpPlugin implements DuplexPlugin {
 	private static final Logger LOG =
 			Logger.getLogger(TcpPlugin.class.getName());
 
-	protected final Executor ioExecutor;
+	protected final Executor ioExecutor, bindExecutor;
 	protected final Backoff backoff;
 	protected final DuplexPluginCallback callback;
 	protected final int maxLatency, maxIdleTime, socketTimeout;
@@ -90,6 +91,8 @@ abstract class TcpPlugin implements DuplexPlugin {
 		if (maxIdleTime > Integer.MAX_VALUE / 2)
 			socketTimeout = Integer.MAX_VALUE;
 		else socketTimeout = maxIdleTime * 2;
+		// Don't execute more than one bind operation at a time
+		bindExecutor = new PoliteExecutor("TcpPlugin", ioExecutor, 1);
 	}
 
 	@Override
@@ -110,8 +113,9 @@ abstract class TcpPlugin implements DuplexPlugin {
 	}
 
 	protected void bind() {
-		ioExecutor.execute(() -> {
+		bindExecutor.execute(() -> {
 			if (!running) return;
+			if (socket != null && !socket.isClosed()) return;
 			ServerSocket ss = null;
 			for (InetSocketAddress addr : getLocalSocketAddresses()) {
 				try {
@@ -243,10 +247,11 @@ abstract class TcpPlugin implements DuplexPlugin {
 				}
 				continue;
 			}
-			Socket s = new Socket();
 			try {
 				if (LOG.isLoggable(INFO))
 					LOG.info("Connecting to " + scrubSocketAddress(remote));
+				Socket s = createSocket();
+				s.bind(new InetSocketAddress(socket.getInetAddress(), 0));
 				s.connect(remote);
 				s.setSoTimeout(socketTimeout);
 				if (LOG.isLoggable(INFO))
@@ -261,6 +266,10 @@ abstract class TcpPlugin implements DuplexPlugin {
 		return null;
 	}
 
+	protected Socket createSocket() throws IOException {
+		return new Socket();
+	}
+
 	@Nullable
 	InetSocketAddress parseSocketAddress(String ipPort) {
 		if (StringUtils.isNullOrEmpty(ipPort)) return null;

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;
 	}
 
@@ -42,12 +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.registerAddContactHook(transportPropertyManager);
+		contactManager.registerContactHook(transportPropertyManager);
-		contactManager.registerRemoveContactHook(transportPropertyManager);
+		clientVersioningManager.registerClient(CLIENT_ID, MAJOR_VERSION,
+				MINOR_VERSION, transportPropertyManager);
 		return transportPropertyManager;
 	}
 }

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

@@ -5,8 +5,7 @@ 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.AddContactHook;
+import org.briarproject.bramble.api.contact.ContactManager.ContactHook;
-import org.briarproject.bramble.api.contact.ContactManager.RemoveContactHook;
 import org.briarproject.bramble.api.data.BdfDictionary;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.MetadataParser;
@@ -20,12 +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;
@@ -35,15 +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, AddContactHook, RemoveContactHook, 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;
@@ -51,22 +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);
 	}
 
@@ -74,11 +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()) {
@@ -92,6 +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 {
@@ -290,7 +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,
@@ -348,10 +360,7 @@ class TransportPropertyManagerImpl implements TransportPropertyManager,
 			throws FormatException {
 		// Transport ID, version, properties
 		BdfDictionary dictionary = message.getDictionary(2);
-		TransportProperties p = new TransportProperties();
+		return clientHelper.parseAndValidateTransportProperties(dictionary);
-		for (String key : dictionary.keySet())
-			p.put(key, dictionary.getString(key));
-		return p;
 	}
 
 	private static class LatestUpdate {

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

@@ -15,8 +15,6 @@ import org.briarproject.bramble.api.system.Clock;
 import javax.annotation.concurrent.Immutable;
 
 import static org.briarproject.bramble.api.plugin.TransportId.MAX_TRANSPORT_ID_LENGTH;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTIES_PER_TRANSPORT;
-import static org.briarproject.bramble.api.properties.TransportPropertyConstants.MAX_PROPERTY_LENGTH;
 import static org.briarproject.bramble.util.ValidationUtils.checkLength;
 import static org.briarproject.bramble.util.ValidationUtils.checkSize;
 
@@ -42,12 +40,7 @@ class TransportPropertyValidator extends BdfMessageValidator {
 		if (version < 0) throw new FormatException();
 		// Properties
 		BdfDictionary dictionary = body.getDictionary(2);
-		checkSize(dictionary, 0, MAX_PROPERTIES_PER_TRANSPORT);
+		clientHelper.parseAndValidateTransportProperties(dictionary);
-		for (String key : dictionary.keySet()) {
-			checkLength(key, 0, MAX_PROPERTY_LENGTH);
-			String value = dictionary.getString(key);
-			checkLength(value, 0, MAX_PROPERTY_LENGTH);
-		}
 		// Return the metadata
 		BdfDictionary meta = new BdfDictionary();
 		meta.put("transportId", transportId);

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;
@@ -23,6 +23,7 @@ import org.briarproject.bramble.api.sync.event.MessageSharedEvent;
 import org.briarproject.bramble.api.sync.event.MessageToAckEvent;
 import org.briarproject.bramble.api.sync.event.MessageToRequestEvent;
 import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.transport.StreamWriter;
 
 import java.io.IOException;
 import java.util.Collection;
@@ -39,8 +40,8 @@ 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 +68,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 	private final Clock clock;
 	private final ContactId contactId;
 	private final int maxLatency, maxIdleTime;
-	private final RecordWriter recordWriter;
+	private final StreamWriter streamWriter;
+	private final SyncRecordWriter recordWriter;
 	private final BlockingQueue<ThrowingRunnable<IOException>> writerTasks;
 
 	private final AtomicBoolean generateAckQueued = new AtomicBoolean(false);
@@ -81,7 +83,8 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 
 	DuplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
 			EventBus eventBus, Clock clock, ContactId contactId, int maxLatency,
-			int maxIdleTime, RecordWriter recordWriter) {
+			int maxIdleTime, StreamWriter streamWriter,
+			SyncRecordWriter recordWriter) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
@@ -89,6 +92,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 		this.contactId = contactId;
 		this.maxLatency = maxLatency;
 		this.maxIdleTime = maxIdleTime;
+		this.streamWriter = streamWriter;
 		this.recordWriter = recordWriter;
 		writerTasks = new LinkedBlockingQueue<>();
 	}
@@ -149,7 +153,7 @@ class DuplexOutgoingSession implements SyncSession, EventListener {
 						dataToFlush = true;
 					}
 				}
-				if (dataToFlush) recordWriter.flush();
+				streamWriter.sendEndOfStream();
 			} catch (InterruptedException e) {
 				LOG.info("Interrupted while waiting for a record to write");
 				Thread.currentThread().interrupt();
@@ -273,7 +277,7 @@ 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

@@ -12,14 +12,17 @@ import org.briarproject.bramble.util.StringUtils;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.sync.Group.FORMAT_VERSION;
 import static org.briarproject.bramble.api.sync.GroupId.LABEL;
-import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
 
 @Immutable
 @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[] {PROTOCOL_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;
@@ -63,7 +63,11 @@ class IncomingSession implements SyncSession, EventListener {
 		eventBus.addListener(this);
 		try {
 			// Read records until interrupted or EOF
-			while (!interrupted && !recordReader.eof()) {
+			while (!interrupted) {
+				if (recordReader.eof()) {
+					LOG.info("End of stream");
+					return;
+				}
 				if (recordReader.hasAck()) {
 					Ack a = recordReader.readAck();
 					dbExecutor.execute(new ReceiveAck(a));

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

@@ -12,15 +12,21 @@ import org.briarproject.bramble.util.ByteUtils;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
-import static org.briarproject.bramble.api.sync.MessageId.LABEL;
+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.api.sync.SyncConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 
 @Immutable
 @NotNullByDefault
 class MessageFactoryImpl implements MessageFactory {
 
+	private static final byte[] FORMAT_VERSION_BYTES =
+			new byte[] {FORMAT_VERSION};
+
 	private final CryptoComponent crypto;
 
 	@Inject
@@ -32,11 +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[] timeBytes = new byte[ByteUtils.INT_64_BYTES];
+		MessageId id = getMessageId(g, timestamp, body);
-		ByteUtils.writeUint64(timestamp, timeBytes, 0);
-		byte[] hash = crypto.hash(LABEL, new byte[] {PROTOCOL_VERSION},
-				g.getBytes(), timeBytes, body);
-		MessageId id = new MessageId(hash);
 		byte[] raw = new byte[MESSAGE_HEADER_LENGTH + body.length];
 		System.arraycopy(g.getBytes(), 0, raw, 0, UniqueId.LENGTH);
 		ByteUtils.writeUint64(timestamp, raw, UniqueId.LENGTH);
@@ -44,10 +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

@@ -13,8 +13,9 @@ 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 org.briarproject.bramble.api.transport.StreamWriter;
 
 import java.io.IOException;
 import java.util.Collection;
@@ -29,8 +30,8 @@ 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
@@ -51,20 +52,22 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 	private final EventBus eventBus;
 	private final ContactId contactId;
 	private final int maxLatency;
-	private final RecordWriter recordWriter;
+	private final StreamWriter streamWriter;
+	private final SyncRecordWriter recordWriter;
 	private final AtomicInteger outstandingQueries;
 	private final BlockingQueue<ThrowingRunnable<IOException>> writerTasks;
 
 	private volatile boolean interrupted = false;
 
 	SimplexOutgoingSession(DatabaseComponent db, Executor dbExecutor,
-			EventBus eventBus, ContactId contactId,
+			EventBus eventBus, ContactId contactId, int maxLatency,
-			int maxLatency, RecordWriter recordWriter) {
+			StreamWriter streamWriter, SyncRecordWriter recordWriter) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.eventBus = eventBus;
 		this.contactId = contactId;
 		this.maxLatency = maxLatency;
+		this.streamWriter = streamWriter;
 		this.recordWriter = recordWriter;
 		outstandingQueries = new AtomicInteger(2); // One per type of record
 		writerTasks = new LinkedBlockingQueue<>();
@@ -85,7 +88,7 @@ class SimplexOutgoingSession implements SyncSession, EventListener {
 					if (task == CLOSE) break;
 					task.run();
 				}
-				recordWriter.flush();
+				streamWriter.sendEndOfStream();
 			} catch (InterruptedException e) {
 				LOG.info("Interrupted while waiting for a record to write");
 				Thread.currentThread().interrupt();
@@ -171,7 +174,7 @@ 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);
+	}
+}