Bumped expiry date to 1 May 2017.

.gitignore

@@ -9,18 +9,17 @@ Thumbs.db
 .DS_Store
 
 # Eclipse project files
-.classpath
+#.classpath
-.project
+#.project
-.settings
 
 # Local configuration file (sdk path, etc)
 local.properties
 
 # Android Studio
 .idea/*
-!.idea/runConfigurations/
 !.idea/codeStyleSettings.xml
 .gradle
 build/
 *.iml
-projectFilesBackup/
+.gitignore
+src/test/

.gitlab-ci.yml

@@ -1,29 +0,0 @@
-image: registry.gitlab.com/fdroid/ci-images-base:latest
-
-cache:
-  paths:
-    - .gradle/wrapper
-    - .gradle/caches
-
-before_script:
-  - set -e
-  - export GRADLE_USER_HOME=$PWD/.gradle
-  # Accept the license for the Android build tools
-  - echo y | /opt/android-sdk/tools/bin/sdkmanager "build-tools;26.0.2"
-  # Download OpenJDK 6 so we can compile against its standard library
-  - JDK_FILE=openjdk-6-jre-headless_6b38-1.13.10-1~deb7u1_amd64.deb
-  - if [ ! -d openjdk ]
-  - then
-  - wget -q http://ftp.uk.debian.org/debian/pool/main/o/openjdk-6/$JDK_FILE
-  - dpkg-deb -x $JDK_FILE openjdk
-  - fi
-  - export JAVA_6_HOME=$PWD/openjdk/usr/lib/jvm/java-6-openjdk-amd64
-
-test:
-  script:
-    - ./gradlew test
-
-after_script:
-    # this file changes every time but should not be cached
-    - rm -f $GRADLE_USER_HOME/caches/modules-2/modules-2.lock
-    - rm -fr $GRADLE_USER_HOME/caches/*/plugin-resolution/

.idea/runConfigurations/All_tests.xml

@@ -1,28 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="All tests" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
-    <module name="briar-android" />
-    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
-    <option name="ALTERNATIVE_JRE_PATH" />
-    <option name="PACKAGE_NAME" value="" />
-    <option name="MAIN_CLASS_NAME" value="" />
-    <option name="METHOD_NAME" value="" />
-    <option name="TEST_OBJECT" value="package" />
-    <option name="VM_PARAMETERS" value="-ea" />
-    <option name="PARAMETERS" value="" />
-    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/briar-android" />
-    <option name="ENV_VARIABLES" />
-    <option name="PASS_PARENT_ENVS" value="true" />
-    <option name="TEST_SEARCH_SCOPE">
-      <value defaultName="singleModule" />
-    </option>
-    <envs />
-    <patterns />
-    <method>
-      <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in bramble-api" run_configuration_type="AndroidJUnit" />
-      <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in bramble-core" run_configuration_type="AndroidJUnit" />
-      <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in bramble-j2se" run_configuration_type="AndroidJUnit" />
-      <option name="RunConfigurationTask" enabled="true" run_configuration_name="All tests in briar-core" run_configuration_type="AndroidJUnit" />
-    </method>
-  </configuration>
-</component>

.idea/runConfigurations/All_tests_in_bramble_api.xml

@@ -1,23 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="All tests in bramble-api" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
-    <module name="bramble-api" />
-    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
-    <option name="ALTERNATIVE_JRE_PATH" />
-    <option name="PACKAGE_NAME" value="" />
-    <option name="MAIN_CLASS_NAME" value="" />
-    <option name="METHOD_NAME" value="" />
-    <option name="TEST_OBJECT" value="package" />
-    <option name="VM_PARAMETERS" value="-ea" />
-    <option name="PARAMETERS" value="" />
-    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-api" />
-    <option name="ENV_VARIABLES" />
-    <option name="PASS_PARENT_ENVS" value="true" />
-    <option name="TEST_SEARCH_SCOPE">
-      <value defaultName="singleModule" />
-    </option>
-    <envs />
-    <patterns />
-    <method />
-  </configuration>
-</component>

.idea/runConfigurations/All_tests_in_bramble_core.xml

@@ -1,23 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="All tests in bramble-core" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
-    <module name="bramble-core" />
-    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
-    <option name="ALTERNATIVE_JRE_PATH" />
-    <option name="PACKAGE_NAME" value="" />
-    <option name="MAIN_CLASS_NAME" value="" />
-    <option name="METHOD_NAME" value="" />
-    <option name="TEST_OBJECT" value="package" />
-    <option name="VM_PARAMETERS" value="-ea" />
-    <option name="PARAMETERS" value="" />
-    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-core" />
-    <option name="ENV_VARIABLES" />
-    <option name="PASS_PARENT_ENVS" value="true" />
-    <option name="TEST_SEARCH_SCOPE">
-      <value defaultName="singleModule" />
-    </option>
-    <envs />
-    <patterns />
-    <method />
-  </configuration>
-</component>

.idea/runConfigurations/All_tests_in_bramble_j2se.xml

@@ -1,23 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="All tests in bramble-j2se" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
-    <module name="bramble-j2se" />
-    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
-    <option name="ALTERNATIVE_JRE_PATH" />
-    <option name="PACKAGE_NAME" value="" />
-    <option name="MAIN_CLASS_NAME" value="" />
-    <option name="METHOD_NAME" value="" />
-    <option name="TEST_OBJECT" value="package" />
-    <option name="VM_PARAMETERS" value="-ea -Djava.library.path=libs" />
-    <option name="PARAMETERS" value="" />
-    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/bramble-j2se" />
-    <option name="ENV_VARIABLES" />
-    <option name="PASS_PARENT_ENVS" value="true" />
-    <option name="TEST_SEARCH_SCOPE">
-      <value defaultName="singleModule" />
-    </option>
-    <envs />
-    <patterns />
-    <method />
-  </configuration>
-</component>

.idea/runConfigurations/All_tests_in_briar_android.xml

@@ -1,23 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="All tests in briar-android" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
-    <module name="briar-android" />
-    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
-    <option name="ALTERNATIVE_JRE_PATH" />
-    <option name="PACKAGE_NAME" value="" />
-    <option name="MAIN_CLASS_NAME" value="" />
-    <option name="METHOD_NAME" value="" />
-    <option name="TEST_OBJECT" value="package" />
-    <option name="VM_PARAMETERS" value="-ea" />
-    <option name="PARAMETERS" value="" />
-    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/briar-android" />
-    <option name="ENV_VARIABLES" />
-    <option name="PASS_PARENT_ENVS" value="true" />
-    <option name="TEST_SEARCH_SCOPE">
-      <value defaultName="singleModule" />
-    </option>
-    <envs />
-    <patterns />
-    <method />
-  </configuration>
-</component>

.idea/runConfigurations/All_tests_in_briar_core.xml

@@ -1,23 +0,0 @@
-<component name="ProjectRunConfigurationManager">
-  <configuration default="false" name="All tests in briar-core" type="AndroidJUnit" factoryName="Android JUnit">
-    <extension name="coverage" enabled="false" merge="false" sample_coverage="true" runner="idea" />
-    <module name="briar-core" />
-    <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="false" />
-    <option name="ALTERNATIVE_JRE_PATH" />
-    <option name="PACKAGE_NAME" value="" />
-    <option name="MAIN_CLASS_NAME" value="" />
-    <option name="METHOD_NAME" value="" />
-    <option name="TEST_OBJECT" value="package" />
-    <option name="VM_PARAMETERS" value="-ea" />
-    <option name="PARAMETERS" value="" />
-    <option name="WORKING_DIRECTORY" value="file://$PROJECT_DIR$/briar-core" />
-    <option name="ENV_VARIABLES" />
-    <option name="PASS_PARENT_ENVS" value="true" />
-    <option name="TEST_SEARCH_SCOPE">
-      <value defaultName="singleModule" />
-    </option>
-    <envs />
-    <patterns />
-    <method />
-  </configuration>
-</component>

bramble-android/build.gradle

@@ -6,90 +6,99 @@ apply plugin: 'witness'
 apply plugin: 'de.undercouch.download'
 
 android {
-	compileSdkVersion 27
+	compileSdkVersion 23
-	buildToolsVersion '26.0.2'
+	buildToolsVersion "23.0.3"
 
 	defaultConfig {
 		minSdkVersion 14
-		targetSdkVersion 26
+		targetSdkVersion 22
-		versionCode 1618
+		versionCode 1
-		versionName "0.16.18"
+		versionName "1.0"
 		consumerProguardFiles 'proguard-rules.txt'
 	}
 
 	compileOptions {
-		sourceCompatibility JavaVersion.VERSION_1_8
+		sourceCompatibility JavaVersion.VERSION_1_7
-		targetCompatibility JavaVersion.VERSION_1_8
+		targetCompatibility JavaVersion.VERSION_1_7
 	}
 }
 
 dependencies {
-	implementation project(path: ':bramble-core', configuration: 'default')
+	compile project(':bramble-core')
-	implementation fileTree(dir: 'libs', include: '*.jar')
+	compile fileTree(dir: 'libs', include: ['*.jar'])
-
+	provided 'javax.annotation:jsr250-api:1.0'
-	annotationProcessor 'com.google.dagger:dagger-compiler:2.0.2'
-
-	compileOnly 'javax.annotation:jsr250-api:1.0'
 }
 
-dependencyVerification {
+def torBinaryDir = 'src/main/res/raw'
-	verify = [
+
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
+task downloadTorGeoIp(type: Download) {
-			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
+	src 'https://briarproject.org/build/geoip-2015-12-01.zip'
-			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
+	dest "$torBinaryDir/geoip.zip"
-			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
+	onlyIfNewer true
-			'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
-			'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
-			'javax.annotation:jsr250-api:1.0:jsr250-api-1.0.jar:a1a922d0d9b6d183ed3800dfac01d1e1eb159f0e8c6f94736931c1def54a941f',
-			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
-			'org.bitlet:weupnp:0.1.4:weupnp-0.1.4.jar:88df7e6504929d00bdb832863761385c68ab92af945b04f0770b126270a444fb',
-			'org.jacoco:org.jacoco.agent:0.7.4.201502262128:org.jacoco.agent-0.7.4.201502262128-runtime.jar:e357a0f1d573c2f702a273992b1b6cb661734f66311854efb3778a888515c5b5',
-			'org.jacoco:org.jacoco.agent:0.7.4.201502262128:org.jacoco.agent-0.7.4.201502262128.jar:47b4bec6df11a1118da3953da8b9fa1e7079d6fec857faa1a3cf912e53a6fd4e',
-			'org.jacoco:org.jacoco.ant:0.7.4.201502262128:org.jacoco.ant-0.7.4.201502262128.jar:013ce2a68ba57a3c59215ae0dec4df3498c078062a38c3b94c841fc14450f283',
-			'org.jacoco:org.jacoco.core:0.7.4.201502262128:org.jacoco.core-0.7.4.201502262128.jar:ec4c74554312fac5116350164786f91b35c9e082fa4ea598bfa42b5db05d7abb',
-			'org.jacoco:org.jacoco.report:0.7.4.201502262128:org.jacoco.report-0.7.4.201502262128.jar:7a3554c605e088e7e323b1084656243f0444fa353e2f2dee1f1a4204eb64ff09',
-			'org.ow2.asm:asm-debug-all:5.0.1:asm-debug-all-5.0.1.jar:4734de5b515a454b0096db6971fb068e5f70e6f10bbee2b3bd2fdfe5d978ed57',
-	]
 }
 
-ext.torBinaryDir = 'src/main/res/raw'
+task downloadTorBinaryArm(type: Download) {
-ext.torVersion = '0.2.9.14'
+	src 'https://briarproject.org/build/tor-0.2.7.6-arm.zip'
-ext.geoipVersion = '2017-11-06'
+	dest "$torBinaryDir/tor_arm.zip"
-ext.torDownloadUrl = 'https://briarproject.org/build/'
+	onlyIfNewer true
-
-def torBinaries = [
-		"tor_arm"    : '1710ea6c47b7f4c1a88bdf4858c7893837635db10e8866854eed8d61629f50e8',
-		"tor_arm_pie": '974e6949507db8fa2ea45231817c2c3677ed4ccf5488a2252317d744b0be1917',
-		"tor_x86"    : '3a5e45b3f051fcda9353b098b7086e762ffe7ba9242f7d7c8bf6523faaa8b1e9',
-		"tor_x86_pie": 'd1d96d8ce1a4b68accf04850185780d10cd5563d3552f7e1f040f8ca32cb4e51',
-		"geoip"      : '8239b98374493529a29096e45fc5877d4d6fdad0146ad8380b291f90d61484ea'
-]
-
-def downloadBinary(name) {
-	return tasks.create("downloadBinary${name}", Download) {
-		src "${torDownloadUrl}${name}.zip"
-				.replace('tor_', "tor-${torVersion}-")
-				.replace('geoip', "geoip-${geoipVersion}")
-				.replaceAll('_', '-')
-		dest "${torBinaryDir}/${name}.zip"
-		onlyIfNewer true
-	}
 }
 
-def verifyBinary(name, chksum) {
+task downloadTorBinaryArmPie(type: Download) {
-	return tasks.create([
+	src 'https://briarproject.org/build/tor-0.2.7.6-arm-pie.zip'
-			name     : "verifyBinary${name}",
+	dest "$torBinaryDir/tor_arm_pie.zip"
-			type     : Verify,
+	onlyIfNewer true
-			dependsOn: downloadBinary(name)]) {
+}
-		src "${torBinaryDir}/${name}.zip"
+
-		algorithm 'SHA-256'
+task downloadTorBinaryX86(type: Download) {
-		checksum chksum
+	src 'https://briarproject.org/build/tor-0.2.7.6-x86.zip'
-	}
+	dest "$torBinaryDir/tor_x86.zip"
+	onlyIfNewer true
+}
+
+task downloadTorBinaryX86Pie(type: Download) {
+	src 'https://briarproject.org/build/tor-0.2.7.6-x86-pie.zip'
+	dest "$torBinaryDir/tor_x86_pie.zip"
+	onlyIfNewer true
+}
+
+task verifyTorGeoIp(type: Verify, dependsOn: 'downloadTorGeoIp') {
+	src "$torBinaryDir/geoip.zip"
+	algorithm 'SHA-256'
+	checksum '9bcdaf0a7ba0933735328d8ec466c25c25dbb459efc2bce9e55c774eabea5162'
+}
+
+task verifyTorBinaryArm(type: Verify, dependsOn: 'downloadTorBinaryArm') {
+	src "$torBinaryDir/tor_arm.zip"
+	algorithm 'SHA-256'
+	checksum '83272962eda701cd5d74d2418651c4ff0f0b1dff51f558a292d1a1c42bf12146'
+}
+
+task verifyTorBinaryArmPie(type: Verify, dependsOn: 'downloadTorBinaryArmPie') {
+	src "$torBinaryDir/tor_arm_pie.zip"
+	algorithm 'SHA-256'
+	checksum 'd0300d1e45de11ebb24ed62b9c492be9c2e88590b7822195ab38c7a76ffcf646'
+}
+
+task verifyTorBinaryX86(type: Verify, dependsOn: 'downloadTorBinaryX86') {
+	src "$torBinaryDir/tor_x86.zip"
+	algorithm 'SHA-256'
+	checksum 'b8813d97b01ee1b9c9a4233c1b9bbe9f9f6b494ae6f9cbd84de8a3911911615e'
+}
+
+task verifyTorBinaryX86Pie(type: Verify, dependsOn: 'downloadTorBinaryX86Pie') {
+	src "$torBinaryDir/tor_x86_pie.zip"
+	algorithm 'SHA-256'
+	checksum '9c66e765aa196dc089951a1b2140cc8290305c2fcbf365121f99e01a233baf4e'
 }
 
 project.afterEvaluate {
-	torBinaries.every { key, value ->
+	preBuild.dependsOn {
-		preBuild.dependsOn.add(verifyBinary(key, value))
+		[
+				'verifyTorGeoIp',
+				'verifyTorBinaryArm',
+				'verifyTorBinaryArmPie',
+				'verifyTorBinaryX86',
+				'verifyTorBinaryX86Pie'
+		]
 	}
 }

bramble-android/src/main/AndroidManifest.xml

@@ -11,6 +11,8 @@
 	<uses-permission android:name="android.permission.INTERNET"/>
 	<uses-permission android:name="android.permission.READ_LOGS"/>
 	<uses-permission android:name="android.permission.WAKE_LOCK"/>
+	<!-- Since API 23, this is needed to add contacts via Bluetooth -->
+	<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
 
 	<application
 		android:allowBackup="false"

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

@@ -13,7 +13,6 @@ import org.briarproject.bramble.api.plugin.simplex.SimplexPluginFactory;
 import org.briarproject.bramble.api.reporting.DevReporter;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.api.system.LocationUtils;
-import org.briarproject.bramble.api.system.Scheduler;
 import org.briarproject.bramble.plugin.droidtooth.DroidtoothPluginFactory;
 import org.briarproject.bramble.plugin.tcp.AndroidLanTcpPluginFactory;
 import org.briarproject.bramble.plugin.tor.TorPluginFactory;
@@ -23,7 +22,6 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 
 import javax.net.SocketFactory;
 
@@ -35,20 +33,19 @@ public class AndroidPluginModule {
 
 	@Provides
 	PluginConfig providePluginConfig(@IoExecutor Executor ioExecutor,
-			@Scheduler ScheduledExecutorService scheduler,
 			AndroidExecutor androidExecutor, SecureRandom random,
 			SocketFactory torSocketFactory, BackoffFactory backoffFactory,
 			Application app, LocationUtils locationUtils, DevReporter reporter,
 			EventBus eventBus) {
 		Context appContext = app.getApplicationContext();
 		DuplexPluginFactory bluetooth = new DroidtoothPluginFactory(ioExecutor,
-				androidExecutor, appContext, random, eventBus, backoffFactory);
+				androidExecutor, appContext, random, backoffFactory);
-		DuplexPluginFactory tor = new TorPluginFactory(ioExecutor, scheduler,
+		DuplexPluginFactory tor = new TorPluginFactory(ioExecutor, appContext,
-				appContext, locationUtils, reporter, eventBus,
+				locationUtils, reporter, eventBus, torSocketFactory,
-				torSocketFactory, backoffFactory);
+				backoffFactory);
 		DuplexPluginFactory lan = new AndroidLanTcpPluginFactory(ioExecutor,
 				backoffFactory, appContext);
-		Collection<DuplexPluginFactory> duplex =
+		final Collection<DuplexPluginFactory> duplex =
 				Arrays.asList(bluetooth, tor, lan);
 		@NotNullByDefault
 		PluginConfig pluginConfig = new PluginConfig() {

bramble-android/src/main/java/org/briarproject/bramble/plugin/droidtooth/DroidtoothPlugin.java

@@ -11,9 +11,8 @@ import android.content.IntentFilter;
 
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
 import org.briarproject.bramble.api.data.BdfList;
-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.nullsafety.MethodsNotNullByDefault;
@@ -24,8 +23,6 @@ import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.plugin.event.DisableBluetoothEvent;
-import org.briarproject.bramble.api.plugin.event.EnableBluetoothEvent;
 import org.briarproject.bramble.api.properties.TransportProperties;
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.util.AndroidUtils;
@@ -33,14 +30,23 @@ import org.briarproject.bramble.util.StringUtils;
 
 import java.io.Closeable;
 import java.io.IOException;
+import java.io.InputStream;
 import java.security.SecureRandom;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.UUID;
 import java.util.concurrent.Callable;
+import java.util.concurrent.CompletionService;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorCompletionService;
+import java.util.concurrent.Future;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
 
@@ -55,11 +61,12 @@ import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERA
 import static android.bluetooth.BluetoothAdapter.SCAN_MODE_NONE;
 import static android.bluetooth.BluetoothAdapter.STATE_OFF;
 import static android.bluetooth.BluetoothAdapter.STATE_ON;
+import static android.bluetooth.BluetoothDevice.EXTRA_DEVICE;
+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.keyagreement.KeyAgreementConstants.TRANSPORT_ID_BLUETOOTH;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
-import static org.briarproject.bramble.api.plugin.BluetoothConstants.PREF_BT_ENABLE;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_ADDRESS;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.PROP_UUID;
 import static org.briarproject.bramble.api.plugin.BluetoothConstants.UUID_BYTES;
@@ -67,10 +74,14 @@ import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class DroidtoothPlugin implements DuplexPlugin, EventListener {
+class DroidtoothPlugin implements DuplexPlugin {
 
 	private static final Logger LOG =
 			Logger.getLogger(DroidtoothPlugin.class.getName());
+	private static final String FOUND =
+			"android.bluetooth.device.action.FOUND";
+	private static final String DISCOVERY_FINISHED =
+			"android.bluetooth.adapter.action.DISCOVERY_FINISHED";
 
 	private final Executor ioExecutor;
 	private final AndroidExecutor androidExecutor;
@@ -124,7 +135,12 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		// with a message queue, so submit it to the AndroidExecutor
 		try {
 			adapter = androidExecutor.runOnBackgroundThread(
-					BluetoothAdapter::getDefaultAdapter).get();
+					new Callable<BluetoothAdapter>() {
+						@Override
+						public BluetoothAdapter call() throws Exception {
+							return BluetoothAdapter.getDefaultAdapter();
+						}
+					}).get();
 		} catch (InterruptedException e) {
 			Thread.currentThread().interrupt();
 			LOG.warning("Interrupted while getting BluetoothAdapter");
@@ -148,8 +164,10 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 			bind();
 		} else {
 			// Enable Bluetooth if settings allow
-			if (callback.getSettings().getBoolean(PREF_BT_ENABLE, false)) {
+			if (callback.getSettings().getBoolean("enable", false)) {
-				enableAdapter();
+				wasEnabledByUs = true;
+				if (adapter.enable()) LOG.info("Enabling Bluetooth");
+				else LOG.info("Could not enable Bluetooth");
 			} else {
 				LOG.info("Not enabling Bluetooth");
 			}
@@ -157,36 +175,40 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 	}
 
 	private void bind() {
-		ioExecutor.execute(() -> {
+		ioExecutor.execute(new Runnable() {
-			if (!isRunning()) return;
+			@Override
-			String address = AndroidUtils.getBluetoothAddress(appContext,
+			public void run() {
-					adapter);
+				if (!isRunning()) return;
-			if (LOG.isLoggable(INFO))
+				String address = AndroidUtils.getBluetoothAddress(appContext,
-				LOG.info("Local address " + scrubMacAddress(address));
+						adapter);
-			if (!StringUtils.isNullOrEmpty(address)) {
+				if (LOG.isLoggable(INFO))
-				// Advertise the Bluetooth address to contacts
+					LOG.info("Local address " + scrubMacAddress(address));
-				TransportProperties p = new TransportProperties();
+				if (!StringUtils.isNullOrEmpty(address)) {
-				p.put(PROP_ADDRESS, address);
+					// Advertise the Bluetooth address to contacts
-				callback.mergeLocalProperties(p);
+					TransportProperties p = new TransportProperties();
+					p.put(PROP_ADDRESS, address);
+					callback.mergeLocalProperties(p);
+				}
+				// Bind a server socket to accept connections from contacts
+				BluetoothServerSocket ss;
+				try {
+					ss = adapter.listenUsingInsecureRfcommWithServiceRecord(
+							"RFCOMM", getUuid());
+				} catch (IOException e) {
+					if (LOG.isLoggable(WARNING))
+						LOG.log(WARNING, e.toString(), e);
+					return;
+				}
+				if (!isRunning()) {
+					tryToClose(ss);
+					return;
+				}
+				LOG.info("Socket bound");
+				socket = ss;
+				backoff.reset();
+				callback.transportEnabled();
+				acceptContactConnections();
 			}
-			// Bind a server socket to accept connections from contacts
-			BluetoothServerSocket ss;
-			try {
-				ss = adapter.listenUsingInsecureRfcommWithServiceRecord(
-						"RFCOMM", getUuid());
-			} catch (IOException e) {
-				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-				return;
-			}
-			if (!isRunning()) {
-				tryToClose(ss);
-				return;
-			}
-			LOG.info("Socket bound");
-			socket = ss;
-			backoff.reset();
-			callback.transportEnabled();
-			acceptContactConnections();
 		});
 	}
 
@@ -236,27 +258,13 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		return new DroidtoothTransportConnection(this, s);
 	}
 
-	private void enableAdapter() {
-		if (adapter != null && !adapter.isEnabled()) {
-			if (adapter.enable()) {
-				LOG.info("Enabling Bluetooth");
-				wasEnabledByUs = true;
-			} else {
-				LOG.info("Could not enable Bluetooth");
-			}
-		}
-	}
-
 	@Override
 	public void stop() {
 		running = false;
 		if (receiver != null) appContext.unregisterReceiver(receiver);
 		tryToClose(socket);
-		disableAdapter();
+		// Disable Bluetooth if we enabled it and it's still enabled
-	}
+		if (wasEnabledByUs && adapter.isEnabled()) {
-
-	private void disableAdapter() {
-		if (adapter != null && adapter.isEnabled() && wasEnabledByUs) {
 			if (adapter.disable()) LOG.info("Disabling Bluetooth");
 			else LOG.info("Could not disable Bluetooth");
 		}
@@ -285,18 +293,21 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		Map<ContactId, TransportProperties> remote =
 				callback.getRemoteProperties();
 		for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
-			ContactId c = e.getKey();
+			final ContactId c = e.getKey();
 			if (connected.contains(c)) continue;
-			String address = e.getValue().get(PROP_ADDRESS);
+			final String address = e.getValue().get(PROP_ADDRESS);
 			if (StringUtils.isNullOrEmpty(address)) continue;
-			String uuid = e.getValue().get(PROP_UUID);
+			final String uuid = e.getValue().get(PROP_UUID);
 			if (StringUtils.isNullOrEmpty(uuid)) continue;
-			ioExecutor.execute(() -> {
+			ioExecutor.execute(new Runnable() {
-				if (!running) return;
+				@Override
-				BluetoothSocket s = connect(address, uuid);
+				public void run() {
-				if (s != null) {
+					if (!running) return;
-					backoff.reset();
+					BluetoothSocket s = connect(address, uuid);
-					callback.outgoingConnectionCreated(c, wrapSocket(s));
+					if (s != null) {
+						backoff.reset();
+						callback.outgoingConnectionCreated(c, wrapSocket(s));
+					}
 				}
 			});
 		}
@@ -351,7 +362,8 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 	@Override
 	public DuplexTransportConnection createConnection(ContactId c) {
 		if (!isRunning()) return null;
-		TransportProperties p = callback.getRemoteProperties(c);
+		TransportProperties p = callback.getRemoteProperties().get(c);
+		if (p == null) return null;
 		String address = p.get(PROP_ADDRESS);
 		if (StringUtils.isNullOrEmpty(address)) return null;
 		String uuid = p.get(PROP_UUID);
@@ -361,6 +373,90 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		return new DroidtoothTransportConnection(this, s);
 	}
 
+	@Override
+	public boolean supportsInvitations() {
+		return true;
+	}
+
+	@Override
+	public DuplexTransportConnection createInvitationConnection(PseudoRandom r,
+			long timeout, boolean alice) {
+		if (!isRunning()) return null;
+		// Use the invitation codes to generate the UUID
+		byte[] b = r.nextBytes(UUID_BYTES);
+		UUID uuid = UUID.nameUUIDFromBytes(b);
+		if (LOG.isLoggable(INFO)) LOG.info("Invitation UUID " + uuid);
+		// Bind a server socket for receiving invitation connections
+		BluetoothServerSocket ss;
+		try {
+			ss = adapter.listenUsingInsecureRfcommWithServiceRecord(
+					"RFCOMM", uuid);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			return null;
+		}
+		// Create the background tasks
+		CompletionService<BluetoothSocket> complete =
+				new ExecutorCompletionService<>(ioExecutor);
+		List<Future<BluetoothSocket>> futures = new ArrayList<>();
+		if (alice) {
+			// Return the first connected socket
+			futures.add(complete.submit(new ListeningTask(ss)));
+			futures.add(complete.submit(new DiscoveryTask(uuid.toString())));
+		} else {
+			// Return the first socket with readable data
+			futures.add(complete.submit(new ReadableTask(
+					new ListeningTask(ss))));
+			futures.add(complete.submit(new ReadableTask(
+					new DiscoveryTask(uuid.toString()))));
+		}
+		BluetoothSocket chosen = null;
+		try {
+			Future<BluetoothSocket> f = complete.poll(timeout, MILLISECONDS);
+			if (f == null) return null; // No task completed within the timeout
+			chosen = f.get();
+			return new DroidtoothTransportConnection(this, chosen);
+		} catch (InterruptedException e) {
+			LOG.info("Interrupted while exchanging invitations");
+			Thread.currentThread().interrupt();
+			return null;
+		} catch (ExecutionException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			return null;
+		} finally {
+			// Closing the socket will terminate the listener task
+			tryToClose(ss);
+			closeSockets(futures, chosen);
+		}
+	}
+
+	private void closeSockets(final List<Future<BluetoothSocket>> futures,
+			@Nullable final BluetoothSocket chosen) {
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				for (Future<BluetoothSocket> f : futures) {
+					try {
+						if (f.cancel(true)) {
+							LOG.info("Cancelled task");
+						} else {
+							BluetoothSocket s = f.get();
+							if (s != null && s != chosen) {
+								LOG.info("Closing unwanted socket");
+								s.close();
+							}
+						}
+					} catch (InterruptedException e) {
+						LOG.info("Interrupted while closing sockets");
+						return;
+					} catch (ExecutionException | IOException e) {
+						if (LOG.isLoggable(INFO)) LOG.info(e.toString());
+					}
+				}
+			}
+		});
+	}
+
 	@Override
 	public boolean supportsKeyAgreement() {
 		return true;
@@ -375,7 +471,7 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		// No truncation necessary because COMMIT_LENGTH = 16
 		UUID uuid = UUID.nameUUIDFromBytes(commitment);
 		if (LOG.isLoggable(INFO)) LOG.info("Key agreement UUID " + uuid);
-		// Bind a server socket for receiving key agreement connections
+		// Bind a server socket for receiving invitation connections
 		BluetoothServerSocket ss;
 		try {
 			ss = adapter.listenUsingInsecureRfcommWithServiceRecord(
@@ -416,23 +512,6 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		return StringUtils.macToString(mac);
 	}
 
-	@Override
-	public void eventOccurred(Event e) {
-		if (e instanceof EnableBluetoothEvent) {
-			enableAdapterAsync();
-		} else if (e instanceof DisableBluetoothEvent) {
-			disableAdapterAsync();
-		}
-	}
-
-	private void enableAdapterAsync() {
-		ioExecutor.execute(this::enableAdapter);
-	}
-
-	private void disableAdapterAsync() {
-		ioExecutor.execute(this::disableAdapter);
-	}
-
 	private class BluetoothStateReceiver extends BroadcastReceiver {
 
 		@Override
@@ -456,6 +535,115 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 		}
 	}
 
+	private class DiscoveryTask implements Callable<BluetoothSocket> {
+
+		private final String uuid;
+
+		private DiscoveryTask(String uuid) {
+			this.uuid = uuid;
+		}
+
+		@Override
+		public BluetoothSocket call() throws Exception {
+			// Repeat discovery until we connect or get interrupted
+			while (true) {
+				// Discover nearby devices
+				LOG.info("Discovering nearby devices");
+				List<String> addresses = discoverDevices();
+				if (addresses.isEmpty()) {
+					LOG.info("No devices discovered");
+					continue;
+				}
+				// Connect to any device with the right UUID
+				for (String address : addresses) {
+					BluetoothSocket s = connect(address, uuid);
+					if (s != null) {
+						LOG.info("Outgoing connection");
+						return s;
+					}
+				}
+			}
+		}
+
+		private List<String> discoverDevices() throws InterruptedException {
+			IntentFilter filter = new IntentFilter();
+			filter.addAction(FOUND);
+			filter.addAction(DISCOVERY_FINISHED);
+			DiscoveryReceiver disco = new DiscoveryReceiver();
+			appContext.registerReceiver(disco, filter);
+			LOG.info("Starting discovery");
+			adapter.startDiscovery();
+			return disco.waitForAddresses();
+		}
+	}
+
+	private static class DiscoveryReceiver extends BroadcastReceiver {
+
+		private final CountDownLatch finished = new CountDownLatch(1);
+		private final List<String> addresses = new CopyOnWriteArrayList<>();
+
+		@Override
+		public void onReceive(Context ctx, Intent intent) {
+			String action = intent.getAction();
+			if (action.equals(DISCOVERY_FINISHED)) {
+				LOG.info("Discovery finished");
+				ctx.unregisterReceiver(this);
+				finished.countDown();
+			} else if (action.equals(FOUND)) {
+				BluetoothDevice d = intent.getParcelableExtra(EXTRA_DEVICE);
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Discovered device: " +
+							scrubMacAddress(d.getAddress()));
+				}
+				addresses.add(d.getAddress());
+			}
+		}
+
+		private List<String> waitForAddresses() throws InterruptedException {
+			finished.await();
+			List<String> shuffled = new ArrayList<>(addresses);
+			Collections.shuffle(shuffled);
+			return shuffled;
+		}
+	}
+
+	private static class ListeningTask implements Callable<BluetoothSocket> {
+
+		private final BluetoothServerSocket serverSocket;
+
+		private ListeningTask(BluetoothServerSocket serverSocket) {
+			this.serverSocket = serverSocket;
+		}
+
+		@Override
+		public BluetoothSocket call() throws IOException {
+			BluetoothSocket s = serverSocket.accept();
+			LOG.info("Incoming connection");
+			return s;
+		}
+	}
+
+	private static class ReadableTask implements Callable<BluetoothSocket> {
+
+		private final Callable<BluetoothSocket> connectionTask;
+
+		private ReadableTask(Callable<BluetoothSocket> connectionTask) {
+			this.connectionTask = connectionTask;
+		}
+
+		@Override
+		public BluetoothSocket call() throws Exception {
+			BluetoothSocket s = connectionTask.call();
+			InputStream in = s.getInputStream();
+			while (in.available() == 0) {
+				LOG.info("Waiting for data");
+				Thread.sleep(1000);
+			}
+			LOG.info("Data available");
+			return s;
+		}
+	}
+
 	private class BluetoothKeyAgreementListener extends KeyAgreementListener {
 
 		private final BluetoothServerSocket ss;
@@ -468,13 +656,16 @@ class DroidtoothPlugin implements DuplexPlugin, EventListener {
 
 		@Override
 		public Callable<KeyAgreementConnection> listen() {
-			return () -> {
+			return new Callable<KeyAgreementConnection>() {
-				BluetoothSocket s = ss.accept();
+				@Override
-				if (LOG.isLoggable(INFO))
+				public KeyAgreementConnection call() throws IOException {
-					LOG.info(ID.getString() + ": Incoming connection");
+					BluetoothSocket s = ss.accept();
-				return new KeyAgreementConnection(
+					if (LOG.isLoggable(INFO))
-						new DroidtoothTransportConnection(
+						LOG.info(ID.getString() + ": Incoming connection");
-								DroidtoothPlugin.this, s), ID);
+					return new KeyAgreementConnection(
+							new DroidtoothTransportConnection(
+									DroidtoothPlugin.this, s), ID);
+				}
 			};
 		}
 

bramble-android/src/main/java/org/briarproject/bramble/plugin/droidtooth/DroidtoothPluginFactory.java

@@ -2,7 +2,6 @@ package org.briarproject.bramble.plugin.droidtooth;
 
 import android.content.Context;
 
-import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Backoff;
 import org.briarproject.bramble.api.plugin.BackoffFactory;
@@ -32,18 +31,15 @@ public class DroidtoothPluginFactory implements DuplexPluginFactory {
 	private final AndroidExecutor androidExecutor;
 	private final Context appContext;
 	private final SecureRandom secureRandom;
-	private final EventBus eventBus;
 	private final BackoffFactory backoffFactory;
 
 	public DroidtoothPluginFactory(Executor ioExecutor,
 			AndroidExecutor androidExecutor, Context appContext,
-			SecureRandom secureRandom, EventBus eventBus,
+			SecureRandom secureRandom, BackoffFactory backoffFactory) {
-			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
 		this.androidExecutor = androidExecutor;
 		this.appContext = appContext;
 		this.secureRandom = secureRandom;
-		this.eventBus = eventBus;
 		this.backoffFactory = backoffFactory;
 	}
 
@@ -61,10 +57,7 @@ public class DroidtoothPluginFactory implements DuplexPluginFactory {
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		DroidtoothPlugin plugin = new DroidtoothPlugin(ioExecutor,
+		return new DroidtoothPlugin(ioExecutor, androidExecutor, appContext,
-				androidExecutor, appContext, secureRandom, backoff, callback,
+				secureRandom, backoff, callback, MAX_LATENCY);
-				MAX_LATENCY);
-		eventBus.addListener(plugin);
-		return plugin;
 	}
 }

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

@@ -17,6 +17,7 @@ import net.freehaven.tor.control.EventHandler;
 import net.freehaven.tor.control.TorControlConnection;
 
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventListener;
@@ -55,16 +56,10 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.Scanner;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
-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;
@@ -75,33 +70,22 @@ import javax.net.SocketFactory;
 import static android.content.Context.CONNECTIVITY_SERVICE;
 import static android.content.Context.MODE_PRIVATE;
 import static android.content.Context.POWER_SERVICE;
-import static android.content.Intent.ACTION_SCREEN_OFF;
-import static android.content.Intent.ACTION_SCREEN_ON;
 import static android.net.ConnectivityManager.CONNECTIVITY_ACTION;
 import static android.net.ConnectivityManager.TYPE_WIFI;
-import static android.os.Build.VERSION.SDK_INT;
-import static android.os.PowerManager.ACTION_DEVICE_IDLE_MODE_CHANGED;
 import static android.os.PowerManager.PARTIAL_WAKE_LOCK;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
-import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static net.freehaven.tor.control.TorControlCommands.HS_ADDRESS;
 import static net.freehaven.tor.control.TorControlCommands.HS_PRIVKEY;
 import static org.briarproject.bramble.api.plugin.TorConstants.CONTROL_PORT;
-import static org.briarproject.bramble.api.plugin.TorConstants.ID;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_ALWAYS;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_NEVER;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_WIFI;
-import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_PORT;
-import static org.briarproject.bramble.api.plugin.TorConstants.PROP_ONION;
 import static org.briarproject.bramble.util.PrivacyUtils.scrubOnion;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
+	private static final String PROP_ONION = "onion";
 	private static final String[] EVENTS = {
 			"CIRC", "ORCONN", "HS_DESC", "NOTICE", "WARN", "ERR"
 	};
@@ -112,7 +96,6 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 			Logger.getLogger(TorPlugin.class.getName());
 
 	private final Executor ioExecutor;
-	private final ScheduledExecutorService scheduler;
 	private final Context appContext;
 	private final LocationUtils locationUtils;
 	private final DevReporter reporter;
@@ -125,9 +108,6 @@ 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);
 
 	private volatile boolean running = false;
@@ -136,13 +116,12 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private volatile TorControlConnection controlConnection = null;
 	private volatile BroadcastReceiver networkStateReceiver = null;
 
-	TorPlugin(Executor ioExecutor, ScheduledExecutorService scheduler,
+	TorPlugin(Executor ioExecutor, Context appContext,
-			Context appContext, LocationUtils locationUtils,
+			LocationUtils locationUtils, DevReporter reporter,
-			DevReporter reporter, SocketFactory torSocketFactory,
+			SocketFactory torSocketFactory, Backoff backoff,
-			Backoff backoff, DuplexPluginCallback callback,
+			DuplexPluginCallback callback, String architecture, int maxLatency,
-			String architecture, int maxLatency, int maxIdleTime) {
+			int maxIdleTime) {
 		this.ioExecutor = ioExecutor;
-		this.scheduler = scheduler;
 		this.appContext = appContext;
 		this.locationUtils = locationUtils;
 		this.reporter = reporter;
@@ -164,10 +143,8 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		cookieFile = new File(torDirectory, ".tor/control_auth_cookie");
 		Object o = appContext.getSystemService(POWER_SERVICE);
 		PowerManager pm = (PowerManager) o;
-		// This tag will prevent Huawei's powermanager from killing us.
+		wakeLock = pm.newWakeLock(PARTIAL_WAKE_LOCK, "TorPlugin");
-		wakeLock = pm.newWakeLock(PARTIAL_WAKE_LOCK, "LocationManagerService");
 		wakeLock.setReferenceCounted(false);
-		connectionStatusLock = new ReentrantLock();
 	}
 
 	@Override
@@ -205,31 +182,19 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		String torPath = torFile.getAbsolutePath();
 		String configPath = configFile.getAbsolutePath();
 		String pid = String.valueOf(android.os.Process.myPid());
+		String[] cmd = {torPath, "-f", configPath, OWNER, pid};
+		String[] env = {"HOME=" + torDirectory.getAbsolutePath()};
 		Process torProcess;
-		ProcessBuilder pb =
-				new ProcessBuilder(torPath, "-f", configPath, OWNER, pid);
-		Map<String, String> env = pb.environment();
-		env.put("HOME", torDirectory.getAbsolutePath());
-		pb.directory(torDirectory);
 		try {
-			torProcess = pb.start();
+			torProcess = Runtime.getRuntime().exec(cmd, env, torDirectory);
 		} catch (SecurityException | IOException e) {
 			throw new PluginException(e);
 		}
 		// Log the process's standard output until it detaches
 		if (LOG.isLoggable(INFO)) {
 			Scanner stdout = new Scanner(torProcess.getInputStream());
-			Scanner stderr = new Scanner(torProcess.getErrorStream());
+			while (stdout.hasNextLine()) LOG.info(stdout.nextLine());
-			while (stdout.hasNextLine() || stderr.hasNextLine()) {
-				if (stdout.hasNextLine()) {
-					LOG.info(stdout.nextLine());
-				}
-				if (stderr.hasNextLine()) {
-					LOG.info(stderr.nextLine());
-				}
-			}
 			stdout.close();
-			stderr.close();
 		}
 		try {
 			// Wait for the process to detach or exit
@@ -273,11 +238,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 		// Register to receive network status events
 		networkStateReceiver = new NetworkStateReceiver();
-		IntentFilter filter = new IntentFilter();
+		IntentFilter filter = new IntentFilter(CONNECTIVITY_ACTION);
-		filter.addAction(CONNECTIVITY_ACTION);
-		filter.addAction(ACTION_SCREEN_ON);
-		filter.addAction(ACTION_SCREEN_OFF);
-		if (SDK_INT >= 23) filter.addAction(ACTION_DEVICE_IDLE_MODE_CHANGED);
 		appContext.registerReceiver(networkStateReceiver, filter);
 		// Bind a server socket to receive incoming hidden service connections
 		bind();
@@ -390,45 +351,57 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void sendDevReports() {
-		ioExecutor.execute(() -> {
+		ioExecutor.execute(new Runnable() {
-			// TODO: Trigger this with a TransportEnabledEvent
+			@Override
-			File reportDir = AndroidUtils.getReportDir(appContext);
+			public void run() {
-			reporter.sendReports(reportDir);
+				// TODO: Trigger this with a TransportEnabledEvent
+				File reportDir = AndroidUtils.getReportDir(appContext);
+				reporter.sendReports(reportDir);
+			}
 		});
 	}
 
 	private void bind() {
-		ioExecutor.execute(() -> {
+		ioExecutor.execute(new Runnable() {
-			// If there's already a port number stored in config, reuse it
+			@Override
-			String portString = callback.getSettings().get(PREF_TOR_PORT);
+			public void run() {
-			int port;
+				// If there's already a port number stored in config, reuse it
-			if (StringUtils.isNullOrEmpty(portString)) port = 0;
+				String portString = callback.getSettings().get("port");
-			else port = Integer.parseInt(portString);
+				int port;
-			// Bind a server socket to receive connections from Tor
+				if (StringUtils.isNullOrEmpty(portString)) port = 0;
-			ServerSocket ss = null;
+				else port = Integer.parseInt(portString);
-			try {
+				// Bind a server socket to receive connections from Tor
-				ss = new ServerSocket();
+				ServerSocket ss = null;
-				ss.bind(new InetSocketAddress("127.0.0.1", port));
+				try {
-			} catch (IOException e) {
+					ss = new ServerSocket();
-				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+					ss.bind(new InetSocketAddress("127.0.0.1", port));
-				tryToClose(ss);
+				} catch (IOException e) {
-				return;
+					if (LOG.isLoggable(WARNING))
+						LOG.log(WARNING, e.toString(), e);
+					tryToClose(ss);
+					return;
+				}
+				if (!running) {
+					tryToClose(ss);
+					return;
+				}
+				socket = ss;
+				// Store the port number
+				final String localPort = String.valueOf(ss.getLocalPort());
+				Settings s = new Settings();
+				s.put("port", localPort);
+				callback.mergeSettings(s);
+				// Create a hidden service if necessary
+				ioExecutor.execute(new Runnable() {
+					@Override
+					public void run() {
+						publishHiddenService(localPort);
+					}
+				});
+				backoff.reset();
+				// Accept incoming hidden service connections from Tor
+				acceptContactConnections(ss);
 			}
-			if (!running) {
-				tryToClose(ss);
-				return;
-			}
-			socket = ss;
-			// Store the port number
-			String localPort = String.valueOf(ss.getLocalPort());
-			Settings s = new Settings();
-			s.put(PREF_TOR_PORT, localPort);
-			callback.mergeSettings(s);
-			// Create a hidden service if necessary
-			ioExecutor.execute(() -> publishHiddenService(localPort));
-			backoff.reset();
-			// Accept incoming hidden service connections from Tor
-			acceptContactConnections(ss);
 		});
 	}
 
@@ -548,21 +521,20 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	public void poll(Collection<ContactId> connected) {
 		if (!isRunning()) return;
 		backoff.increment();
-		Map<ContactId, TransportProperties> remote =
+		// TODO: Pass properties to connectAndCallBack()
-				callback.getRemoteProperties();
+		for (ContactId c : callback.getRemoteProperties().keySet())
-		for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
+			if (!connected.contains(c)) connectAndCallBack(c);
-			ContactId c = e.getKey();
-			if (!connected.contains(c)) connectAndCallBack(c, e.getValue());
-		}
 	}
 
-	private void connectAndCallBack(ContactId c, TransportProperties p) {
+	private void connectAndCallBack(final ContactId c) {
-		ioExecutor.execute(() -> {
+		ioExecutor.execute(new Runnable() {
-			if (!isRunning()) return;
+			@Override
-			DuplexTransportConnection d = createConnection(p);
+			public void run() {
-			if (d != null) {
+				DuplexTransportConnection d = createConnection(c);
-				backoff.reset();
+				if (d != null) {
-				callback.outgoingConnectionCreated(c, d);
+					backoff.reset();
+					callback.outgoingConnectionCreated(c, d);
+				}
 			}
 		});
 	}
@@ -570,11 +542,8 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public DuplexTransportConnection createConnection(ContactId c) {
 		if (!isRunning()) return null;
-		return createConnection(callback.getRemoteProperties(c));
+		TransportProperties p = callback.getRemoteProperties().get(c);
-	}
+		if (p == null) return null;
-
-	@Nullable
-	private DuplexTransportConnection createConnection(TransportProperties p) {
 		String onion = p.get(PROP_ONION);
 		if (StringUtils.isNullOrEmpty(onion)) return null;
 		if (!ONION.matcher(onion).matches()) {
@@ -602,6 +571,17 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 	}
 
+	@Override
+	public boolean supportsInvitations() {
+		return false;
+	}
+
+	@Override
+	public DuplexTransportConnection createInvitationConnection(PseudoRandom r,
+			long timeout, boolean alice) {
+		throw new UnsupportedOperationException();
+	}
+
 	@Override
 	public boolean supportsKeyAgreement() {
 		return false;
@@ -638,8 +618,6 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public void orConnStatus(String status, String orName) {
 		if (LOG.isLoggable(INFO)) LOG.info("OR connection " + status);
-		if (status.equals("CLOSED") || status.equals("FAILED"))
-			updateConnectionStatus(); // Check whether we've lost connectivity
 	}
 
 	@Override
@@ -679,7 +657,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 
 		@Override
-		public void onEvent(int event, @Nullable String path) {
+		public void onEvent(int event, String path) {
 			stopWatching();
 			latch.countDown();
 		}
@@ -688,8 +666,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public void eventOccurred(Event e) {
 		if (e instanceof SettingsUpdatedEvent) {
-			SettingsUpdatedEvent s = (SettingsUpdatedEvent) e;
+			if (((SettingsUpdatedEvent) e).getNamespace().equals("tor")) {
-			if (s.getNamespace().equals(ID.getString())) {
 				LOG.info("Tor settings updated");
 				updateConnectionStatus();
 			}
@@ -697,75 +674,58 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void updateConnectionStatus() {
-		ioExecutor.execute(() -> {
+		ioExecutor.execute(new Runnable() {
-			if (!running) return;
+			@Override
-			try {
+			public void run() {
-				connectionStatusLock.lock();
+				if (!running) return;
-				updateConnectionStatusLocked();
+
-			} finally {
+				Object o = appContext.getSystemService(CONNECTIVITY_SERVICE);
-				connectionStatusLock.unlock();
+				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();
+				boolean useMobileData = s.getBoolean("torOverMobile", true);
+
+				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 (!wifi && !useMobileData) {
+						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);
-		Future<?> oldConnectivityCheck =
-				connectivityCheck.getAndSet(newConnectivityCheck);
-		if (oldConnectivityCheck != null) oldConnectivityCheck.cancel(false);
-	}
-
 	private class NetworkStateReceiver extends BroadcastReceiver {
 
 		@Override
 		public void onReceive(Context ctx, Intent i) {
 			if (!running) return;
-			String action = i.getAction();
+			if (CONNECTIVITY_ACTION.equals(i.getAction())) {
-			if (LOG.isLoggable(INFO)) LOG.info("Received broadcast " + action);
+				LOG.info("Detected connectivity change");
-			updateConnectionStatus();
+				updateConnectionStatus();
-			if (ACTION_SCREEN_ON.equals(action)
-					|| ACTION_SCREEN_OFF.equals(action)) {
-				scheduleConnectionStatusUpdate();
 			}
 		}
 	}

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

@@ -17,7 +17,6 @@ import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.util.AndroidUtils;
 
 import java.util.concurrent.Executor;
-import java.util.concurrent.ScheduledExecutorService;
 import java.util.logging.Logger;
 
 import javax.annotation.concurrent.Immutable;
@@ -37,7 +36,6 @@ public class TorPluginFactory implements DuplexPluginFactory {
 	private static final double BACKOFF_BASE = 1.2;
 
 	private final Executor ioExecutor;
-	private final ScheduledExecutorService scheduler;
 	private final Context appContext;
 	private final LocationUtils locationUtils;
 	private final DevReporter reporter;
@@ -45,13 +43,11 @@ public class TorPluginFactory implements DuplexPluginFactory {
 	private final SocketFactory torSocketFactory;
 	private final BackoffFactory backoffFactory;
 
-	public TorPluginFactory(Executor ioExecutor,
+	public TorPluginFactory(Executor ioExecutor, Context appContext,
-			ScheduledExecutorService scheduler, Context appContext,
 			LocationUtils locationUtils, DevReporter reporter,
 			EventBus eventBus, SocketFactory torSocketFactory,
 			BackoffFactory backoffFactory) {
 		this.ioExecutor = ioExecutor;
-		this.scheduler = scheduler;
 		this.appContext = appContext;
 		this.locationUtils = locationUtils;
 		this.reporter = reporter;
@@ -93,9 +89,9 @@ public class TorPluginFactory implements DuplexPluginFactory {
 
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		TorPlugin plugin = new TorPlugin(ioExecutor, scheduler, appContext,
+		TorPlugin plugin = new TorPlugin(ioExecutor, appContext, locationUtils,
-				locationUtils, reporter, torSocketFactory, backoff, callback,
+				reporter, torSocketFactory, backoff, callback, architecture,
-				architecture, MAX_LATENCY, MAX_IDLE_TIME);
+				MAX_LATENCY, MAX_IDLE_TIME);
 		eventBus.addListener(plugin);
 		return plugin;
 	}

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

@@ -3,7 +3,6 @@ package org.briarproject.bramble.plugin.tor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.Plugin;
 import org.briarproject.bramble.api.plugin.duplex.AbstractDuplexTransportConnection;
-import org.briarproject.bramble.util.IoUtils;
 
 import java.io.IOException;
 import java.io.InputStream;
@@ -22,12 +21,12 @@ class TorTransportConnection extends AbstractDuplexTransportConnection {
 
 	@Override
 	protected InputStream getInputStream() throws IOException {
-		return IoUtils.getInputStream(socket);
+		return socket.getInputStream();
 	}
 
 	@Override
 	protected OutputStream getOutputStream() throws IOException {
-		return IoUtils.getOutputStream(socket);
+		return socket.getOutputStream();
 	}
 
 	@Override

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidExecutorImpl.java

@@ -27,11 +27,14 @@ class AndroidExecutorImpl implements AndroidExecutor {
 	@Inject
 	AndroidExecutorImpl(Application app) {
 		uiHandler = new Handler(app.getApplicationContext().getMainLooper());
-		loop = () -> {
+		loop = new Runnable() {
-			Looper.prepare();
+			@Override
-			backgroundHandler = new Handler();
+			public void run() {
-			startLatch.countDown();
+				Looper.prepare();
-			Looper.loop();
+				backgroundHandler = new Handler();
+				startLatch.countDown();
+				Looper.loop();
+			}
 		};
 	}
 

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSecureRandomProvider.java

@@ -1,93 +0,0 @@
-package org.briarproject.bramble.system;
-
-import android.app.Application;
-import android.bluetooth.BluetoothAdapter;
-import android.bluetooth.BluetoothDevice;
-import android.content.ContentResolver;
-import android.content.Context;
-import android.net.wifi.WifiConfiguration;
-import android.net.wifi.WifiManager;
-import android.os.Build;
-import android.os.Parcel;
-import android.provider.Settings;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.io.DataOutputStream;
-import java.io.IOException;
-import java.util.List;
-
-import javax.annotation.concurrent.Immutable;
-import javax.inject.Inject;
-
-import static android.content.Context.WIFI_SERVICE;
-import static android.provider.Settings.Secure.ANDROID_ID;
-
-@Immutable
-@NotNullByDefault
-class AndroidSecureRandomProvider extends LinuxSecureRandomProvider {
-
-	private static final int SEED_LENGTH = 32;
-
-	private final Context appContext;
-
-	@Inject
-	AndroidSecureRandomProvider(Application app) {
-		appContext = app.getApplicationContext();
-	}
-
-	@Override
-	protected void writeToEntropyPool(DataOutputStream out) throws IOException {
-		super.writeToEntropyPool(out);
-		out.writeInt(android.os.Process.myPid());
-		out.writeInt(android.os.Process.myTid());
-		out.writeInt(android.os.Process.myUid());
-		if (Build.FINGERPRINT != null) out.writeUTF(Build.FINGERPRINT);
-		if (Build.SERIAL != null) out.writeUTF(Build.SERIAL);
-		ContentResolver contentResolver = appContext.getContentResolver();
-		String id = Settings.Secure.getString(contentResolver, ANDROID_ID);
-		if (id != null) out.writeUTF(id);
-		Parcel parcel = Parcel.obtain();
-		WifiManager wm =
-				(WifiManager) appContext.getSystemService(WIFI_SERVICE);
-		List<WifiConfiguration> configs = wm.getConfiguredNetworks();
-		if (configs != null) {
-			for (WifiConfiguration config : configs)
-				parcel.writeParcelable(config, 0);
-		}
-		BluetoothAdapter bt = BluetoothAdapter.getDefaultAdapter();
-		if (bt != null) {
-			for (BluetoothDevice device : bt.getBondedDevices())
-				parcel.writeParcelable(device, 0);
-		}
-		out.write(parcel.marshall());
-		parcel.recycle();
-	}
-
-	@Override
-	protected void writeSeed() {
-		super.writeSeed();
-		if (Build.VERSION.SDK_INT >= 16 && Build.VERSION.SDK_INT <= 18)
-			applyOpenSslFix();
-	}
-
-	// Based on https://android-developers.googleblog.com/2013/08/some-securerandom-thoughts.html
-	private void applyOpenSslFix() {
-		byte[] seed = new LinuxSecureRandomSpi().engineGenerateSeed(
-				SEED_LENGTH);
-		try {
-			// Seed the OpenSSL PRNG
-			Class.forName("org.apache.harmony.xnet.provider.jsse.NativeCrypto")
-					.getMethod("RAND_seed", byte[].class)
-					.invoke(null, seed);
-			// Mix the output of the Linux PRNG into the OpenSSL PRNG
-			int bytesRead = (Integer) Class.forName(
-					"org.apache.harmony.xnet.provider.jsse.NativeCrypto")
-					.getMethod("RAND_load_file", String.class, long.class)
-					.invoke(null, "/dev/urandom", 1024);
-			if (bytesRead != 1024) throw new IOException();
-		} catch (Exception e) {
-			throw new SecurityException(e);
-		}
-	}
-}

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSeedProvider.java

@@ -0,0 +1,42 @@
+package org.briarproject.bramble.system;
+
+import android.app.Application;
+import android.content.ContentResolver;
+import android.content.Context;
+import android.os.Build;
+import android.provider.Settings;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+import static android.provider.Settings.Secure.ANDROID_ID;
+
+@Immutable
+@NotNullByDefault
+class AndroidSeedProvider extends LinuxSeedProvider {
+
+	private final Context appContext;
+
+	@Inject
+	AndroidSeedProvider(Application app) {
+		appContext = app.getApplicationContext();
+	}
+
+	@Override
+	void writeToEntropyPool(DataOutputStream out) throws IOException {
+		out.writeInt(android.os.Process.myPid());
+		out.writeInt(android.os.Process.myTid());
+		out.writeInt(android.os.Process.myUid());
+		if (Build.FINGERPRINT != null) out.writeUTF(Build.FINGERPRINT);
+		if (Build.SERIAL != null) out.writeUTF(Build.SERIAL);
+		ContentResolver contentResolver = appContext.getContentResolver();
+		String id = Settings.Secure.getString(contentResolver, ANDROID_ID);
+		if (id != null) out.writeUTF(id);
+		super.writeToEntropyPool(out);
+	}
+}

bramble-android/src/main/java/org/briarproject/bramble/system/AndroidSystemModule.java

@@ -4,7 +4,7 @@ import android.app.Application;
 
 import org.briarproject.bramble.api.system.AndroidExecutor;
 import org.briarproject.bramble.api.system.LocationUtils;
-import org.briarproject.bramble.api.system.SecureRandomProvider;
+import org.briarproject.bramble.api.system.SeedProvider;
 
 import javax.inject.Singleton;
 
@@ -16,8 +16,8 @@ public class AndroidSystemModule {
 
 	@Provides
 	@Singleton
-	SecureRandomProvider provideSecureRandomProvider(Application app) {
+	SeedProvider provideSeedProvider(Application app) {
-		return new AndroidSecureRandomProvider(app);
+		return new AndroidSeedProvider(app);
 	}
 
 	@Provides

bramble-api/build.gradle

@@ -1,39 +1,30 @@
-apply plugin: 'java-library'
+apply plugin: 'java'
-sourceCompatibility = 1.8
+sourceCompatibility = 1.6
-targetCompatibility = 1.8
+targetCompatibility = 1.6
 
 apply plugin: 'witness'
 
 dependencies {
-	implementation "com.google.dagger:dagger:2.0.2"
+	compile "com.google.dagger:dagger:2.0.2"
-	implementation 'com.google.code.findbugs:jsr305:3.0.2'
+	compile 'com.google.dagger:dagger-compiler:2.0.2'
+	compile 'com.google.code.findbugs:jsr305:3.0.1'
 
-	testImplementation 'junit:junit:4.12'
+	testCompile 'junit:junit:4.12'
-	testImplementation "org.jmock:jmock:2.8.2"
+	testCompile "org.jmock:jmock:2.8.1"
-	testImplementation "org.jmock:jmock-junit4:2.8.2"
+	testCompile "org.jmock:jmock-junit4:2.8.1"
-	testImplementation "org.jmock:jmock-legacy:2.8.2"
+	testCompile "org.jmock:jmock-legacy:2.8.1"
-	testImplementation "org.hamcrest:hamcrest-library:1.3"
+	testCompile "org.hamcrest:hamcrest-library:1.3"
-	testImplementation "org.hamcrest:hamcrest-core:1.3"
+	testCompile "org.hamcrest:hamcrest-core:1.3"
 }
 
 dependencyVerification {
 	verify = [
-			'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
+			'com.google.dagger:dagger:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
+			'com.google.dagger:dagger-compiler:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
-			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
+			'com.google.code.findbugs:jsr305:c885ce34249682bc0236b4a7d56efcc12048e6135a5baf7a9cde8ad8cda13fcd',
-			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
+			'javax.inject:javax.inject:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
-			'junit:junit:4.12:junit-4.12.jar:59721f0805e223d84b90677887d9ff567dc534d7c502ca903c0c2b17f05c116a',
+			'com.google.dagger:dagger-producers:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
-			'org.apache.ant:ant-launcher:1.9.4:ant-launcher-1.9.4.jar:7bccea20b41801ca17bcbc909a78c835d0f443f12d639c77bd6ae3d05861608d',
+			'com.google.guava:guava:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'org.apache.ant:ant:1.9.4:ant-1.9.4.jar:649ae0730251de07b8913f49286d46bba7b92d47c5f332610aa426c4f02161d8',
-			'org.beanshell:bsh:1.3.0:bsh-1.3.0.jar:9b04edc75d19db54f1b4e8b5355e9364384c6cf71eb0a1b9724c159d779879f8',
-			'org.hamcrest:hamcrest-core:1.3:hamcrest-core-1.3.jar:66fdef91e9739348df7a096aa384a5685f4e875584cce89386a7a47251c4d8e9',
-			'org.hamcrest:hamcrest-library:1.3:hamcrest-library-1.3.jar:711d64522f9ec410983bd310934296da134be4254a125080a0416ec178dfad1c',
-			'org.jmock:jmock-junit4:2.8.2:jmock-junit4-2.8.2.jar:f7ee4df4f7bd7b7f1cafad3b99eb74d579f109d5992ff625347352edb55e674c',
-			'org.jmock:jmock-legacy:2.8.2:jmock-legacy-2.8.2.jar:f2b985a5c08a9edb7f37612330c058809da3f6a6d63ce792426ebf8ff0d6d31b',
-			'org.jmock:jmock-testjar:2.8.2:jmock-testjar-2.8.2.jar:8900860f72c474e027cf97fe78dcbf154a1aa7fc62b6845c5fb4e4f3c7bc8760',
-			'org.jmock:jmock:2.8.2:jmock-2.8.2.jar:6c73cb4a2e6dbfb61fd99c9a768539c170ab6568e57846bd60dbf19596b65b16',
-			'org.objenesis:objenesis:2.1:objenesis-2.1.jar:c74330cc6b806c804fd37e74487b4fe5d7c2750c5e15fbc6efa13bdee1bdef80',
-			'org.ow2.asm:asm:5.0.4:asm-5.0.4.jar:896618ed8ae62702521a78bc7be42b7c491a08e6920a15f89a3ecdec31e9a220',
 	]
 }
 
@@ -48,8 +39,3 @@ task jarTest(type: Jar, dependsOn: testClasses) {
 artifacts {
 	testOutput jarTest
 }
-
-// If a Java 6 JRE is available, check we're not using any Java 7 or 8 APIs
-tasks.withType(JavaCompile) {
-	useJava6StandardLibrary(it)
-}

bramble-api/src/main/java/org/briarproject/bramble/api/Bytes.java

@@ -1,7 +1,6 @@
 package org.briarproject.bramble.api;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.util.StringUtils;
 
 import java.util.Arrays;
 import java.util.Comparator;
@@ -54,12 +53,6 @@ public class Bytes implements Comparable<Bytes> {
 		return aBytes.length - bBytes.length;
 	}
 
-	@Override
-	public String toString() {
-		return getClass().getSimpleName() +
-				"(" + StringUtils.toHexString(getBytes()) + ")";
-	}
-
 	public static class BytesComparator implements Comparator<Bytes> {
 
 		@Override

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

@@ -23,7 +23,7 @@ public class BdfMessageContext {
 	}
 
 	public BdfMessageContext(BdfDictionary dictionary) {
-		this(dictionary, Collections.emptyList());
+		this(dictionary, Collections.<MessageId>emptyList());
 	}
 
 	public BdfDictionary getDictionary() {

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

@@ -10,6 +10,8 @@ public interface CryptoComponent {
 
 	SecretKey generateSecretKey();
 
+	PseudoRandom getPseudoRandom(int seed1, int seed2);
+
 	SecureRandom getSecureRandom();
 
 	KeyPair generateAgreementKeyPair();
@@ -22,6 +24,15 @@ public interface CryptoComponent {
 
 	KeyParser getMessageKeyParser();
 
+	/** Generates a random invitation code. */
+	int generateBTInvitationCode();
+
+	/**
+	 * Derives a confirmation code from the given master secret.
+	 * @param alice whether the code is for use by Alice or Bob.
+	 */
+	int deriveBTConfirmationCode(SecretKey master, boolean alice);
+
 	/**
 	 * Derives a stream header key from the given master secret.
 	 * @param alice whether the key is for use by Alice or Bob.
@@ -126,8 +137,7 @@ public interface CryptoComponent {
 	TransportKeys rotateTransportKeys(TransportKeys k, long rotationPeriod);
 
 	/** Encodes the pseudo-random tag that is used to recognise a stream. */
-	void encodeTag(byte[] tag, SecretKey tagKey, int protocolVersion,
+	void encodeTag(byte[] tag, SecretKey tagKey, long streamNumber);
-			long streamNumber);
 
 	/**
 	 * Signs the given byte[] with the given PrivateKey.

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

@@ -6,9 +6,9 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 public interface PasswordStrengthEstimator {
 
 	float NONE = 0;
-	float WEAK = 0.25f;
+	float WEAK = 0.4f;
-	float QUITE_WEAK = 0.5f;
+	float QUITE_WEAK = 0.6f;
-	float QUITE_STRONG = 0.75f;
+	float QUITE_STRONG = 0.8f;
 	float STRONG = 1;
 
 	/**

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

@@ -0,0 +1,12 @@
+package org.briarproject.bramble.api.crypto;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+/**
+ * A deterministic pseudo-random number generator.
+ */
+@NotNullByDefault
+public interface PseudoRandom {
+
+	byte[] nextBytes(int bytes);
+}

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

@@ -14,9 +14,8 @@ public interface StreamDecrypterFactory {
 	StreamDecrypter createStreamDecrypter(InputStream in, StreamContext ctx);
 
 	/**
-	 * Creates a {@link StreamDecrypter} for decrypting a contact exchange
+	 * Creates a {@link StreamDecrypter} for decrypting an invitation stream.
-	 * stream.
 	 */
-	StreamDecrypter createContactExchangeStreamDecrypter(InputStream in,
+	StreamDecrypter createInvitationStreamDecrypter(InputStream in,
 			SecretKey headerKey);
 }

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

@@ -14,9 +14,8 @@ public interface StreamEncrypterFactory {
 	StreamEncrypter createStreamEncrypter(OutputStream out, StreamContext ctx);
 
 	/**
-	 * Creates a {@link StreamEncrypter} for encrypting a contact exchange
+	 * Creates a {@link StreamEncrypter} for encrypting an invitation stream.
-	 * stream.
 	 */
-	StreamEncrypter createContactExchangeStreamDecrypter(OutputStream out,
+	StreamEncrypter createInvitationStreamEncrypter(OutputStream out,
 			SecretKey headerKey);
 }

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

@@ -4,14 +4,11 @@ import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.api.FormatException;
 
 import java.util.Map;
-import java.util.Map.Entry;
+import java.util.concurrent.ConcurrentSkipListMap;
-import java.util.TreeMap;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.NotThreadSafe;
 
-@NotThreadSafe
+public class BdfDictionary extends ConcurrentSkipListMap<String, Object> {
-public class BdfDictionary extends TreeMap<String, Object> {
 
 	public static final Object NULL_VALUE = new Object();
 

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

@@ -3,17 +3,15 @@ package org.briarproject.bramble.api.data;
 import org.briarproject.bramble.api.Bytes;
 import org.briarproject.bramble.api.FormatException;
 
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Vector;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.NotThreadSafe;
 
 import static org.briarproject.bramble.api.data.BdfDictionary.NULL_VALUE;
 
-@NotThreadSafe
+public class BdfList extends Vector<Object> {
-public class BdfList extends ArrayList<Object> {
 
 	/**
 	 * Factory method for constructing lists inline.

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

@@ -1,7 +0,0 @@
-package org.briarproject.bramble.api.db;
-
-/**
- * Thrown when the database uses a newer schema than the current code.
- */
-public class DataTooNewException extends DbException {
-}

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

@@ -1,8 +0,0 @@
-package org.briarproject.bramble.api.db;
-
-/**
- * Thrown when the database uses an older schema than the current code and
- * cannot be migrated.
- */
-public class DataTooOldException extends DbException {
-}

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

@@ -37,11 +37,6 @@ public interface DatabaseComponent {
 
 	/**
 	 * Opens the database and returns true if the database already existed.
-	 *
-	 * @throws DataTooNewException if the data uses a newer schema than the
-	 * current code
-	 * @throws DataTooOldException if the data uses an older schema than the
-	 * current code and cannot be migrated
 	 */
 	boolean open() throws DbException;
 
@@ -127,9 +122,8 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Deletes the message with the given ID. Unlike
+	 * Deletes the message with the given ID. The message ID and any other
-	 * {@link #removeMessage(Transaction, MessageId)}, the message ID and any
+	 * associated data are not deleted.
-	 * other associated data are not deleted.
 	 */
 	void deleteMessage(Transaction txn, MessageId m) throws DbException;
 
@@ -458,11 +452,6 @@ public interface DatabaseComponent {
 	 */
 	void removeLocalAuthor(Transaction txn, AuthorId a) throws DbException;
 
-	/**
-	 * Removes a message (and all associated state) from the database.
-	 */
-	void removeMessage(Transaction txn, MessageId m) throws DbException;
-
 	/**
 	 * Removes a transport (and all associated state) from the database.
 	 */

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

@@ -1,11 +1,11 @@
 package org.briarproject.bramble.api.db;
 
-import java.util.TreeMap;
+import java.util.Hashtable;
 
-import javax.annotation.concurrent.NotThreadSafe;
+import javax.annotation.concurrent.ThreadSafe;
 
-@NotThreadSafe
+@ThreadSafe
-public class Metadata extends TreeMap<String, byte[]> {
+public class Metadata extends Hashtable<String, byte[]> {
 
 	/**
 	 * Special value to indicate that a key is being removed.

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

@@ -45,7 +45,7 @@ public class Transaction {
 	 * committed.
 	 */
 	public void attach(Event e) {
-		if (events == null) events = new ArrayList<>();
+		if (events == null) events = new ArrayList<Event>();
 		events.add(e);
 	}
 

bramble-api/src/main/java/org/briarproject/bramble/api/identity/Author.java

@@ -13,9 +13,7 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 public class Author {
 
-	public enum Status {
+	public enum Status {ANONYMOUS, UNKNOWN, UNVERIFIED, VERIFIED, OURSELVES}
-		NONE, ANONYMOUS, UNKNOWN, UNVERIFIED, VERIFIED, OURSELVES
-	}
 
 	private final AuthorId id;
 	private final String name;

bramble-api/src/main/java/org/briarproject/bramble/api/invitation/InvitationConstants.java

@@ -0,0 +1,20 @@
+package org.briarproject.bramble.api.invitation;
+
+public interface InvitationConstants {
+
+	/**
+	 * The connection timeout in milliseconds.
+	 */
+	long CONNECTION_TIMEOUT = 60 * 1000;
+
+	/**
+	 * The confirmation timeout in milliseconds.
+	 */
+	long CONFIRMATION_TIMEOUT = 60 * 1000;
+
+	/**
+	 * The number of bits in an invitation or confirmation code. Codes must fit
+	 * into six decimal digits.
+	 */
+	int CODE_BITS = 19;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/invitation/InvitationListener.java

@@ -0,0 +1,47 @@
+package org.briarproject.bramble.api.invitation;
+
+/**
+ * An interface for receiving updates about the state of an
+ * {@link InvitationTask}.
+ */
+public interface InvitationListener {
+
+	/** Called if a connection to the remote peer is established. */
+	void connectionSucceeded();
+
+	/**
+	 * Called if a connection to the remote peer cannot be established. This
+	 * indicates that the protocol has ended unsuccessfully.
+	 */
+	void connectionFailed();
+
+	/** Called if key agreement with the remote peer succeeds. */
+	void keyAgreementSucceeded(int localCode, int remoteCode);
+
+	/**
+	 * Called if key agreement with the remote peer fails or the connection is
+	 * lost. This indicates that the protocol has ended unsuccessfully.
+	 */
+	void keyAgreementFailed();
+
+	/** Called if the remote peer's confirmation check succeeds. */
+	void remoteConfirmationSucceeded();
+
+	/**
+	 * Called if remote peer's confirmation check fails or the connection is
+	 * lost. This indicates that the protocol has ended unsuccessfully.
+	 */
+	void remoteConfirmationFailed();
+
+	/**
+	 * Called if the exchange of pseudonyms succeeds. This indicates that the
+	 * protocol has ended successfully.
+	 */
+	void pseudonymExchangeSucceeded(String remoteName);
+
+	/**
+	 * Called if the exchange of pseudonyms fails or the connection is lost.
+	 * This indicates that the protocol has ended unsuccessfully.
+	 */
+	void pseudonymExchangeFailed();
+}

bramble-api/src/main/java/org/briarproject/bramble/api/invitation/InvitationState.java

@@ -0,0 +1,85 @@
+package org.briarproject.bramble.api.invitation;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A snapshot of the state of an {@link InvitationTask}.
+ */
+@Immutable
+@NotNullByDefault
+public class InvitationState {
+
+	private final int localInvitationCode, remoteInvitationCode;
+	private final int localConfirmationCode, remoteConfirmationCode;
+	private final boolean connected, connectionFailed;
+	private final boolean localCompared, remoteCompared;
+	private final boolean localMatched, remoteMatched;
+	@Nullable
+	private final String contactName;
+
+	public InvitationState(int localInvitationCode, int remoteInvitationCode,
+			int localConfirmationCode, int remoteConfirmationCode,
+			boolean connected, boolean connectionFailed, boolean localCompared,
+			boolean remoteCompared, boolean localMatched,
+			boolean remoteMatched, @Nullable String contactName) {
+		this.localInvitationCode = localInvitationCode;
+		this.remoteInvitationCode = remoteInvitationCode;
+		this.localConfirmationCode = localConfirmationCode;
+		this.remoteConfirmationCode = remoteConfirmationCode;
+		this.connected = connected;
+		this.connectionFailed = connectionFailed;
+		this.localCompared = localCompared;
+		this.remoteCompared = remoteCompared;
+		this.localMatched = localMatched;
+		this.remoteMatched = remoteMatched;
+		this.contactName = contactName;
+	}
+
+	public int getLocalInvitationCode() {
+		return localInvitationCode;
+	}
+
+	public int getRemoteInvitationCode() {
+		return remoteInvitationCode;
+	}
+
+	public int getLocalConfirmationCode() {
+		return localConfirmationCode;
+	}
+
+	public int getRemoteConfirmationCode() {
+		return remoteConfirmationCode;
+	}
+
+	public boolean getConnected() {
+		return connected;
+	}
+
+	public boolean getConnectionFailed() {
+		return connectionFailed;
+	}
+
+	public boolean getLocalCompared() {
+		return localCompared;
+	}
+
+	public boolean getRemoteCompared() {
+		return remoteCompared;
+	}
+
+	public boolean getLocalMatched() {
+		return localMatched;
+	}
+
+	public boolean getRemoteMatched() {
+		return remoteMatched;
+	}
+
+	@Nullable
+	public String getContactName() {
+		return contactName;
+	}
+}

bramble-api/src/main/java/org/briarproject/bramble/api/invitation/InvitationTask.java

@@ -0,0 +1,38 @@
+package org.briarproject.bramble.api.invitation;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+/**
+ * A task for exchanging invitations with a remote peer.
+ */
+@NotNullByDefault
+public interface InvitationTask {
+
+	/**
+	 * Adds a listener to be informed of state changes and returns the
+	 * task's current state.
+	 */
+	InvitationState addListener(InvitationListener l);
+
+	/**
+	 * Removes the given listener.
+	 */
+	void removeListener(InvitationListener l);
+
+	/**
+	 * Asynchronously starts the connection process.
+	 */
+	void connect();
+
+	/**
+	 * Asynchronously informs the remote peer that the local peer's
+	 * confirmation codes matched.
+	 */
+	void localConfirmationSucceeded();
+
+	/**
+	 * Asynchronously informs the remote peer that the local peer's
+	 * confirmation codes did not match.
+	 */
+	void localConfirmationFailed();
+}

bramble-api/src/main/java/org/briarproject/bramble/api/invitation/InvitationTaskFactory.java

@@ -0,0 +1,15 @@
+package org.briarproject.bramble.api.invitation;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+/**
+ * Creates tasks for exchanging invitations with remote peers.
+ */
+@NotNullByDefault
+public interface InvitationTaskFactory {
+
+	/**
+	 * Creates a task using the given local and remote invitation codes.
+	 */
+	InvitationTask createTask(int localCode, int remoteCode);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/BluetoothConstants.java

@@ -9,5 +9,4 @@ public interface BluetoothConstants {
 	String PROP_ADDRESS = "address";
 	String PROP_UUID = "uuid";
 
-	String PREF_BT_ENABLE = "enable";
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/LanTcpConstants.java

@@ -4,10 +4,4 @@ public interface LanTcpConstants {
 
 	TransportId ID = new TransportId("org.briarproject.bramble.lan");
 
-	// a transport property (shared with contacts)
-	String PROP_IP_PORTS = "ipPorts";
-
-	// a local setting
-	String PREF_LAN_IP_PORTS = "ipPorts";
-
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/PluginCallback.java

@@ -29,11 +29,6 @@ public interface PluginCallback {
 	 */
 	Map<ContactId, TransportProperties> getRemoteProperties();
 
-	/**
-	 * Returns the plugin's remote transport properties for the given contact.
-	 */
-	TransportProperties getRemoteProperties(ContactId c);
-
 	/**
 	 * Merges the given settings with the namespaced settings
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/PluginManager.java

@@ -32,6 +32,11 @@ public interface PluginManager {
 	 */
 	Collection<DuplexPlugin> getDuplexPlugins();
 
+	/**
+	 * Returns any duplex plugins that support invitations.
+	 */
+	Collection<DuplexPlugin> getInvitationPlugins();
+
 	/**
 	 * Returns any duplex plugins that support key agreement.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/TorConstants.java

@@ -4,19 +4,8 @@ public interface TorConstants {
 
 	TransportId ID = new TransportId("org.briarproject.bramble.tor");
 
-	String PROP_ONION = "onion";
-
 	int SOCKS_PORT = 59050;
 	int CONTROL_PORT = 59051;
 
 	int CONNECT_TO_PROXY_TIMEOUT = 5000; // Milliseconds
-	int EXTRA_SOCKET_TIMEOUT = 30000; // Milliseconds
-
-	String PREF_TOR_NETWORK = "network";
-	String PREF_TOR_PORT = "port";
-
-	int PREF_TOR_NETWORK_NEVER = 0;
-	int PREF_TOR_NETWORK_WIFI = 1;
-	int PREF_TOR_NETWORK_ALWAYS = 2;
-
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/duplex/DuplexPlugin.java

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.api.plugin.duplex;
 
 import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
@@ -22,6 +23,20 @@ public interface DuplexPlugin extends Plugin {
 	@Nullable
 	DuplexTransportConnection createConnection(ContactId c);
 
+	/**
+	 * Returns true if the plugin supports exchanging invitations.
+	 */
+	boolean supportsInvitations();
+
+	/**
+	 * Attempts to create and return an invitation connection to the remote
+	 * peer. Returns null if no connection can be established within the given
+	 * time.
+	 */
+	@Nullable
+	DuplexTransportConnection createInvitationConnection(PseudoRandom r,
+			long timeout, boolean alice);
+
 	/**
 	 * Returns true if the plugin supports short-range key agreement.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/DisableBluetoothEvent.java

@@ -1,15 +0,0 @@
-package org.briarproject.bramble.api.plugin.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event that asks the Bluetooth plugin to disable the Bluetooth adapter if
- * we previously enabled it.
- */
-@Immutable
-@NotNullByDefault
-public class DisableBluetoothEvent extends Event {
-}

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/EnableBluetoothEvent.java

@@ -1,14 +0,0 @@
-package org.briarproject.bramble.api.plugin.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import javax.annotation.concurrent.Immutable;
-
-/**
- * An event asks the Bluetooth plugin to enable the Bluetooth adapter.
- */
-@Immutable
-@NotNullByDefault
-public class EnableBluetoothEvent extends Event {
-}

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

@@ -33,7 +33,7 @@ public interface TransportPropertyManager {
 	/**
 	 * Returns the local transport properties for all transports.
 	 * <br/>
-	 * TODO: Transaction can be read-only when code is simplified
+	 * Read-Only
 	 */
 	Map<TransportId, TransportProperties> getLocalProperties(Transaction txn)
 			throws DbException;
@@ -49,13 +49,6 @@ public interface TransportPropertyManager {
 	Map<ContactId, TransportProperties> getRemoteProperties(TransportId t)
 			throws DbException;
 
-	/**
-	 * Returns the remote transport properties for the given contact and
-	 * transport.
-	 */
-	TransportProperties getRemoteProperties(ContactId c, TransportId t)
-			throws DbException;
-
 	/**
 	 * Merges the given properties with the existing local properties for the
 	 * given transport.

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

@@ -22,7 +22,7 @@ public class MessageContext {
 	}
 
 	public MessageContext(Metadata metadata) {
-		this(metadata, Collections.emptyList());
+		this(metadata, Collections.<MessageId>emptyList());
 	}
 
 	public Metadata getMetadata() {

bramble-api/src/main/java/org/briarproject/bramble/api/system/SecureRandomProvider.java

@@ -1,23 +0,0 @@
-package org.briarproject.bramble.api.system;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.security.Provider;
-import java.security.SecureRandom;
-
-import javax.annotation.Nullable;
-
-/**
- * Wrapper for a platform-specific secure random number generator.
- */
-@NotNullByDefault
-public interface SecureRandomProvider {
-
-	/**
-	 * Returns a {@link Provider} that provides a strong {@link SecureRandom}
-	 * implementation, or null if the platform's default implementation should
-	 * be used.
-	 */
-	@Nullable
-	Provider getProvider();
-}

bramble-api/src/main/java/org/briarproject/bramble/api/system/SeedProvider.java

@@ -0,0 +1,18 @@
+package org.briarproject.bramble.api.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+/**
+ * Uses a platform-specific source to provide a seed for a pseudo-random
+ * number generator.
+ */
+@NotNullByDefault
+public interface SeedProvider {
+
+	/**
+	 * The length of the seed in bytes.
+	 */
+	int SEED_BYTES = 32;
+
+	byte[] getSeed();
+}

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

@@ -15,9 +15,9 @@ public interface StreamReaderFactory {
 	InputStream createStreamReader(InputStream in, StreamContext ctx);
 
 	/**
-	 * Creates an {@link InputStream InputStream} for reading from a contact
+	 * Creates an {@link InputStream InputStream} for reading from an
-	 * exchangestream.
+	 * invitation stream.
 	 */
-	InputStream createContactExchangeStreamReader(InputStream in,
+	InputStream createInvitationStreamReader(InputStream in,
 			SecretKey headerKey);
 }

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

@@ -15,9 +15,9 @@ public interface StreamWriterFactory {
 	OutputStream createStreamWriter(OutputStream out, StreamContext ctx);
 
 	/**
-	 * Creates an {@link OutputStream OutputStream} for writing to a contact
+	 * Creates an {@link OutputStream OutputStream} for writing to an
-	 * exchange stream.
+	 * invitation stream.
 	 */
-	OutputStream createContactExchangeStreamWriter(OutputStream out,
+	OutputStream createInvitationStreamWriter(OutputStream out,
 			SecretKey headerKey);
 }

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

@@ -4,11 +4,6 @@ import org.briarproject.bramble.api.crypto.SecretKey;
 
 public interface TransportConstants {
 
-	/**
-	 * The current version of the transport protocol.
-	 */
-	int PROTOCOL_VERSION = 3;
-
 	/**
 	 * The length of the pseudo-random tag in bytes.
 	 */
@@ -19,22 +14,21 @@ public interface TransportConstants {
 	 */
 	int STREAM_HEADER_NONCE_LENGTH = 24;
 
+	/**
+	 * The length of the stream header initialisation vector (IV) in bytes.
+	 */
+	int STREAM_HEADER_IV_LENGTH = STREAM_HEADER_NONCE_LENGTH - 8;
+
 	/**
 	 * The length of the message authentication code (MAC) in bytes.
 	 */
 	int MAC_LENGTH = 16;
 
-	/**
-	 * The length of the stream header plaintext in bytes. The stream header
-	 * contains the protocol version, stream number and frame key.
-	 */
-	int STREAM_HEADER_PLAINTEXT_LENGTH = 2 + 8 + SecretKey.LENGTH;
-
 	/**
 	 * The length of the stream header in bytes.
 	 */
-	int STREAM_HEADER_LENGTH = STREAM_HEADER_NONCE_LENGTH
+	int STREAM_HEADER_LENGTH = STREAM_HEADER_IV_LENGTH + SecretKey.LENGTH
-			+ STREAM_HEADER_PLAINTEXT_LENGTH + MAC_LENGTH;
+			+ MAC_LENGTH;
 
 	/**
 	 * The length of the frame nonce in bytes.

bramble-api/src/main/java/org/briarproject/bramble/util/IoUtils.java

@@ -8,7 +8,6 @@ import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-import java.net.Socket;
 
 import javax.annotation.Nullable;
 
@@ -60,24 +59,4 @@ public class IoUtils {
 			offset += read;
 		}
 	}
-
-	// Workaround for a bug in Android 7, see
-	// https://android-review.googlesource.com/#/c/271775/
-	public static InputStream getInputStream(Socket s) throws IOException {
-		try {
-			return s.getInputStream();
-		} catch (NullPointerException e) {
-			throw new IOException(e);
-		}
-	}
-
-	// Workaround for a bug in Android 7, see
-	// https://android-review.googlesource.com/#/c/271775/
-	public static OutputStream getOutputStream(Socket s) throws IOException {
-		try {
-			return s.getOutputStream();
-		} catch (NullPointerException e) {
-			throw new IOException(e);
-		}
-	}
 }

bramble-api/src/main/java/org/briarproject/bramble/util/PrivacyUtils.java

@@ -19,7 +19,7 @@ public class PrivacyUtils {
 
 	@Nullable
 	public static String scrubMacAddress(@Nullable String address) {
-		if (address == null || address.length() == 0) return null;
+		if (address == null) return null;
 		// this is a fake address we need to know about
 		if (address.equals("02:00:00:00:00:00")) return address;
 		// keep first and last octet of MAC address

bramble-api/src/main/java/org/briarproject/bramble/util/StringUtils.java

@@ -8,7 +8,6 @@ import java.nio.charset.CharacterCodingException;
 import java.nio.charset.Charset;
 import java.nio.charset.CharsetDecoder;
 import java.util.Collection;
-import java.util.Random;
 import java.util.regex.Pattern;
 
 import javax.annotation.Nullable;
@@ -28,7 +27,6 @@ public class StringUtils {
 			'0', '1', '2', '3', '4', '5', '6', '7',
 			'8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
 	};
-	private static final Random random = new Random();
 
 	public static boolean isNullOrEmpty(@Nullable String s) {
 		return s == null || s.length() == 0;
@@ -141,12 +139,4 @@ public class StringUtils {
 		}
 		return s.toString();
 	}
-
-	public static String getRandomString(int length) {
-		char[] c = new char[length];
-		for (int i = 0; i < length; i++)
-			c[i] = (char) ('a' + random.nextInt(26));
-		return new String(c);
-	}
-
 }

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

@@ -3,7 +3,8 @@ package org.briarproject.bramble.test;
 import org.jmock.Mockery;
 import org.junit.After;
 
-public abstract class BrambleMockTestCase extends BrambleTestCase {
+public abstract class BrambleMockTestCase extends
+		BrambleTestCase {
 
 	protected final Mockery context = new Mockery();
 

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

@@ -8,9 +8,12 @@ public abstract class BrambleTestCase {
 
 	public BrambleTestCase() {
 		// Ensure exceptions thrown on worker threads cause tests to fail
-		UncaughtExceptionHandler fail = (thread, throwable) -> {
+		UncaughtExceptionHandler fail = new UncaughtExceptionHandler() {
-			throwable.printStackTrace();
+			@Override
-			fail();
+			public void uncaughtException(Thread thread, Throwable throwable) {
+				throwable.printStackTrace();
+				fail();
+			}
 		};
 		Thread.setDefaultUncaughtExceptionHandler(fail);
 	}

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

@@ -2,27 +2,12 @@ package org.briarproject.bramble.test;
 
 import org.briarproject.bramble.api.UniqueId;
 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.sync.ClientId;
-import org.briarproject.bramble.api.sync.Group;
-import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.Message;
-import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.util.IoUtils;
 
 import java.io.File;
 import java.util.Random;
 import java.util.concurrent.atomic.AtomicInteger;
 
-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.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;
-import static org.briarproject.bramble.util.StringUtils.getRandomString;
-
 public class TestUtils {
 
 	private static final AtomicInteger nextTestDir =
@@ -49,54 +34,15 @@ public class TestUtils {
 		return getRandomBytes(UniqueId.LENGTH);
 	}
 
+	public static String getRandomString(int length) {
+		char[] c = new char[length];
+		for (int i = 0; i < length; i++)
+			c[i] = (char) ('a' + random.nextInt(26));
+		return new String(c);
+	}
+
 	public static SecretKey getSecretKey() {
 		return new SecretKey(getRandomBytes(SecretKey.LENGTH));
 	}
 
-	public static LocalAuthor getLocalAuthor() {
-		return getLocalAuthor(1 + random.nextInt(MAX_AUTHOR_NAME_LENGTH));
-	}
-
-	public static LocalAuthor getLocalAuthor(int nameLength) {
-		AuthorId id = new AuthorId(getRandomId());
-		String name = getRandomString(nameLength);
-		byte[] publicKey = getRandomBytes(MAX_PUBLIC_KEY_LENGTH);
-		byte[] privateKey = getRandomBytes(MAX_PUBLIC_KEY_LENGTH);
-		long created = System.currentTimeMillis();
-		return new LocalAuthor(id, name, publicKey, privateKey, created);
-	}
-
-	public static Author getAuthor() {
-		return getAuthor(1 + random.nextInt(MAX_AUTHOR_NAME_LENGTH));
-	}
-
-	public static Author getAuthor(int nameLength) {
-		AuthorId id = new AuthorId(getRandomId());
-		String name = getRandomString(nameLength);
-		byte[] publicKey = getRandomBytes(MAX_PUBLIC_KEY_LENGTH);
-		return new Author(id, name, publicKey);
-	}
-
-	public static Group getGroup(ClientId clientId) {
-		int descriptorLength = 1 + random.nextInt(MAX_GROUP_DESCRIPTOR_LENGTH);
-		return getGroup(clientId, descriptorLength);
-	}
-
-	public static Group getGroup(ClientId clientId, int descriptorLength) {
-		GroupId groupId = new GroupId(getRandomId());
-		byte[] descriptor = getRandomBytes(descriptorLength);
-		return new Group(groupId, clientId, descriptor);
-	}
-
-	public static Message getMessage(GroupId groupId) {
-		int bodyLength = 1 + random.nextInt(MAX_MESSAGE_BODY_LENGTH);
-		return getMessage(groupId, MESSAGE_HEADER_LENGTH + bodyLength);
-	}
-
-	public static Message getMessage(GroupId groupId, int rawLength) {
-		MessageId id = new MessageId(getRandomId());
-		byte[] raw = getRandomBytes(rawLength);
-		long timestamp = System.currentTimeMillis();
-		return new Message(id, groupId, timestamp, raw);
-	}
 }

bramble-core/build.gradle

@@ -1,54 +1,26 @@
-apply plugin: 'java-library'
+plugins {
-sourceCompatibility = 1.8
+	id "java"
-targetCompatibility = 1.8
+	id "net.ltgt.apt" version "0.9"
+	id "idea"
+}
+sourceCompatibility = 1.6
+targetCompatibility = 1.6
 
-apply plugin: 'net.ltgt.apt'
-apply plugin: 'idea'
 apply plugin: 'witness'
 
 dependencies {
-	implementation project(path: ':bramble-api', configuration: 'default')
+	compile project(':bramble-api')
-	implementation 'com.madgag.spongycastle:core:1.58.0.0'
+	compile fileTree(dir: 'libs', include: '*.jar')
-	implementation 'com.h2database:h2:1.4.192' // This is the last version that supports Java 1.6
+	compile 'com.madgag.spongycastle:core:1.54.0.0'
-	implementation 'org.bitlet:weupnp:0.1.4'
+	compile 'com.h2database:h2:1.4.190'
 
-	apt 'com.google.dagger:dagger-compiler:2.0.2'
+	testCompile project(path: ':bramble-api', configuration: 'testOutput')
-
-	testImplementation project(path: ':bramble-api', configuration: 'testOutput')
-	testImplementation 'junit:junit:4.12'
-	testImplementation "org.jmock:jmock:2.8.2"
-	testImplementation "org.jmock:jmock-junit4:2.8.2"
-	testImplementation "org.jmock:jmock-legacy:2.8.2"
-	testImplementation "org.hamcrest:hamcrest-library:1.3"
-	testImplementation "org.hamcrest:hamcrest-core:1.3"
-
-	testApt 'com.google.dagger:dagger-compiler:2.0.2'
 }
 
 dependencyVerification {
 	verify = [
-			'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
+			'com.madgag.spongycastle:core:1e7fa4b19ccccd1011364ab838d0b4702470c178bbbdd94c5c90b2d4d749ea1e',
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
+			'com.h2database:h2:23ba495a07bbbb3bd6c3084d10a96dad7a23741b8b6d64b213459a784195a98c'
-			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
-			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
-			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
-			'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
-			'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
-			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
-			'junit:junit:4.12:junit-4.12.jar:59721f0805e223d84b90677887d9ff567dc534d7c502ca903c0c2b17f05c116a',
-			'org.apache.ant:ant-launcher:1.9.4:ant-launcher-1.9.4.jar:7bccea20b41801ca17bcbc909a78c835d0f443f12d639c77bd6ae3d05861608d',
-			'org.apache.ant:ant:1.9.4:ant-1.9.4.jar:649ae0730251de07b8913f49286d46bba7b92d47c5f332610aa426c4f02161d8',
-			'org.beanshell:bsh:1.3.0:bsh-1.3.0.jar:9b04edc75d19db54f1b4e8b5355e9364384c6cf71eb0a1b9724c159d779879f8',
-			'org.bitlet:weupnp:0.1.4:weupnp-0.1.4.jar:88df7e6504929d00bdb832863761385c68ab92af945b04f0770b126270a444fb',
-			'org.hamcrest:hamcrest-core:1.3:hamcrest-core-1.3.jar:66fdef91e9739348df7a096aa384a5685f4e875584cce89386a7a47251c4d8e9',
-			'org.hamcrest:hamcrest-library:1.3:hamcrest-library-1.3.jar:711d64522f9ec410983bd310934296da134be4254a125080a0416ec178dfad1c',
-			'org.jmock:jmock-junit4:2.8.2:jmock-junit4-2.8.2.jar:f7ee4df4f7bd7b7f1cafad3b99eb74d579f109d5992ff625347352edb55e674c',
-			'org.jmock:jmock-legacy:2.8.2:jmock-legacy-2.8.2.jar:f2b985a5c08a9edb7f37612330c058809da3f6a6d63ce792426ebf8ff0d6d31b',
-			'org.jmock:jmock-testjar:2.8.2:jmock-testjar-2.8.2.jar:8900860f72c474e027cf97fe78dcbf154a1aa7fc62b6845c5fb4e4f3c7bc8760',
-			'org.jmock:jmock:2.8.2:jmock-2.8.2.jar:6c73cb4a2e6dbfb61fd99c9a768539c170ab6568e57846bd60dbf19596b65b16',
-			'org.objenesis:objenesis:2.1:objenesis-2.1.jar:c74330cc6b806c804fd37e74487b4fe5d7c2750c5e15fbc6efa13bdee1bdef80',
-			'org.ow2.asm:asm:5.0.4:asm-5.0.4.jar:896618ed8ae62702521a78bc7be42b7c491a08e6920a15f89a3ecdec31e9a220',
 	]
 }
 
@@ -63,8 +35,3 @@ task jarTest(type: Jar, dependsOn: testClasses) {
 artifacts {
 	testOutput jarTest
 }
-
-// If a Java 6 JRE is available, check we're not using any Java 7 or 8 APIs
-tasks.withType(JavaCompile) {
-	useJava6StandardLibrary(it)
-}

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

@@ -8,6 +8,7 @@ import org.briarproject.bramble.db.DatabaseExecutorModule;
 import org.briarproject.bramble.db.DatabaseModule;
 import org.briarproject.bramble.event.EventModule;
 import org.briarproject.bramble.identity.IdentityModule;
+import org.briarproject.bramble.invitation.InvitationModule;
 import org.briarproject.bramble.keyagreement.KeyAgreementModule;
 import org.briarproject.bramble.lifecycle.LifecycleModule;
 import org.briarproject.bramble.plugin.PluginModule;
@@ -31,6 +32,7 @@ import dagger.Module;
 		DatabaseExecutorModule.class,
 		EventModule.class,
 		IdentityModule.class,
+		InvitationModule.class,
 		KeyAgreementModule.class,
 		LifecycleModule.class,
 		PluginModule.class,
@@ -52,7 +54,6 @@ public class BrambleCoreModule {
 		c.inject(new IdentityModule.EagerSingletons());
 		c.inject(new LifecycleModule.EagerSingletons());
 		c.inject(new PluginModule.EagerSingletons());
-		c.inject(new PropertiesModule.EagerSingletons());
 		c.inject(new SyncModule.EagerSingletons());
 		c.inject(new SystemModule.EagerSingletons());
 		c.inject(new TransportModule.EagerSingletons());

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

@@ -1,81 +0,0 @@
-package org.briarproject.bramble;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.LinkedList;
-import java.util.Queue;
-import java.util.concurrent.Executor;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-import javax.annotation.concurrent.GuardedBy;
-
-import static java.util.logging.Level.FINE;
-
-/**
- * An {@link Executor} that delegates its tasks to another {@link Executor}
- * while limiting the number of tasks that are delegated concurrently. Tasks
- * are delegated in the order they are submitted to this executor.
- */
-@NotNullByDefault
-public class PoliteExecutor implements Executor {
-
-	private static final Level LOG_LEVEL = FINE;
-
-	private final Object lock = new Object();
-	@GuardedBy("lock")
-	private final Queue<Runnable> queue = new LinkedList<>();
-	private final Executor delegate;
-	private final int maxConcurrentTasks;
-	private final Logger log;
-
-	@GuardedBy("lock")
-	private int concurrentTasks = 0;
-
-	/**
-	 * @param tag the tag to be used for logging
-	 * @param delegate the executor to which tasks will be delegated
-	 * @param maxConcurrentTasks the maximum number of tasks that will be
-	 * delegated concurrently. If this is set to 1, tasks submitted to this
-	 * executor will run in the order they are submitted and will not run
-	 * concurrently
-	 */
-	public PoliteExecutor(String tag, Executor delegate,
-			int maxConcurrentTasks) {
-		this.delegate = delegate;
-		this.maxConcurrentTasks = maxConcurrentTasks;
-		log = Logger.getLogger(tag);
-	}
-
-	@Override
-	public void execute(Runnable r) {
-		long submitted = System.currentTimeMillis();
-		Runnable wrapped = () -> {
-			if (log.isLoggable(LOG_LEVEL)) {
-				long queued = System.currentTimeMillis() - submitted;
-				log.log(LOG_LEVEL, "Queue time " + queued + " ms");
-			}
-			try {
-				r.run();
-			} finally {
-				scheduleNext();
-			}
-		};
-		synchronized (lock) {
-			if (concurrentTasks < maxConcurrentTasks) {
-				concurrentTasks++;
-				delegate.execute(wrapped);
-			} else {
-				queue.add(wrapped);
-			}
-		}
-	}
-
-	private void scheduleNext() {
-		synchronized (lock) {
-			Runnable next = queue.poll();
-			if (next == null) concurrentTasks--;
-			else delegate.execute(next);
-		}
-	}
-}

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

@@ -1,46 +0,0 @@
-package org.briarproject.bramble;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.util.concurrent.BlockingQueue;
-import java.util.concurrent.RejectedExecutionHandler;
-import java.util.concurrent.ThreadPoolExecutor;
-import java.util.concurrent.TimeUnit;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-import static java.util.logging.Level.FINE;
-
-@NotNullByDefault
-public class TimeLoggingExecutor extends ThreadPoolExecutor {
-
-	private static final Level LOG_LEVEL = FINE;
-
-	private final Logger log;
-
-	public TimeLoggingExecutor(String tag, int corePoolSize, int maxPoolSize,
-			long keepAliveTime, TimeUnit unit,
-			BlockingQueue<Runnable> workQueue,
-			RejectedExecutionHandler handler) {
-		super(corePoolSize, maxPoolSize, keepAliveTime, unit, workQueue,
-				handler);
-		log = Logger.getLogger(tag);
-	}
-
-	@Override
-	public void execute(Runnable r) {
-		if (log.isLoggable(LOG_LEVEL)) {
-			long submitted = System.currentTimeMillis();
-			super.execute(() -> {
-				long started = System.currentTimeMillis();
-				long queued = started - submitted;
-				log.log(LOG_LEVEL, "Queue time " + queued + " ms");
-				r.run();
-				long executing = System.currentTimeMillis() - started;
-				log.log(LOG_LEVEL, "Execution time " + executing + " ms");
-			});
-		} else {
-			super.execute(r);
-		}
-	}
-}

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

@@ -201,7 +201,8 @@ class ClientHelperImpl implements ClientHelper {
 	public Map<MessageId, BdfDictionary> getMessageMetadataAsDictionary(
 			Transaction txn, GroupId g) throws DbException, FormatException {
 		Map<MessageId, Metadata> raw = db.getMessageMetadata(txn, g);
-		Map<MessageId, BdfDictionary> parsed = new HashMap<>(raw.size());
+		Map<MessageId, BdfDictionary> parsed =
+				new HashMap<MessageId, BdfDictionary>(raw.size());
 		for (Entry<MessageId, Metadata> e : raw.entrySet())
 			parsed.put(e.getKey(), metadataParser.parse(e.getValue()));
 		return parsed;
@@ -228,7 +229,8 @@ class ClientHelperImpl implements ClientHelper {
 			FormatException {
 		Metadata metadata = metadataEncoder.encode(query);
 		Map<MessageId, Metadata> raw = db.getMessageMetadata(txn, g, metadata);
-		Map<MessageId, BdfDictionary> parsed = new HashMap<>(raw.size());
+		Map<MessageId, BdfDictionary> parsed =
+				new HashMap<MessageId, BdfDictionary>(raw.size());
 		for (Entry<MessageId, Metadata> e : raw.entrySet())
 			parsed.put(e.getKey(), metadataParser.parse(e.getValue()));
 		return parsed;

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

@@ -80,7 +80,7 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 	private volatile boolean alice;
 
 	@Inject
-	ContactExchangeTaskImpl(DatabaseComponent db,
+	public ContactExchangeTaskImpl(DatabaseComponent db,
 			AuthorFactory authorFactory, BdfReaderFactory bdfReaderFactory,
 			BdfWriterFactory bdfWriterFactory, Clock clock,
 			ConnectionManager connectionManager, ContactManager contactManager,
@@ -146,12 +146,12 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 
 		// Create the readers
 		InputStream streamReader =
-				streamReaderFactory.createContactExchangeStreamReader(in,
+				streamReaderFactory.createInvitationStreamReader(in,
 						alice ? bobHeaderKey : aliceHeaderKey);
 		BdfReader r = bdfReaderFactory.createReader(streamReader);
 		// Create the writers
 		OutputStream streamWriter =
-				streamWriterFactory.createContactExchangeStreamWriter(out,
+				streamWriterFactory.createInvitationStreamWriter(out,
 						alice ? aliceHeaderKey : bobHeaderKey);
 		BdfWriter w = bdfWriterFactory.createWriter(streamWriter);
 
@@ -184,7 +184,12 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 			// Close the outgoing stream and expect EOF on the incoming stream
 			w.close();
 			if (!r.eof()) LOG.warning("Unexpected data at end of connection");
-		} catch (GeneralSecurityException | IOException e) {
+		} catch (GeneralSecurityException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			listener.contactExchangeFailed();
+			tryToClose(conn, true);
+			return;
+		} catch (IOException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			listener.contactExchangeFailed();
 			tryToClose(conn, true);
@@ -271,7 +276,8 @@ class ContactExchangeTaskImpl extends Thread implements ContactExchangeTask {
 
 	private Map<TransportId, TransportProperties> receiveTransportProperties(
 			BdfReader r) throws IOException {
-		Map<TransportId, TransportProperties> remote = new HashMap<>();
+		Map<TransportId, TransportProperties> remote =
+				new HashMap<TransportId, TransportProperties>();
 		r.readListStart();
 		while (!r.hasListEnd()) {
 			r.readListStart();

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

@@ -34,8 +34,8 @@ class ContactManagerImpl implements ContactManager {
 	ContactManagerImpl(DatabaseComponent db, KeyManager keyManager) {
 		this.db = db;
 		this.keyManager = keyManager;
-		addHooks = new CopyOnWriteArrayList<>();
+		addHooks = new CopyOnWriteArrayList<AddContactHook>();
-		removeHooks = new CopyOnWriteArrayList<>();
+		removeHooks = new CopyOnWriteArrayList<RemoveContactHook>();
 	}
 
 	@Override
@@ -125,7 +125,7 @@ class ContactManagerImpl implements ContactManager {
 		} finally {
 			db.endTransaction(txn);
 		}
-		List<Contact> active = new ArrayList<>(contacts.size());
+		List<Contact> active = new ArrayList<Contact>(contacts.size());
 		for (Contact c : contacts) if (c.isActive()) active.add(c);
 		return active;
 	}

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

@@ -0,0 +1,62 @@
+package org.briarproject.bramble.crypto;
+
+import java.security.Provider;
+import java.security.SecureRandom;
+import java.security.SecureRandomSpi;
+
+/**
+ * A {@link SecureRandom} implementation that combines the outputs of two or
+ * more other implementations using XOR.
+ */
+class CombinedSecureRandom extends SecureRandom {
+
+	private static final Provider PROVIDER = new CombinedProvider();
+
+	CombinedSecureRandom(SecureRandom... randoms) {
+		super(new CombinedSecureRandomSpi(randoms), PROVIDER);
+	}
+
+	private static class CombinedSecureRandomSpi extends SecureRandomSpi {
+
+		private final SecureRandom[] randoms;
+
+		private CombinedSecureRandomSpi(SecureRandom... randoms) {
+			if (randoms.length < 2) throw new IllegalArgumentException();
+			this.randoms = randoms;
+		}
+
+		@Override
+		protected byte[] engineGenerateSeed(int numBytes) {
+			byte[] combined = new byte[numBytes];
+			for (SecureRandom random : randoms) {
+				byte[] b = random.generateSeed(numBytes);
+				int length = Math.min(numBytes, b.length);
+				for (int i = 0; i < length; i++)
+					combined[i] = (byte) (combined[i] ^ b[i]);
+			}
+			return combined;
+		}
+
+		@Override
+		protected void engineNextBytes(byte[] b) {
+			byte[] temp = new byte[b.length];
+			for (SecureRandom random : randoms) {
+				random.nextBytes(temp);
+				for (int i = 0; i < b.length; i++)
+					b[i] = (byte) (b[i] ^ temp[i]);
+			}
+		}
+
+		@Override
+		protected void engineSetSeed(byte[] seed) {
+			for (SecureRandom random : randoms) random.setSeed(seed);
+		}
+	}
+
+	private static class CombinedProvider extends Provider {
+
+		private CombinedProvider() {
+			super("Combined", 1.0, "");
+		}
+	}
+}

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

@@ -4,10 +4,11 @@ import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
 import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.PrivateKey;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.plugin.TransportId;
-import org.briarproject.bramble.api.system.SecureRandomProvider;
+import org.briarproject.bramble.api.system.SeedProvider;
 import org.briarproject.bramble.api.transport.IncomingKeys;
 import org.briarproject.bramble.api.transport.OutgoingKeys;
 import org.briarproject.bramble.api.transport.TransportKeys;
@@ -28,10 +29,7 @@ import org.spongycastle.crypto.params.KeyParameter;
 
 import java.nio.charset.Charset;
 import java.security.GeneralSecurityException;
-import java.security.NoSuchAlgorithmException;
-import java.security.Provider;
 import java.security.SecureRandom;
-import java.security.Security;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -40,13 +38,12 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.INFO;
+import static org.briarproject.bramble.api.invitation.InvitationConstants.CODE_BITS;
 import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.COMMIT_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
 import static org.briarproject.bramble.crypto.EllipticCurveConstants.PARAMETERS;
-import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
-import static org.briarproject.bramble.util.ByteUtils.MAX_16_BIT_UNSIGNED;
 import static org.briarproject.bramble.util.ByteUtils.MAX_32_BIT_UNSIGNED;
 
 class CryptoComponentImpl implements CryptoComponent {
@@ -66,6 +63,9 @@ class CryptoComponentImpl implements CryptoComponent {
 		return s.getBytes(Charset.forName("US-ASCII"));
 	}
 
+	// KDF labels for bluetooth confirmation code derivation
+	private static final byte[] BT_A_CONFIRM = ascii("ALICE_CONFIRMATION_CODE");
+	private static final byte[] BT_B_CONFIRM = ascii("BOB_CONFIRMATION_CODE");
 	// KDF labels for contact exchange stream header key derivation
 	private static final byte[] A_INVITE = ascii("ALICE_INVITATION_KEY");
 	private static final byte[] B_INVITE = ascii("BOB_INVITATION_KEY");
@@ -101,26 +101,16 @@ class CryptoComponentImpl implements CryptoComponent {
 	private final MessageEncrypter messageEncrypter;
 
 	@Inject
-	CryptoComponentImpl(SecureRandomProvider secureRandomProvider) {
+	CryptoComponentImpl(SeedProvider seedProvider) {
+		if (!FortunaSecureRandom.selfTest()) throw new RuntimeException();
+		SecureRandom platformSecureRandom = new SecureRandom();
 		if (LOG.isLoggable(INFO)) {
-			SecureRandom defaultSecureRandom = new SecureRandom();
+			String provider = platformSecureRandom.getProvider().getName();
-			String name = defaultSecureRandom.getProvider().getName();
+			String algorithm = platformSecureRandom.getAlgorithm();
-			String algorithm = defaultSecureRandom.getAlgorithm();
+			LOG.info("Default SecureRandom: " + provider + " " + algorithm);
-			LOG.info("Default SecureRandom: " + name + " " + algorithm);
 		}
-		Provider provider = secureRandomProvider.getProvider();
+		SecureRandom fortuna = new FortunaSecureRandom(seedProvider.getSeed());
-		if (provider == null) {
+		secureRandom = new CombinedSecureRandom(platformSecureRandom, fortuna);
-			LOG.info("Using default");
-		} else {
-			installSecureRandomProvider(provider);
-			if (LOG.isLoggable(INFO)) {
-				SecureRandom installedSecureRandom = new SecureRandom();
-				String name = installedSecureRandom.getProvider().getName();
-				String algorithm = installedSecureRandom.getAlgorithm();
-				LOG.info("Installed SecureRandom: " + name + " " + algorithm);
-			}
-		}
-		secureRandom = new SecureRandom();
 		ECKeyGenerationParameters params = new ECKeyGenerationParameters(
 				PARAMETERS, secureRandom);
 		agreementKeyPairGenerator = new ECKeyPairGenerator();
@@ -134,31 +124,6 @@ class CryptoComponentImpl implements CryptoComponent {
 		messageEncrypter = new MessageEncrypter(secureRandom);
 	}
 
-	// Based on https://android-developers.googleblog.com/2013/08/some-securerandom-thoughts.html
-	private void installSecureRandomProvider(Provider provider) {
-		Provider[] providers = Security.getProviders("SecureRandom.SHA1PRNG");
-		if (providers == null || providers.length == 0
-				|| !provider.getClass().equals(providers[0].getClass())) {
-			Security.insertProviderAt(provider, 1);
-		}
-		// Check the new provider is the default when no algorithm is specified
-		SecureRandom random = new SecureRandom();
-		if (!provider.getClass().equals(random.getProvider().getClass())) {
-			throw new SecurityException("Wrong SecureRandom provider: "
-					+ random.getProvider().getClass());
-		}
-		// Check the new provider is the default when SHA1PRNG is specified
-		try {
-			random = SecureRandom.getInstance("SHA1PRNG");
-		} catch (NoSuchAlgorithmException e) {
-			throw new SecurityException(e);
-		}
-		if (!provider.getClass().equals(random.getProvider().getClass())) {
-			throw new SecurityException("Wrong SHA1PRNG provider: "
-					+ random.getProvider().getClass());
-		}
-	}
-
 	@Override
 	public SecretKey generateSecretKey() {
 		byte[] b = new byte[SecretKey.LENGTH];
@@ -166,6 +131,11 @@ class CryptoComponentImpl implements CryptoComponent {
 		return new SecretKey(b);
 	}
 
+	@Override
+	public PseudoRandom getPseudoRandom(int seed1, int seed2) {
+		return new PseudoRandomImpl(seed1, seed2);
+	}
+
 	@Override
 	public SecureRandom getSecureRandom() {
 		return secureRandom;
@@ -237,6 +207,20 @@ class CryptoComponentImpl implements CryptoComponent {
 		return messageEncrypter.getKeyParser();
 	}
 
+	@Override
+	public int generateBTInvitationCode() {
+		int codeBytes = (CODE_BITS + 7) / 8;
+		byte[] random = new byte[codeBytes];
+		secureRandom.nextBytes(random);
+		return ByteUtils.readUint(random, CODE_BITS);
+	}
+
+	@Override
+	public int deriveBTConfirmationCode(SecretKey master, boolean alice) {
+		byte[] b = macKdf(master, alice ? BT_A_CONFIRM : BT_B_CONFIRM);
+		return ByteUtils.readUint(b, CODE_BITS);
+	}
+
 	@Override
 	public SecretKey deriveHeaderKey(SecretKey master,
 			boolean alice) {
@@ -312,7 +296,7 @@ class CryptoComponentImpl implements CryptoComponent {
 	public SecretKey deriveMasterSecret(byte[] theirPublicKey,
 			KeyPair ourKeyPair, boolean alice) throws GeneralSecurityException {
 		return deriveMasterSecret(deriveSharedSecret(
-				theirPublicKey, ourKeyPair, alice));
+				theirPublicKey,ourKeyPair, alice));
 	}
 
 	@Override
@@ -387,11 +371,8 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
-	public void encodeTag(byte[] tag, SecretKey tagKey, int protocolVersion,
+	public void encodeTag(byte[] tag, SecretKey tagKey, long streamNumber) {
-			long streamNumber) {
 		if (tag.length < TAG_LENGTH) throw new IllegalArgumentException();
-		if (protocolVersion < 0 || protocolVersion > MAX_16_BIT_UNSIGNED)
-			throw new IllegalArgumentException();
 		if (streamNumber < 0 || streamNumber > MAX_32_BIT_UNSIGNED)
 			throw new IllegalArgumentException();
 		// Initialise the PRF
@@ -399,14 +380,10 @@ class CryptoComponentImpl implements CryptoComponent {
 		// The output of the PRF must be long enough to use as a tag
 		int macLength = prf.getDigestSize();
 		if (macLength < TAG_LENGTH) throw new IllegalStateException();
-		// The input is the protocol version as a 16-bit integer, followed by
+		// The input is the stream number as a 64-bit integer
-		// the stream number as a 64-bit integer
+		byte[] input = new byte[INT_64_BYTES];
-		byte[] protocolVersionBytes = new byte[INT_16_BYTES];
+		ByteUtils.writeUint64(streamNumber, input, 0);
-		ByteUtils.writeUint16(protocolVersion, protocolVersionBytes, 0);
+		prf.update(input, 0, input.length);
-		prf.update(protocolVersionBytes, 0, protocolVersionBytes.length);
-		byte[] streamNumberBytes = new byte[INT_64_BYTES];
-		ByteUtils.writeUint64(streamNumber, streamNumberBytes, 0);
-		prf.update(streamNumberBytes, 0, streamNumberBytes.length);
 		byte[] mac = new byte[macLength];
 		prf.doFinal(mac, 0);
 		// The output is the first TAG_LENGTH bytes of the MAC
@@ -602,8 +579,8 @@ class CryptoComponentImpl implements CryptoComponent {
 
 	// Package access for testing
 	int chooseIterationCount(int targetMillis) {
-		List<Long> quickSamples = new ArrayList<>(PBKDF_SAMPLES);
+		List<Long> quickSamples = new ArrayList<Long>(PBKDF_SAMPLES);
-		List<Long> slowSamples = new ArrayList<>(PBKDF_SAMPLES);
+		List<Long> slowSamples = new ArrayList<Long>(PBKDF_SAMPLES);
 		long iterationNanos = 0, initNanos = 0;
 		while (iterationNanos <= 0 || initNanos <= 0) {
 			// Sample the running time with one iteration and two iterations
@@ -630,7 +607,7 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	private long sampleRunningTime(int iterations) {
-		byte[] password = {'p', 'a', 's', 's', 'w', 'o', 'r', 'd'};
+		byte[] password = { 'p', 'a', 's', 's', 'w', 'o', 'r', 'd' };
 		byte[] salt = new byte[PBKDF_SALT_BYTES];
 		int keyLengthInBits = SecretKey.LENGTH * 8;
 		long start = System.nanoTime();

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

@@ -1,13 +1,12 @@
 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.PasswordStrengthEstimator;
 import org.briarproject.bramble.api.crypto.StreamDecrypterFactory;
 import org.briarproject.bramble.api.crypto.StreamEncrypterFactory;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
-import org.briarproject.bramble.api.system.SecureRandomProvider;
+import org.briarproject.bramble.api.system.SeedProvider;
 
 import java.security.SecureRandom;
 import java.util.concurrent.BlockingQueue;
@@ -32,29 +31,26 @@ public class CryptoModule {
 	public static class EagerSingletons {
 		@Inject
 		@CryptoExecutor
-		ExecutorService cryptoExecutor;
+		Executor 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);
+			Runtime.getRuntime().availableProcessors();
 
 	private final ExecutorService cryptoExecutor;
 
 	public CryptoModule() {
 		// Use an unbounded queue
-		BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>();
+		BlockingQueue<Runnable> queue = new LinkedBlockingQueue<Runnable>();
 		// 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,
+		cryptoExecutor = new ThreadPoolExecutor(0, MAX_EXECUTOR_THREADS,
-				MAX_EXECUTOR_THREADS, 60, SECONDS, queue, policy);
+				60, SECONDS, queue, policy);
 	}
 
 	@Provides
@@ -64,9 +60,8 @@ public class CryptoModule {
 
 	@Provides
 	@Singleton
-	CryptoComponent provideCryptoComponent(
+	CryptoComponent provideCryptoComponent(SeedProvider seedProvider) {
-			SecureRandomProvider secureRandomProvider) {
+		return new CryptoComponentImpl(seedProvider);
-		return new CryptoComponentImpl(secureRandomProvider);
 	}
 
 	@Provides
@@ -89,18 +84,11 @@ public class CryptoModule {
 	@Provides
 	@Singleton
 	@CryptoExecutor
-	ExecutorService getCryptoExecutorService(
+	Executor getCryptoExecutor(LifecycleManager lifecycleManager) {
-			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/DoubleDigest.java

@@ -0,0 +1,76 @@
+package org.briarproject.bramble.crypto;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.spongycastle.crypto.Digest;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+/**
+ * A message digest that prevents length extension attacks - see Ferguson and
+ * Schneier, <i>Practical Cryptography</i>, chapter 6.
+ * <p>
+ * "Let h be an interative hash function. The hash function h<sub>d</sub> is
+ * defined by h<sub>d</sub> := h(h(m)), and has a claimed security level of
+ * min(k, n/2) where k is the security level of h and n is the size of the hash
+ * result."
+ */
+@NotThreadSafe
+@NotNullByDefault
+class DoubleDigest implements Digest {
+
+	private final Digest delegate;
+
+	DoubleDigest(Digest delegate) {
+		this.delegate = delegate;
+	}
+
+	private byte[] digest() {
+		byte[] digest = new byte[delegate.getDigestSize()];
+		delegate.doFinal(digest, 0); // h(m)
+		delegate.update(digest, 0, digest.length);
+		delegate.doFinal(digest, 0); // h(h(m))
+		return digest;
+	}
+
+	public int digest(byte[] buf, int offset, int len) {
+		byte[] digest = digest();
+		len = Math.min(len, digest.length);
+		System.arraycopy(digest, 0, buf, offset, len);
+		return len;
+	}
+
+	@Override
+	public int getDigestSize() {
+		return delegate.getDigestSize();
+	}
+
+	@Override
+	public String getAlgorithmName() {
+		return "Double " + delegate.getAlgorithmName();
+	}
+
+	@Override
+	public void reset() {
+		delegate.reset();
+	}
+
+	@Override
+	public void update(byte input) {
+		delegate.update(input);
+	}
+
+	public void update(byte[] input) {
+		delegate.update(input, 0, input.length);
+	}
+
+	@Override
+	public void update(byte[] input, int offset, int len) {
+		delegate.update(input, offset, len);
+	}
+
+	@Override
+	public int doFinal(byte[] out, int outOff) {
+		return digest(out, outOff, delegate.getDigestSize());
+	}
+
+}

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

@@ -0,0 +1,114 @@
+package org.briarproject.bramble.crypto;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.spongycastle.crypto.BlockCipher;
+import org.spongycastle.crypto.digests.SHA256Digest;
+import org.spongycastle.crypto.engines.AESLightEngine;
+import org.spongycastle.crypto.params.KeyParameter;
+
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * Implements the Fortuna pseudo-random number generator, as described in
+ * Ferguson and Schneier, <i>Practical Cryptography</i>, chapter 9.
+ */
+@ThreadSafe
+@NotNullByDefault
+class FortunaGenerator {
+
+	private static final int MAX_BYTES_PER_REQUEST = 1024 * 1024;
+	private static final int KEY_BYTES = 32;
+	private static final int BLOCK_BYTES = 16;
+
+	private final Lock lock = new ReentrantLock();
+
+	// The following are locking: lock
+	private final DoubleDigest digest = new DoubleDigest(new SHA256Digest());
+	private final BlockCipher cipher = new AESLightEngine();
+	private final byte[] key = new byte[KEY_BYTES];
+	private final byte[] counter = new byte[BLOCK_BYTES];
+	private final byte[] buffer = new byte[BLOCK_BYTES];
+	private final byte[] newKey = new byte[KEY_BYTES];
+
+	FortunaGenerator(byte[] seed) {
+		reseed(seed);
+	}
+
+	void reseed(byte[] seed) {
+		lock.lock();
+		try {
+			digest.update(key);
+			digest.update(seed);
+			digest.digest(key, 0, KEY_BYTES);
+			incrementCounter();
+		} finally {
+			lock.unlock();
+		}
+
+	}
+
+	// Package access for testing
+	void incrementCounter() {
+		lock.lock();
+		try {
+			counter[0]++;
+			for (int i = 0; counter[i] == 0; i++) {
+				if (i + 1 == BLOCK_BYTES)
+					throw new RuntimeException("Counter exhausted");
+				counter[i + 1]++;
+			}
+		} finally {
+			lock.unlock();
+		}
+	}
+
+	// Package access for testing
+	byte[] getCounter() {
+		lock.lock();
+		try {
+			return counter;
+		} finally {
+			lock.unlock();
+		}
+
+	}
+
+	int nextBytes(byte[] dest, int off, int len) {
+		lock.lock();
+		try {
+			// Don't write more than the maximum number of bytes in one request
+			if (len > MAX_BYTES_PER_REQUEST) len = MAX_BYTES_PER_REQUEST;
+			cipher.init(true, new KeyParameter(key));
+			// Generate full blocks directly into the output buffer
+			int fullBlocks = len / BLOCK_BYTES;
+			for (int i = 0; i < fullBlocks; i++) {
+				cipher.processBlock(counter, 0, dest, off + i * BLOCK_BYTES);
+				incrementCounter();
+			}
+			// Generate a partial block if needed
+			int done = fullBlocks * BLOCK_BYTES, remaining = len - done;
+			if (remaining >= BLOCK_BYTES) throw new AssertionError();
+			if (remaining > 0) {
+				cipher.processBlock(counter, 0, buffer, 0);
+				incrementCounter();
+				// Copy the partial block to the output buffer and erase our copy
+				System.arraycopy(buffer, 0, dest, off + done, remaining);
+				for (int i = 0; i < BLOCK_BYTES; i++) buffer[i] = 0;
+			}
+			// Generate a new key
+			for (int i = 0; i < KEY_BYTES / BLOCK_BYTES; i++) {
+				cipher.processBlock(counter, 0, newKey, i * BLOCK_BYTES);
+				incrementCounter();
+			}
+			System.arraycopy(newKey, 0, key, 0, KEY_BYTES);
+			for (int i = 0; i < KEY_BYTES; i++) newKey[i] = 0;
+			// Return the number of bytes written
+			return len;
+		} finally {
+			lock.unlock();
+		}
+	}
+}

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

@@ -0,0 +1,81 @@
+package org.briarproject.bramble.crypto;
+
+import org.briarproject.bramble.util.StringUtils;
+
+import java.security.Provider;
+import java.security.SecureRandom;
+import java.security.SecureRandomSpi;
+import java.util.Arrays;
+
+/**
+ * A {@link java.security.SecureRandom SecureRandom} implementation based on a
+ * {@link FortunaGenerator}.
+ */
+class FortunaSecureRandom extends SecureRandom {
+
+	// Package access for testing
+	static final byte[] SELF_TEST_VECTOR_1 =
+			StringUtils.fromHexString("4BD6EA599D47E3EE9DD911833C29CA22");
+	static final byte[] SELF_TEST_VECTOR_2 =
+			StringUtils.fromHexString("10984D576E6850E505CA9F42A9BFD88A");
+	static final byte[] SELF_TEST_VECTOR_3 =
+			StringUtils.fromHexString("1E12DA166BD86DCECDE50A8296018DE2");
+
+	private static final Provider PROVIDER = new FortunaProvider();
+
+	FortunaSecureRandom(byte[] seed) {
+		super(new FortunaSecureRandomSpi(seed), PROVIDER);
+	}
+
+	/**
+	 * Tests that the {@link #nextBytes(byte[])} and {@link #setSeed(byte[])}
+	 * methods are passed through to the generator in the expected way.
+	 */
+	static boolean selfTest() {
+		byte[] seed = new byte[32];
+		SecureRandom r = new FortunaSecureRandom(seed);
+		byte[] output = new byte[16];
+		r.nextBytes(output);
+		if (!Arrays.equals(SELF_TEST_VECTOR_1, output)) return false;
+		r.nextBytes(output);
+		if (!Arrays.equals(SELF_TEST_VECTOR_2, output)) return false;
+		r.setSeed(seed);
+		r.nextBytes(output);
+		return Arrays.equals(SELF_TEST_VECTOR_3, output);
+	}
+
+	private static class FortunaSecureRandomSpi extends SecureRandomSpi {
+
+		private final FortunaGenerator generator;
+
+		private FortunaSecureRandomSpi(byte[] seed) {
+			generator = new FortunaGenerator(seed);
+		}
+
+		@Override
+		protected byte[] engineGenerateSeed(int numBytes) {
+			byte[] b = new byte[numBytes];
+			engineNextBytes(b);
+			return b;
+		}
+
+		@Override
+		protected void engineNextBytes(byte[] b) {
+			int offset = 0;
+			while (offset < b.length)
+				offset += generator.nextBytes(b, offset, b.length - offset);
+		}
+
+		@Override
+		protected void engineSetSeed(byte[] seed) {
+			generator.reseed(seed);
+		}
+	}
+
+	private static class FortunaProvider extends Provider {
+
+		private FortunaProvider() {
+			super("Fortuna", 1.0, "");
+		}
+	}
+}

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

@@ -11,14 +11,31 @@ import javax.annotation.concurrent.Immutable;
 @NotNullByDefault
 class PasswordStrengthEstimatorImpl implements PasswordStrengthEstimator {
 
-	// The minimum number of unique characters in a strong password
+	private static final int LOWER = 26;
-	private static final int STRONG_UNIQUE_CHARS = 12;
+	private static final int UPPER = 26;
+	private static final int DIGIT = 10;
+	private static final int OTHER = 10;
+	private static final double STRONG = Math.log(Math.pow(LOWER + UPPER +
+			DIGIT + OTHER, 10));
 
 	@Override
 	public float estimateStrength(String password) {
-		HashSet<Character> unique = new HashSet<>();
+		HashSet<Character> unique = new HashSet<Character>();
 		int length = password.length();
 		for (int i = 0; i < length; i++) unique.add(password.charAt(i));
-		return Math.min(1, (float) unique.size() / STRONG_UNIQUE_CHARS);
+		boolean lower = false, upper = false, digit = false, other = false;
+		for (char c : unique) {
+			if (Character.isLowerCase(c)) lower = true;
+			else if (Character.isUpperCase(c)) upper = true;
+			else if (Character.isDigit(c)) digit = true;
+			else other = true;
+		}
+		int alphabetSize = 0;
+		if (lower) alphabetSize += LOWER;
+		if (upper) alphabetSize += UPPER;
+		if (digit) alphabetSize += DIGIT;
+		if (other) alphabetSize += OTHER;
+		double score = Math.log(Math.pow(alphabetSize, unique.size()));
+		return Math.min(1, (float) (score / STRONG));
 	}
 }

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

@@ -0,0 +1,31 @@
+package org.briarproject.bramble.crypto;
+
+import org.briarproject.bramble.api.crypto.PseudoRandom;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.ByteUtils;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+import static org.briarproject.bramble.util.ByteUtils.INT_32_BYTES;
+
+@NotThreadSafe
+@NotNullByDefault
+class PseudoRandomImpl implements PseudoRandom {
+
+	private final FortunaGenerator generator;
+
+	PseudoRandomImpl(int seed1, int seed2) {
+		byte[] seed = new byte[INT_32_BYTES * 2];
+		ByteUtils.writeUint32(seed1, seed, 0);
+		ByteUtils.writeUint32(seed2, seed, INT_32_BYTES);
+		generator = new FortunaGenerator(seed);
+	}
+
+	@Override
+	public byte[] nextBytes(int length) {
+		byte[] b = new byte[length];
+		int offset = 0;
+		while (offset < length) offset += generator.nextBytes(b, offset, length);
+		return b;
+	}
+}

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

@@ -32,7 +32,7 @@ class StreamDecrypterFactoryImpl implements StreamDecrypterFactory {
 	}
 
 	@Override
-	public StreamDecrypter createContactExchangeStreamDecrypter(InputStream in,
+	public StreamDecrypter createInvitationStreamDecrypter(InputStream in,
 			SecretKey headerKey) {
 		return new StreamDecrypterImpl(in, cipherProvider.get(), 0, headerKey);
 	}

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

@@ -20,11 +20,9 @@ import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_NO
 import static org.briarproject.bramble.api.transport.TransportConstants.MAC_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_FRAME_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
-import static org.briarproject.bramble.api.transport.TransportConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_IV_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_NONCE_LENGTH;
-import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_PLAINTEXT_LENGTH;
-import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 
 @NotThreadSafe
@@ -119,7 +117,7 @@ class StreamDecrypterImpl implements StreamDecrypter {
 
 	private void readStreamHeader() throws IOException {
 		byte[] streamHeaderCiphertext = new byte[STREAM_HEADER_LENGTH];
-		byte[] streamHeaderPlaintext = new byte[STREAM_HEADER_PLAINTEXT_LENGTH];
+		byte[] streamHeaderPlaintext = new byte[SecretKey.LENGTH];
 		// Read the stream header
 		int offset = 0;
 		while (offset < STREAM_HEADER_LENGTH) {
@@ -128,35 +126,21 @@ class StreamDecrypterImpl implements StreamDecrypter {
 			if (read == -1) throw new EOFException();
 			offset += read;
 		}
-		// Extract the nonce
+		// The nonce consists of the stream number followed by the IV
 		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
-		System.arraycopy(streamHeaderCiphertext, 0, streamHeaderNonce, 0,
+		ByteUtils.writeUint64(streamNumber, streamHeaderNonce, 0);
-				STREAM_HEADER_NONCE_LENGTH);
+		System.arraycopy(streamHeaderCiphertext, 0, streamHeaderNonce,
+				INT_64_BYTES, STREAM_HEADER_IV_LENGTH);
 		// Decrypt and authenticate the stream header
 		try {
 			cipher.init(false, streamHeaderKey, streamHeaderNonce);
 			int decrypted = cipher.process(streamHeaderCiphertext,
-					STREAM_HEADER_NONCE_LENGTH,
+					STREAM_HEADER_IV_LENGTH, SecretKey.LENGTH + MAC_LENGTH,
-					STREAM_HEADER_PLAINTEXT_LENGTH + MAC_LENGTH,
 					streamHeaderPlaintext, 0);
-			if (decrypted != STREAM_HEADER_PLAINTEXT_LENGTH)
+			if (decrypted != SecretKey.LENGTH) throw new RuntimeException();
-				throw new RuntimeException();
 		} catch (GeneralSecurityException e) {
 			throw new FormatException();
 		}
-		// Check the protocol version
+		frameKey = new SecretKey(streamHeaderPlaintext);
-		int receivedProtocolVersion =
-				ByteUtils.readUint16(streamHeaderPlaintext, 0);
-		if (receivedProtocolVersion != PROTOCOL_VERSION)
-			throw new FormatException();
-		// Check the stream number
-		long receivedStreamNumber = ByteUtils.readUint64(streamHeaderPlaintext,
-				INT_16_BYTES);
-		if (receivedStreamNumber != streamNumber) throw new FormatException();
-		// Extract the frame key
-		byte[] frameKeyBytes = new byte[SecretKey.LENGTH];
-		System.arraycopy(streamHeaderPlaintext, INT_16_BYTES + INT_64_BYTES,
-				frameKeyBytes, 0, SecretKey.LENGTH);
-		frameKey = new SecretKey(frameKeyBytes);
 	}
 }

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

@@ -13,8 +13,7 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 import javax.inject.Provider;
 
-import static org.briarproject.bramble.api.transport.TransportConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_IV_LENGTH;
-import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_NONCE_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
 
 @Immutable
@@ -37,22 +36,22 @@ class StreamEncrypterFactoryImpl implements StreamEncrypterFactory {
 		AuthenticatedCipher cipher = cipherProvider.get();
 		long streamNumber = ctx.getStreamNumber();
 		byte[] tag = new byte[TAG_LENGTH];
-		crypto.encodeTag(tag, ctx.getTagKey(), PROTOCOL_VERSION, streamNumber);
+		crypto.encodeTag(tag, ctx.getTagKey(), streamNumber);
-		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
+		byte[] streamHeaderIv = new byte[STREAM_HEADER_IV_LENGTH];
-		crypto.getSecureRandom().nextBytes(streamHeaderNonce);
+		crypto.getSecureRandom().nextBytes(streamHeaderIv);
 		SecretKey frameKey = crypto.generateSecretKey();
 		return new StreamEncrypterImpl(out, cipher, streamNumber, tag,
-				streamHeaderNonce, ctx.getHeaderKey(), frameKey);
+				streamHeaderIv, ctx.getHeaderKey(), frameKey);
 	}
 
 	@Override
-	public StreamEncrypter createContactExchangeStreamDecrypter(
+	public StreamEncrypter createInvitationStreamEncrypter(OutputStream out,
-			OutputStream out, SecretKey headerKey) {
+			SecretKey headerKey) {
 		AuthenticatedCipher cipher = cipherProvider.get();
-		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
+		byte[] streamHeaderIv = new byte[STREAM_HEADER_IV_LENGTH];
-		crypto.getSecureRandom().nextBytes(streamHeaderNonce);
+		crypto.getSecureRandom().nextBytes(streamHeaderIv);
 		SecretKey frameKey = crypto.generateSecretKey();
-		return new StreamEncrypterImpl(out, cipher, 0, null, streamHeaderNonce,
+		return new StreamEncrypterImpl(out, cipher, 0, null, streamHeaderIv,
 				headerKey, frameKey);
 	}
 }

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

@@ -18,11 +18,9 @@ import static org.briarproject.bramble.api.transport.TransportConstants.FRAME_NO
 import static org.briarproject.bramble.api.transport.TransportConstants.MAC_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_FRAME_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
-import static org.briarproject.bramble.api.transport.TransportConstants.PROTOCOL_VERSION;
+import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_IV_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_LENGTH;
 import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_NONCE_LENGTH;
-import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_PLAINTEXT_LENGTH;
-import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 
 @NotThreadSafe
@@ -35,7 +33,7 @@ class StreamEncrypterImpl implements StreamEncrypter {
 	private final long streamNumber;
 	@Nullable
 	private final byte[] tag;
-	private final byte[] streamHeaderNonce;
+	private final byte[] streamHeaderIv;
 	private final byte[] frameNonce, frameHeader;
 	private final byte[] framePlaintext, frameCiphertext;
 
@@ -43,13 +41,13 @@ class StreamEncrypterImpl implements StreamEncrypter {
 	private boolean writeTag, writeStreamHeader;
 
 	StreamEncrypterImpl(OutputStream out, AuthenticatedCipher cipher,
-			long streamNumber, @Nullable byte[] tag, byte[] streamHeaderNonce,
+			long streamNumber, @Nullable byte[] tag, byte[] streamHeaderIv,
 			SecretKey streamHeaderKey, SecretKey frameKey) {
 		this.out = out;
 		this.cipher = cipher;
 		this.streamNumber = streamNumber;
 		this.tag = tag;
-		this.streamHeaderNonce = streamHeaderNonce;
+		this.streamHeaderIv = streamHeaderIv;
 		this.streamHeaderKey = streamHeaderKey;
 		this.frameKey = frameKey;
 		frameNonce = new byte[FRAME_NONCE_LENGTH];
@@ -64,8 +62,6 @@ class StreamEncrypterImpl implements StreamEncrypter {
 	@Override
 	public void writeFrame(byte[] payload, int payloadLength,
 			int paddingLength, boolean finalFrame) throws IOException {
-		if (payloadLength < 0 || paddingLength < 0)
-			throw new IllegalArgumentException();
 		if (payloadLength + paddingLength > MAX_PAYLOAD_LENGTH)
 			throw new IllegalArgumentException();
 		// Don't allow the frame counter to wrap
@@ -116,23 +112,22 @@ class StreamEncrypterImpl implements StreamEncrypter {
 	}
 
 	private void writeStreamHeader() throws IOException {
-		// The header contains the protocol version, stream number and frame key
+		// The nonce consists of the stream number followed by the IV
-		byte[] streamHeaderPlaintext = new byte[STREAM_HEADER_PLAINTEXT_LENGTH];
+		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
-		ByteUtils.writeUint16(PROTOCOL_VERSION, streamHeaderPlaintext, 0);
+		ByteUtils.writeUint64(streamNumber, streamHeaderNonce, 0);
-		ByteUtils.writeUint64(streamNumber, streamHeaderPlaintext,
+		System.arraycopy(streamHeaderIv, 0, streamHeaderNonce, INT_64_BYTES,
-				INT_16_BYTES);
+				STREAM_HEADER_IV_LENGTH);
-		System.arraycopy(frameKey.getBytes(), 0, streamHeaderPlaintext,
+		byte[] streamHeaderPlaintext = frameKey.getBytes();
-				INT_16_BYTES + INT_64_BYTES, SecretKey.LENGTH);
 		byte[] streamHeaderCiphertext = new byte[STREAM_HEADER_LENGTH];
-		System.arraycopy(streamHeaderNonce, 0, streamHeaderCiphertext, 0,
+		System.arraycopy(streamHeaderIv, 0, streamHeaderCiphertext, 0,
-				STREAM_HEADER_NONCE_LENGTH);
+				STREAM_HEADER_IV_LENGTH);
-		// Encrypt and authenticate the stream header key
+		// Encrypt and authenticate the frame key
 		try {
 			cipher.init(true, streamHeaderKey, streamHeaderNonce);
 			int encrypted = cipher.process(streamHeaderPlaintext, 0,
-					STREAM_HEADER_PLAINTEXT_LENGTH, streamHeaderCiphertext,
+					SecretKey.LENGTH, streamHeaderCiphertext,
-					STREAM_HEADER_NONCE_LENGTH);
+					STREAM_HEADER_IV_LENGTH);
-			if (encrypted != STREAM_HEADER_PLAINTEXT_LENGTH + MAC_LENGTH)
+			if (encrypted != SecretKey.LENGTH + MAC_LENGTH)
 				throw new RuntimeException();
 		} catch (GeneralSecurityException badCipher) {
 			throw new RuntimeException(badCipher);

bramble-core/src/main/java/org/briarproject/bramble/crypto/XSalsa20Poly1305AuthenticatedCipher.java

@@ -70,7 +70,25 @@ class XSalsa20Poly1305AuthenticatedCipher implements AuthenticatedCipher {
 			byte[] subKey = new byte[SUBKEY_LENGTH];
 			xSalsa20Engine.processBytes(zero, 0, SUBKEY_LENGTH, subKey, 0);
 
-			// Clamp the subkey
+			// Reverse the order of the Poly130 subkey
+			//
+			// NaCl and libsodium use the first 32 bytes of XSalsa20 as the
+			// subkey for crypto_onetimeauth_poly1305, which interprets it
+			// as r[0] ... r[15], k[0] ... k[15]. See section 9 of the NaCl
+			// paper (http://cr.yp.to/highspeed/naclcrypto-20090310.pdf),
+			// where the XSalsa20 output is defined as (r, s, t, ...).
+			//
+			// BC's Poly1305 implementation interprets the subkey as
+			// k[0] ... k[15], r[0] ... r[15] (per poly1305_aes_clamp in
+			// the reference implementation).
+			//
+			// To be NaCl-compatible, we reverse the subkey.
+			System.arraycopy(subKey, 0, zero, 0, SUBKEY_LENGTH / 2);
+			System.arraycopy(subKey, SUBKEY_LENGTH / 2, subKey, 0,
+					SUBKEY_LENGTH / 2);
+			System.arraycopy(zero, 0, subKey, SUBKEY_LENGTH / 2,
+					SUBKEY_LENGTH / 2);
+			// Now we can clamp the correct part of the subkey
 			Poly1305KeyGenerator.clamp(subKey);
 
 			// Initialize Poly1305 with the subkey

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

@@ -2,8 +2,6 @@ package org.briarproject.bramble.db;
 
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
-import org.briarproject.bramble.api.db.DataTooNewException;
-import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.identity.Author;
@@ -39,11 +37,6 @@ interface Database<T> {
 
 	/**
 	 * Opens the database and returns true if the database already existed.
-	 *
-	 * @throws DataTooNewException if the data uses a newer schema than the
-	 * current code
-	 * @throws DataTooOldException if the data uses an older schema than the
-	 * current code and cannot be migrated
 	 */
 	boolean open() throws DbException;
 

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

@@ -67,7 +67,6 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
-import static java.util.logging.Level.FINE;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
@@ -90,6 +89,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	private final ReentrantReadWriteLock lock =
 			new ReentrantReadWriteLock(true);
 
+	private volatile int shutdownHandle = -1;
+
 	@Inject
 	DatabaseComponentImpl(Database<T> db, Class<T> txnClass, EventBus eventBus,
 			ShutdownManager shutdown) {
@@ -101,20 +102,26 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 
 	@Override
 	public boolean open() throws DbException {
-		boolean reopened = db.open();
+		Runnable shutdownHook = new Runnable() {
-		shutdown.addShutdownHook(() -> {
+			@Override
-			try {
+			public void run() {
-				close();
+				try {
-			} catch (DbException e) {
+					close();
-				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+				} catch (DbException e) {
+					if (LOG.isLoggable(WARNING))
+						LOG.log(WARNING, e.toString(), e);
+				}
 			}
-		});
+		};
+		boolean reopened = db.open();
+		shutdownHandle = shutdown.addShutdownHook(shutdownHook);
 		return reopened;
 	}
 
 	@Override
 	public void close() throws DbException {
 		if (closed.getAndSet(true)) return;
+		shutdown.removeShutdownHook(shutdownHandle);
 		db.close();
 	}
 
@@ -123,17 +130,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		// Don't allow reentrant locking
 		if (lock.getReadHoldCount() > 0) throw new IllegalStateException();
 		if (lock.getWriteHoldCount() > 0) throw new IllegalStateException();
-		long start = System.currentTimeMillis();
 		if (readOnly) lock.readLock().lock();
 		else lock.writeLock().lock();
-		if (LOG.isLoggable(FINE)) {
-			long duration = System.currentTimeMillis() - start;
-			if (readOnly) LOG.fine("Waited " + duration + " ms for read lock");
-			else LOG.fine("Waited " + duration + " ms for write lock");
-		}
 		try {
 			return new Transaction(db.startTransaction(), readOnly);
-		} catch (DbException | RuntimeException e) {
+		} catch (DbException e) {
+			if (readOnly) lock.readLock().unlock();
+			else lock.writeLock().unlock();
+			throw e;
+		} catch (RuntimeException e) {
 			if (readOnly) lock.readLock().unlock();
 			else lock.writeLock().unlock();
 			throw e;
@@ -319,7 +324,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
 		Collection<MessageId> ids = db.getMessagesToSend(txn, c, maxLength);
-		List<byte[]> messages = new ArrayList<>(ids.size());
+		List<byte[]> messages = new ArrayList<byte[]>(ids.size());
 		for (MessageId m : ids) {
 			messages.add(db.getRawMessage(txn, m));
 			db.updateExpiryTime(txn, c, m, maxLatency);
@@ -369,7 +374,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchContactException();
 		Collection<MessageId> ids = db.getRequestedMessagesToSend(txn, c,
 				maxLength);
-		List<byte[]> messages = new ArrayList<>(ids.size());
+		List<byte[]> messages = new ArrayList<byte[]>(ids.size());
 		for (MessageId m : ids) {
 			messages.add(db.getRawMessage(txn, m));
 			db.updateExpiryTime(txn, c, m, maxLatency);
@@ -649,16 +654,14 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		T txn = unbox(transaction);
 		if (!db.containsContact(txn, c))
 			throw new NoSuchContactException();
-		Collection<MessageId> acked = new ArrayList<>();
+		Collection<MessageId> acked = new ArrayList<MessageId>();
 		for (MessageId m : a.getMessageIds()) {
 			if (db.containsVisibleMessage(txn, c, m)) {
 				db.raiseSeenFlag(txn, c, m);
 				acked.add(m);
 			}
 		}
-		if (acked.size() > 0) {
+		transaction.attach(new MessagesAckedEvent(c, acked));
-			transaction.attach(new MessagesAckedEvent(c, acked));
-		}
 	}
 
 	@Override
@@ -758,16 +761,6 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		transaction.attach(new LocalAuthorRemovedEvent(a));
 	}
 
-	@Override
-	public void removeMessage(Transaction transaction, MessageId m)
-			throws DbException {
-		if (transaction.isReadOnly()) throw new IllegalArgumentException();
-		T txn = unbox(transaction);
-		if (!db.containsMessage(txn, m))
-			throw new NoSuchMessageException();
-		db.removeMessage(txn, m);
-	}
-
 	@Override
 	public void removeTransport(Transaction transaction, TransportId t)
 			throws DbException {
@@ -884,7 +877,8 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			Map<ContactId, TransportKeys> keys) throws DbException {
 		if (transaction.isReadOnly()) throw new IllegalArgumentException();
 		T txn = unbox(transaction);
-		Map<ContactId, TransportKeys> filtered = new HashMap<>();
+		Map<ContactId, TransportKeys> filtered =
+				new HashMap<ContactId, TransportKeys>();
 		for (Entry<ContactId, TransportKeys> e : keys.entrySet()) {
 			ContactId c = e.getKey();
 			TransportKeys k = e.getValue();

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

@@ -23,4 +23,10 @@ interface DatabaseConstants {
 	 */
 	String SCHEMA_VERSION_KEY = "schemaVersion";
 
+	/**
+	 * The {@link Settings} key under which the minimum supported database
+	 * schema version is stored.
+	 */
+	String MIN_SCHEMA_VERSION_KEY = "minSchemaVersion";
+
 }

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

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.db;
 
-import org.briarproject.bramble.TimeLoggingExecutor;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 
@@ -32,13 +31,13 @@ public class DatabaseExecutorModule {
 
 	public DatabaseExecutorModule() {
 		// Use an unbounded queue
-		BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>();
+		BlockingQueue<Runnable> queue = new LinkedBlockingQueue<Runnable>();
 		// Discard tasks that are submitted during shutdown
 		RejectedExecutionHandler policy =
 				new ThreadPoolExecutor.DiscardPolicy();
 		// Use a single thread and keep it in the pool for 60 secs
-		databaseExecutor = new TimeLoggingExecutor("DatabaseExecutor", 0, 1,
+		databaseExecutor = new ThreadPoolExecutor(0, 1, 60, SECONDS, queue,
-				60, SECONDS, queue, policy);
+				policy);
 	}
 
 	@Provides

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

@@ -26,7 +26,7 @@ public class DatabaseModule {
 	@Singleton
 	DatabaseComponent provideDatabaseComponent(Database<Connection> db,
 			EventBus eventBus, ShutdownManager shutdown) {
-		return new DatabaseComponentImpl<>(db, Connection.class, eventBus,
+		return new DatabaseComponentImpl<Connection>(db, Connection.class,
-				shutdown);
+				eventBus, shutdown);
 	}
 }

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

@@ -3,8 +3,6 @@ package org.briarproject.bramble.db;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.crypto.SecretKey;
-import org.briarproject.bramble.api.db.DataTooNewException;
-import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DbClosedException;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Metadata;
@@ -49,7 +47,6 @@ import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
-import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
@@ -60,6 +57,7 @@ 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;
+import static org.briarproject.bramble.db.DatabaseConstants.MIN_SCHEMA_VERSION_KEY;
 import static org.briarproject.bramble.db.DatabaseConstants.SCHEMA_VERSION_KEY;
 import static org.briarproject.bramble.db.ExponentialBackoff.calculateExpiry;
 
@@ -70,8 +68,8 @@ import static org.briarproject.bramble.db.ExponentialBackoff.calculateExpiry;
 @NotNullByDefault
 abstract class JdbcDatabase implements Database<Connection> {
 
-	// Package access for testing
+	private static final int SCHEMA_VERSION = 29;
-	static final int CODE_SCHEMA_VERSION = 31;
+	private static final int MIN_SCHEMA_VERSION = 29;
 
 	private static final String CREATE_SETTINGS =
 			"CREATE TABLE settings"
@@ -150,16 +148,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private static final String CREATE_MESSAGE_METADATA =
 			"CREATE TABLE messageMetadata"
 					+ " (messageId HASH NOT NULL,"
-					+ " groupId HASH NOT NULL," // Denormalised
-					+ " state INT NOT NULL," // Denormalised
 					+ " key VARCHAR NOT NULL,"
 					+ " value BINARY NOT NULL,"
 					+ " PRIMARY KEY (messageId, key),"
 					+ " FOREIGN KEY (messageId)"
 					+ " REFERENCES messages (messageId)"
-					+ " ON DELETE CASCADE,"
-					+ " FOREIGN KEY (groupId)"
-					+ " REFERENCES groups (groupId)"
 					+ " ON DELETE CASCADE)";
 
 	private static final String CREATE_MESSAGE_DEPENDENCIES =
@@ -239,18 +232,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " 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 =
-			"CREATE INDEX IF NOT EXISTS groupsByClientId"
-					+ " ON groups (clientId)";
-
-	private static final String INDEX_MESSAGE_METADATA_BY_GROUP_ID_STATE =
-			"CREATE INDEX IF NOT EXISTS messageMetadataByGroupIdState"
-					+ " ON messageMetadata (groupId, state)";
-
 	private static final Logger LOG =
 			Logger.getLogger(JdbcDatabase.class.getName());
 
@@ -258,8 +239,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private final String hashType, binaryType, counterType, secretType;
 	private final Clock clock;
 
-	// Locking: connectionsLock
+	private final LinkedList<Connection> connections =
-	private final LinkedList<Connection> connections = new LinkedList<>();
+			new LinkedList<Connection>(); // Locking: connectionsLock
 
 	private int openConnections = 0; // Locking: connectionsLock
 	private boolean closed = false; // Locking: connectionsLock
@@ -286,16 +267,15 @@ abstract class JdbcDatabase implements Database<Connection> {
 		} catch (ClassNotFoundException e) {
 			throw new DbException(e);
 		}
-		// Open the database and create the tables and indexes if necessary
+		// Open the database and create the tables if necessary
 		Connection txn = startTransaction();
 		try {
 			if (reopen) {
-				checkSchemaVersion(txn);
+				if (!checkSchemaVersion(txn)) throw new DbException();
 			} else {
 				createTables(txn);
-				storeSchemaVersion(txn, CODE_SCHEMA_VERSION);
+				storeSchemaVersion(txn);
 			}
-			createIndexes(txn);
 			commitTransaction(txn);
 		} catch (DbException e) {
 			abortTransaction(txn);
@@ -303,49 +283,19 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	/**
+	private boolean checkSchemaVersion(Connection txn) throws DbException {
-	 * Compares the schema version stored in the database with the schema
-	 * version used by the current code and applies any suitable migrations to
-	 * the data if necessary.
-	 *
-	 * @throws DataTooNewException if the data uses a newer schema than the
-	 * current code
-	 * @throws DataTooOldException if the data uses an older schema than the
-	 * current code and cannot be migrated
-	 */
-	private void checkSchemaVersion(Connection txn) throws DbException {
 		Settings s = getSettings(txn, DB_SETTINGS_NAMESPACE);
-		int dataSchemaVersion = s.getInt(SCHEMA_VERSION_KEY, -1);
+		int schemaVersion = s.getInt(SCHEMA_VERSION_KEY, -1);
-		if (dataSchemaVersion == -1) throw new DbException();
+		if (schemaVersion == SCHEMA_VERSION) return true;
-		if (dataSchemaVersion == CODE_SCHEMA_VERSION) return;
+		if (schemaVersion < MIN_SCHEMA_VERSION) return false;
-		if (CODE_SCHEMA_VERSION < dataSchemaVersion)
+		int minSchemaVersion = s.getInt(MIN_SCHEMA_VERSION_KEY, -1);
-			throw new DataTooNewException();
+		return SCHEMA_VERSION >= minSchemaVersion;
-		// Apply any suitable migrations in order
-		for (Migration<Connection> m : getMigrations()) {
-			int start = m.getStartVersion(), end = m.getEndVersion();
-			if (start == dataSchemaVersion) {
-				if (LOG.isLoggable(INFO))
-					LOG.info("Migrating from schema " + start + " to " + end);
-				// Apply the migration
-				m.migrate(txn);
-				// Store the new schema version
-				storeSchemaVersion(txn, end);
-				dataSchemaVersion = end;
-			}
-		}
-		if (dataSchemaVersion != CODE_SCHEMA_VERSION)
-			throw new DataTooOldException();
 	}
 
-	// Package access for testing
+	private void storeSchemaVersion(Connection txn) throws DbException {
-	List<Migration<Connection>> getMigrations() {
-		return Collections.singletonList(new Migration30_31());
-	}
-
-	private void storeSchemaVersion(Connection txn, int version)
-			throws DbException {
 		Settings s = new Settings();
-		s.putInt(SCHEMA_VERSION_KEY, version);
+		s.putInt(SCHEMA_VERSION_KEY, SCHEMA_VERSION);
+		s.putInt(MIN_SCHEMA_VERSION_KEY, MIN_SCHEMA_VERSION);
 		mergeSettings(txn, s, DB_SETTINGS_NAMESPACE);
 	}
 
@@ -390,20 +340,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	private void createIndexes(Connection txn) throws DbException {
-		Statement s = null;
-		try {
-			s = txn.createStatement();
-			s.executeUpdate(INDEX_CONTACTS_BY_AUTHOR_ID);
-			s.executeUpdate(INDEX_GROUPS_BY_CLIENT_ID);
-			s.executeUpdate(INDEX_MESSAGE_METADATA_BY_GROUP_ID_STATE);
-			s.close();
-		} catch (SQLException e) {
-			tryToClose(s);
-			throw new DbException(e);
-		}
-	}
-
 	private String insertTypeNames(String s) {
 		s = s.replaceAll("HASH", hashType);
 		s = s.replaceAll("BINARY", binaryType);
@@ -522,8 +458,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			// Create a contact row
 			String sql = "INSERT INTO contacts"
-					+ " (authorId, name, publicKey, localAuthorId,"
+					+ " (authorId, name, publicKey, localAuthorId, verified, active)"
-					+ " verified, active)"
 					+ " VALUES (?, ?, ?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, remote.getId().getBytes());
@@ -1058,7 +993,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " FROM contacts";
 			ps = txn.prepareStatement(sql);
 			rs = ps.executeQuery();
-			List<Contact> contacts = new ArrayList<>();
+			List<Contact> contacts = new ArrayList<Contact>();
 			while (rs.next()) {
 				ContactId contactId = new ContactId(rs.getInt(1));
 				AuthorId authorId = new AuthorId(rs.getBytes(2));
@@ -1092,7 +1027,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, local.getBytes());
 			rs = ps.executeQuery();
-			List<ContactId> ids = new ArrayList<>();
+			List<ContactId> ids = new ArrayList<ContactId>();
 			while (rs.next()) ids.add(new ContactId(rs.getInt(1)));
 			rs.close();
 			ps.close();
@@ -1117,7 +1052,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, remote.getBytes());
 			rs = ps.executeQuery();
-			List<Contact> contacts = new ArrayList<>();
+			List<Contact> contacts = new ArrayList<Contact>();
 			while (rs.next()) {
 				ContactId c = new ContactId(rs.getInt(1));
 				String name = rs.getString(2);
@@ -1173,7 +1108,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, c.getString());
 			rs = ps.executeQuery();
-			List<Group> groups = new ArrayList<>();
+			List<Group> groups = new ArrayList<Group>();
 			while (rs.next()) {
 				GroupId id = new GroupId(rs.getBytes(1));
 				byte[] descriptor = rs.getBytes(2);
@@ -1226,7 +1161,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
 			rs = ps.executeQuery();
-			List<ContactId> visible = new ArrayList<>();
+			List<ContactId> visible = new ArrayList<ContactId>();
 			while (rs.next()) visible.add(new ContactId(rs.getInt(1)));
 			rs.close();
 			ps.close();
@@ -1278,7 +1213,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " FROM localAuthors";
 			ps = txn.prepareStatement(sql);
 			rs = ps.executeQuery();
-			List<LocalAuthor> authors = new ArrayList<>();
+			List<LocalAuthor> authors = new ArrayList<LocalAuthor>();
 			while (rs.next()) {
 				AuthorId authorId = new AuthorId(rs.getBytes(1));
 				String name = rs.getString(2);
@@ -1308,7 +1243,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, g.getBytes());
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1331,7 +1266,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(1, state.getValue());
 			ps.setBytes(2, g.getBytes());
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1353,17 +1288,20 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			// Retrieve the message IDs for each query term and intersect
 			Set<MessageId> intersection = null;
-			String sql = "SELECT messageId FROM messageMetadata"
+			String sql = "SELECT m.messageId"
-					+ " WHERE groupId = ? AND state = ?"
+					+ " FROM messages AS m"
+					+ " JOIN messageMetadata AS md"
+					+ " ON m.messageId = md.messageId"
+					+ " WHERE state = ? AND groupId = ?"
 					+ " AND key = ? AND value = ?";
 			for (Entry<String, byte[]> e : query.entrySet()) {
 				ps = txn.prepareStatement(sql);
-				ps.setBytes(1, g.getBytes());
+				ps.setInt(1, DELIVERED.getValue());
-				ps.setInt(2, DELIVERED.getValue());
+				ps.setBytes(2, g.getBytes());
 				ps.setString(3, e.getKey());
 				ps.setBytes(4, e.getValue());
 				rs = ps.executeQuery();
-				Set<MessageId> ids = new HashSet<>();
+				Set<MessageId> ids = new HashSet<MessageId>();
 				while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 				rs.close();
 				ps.close();
@@ -1387,20 +1325,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT messageId, key, value"
+			String sql = "SELECT m.messageId, key, value"
-					+ " FROM messageMetadata"
+					+ " FROM messages AS m"
-					+ " WHERE groupId = ? AND state = ?";
+					+ " JOIN messageMetadata AS md"
+					+ " ON m.messageId = md.messageId"
+					+ " WHERE state = ? AND groupId = ?"
+					+ " ORDER BY m.messageId";
 			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, g.getBytes());
+			ps.setInt(1, DELIVERED.getValue());
-			ps.setInt(2, DELIVERED.getValue());
+			ps.setBytes(2, g.getBytes());
 			rs = ps.executeQuery();
-			Map<MessageId, Metadata> all = new HashMap<>();
+			Map<MessageId, Metadata> all = new HashMap<MessageId, Metadata>();
+			Metadata metadata = null;
+			MessageId lastMessageId = null;
 			while (rs.next()) {
 				MessageId messageId = new MessageId(rs.getBytes(1));
-				Metadata metadata = all.get(messageId);
+				if (lastMessageId == null || !messageId.equals(lastMessageId)) {
-				if (metadata == null) {
 					metadata = new Metadata();
 					all.put(messageId, metadata);
+					lastMessageId = messageId;
 				}
 				metadata.put(rs.getString(2), rs.getBytes(3));
 			}
@@ -1421,7 +1364,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 		Collection<MessageId> matches = getMessageIds(txn, g, query);
 		if (matches.isEmpty()) return Collections.emptyMap();
 		// Retrieve the metadata for each match
-		Map<MessageId, Metadata> all = new HashMap<>(matches.size());
+		Map<MessageId, Metadata> all = new HashMap<MessageId, Metadata>(
+				matches.size());
 		for (MessageId m : matches) all.put(m, getMessageMetadata(txn, m));
 		return all;
 	}
@@ -1455,8 +1399,10 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT key, value FROM messageMetadata"
+			String sql = "SELECT key, value FROM messageMetadata AS md"
-					+ " WHERE state = ? AND messageId = ?";
+					+ " JOIN messages AS m"
+					+ " ON m.messageId = md.messageId"
+					+ " WHERE m.state = ? AND md.messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, DELIVERED.getValue());
 			ps.setBytes(2, m.getBytes());
@@ -1479,9 +1425,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT key, value FROM messageMetadata"
+			String sql = "SELECT key, value FROM messageMetadata AS md"
-					+ " WHERE (state = ? OR state = ?)"
+					+ " JOIN messages AS m"
-					+ " AND messageId = ?";
+					+ " ON m.messageId = md.messageId"
+					+ " WHERE (m.state = ? OR m.state = ?)"
+					+ " AND md.messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, DELIVERED.getValue());
 			ps.setInt(2, PENDING.getValue());
@@ -1515,7 +1463,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setBytes(1, g.getBytes());
 			ps.setInt(2, c.getInt());
 			rs = ps.executeQuery();
-			List<MessageStatus> statuses = new ArrayList<>();
+			List<MessageStatus> statuses = new ArrayList<MessageStatus>();
 			while (rs.next()) {
 				MessageId messageId = new MessageId(rs.getBytes(1));
 				boolean sent = rs.getBoolean(2);
@@ -1574,7 +1522,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			rs = ps.executeQuery();
-			Map<MessageId, State> dependencies = new HashMap<>();
+			Map<MessageId, State> dependencies = new HashMap<MessageId, State>();
 			while (rs.next()) {
 				MessageId dependency = new MessageId(rs.getBytes(1));
 				State state = State.fromValue(rs.getInt(2));
@@ -1612,7 +1560,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			rs = ps.executeQuery();
-			Map<MessageId, State> dependents = new HashMap<>();
+			Map<MessageId, State> dependents = new HashMap<MessageId, State>();
 			while (rs.next()) {
 				MessageId dependent = new MessageId(rs.getBytes(1));
 				State state = State.fromValue(rs.getInt(2));
@@ -1664,7 +1612,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, maxMessages);
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1700,7 +1648,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setLong(3, now);
 			ps.setInt(4, maxMessages);
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1725,7 +1673,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(1, c.getInt());
 			ps.setInt(2, maxMessages);
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1760,7 +1708,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(2, DELIVERED.getValue());
 			ps.setLong(3, now);
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			int total = 0;
 			while (rs.next()) {
 				int length = rs.getInt(1);
@@ -1802,7 +1750,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(1, state.getValue());
 			ps.setString(2, c.getString());
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1832,7 +1780,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, c.getString());
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			while (rs.next()) ids.add(new MessageId(rs.getBytes(1)));
 			rs.close();
 			ps.close();
@@ -1891,7 +1839,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(2, DELIVERED.getValue());
 			ps.setLong(3, now);
 			rs = ps.executeQuery();
-			List<MessageId> ids = new ArrayList<>();
+			List<MessageId> ids = new ArrayList<MessageId>();
 			int total = 0;
 			while (rs.next()) {
 				int length = rs.getInt(1);
@@ -1945,7 +1893,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, t.getString());
 			rs = ps.executeQuery();
-			List<IncomingKeys> inKeys = new ArrayList<>();
+			List<IncomingKeys> inKeys = new ArrayList<IncomingKeys>();
 			while (rs.next()) {
 				long rotationPeriod = rs.getLong(1);
 				SecretKey tagKey = new SecretKey(rs.getBytes(2));
@@ -1965,7 +1913,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps = txn.prepareStatement(sql);
 			ps.setString(1, t.getString());
 			rs = ps.executeQuery();
-			Map<ContactId, TransportKeys> keys = new HashMap<>();
+			Map<ContactId, TransportKeys> keys =
+					new HashMap<ContactId, TransportKeys>();
 			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();
@@ -2055,7 +2004,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			int[] batchAffected = ps.executeBatch();
 			if (batchAffected.length != requested.size())
 				throw new DbStateException();
-			for (int rows : batchAffected) {
+			for (int rows: batchAffected) {
 				if (rows < 0) throw new DbStateException();
 				if (rows > 1) throw new DbStateException();
 			}
@@ -2069,92 +2018,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 	@Override
 	public void mergeGroupMetadata(Connection txn, GroupId g, Metadata meta)
 			throws DbException {
-		PreparedStatement ps = null;
+		mergeMetadata(txn, g.getBytes(), meta, "groupMetadata", "groupId");
-		try {
-			Map<String, byte[]> added = removeOrUpdateMetadata(txn,
-					g.getBytes(), meta, "groupMetadata", "groupId");
-			if (added.isEmpty()) return;
-			// Insert any keys that don't already exist
-			String sql = "INSERT INTO groupMetadata (groupId, key, value)"
-					+ " VALUES (?, ?, ?)";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, g.getBytes());
-			for (Entry<String, byte[]> e : added.entrySet()) {
-				ps.setString(2, e.getKey());
-				ps.setBytes(3, e.getValue());
-				ps.addBatch();
-			}
-			int[] batchAffected = ps.executeBatch();
-			if (batchAffected.length != added.size())
-				throw new DbStateException();
-			for (int rows : batchAffected)
-				if (rows != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(ps);
-			throw new DbException(e);
-		}
 	}
 
 	@Override
-	public void mergeMessageMetadata(Connection txn, MessageId m,
+	public void mergeMessageMetadata(Connection txn, MessageId m, Metadata meta)
-			Metadata meta) throws DbException {
+			throws DbException {
-		PreparedStatement ps = null;
+		mergeMetadata(txn, m.getBytes(), meta, "messageMetadata", "messageId");
-		ResultSet rs = null;
-		try {
-			Map<String, byte[]> added = removeOrUpdateMetadata(txn,
-					m.getBytes(), meta, "messageMetadata", "messageId");
-			if (added.isEmpty()) return;
-			// Get the group ID and message state for the denormalised columns
-			String sql = "SELECT groupId, state FROM messages"
-					+ " WHERE messageId = ?";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			rs = ps.executeQuery();
-			if (!rs.next()) throw new DbStateException();
-			GroupId g = new GroupId(rs.getBytes(1));
-			State state = State.fromValue(rs.getInt(2));
-			rs.close();
-			ps.close();
-			// Insert any keys that don't already exist
-			sql = "INSERT INTO messageMetadata"
-					+ " (messageId, groupId, state, key, value)"
-					+ " VALUES (?, ?, ?, ?, ?)";
-			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
-			ps.setBytes(2, g.getBytes());
-			ps.setInt(3, state.getValue());
-			for (Entry<String, byte[]> e : added.entrySet()) {
-				ps.setString(4, e.getKey());
-				ps.setBytes(5, e.getValue());
-				ps.addBatch();
-			}
-			int[] batchAffected = ps.executeBatch();
-			if (batchAffected.length != added.size())
-				throw new DbStateException();
-			for (int rows : batchAffected)
-				if (rows != 1) throw new DbStateException();
-			ps.close();
-		} catch (SQLException e) {
-			tryToClose(rs);
-			tryToClose(ps);
-			throw new DbException(e);
-		}
 	}
 
-	// Removes or updates any existing entries, returns any entries that
+	private void mergeMetadata(Connection txn, byte[] id, Metadata meta,
-	// need to be added
+			String tableName, String columnName) throws DbException {
-	private Map<String, byte[]> removeOrUpdateMetadata(Connection txn,
-			byte[] id, Metadata meta, String tableName, String columnName)
-			throws DbException {
 		PreparedStatement ps = null;
 		try {
 			// Determine which keys are being removed
-			List<String> removed = new ArrayList<>();
+			List<String> removed = new ArrayList<String>();
-			Map<String, byte[]> notRemoved = new HashMap<>();
+			Map<String, byte[]> retained = new HashMap<String, byte[]>();
 			for (Entry<String, byte[]> e : meta.entrySet()) {
 				if (e.getValue() == REMOVE) removed.add(e.getKey());
-				else notRemoved.put(e.getKey(), e.getValue());
+				else retained.put(e.getKey(), e.getValue());
 			}
 			// Delete any keys that are being removed
 			if (!removed.isEmpty()) {
@@ -2175,33 +2057,45 @@ abstract class JdbcDatabase implements Database<Connection> {
 				}
 				ps.close();
 			}
-			if (notRemoved.isEmpty()) return Collections.emptyMap();
+			if (retained.isEmpty()) return;
 			// Update any keys that already exist
 			String sql = "UPDATE " + tableName + " SET value = ?"
 					+ " WHERE " + columnName + " = ? AND key = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(2, id);
-			for (Entry<String, byte[]> e : notRemoved.entrySet()) {
+			for (Entry<String, byte[]> e : retained.entrySet()) {
 				ps.setBytes(1, e.getValue());
 				ps.setString(3, e.getKey());
 				ps.addBatch();
 			}
 			int[] batchAffected = ps.executeBatch();
-			if (batchAffected.length != notRemoved.size())
+			if (batchAffected.length != retained.size())
 				throw new DbStateException();
 			for (int rows : batchAffected) {
 				if (rows < 0) throw new DbStateException();
 				if (rows > 1) throw new DbStateException();
 			}
-			ps.close();
+			// Insert any keys that don't already exist
-			// Are there any keys that don't already exist?
+			sql = "INSERT INTO " + tableName
-			Map<String, byte[]> added = new HashMap<>();
+					+ " (" + columnName + ", key, value)"
-			int updateIndex = 0;
+					+ " VALUES (?, ?, ?)";
-			for (Entry<String, byte[]> e : notRemoved.entrySet()) {
+			ps = txn.prepareStatement(sql);
-				if (batchAffected[updateIndex++] == 0)
+			ps.setBytes(1, id);
-					added.put(e.getKey(), e.getValue());
+			int updateIndex = 0, inserted = 0;
+			for (Entry<String, byte[]> e : retained.entrySet()) {
+				if (batchAffected[updateIndex] == 0) {
+					ps.setString(2, e.getKey());
+					ps.setBytes(3, e.getValue());
+					ps.addBatch();
+					inserted++;
+				}
+				updateIndex++;
 			}
-			return added;
+			batchAffected = ps.executeBatch();
+			if (batchAffected.length != inserted) throw new DbStateException();
+			for (int rows : batchAffected)
+				if (rows != 1) throw new DbStateException();
+			ps.close();
 		} catch (SQLException e) {
 			tryToClose(ps);
 			throw new DbException(e);
@@ -2554,8 +2448,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void setMessageShared(Connection txn, MessageId m)
+	public void setMessageShared(Connection txn, MessageId m) throws DbException {
-			throws DbException {
 		PreparedStatement ps = null;
 		try {
 			String sql = "UPDATE messages SET shared = TRUE"
@@ -2583,14 +2476,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 			int affected = ps.executeUpdate();
 			if (affected < 0 || affected > 1) throw new DbStateException();
 			ps.close();
-			// Update denormalised column in messageMetadata
-			sql = "UPDATE messageMetadata SET state = ? 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();
 		} catch (SQLException e) {
 			tryToClose(ps);
 			throw new DbException(e);

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

@@ -1,18 +0,0 @@
-package org.briarproject.bramble.db;
-
-import org.briarproject.bramble.api.db.DbException;
-
-interface Migration<T> {
-
-	/**
-	 * Returns the schema version from which this migration starts.
-	 */
-	int getStartVersion();
-
-	/**
-	 * Returns the schema version at which this migration ends.
-	 */
-	int getEndVersion();
-
-	void migrate(T txn) throws DbException;
-}

bramble-core/src/main/java/org/briarproject/bramble/db/Migration30_31.java

@@ -1,75 +0,0 @@
-package org.briarproject.bramble.db;
-
-import org.briarproject.bramble.api.db.DbException;
-
-import java.sql.Connection;
-import java.sql.SQLException;
-import java.sql.Statement;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-
-import static java.util.logging.Level.WARNING;
-
-class Migration30_31 implements Migration<Connection> {
-
-	private static final Logger LOG =
-			Logger.getLogger(Migration30_31.class.getName());
-
-	@Override
-	public int getStartVersion() {
-		return 30;
-	}
-
-	@Override
-	public int getEndVersion() {
-		return 31;
-	}
-
-	@Override
-	public void migrate(Connection txn) throws DbException {
-		Statement s = null;
-		try {
-			s = txn.createStatement();
-			// Add groupId column
-			s.execute("ALTER TABLE messageMetadata"
-					+ " ADD COLUMN groupId BINARY(32) AFTER messageId");
-			// Populate groupId column
-			s.execute("UPDATE messageMetadata AS mm SET groupId ="
-					+ " (SELECT groupId FROM messages AS m"
-					+ " WHERE mm.messageId = m.messageId)");
-			// Add not null constraint now column has been populated
-			s.execute("ALTER TABLE messageMetadata"
-					+ " ALTER COLUMN groupId"
-					+ " SET NOT NULL");
-			// Add foreign key constraint
-			s.execute("ALTER TABLE messageMetadata"
-					+ " ADD CONSTRAINT groupIdForeignKey"
-					+ " FOREIGN KEY (groupId)"
-					+ " REFERENCES groups (groupId)"
-					+ " ON DELETE CASCADE");
-			// Add state column
-			s.execute("ALTER TABLE messageMetadata"
-					+ " ADD COLUMN state INT AFTER groupId");
-			// Populate state column
-			s.execute("UPDATE messageMetadata AS mm SET state ="
-					+ " (SELECT state FROM messages AS m"
-					+ " WHERE mm.messageId = m.messageId)");
-			// Add not null constraint now column has been populated
-			s.execute("ALTER TABLE messageMetadata"
-					+ " ALTER COLUMN state"
-					+ " SET NOT NULL");
-		} catch (SQLException e) {
-			tryToClose(s);
-			throw new DbException(e);
-		}
-	}
-
-	private void tryToClose(@Nullable Statement s) {
-		try {
-			if (s != null) s.close();
-		} catch (SQLException e) {
-			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-		}
-	}
-}

bramble-core/src/main/java/org/briarproject/bramble/event/EventBusImpl.java

@@ -15,7 +15,7 @@ import javax.annotation.concurrent.ThreadSafe;
 class EventBusImpl implements EventBus {
 
 	private final Collection<EventListener> listeners =
-			new CopyOnWriteArrayList<>();
+			new CopyOnWriteArrayList<EventListener>();
 
 	@Override
 	public void addListener(EventListener l) {

bramble-core/src/main/java/org/briarproject/bramble/invitation/AliceConnector.java

@@ -0,0 +1,119 @@
+package org.briarproject.bramble.invitation;
+
+import org.briarproject.bramble.api.contact.ContactExchangeTask;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
+import org.briarproject.bramble.api.crypto.SecretKey;
+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.identity.LocalAuthor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.security.GeneralSecurityException;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+
+/**
+ * A connection thread for the peer being Alice in the invitation protocol.
+ */
+@NotNullByDefault
+class AliceConnector extends Connector {
+
+	private static final Logger LOG =
+			Logger.getLogger(AliceConnector.class.getName());
+
+	AliceConnector(CryptoComponent crypto, BdfReaderFactory bdfReaderFactory,
+			BdfWriterFactory bdfWriterFactory,
+			ContactExchangeTask contactExchangeTask, ConnectorGroup group,
+			DuplexPlugin plugin, LocalAuthor localAuthor, PseudoRandom random) {
+		super(crypto, bdfReaderFactory, bdfWriterFactory, contactExchangeTask,
+				group, plugin, localAuthor, random);
+	}
+
+	@Override
+	public void run() {
+		// Create an incoming or outgoing connection
+		DuplexTransportConnection conn = createInvitationConnection(true);
+		if (conn == null) return;
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " connected");
+		// Don't proceed with more than one connection
+		if (group.getAndSetConnected()) {
+			if (LOG.isLoggable(INFO)) LOG.info(pluginName + " redundant");
+			tryToClose(conn, false);
+			return;
+		}
+		// Carry out the key agreement protocol
+		InputStream in;
+		OutputStream out;
+		BdfReader r;
+		BdfWriter w;
+		SecretKey master;
+		try {
+			in = conn.getReader().getInputStream();
+			out = conn.getWriter().getOutputStream();
+			r = bdfReaderFactory.createReader(in);
+			w = bdfWriterFactory.createWriter(out);
+			// Alice goes first
+			sendPublicKeyHash(w);
+			byte[] hash = receivePublicKeyHash(r);
+			sendPublicKey(w);
+			byte[] key = receivePublicKey(r);
+			master = deriveMasterSecret(hash, key, true);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			group.keyAgreementFailed();
+			tryToClose(conn, true);
+			return;
+		} catch (GeneralSecurityException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			group.keyAgreementFailed();
+			tryToClose(conn, true);
+			return;
+		}
+		// The key agreement succeeded - derive the confirmation codes
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " agreement succeeded");
+		int aliceCode = crypto.deriveBTConfirmationCode(master, true);
+		int bobCode = crypto.deriveBTConfirmationCode(master, false);
+		group.keyAgreementSucceeded(aliceCode, bobCode);
+		// Exchange confirmation results
+		boolean localMatched, remoteMatched;
+		try {
+			localMatched = group.waitForLocalConfirmationResult();
+			sendConfirmation(w, localMatched);
+			remoteMatched = receiveConfirmation(r);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			group.remoteConfirmationFailed();
+			tryToClose(conn, true);
+			return;
+		} catch (InterruptedException e) {
+			LOG.warning("Interrupted while waiting for confirmation");
+			group.remoteConfirmationFailed();
+			tryToClose(conn, true);
+			Thread.currentThread().interrupt();
+			return;
+		}
+		if (remoteMatched) group.remoteConfirmationSucceeded();
+		else group.remoteConfirmationFailed();
+		if (!(localMatched && remoteMatched)) {
+			if (LOG.isLoggable(INFO))
+				LOG.info(pluginName + " confirmation failed");
+			tryToClose(conn, false);
+			return;
+		}
+		// Confirmation succeeded - upgrade to a secure connection
+		if (LOG.isLoggable(INFO))
+			LOG.info(pluginName + " confirmation succeeded");
+		contactExchangeTask.startExchange(group, localAuthor, master, conn,
+				plugin.getId(), true);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/invitation/BobConnector.java

@@ -0,0 +1,119 @@
+package org.briarproject.bramble.invitation;
+
+import org.briarproject.bramble.api.contact.ContactExchangeTask;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
+import org.briarproject.bramble.api.crypto.SecretKey;
+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.identity.LocalAuthor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.security.GeneralSecurityException;
+import java.util.logging.Logger;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+
+/**
+ * A connection thread for the peer being Bob in the invitation protocol.
+ */
+@NotNullByDefault
+class BobConnector extends Connector {
+
+	private static final Logger LOG =
+			Logger.getLogger(BobConnector.class.getName());
+
+	BobConnector(CryptoComponent crypto, BdfReaderFactory bdfReaderFactory,
+			BdfWriterFactory bdfWriterFactory,
+			ContactExchangeTask contactExchangeTask, ConnectorGroup group,
+			DuplexPlugin plugin, LocalAuthor localAuthor, PseudoRandom random) {
+		super(crypto, bdfReaderFactory, bdfWriterFactory, contactExchangeTask,
+				group, plugin, localAuthor, random);
+	}
+
+	@Override
+	public void run() {
+		// Create an incoming or outgoing connection
+		DuplexTransportConnection conn = createInvitationConnection(false);
+		if (conn == null) return;
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " connected");
+		// Carry out the key agreement protocol
+		InputStream in;
+		OutputStream out;
+		BdfReader r;
+		BdfWriter w;
+		SecretKey master;
+		try {
+			in = conn.getReader().getInputStream();
+			out = conn.getWriter().getOutputStream();
+			r = bdfReaderFactory.createReader(in);
+			w = bdfWriterFactory.createWriter(out);
+			// Alice goes first
+			byte[] hash = receivePublicKeyHash(r);
+			// Don't proceed with more than one connection
+			if (group.getAndSetConnected()) {
+				if (LOG.isLoggable(INFO)) LOG.info(pluginName + " redundant");
+				tryToClose(conn, false);
+				return;
+			}
+			sendPublicKeyHash(w);
+			byte[] key = receivePublicKey(r);
+			sendPublicKey(w);
+			master = deriveMasterSecret(hash, key, false);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			group.keyAgreementFailed();
+			tryToClose(conn, true);
+			return;
+		} catch (GeneralSecurityException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			group.keyAgreementFailed();
+			tryToClose(conn, true);
+			return;
+		}
+		// The key agreement succeeded - derive the confirmation codes
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " agreement succeeded");
+		int aliceCode = crypto.deriveBTConfirmationCode(master, true);
+		int bobCode = crypto.deriveBTConfirmationCode(master, false);
+		group.keyAgreementSucceeded(bobCode, aliceCode);
+		// Exchange confirmation results
+		boolean localMatched, remoteMatched;
+		try {
+			remoteMatched = receiveConfirmation(r);
+			localMatched = group.waitForLocalConfirmationResult();
+			sendConfirmation(w, localMatched);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			group.remoteConfirmationFailed();
+			tryToClose(conn, true);
+			return;
+		} catch (InterruptedException e) {
+			LOG.warning("Interrupted while waiting for confirmation");
+			group.remoteConfirmationFailed();
+			tryToClose(conn, true);
+			Thread.currentThread().interrupt();
+			return;
+		}
+		if (remoteMatched) group.remoteConfirmationSucceeded();
+		else group.remoteConfirmationFailed();
+		if (!(localMatched && remoteMatched)) {
+			if (LOG.isLoggable(INFO))
+				LOG.info(pluginName + " confirmation failed");
+			tryToClose(conn, false);
+			return;
+		}
+		// Confirmation succeeded - upgrade to a secure connection
+		if (LOG.isLoggable(INFO))
+			LOG.info(pluginName + " confirmation succeeded");
+		contactExchangeTask.startExchange(group, localAuthor, master, conn,
+				plugin.getId(), false);
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/invitation/Connector.java

@@ -0,0 +1,150 @@
+package org.briarproject.bramble.invitation;
+
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.contact.ContactExchangeTask;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.crypto.KeyPair;
+import org.briarproject.bramble.api.crypto.KeyParser;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
+import org.briarproject.bramble.api.crypto.SecretKey;
+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.identity.LocalAuthor;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
+import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+
+import java.io.IOException;
+import java.security.GeneralSecurityException;
+import java.util.Arrays;
+import java.util.logging.Logger;
+
+import javax.annotation.Nullable;
+
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
+import static org.briarproject.bramble.api.invitation.InvitationConstants.CONNECTION_TIMEOUT;
+
+// FIXME: This class has way too many dependencies
+@NotNullByDefault
+abstract class Connector extends Thread {
+
+	private static final Logger LOG =
+			Logger.getLogger(Connector.class.getName());
+	private static final String LABEL_PUBLIC_KEY =
+			"org.briarproject.bramble.invitation.PUBLIC_KEY";
+
+	protected final CryptoComponent crypto;
+	protected final BdfReaderFactory bdfReaderFactory;
+	protected final BdfWriterFactory bdfWriterFactory;
+	protected final ContactExchangeTask contactExchangeTask;
+	protected final ConnectorGroup group;
+	protected final DuplexPlugin plugin;
+	protected final LocalAuthor localAuthor;
+	protected final PseudoRandom random;
+	protected final String pluginName;
+
+	private final KeyPair keyPair;
+	private final KeyParser keyParser;
+
+	Connector(CryptoComponent crypto, BdfReaderFactory bdfReaderFactory,
+			BdfWriterFactory bdfWriterFactory,
+			ContactExchangeTask contactExchangeTask, ConnectorGroup group,
+			DuplexPlugin plugin, LocalAuthor localAuthor, PseudoRandom random) {
+		super("Connector");
+		this.crypto = crypto;
+		this.bdfReaderFactory = bdfReaderFactory;
+		this.bdfWriterFactory = bdfWriterFactory;
+		this.contactExchangeTask = contactExchangeTask;
+		this.group = group;
+		this.plugin = plugin;
+		this.localAuthor = localAuthor;
+		this.random = random;
+		pluginName = plugin.getClass().getName();
+		keyPair = crypto.generateAgreementKeyPair();
+		keyParser = crypto.getAgreementKeyParser();
+	}
+
+	@Nullable
+	DuplexTransportConnection createInvitationConnection(boolean alice) {
+		if (LOG.isLoggable(INFO))
+			LOG.info(pluginName + " creating invitation connection");
+		return plugin.createInvitationConnection(random, CONNECTION_TIMEOUT,
+				alice);
+	}
+
+	void sendPublicKeyHash(BdfWriter w) throws IOException {
+		byte[] hash =
+				crypto.hash(LABEL_PUBLIC_KEY, keyPair.getPublic().getEncoded());
+		w.writeRaw(hash);
+		w.flush();
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " sent hash");
+	}
+
+	byte[] receivePublicKeyHash(BdfReader r) throws IOException {
+		int hashLength = crypto.getHashLength();
+		byte[] b = r.readRaw(hashLength);
+		if (b.length < hashLength) throw new FormatException();
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " received hash");
+		return b;
+	}
+
+	void sendPublicKey(BdfWriter w) throws IOException {
+		byte[] key = keyPair.getPublic().getEncoded();
+		w.writeRaw(key);
+		w.flush();
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " sent key");
+	}
+
+	byte[] receivePublicKey(BdfReader r)
+			throws GeneralSecurityException, IOException {
+		byte[] b = r.readRaw(MAX_PUBLIC_KEY_LENGTH);
+		keyParser.parsePublicKey(b);
+		if (LOG.isLoggable(INFO)) LOG.info(pluginName + " received key");
+		return b;
+	}
+
+	SecretKey deriveMasterSecret(byte[] hash, byte[] key, boolean alice)
+			throws GeneralSecurityException {
+		// Check that the hash matches the key
+		byte[] keyHash =
+				crypto.hash(LABEL_PUBLIC_KEY, keyPair.getPublic().getEncoded());
+		if (!Arrays.equals(hash, keyHash)) {
+			if (LOG.isLoggable(INFO))
+				LOG.info(pluginName + " hash does not match key");
+			throw new GeneralSecurityException();
+		}
+		//  Derive the master secret
+		if (LOG.isLoggable(INFO))
+			LOG.info(pluginName + " deriving master secret");
+		return crypto.deriveMasterSecret(key, keyPair, alice);
+	}
+
+	void sendConfirmation(BdfWriter w, boolean confirmed) throws IOException {
+		w.writeBoolean(confirmed);
+		w.flush();
+		if (LOG.isLoggable(INFO))
+			LOG.info(pluginName + " sent confirmation: " + confirmed);
+	}
+
+	boolean receiveConfirmation(BdfReader r) throws IOException {
+		boolean confirmed = r.readBoolean();
+		if (LOG.isLoggable(INFO))
+			LOG.info(pluginName + " received confirmation: " + confirmed);
+		return confirmed;
+	}
+
+	protected void tryToClose(DuplexTransportConnection conn,
+			boolean exception) {
+		try {
+			LOG.info("Closing connection");
+			conn.getReader().dispose(exception, true);
+			conn.getWriter().dispose(exception);
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/invitation/ConnectorGroup.java

@@ -0,0 +1,278 @@
+package org.briarproject.bramble.invitation;
+
+import org.briarproject.bramble.api.contact.ContactExchangeListener;
+import org.briarproject.bramble.api.contact.ContactExchangeTask;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.crypto.PseudoRandom;
+import org.briarproject.bramble.api.data.BdfReaderFactory;
+import org.briarproject.bramble.api.data.BdfWriterFactory;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.identity.Author;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.identity.LocalAuthor;
+import org.briarproject.bramble.api.invitation.InvitationListener;
+import org.briarproject.bramble.api.invitation.InvitationState;
+import org.briarproject.bramble.api.invitation.InvitationTask;
+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.plugin.duplex.DuplexPlugin;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+import java.util.logging.Logger;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.logging.Level.WARNING;
+import static org.briarproject.bramble.api.invitation.InvitationConstants.CONFIRMATION_TIMEOUT;
+
+/**
+ * A task consisting of one or more parallel connection attempts.
+ */
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+class ConnectorGroup extends Thread implements InvitationTask,
+		ContactExchangeListener {
+
+	private static final Logger LOG =
+			Logger.getLogger(ConnectorGroup.class.getName());
+
+	private final CryptoComponent crypto;
+	private final BdfReaderFactory bdfReaderFactory;
+	private final BdfWriterFactory bdfWriterFactory;
+	private final ContactExchangeTask contactExchangeTask;
+	private final IdentityManager identityManager;
+	private final PluginManager pluginManager;
+	private final int localInvitationCode, remoteInvitationCode;
+	private final Collection<InvitationListener> listeners;
+	private final AtomicBoolean connected;
+	private final CountDownLatch localConfirmationLatch;
+	private final Lock lock = new ReentrantLock();
+
+	// The following are locking: lock
+	private int localConfirmationCode = -1, remoteConfirmationCode = -1;
+	private boolean connectionFailed = false;
+	private boolean localCompared = false, remoteCompared = false;
+	private boolean localMatched = false, remoteMatched = false;
+	private String remoteName = null;
+
+	ConnectorGroup(CryptoComponent crypto, BdfReaderFactory bdfReaderFactory,
+			BdfWriterFactory bdfWriterFactory,
+			ContactExchangeTask contactExchangeTask,
+			IdentityManager identityManager, PluginManager pluginManager,
+			int localInvitationCode, int remoteInvitationCode) {
+		super("ConnectorGroup");
+		this.crypto = crypto;
+		this.bdfReaderFactory = bdfReaderFactory;
+		this.bdfWriterFactory = bdfWriterFactory;
+		this.contactExchangeTask = contactExchangeTask;
+		this.identityManager = identityManager;
+		this.pluginManager = pluginManager;
+		this.localInvitationCode = localInvitationCode;
+		this.remoteInvitationCode = remoteInvitationCode;
+		listeners = new CopyOnWriteArrayList<InvitationListener>();
+		connected = new AtomicBoolean(false);
+		localConfirmationLatch = new CountDownLatch(1);
+	}
+
+	@Override
+	public InvitationState addListener(InvitationListener l) {
+		lock.lock();
+		try {
+			listeners.add(l);
+			return new InvitationState(localInvitationCode,
+					remoteInvitationCode, localConfirmationCode,
+					remoteConfirmationCode, connected.get(), connectionFailed,
+					localCompared, remoteCompared, localMatched, remoteMatched,
+					remoteName);
+		} finally {
+			lock.unlock();
+		}
+	}
+
+	@Override
+	public void removeListener(InvitationListener l) {
+		listeners.remove(l);
+	}
+
+	@Override
+	public void connect() {
+		start();
+	}
+
+	@Override
+	public void run() {
+		LocalAuthor localAuthor;
+		// Load the local pseudonym
+		try {
+			localAuthor = identityManager.getLocalAuthor();
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			lock.lock();
+			try {
+				connectionFailed = true;
+			} finally {
+				lock.unlock();
+			}
+			for (InvitationListener l : listeners) l.connectionFailed();
+			return;
+		}
+		// Start the connection threads
+		Collection<Connector> connectors = new ArrayList<Connector>();
+		// Alice is the party with the smaller invitation code
+		if (localInvitationCode < remoteInvitationCode) {
+			for (DuplexPlugin plugin : pluginManager.getInvitationPlugins()) {
+				Connector c = createAliceConnector(plugin, localAuthor);
+				connectors.add(c);
+				c.start();
+			}
+		} else {
+			for (DuplexPlugin plugin : pluginManager.getInvitationPlugins()) {
+				Connector c = createBobConnector(plugin, localAuthor);
+				connectors.add(c);
+				c.start();
+			}
+		}
+		// Wait for the connection threads to finish
+		try {
+			for (Connector c : connectors) c.join();
+		} catch (InterruptedException e) {
+			LOG.warning("Interrupted while waiting for connectors");
+			Thread.currentThread().interrupt();
+		}
+		// If none of the threads connected, inform the listeners
+		if (!connected.get()) {
+			lock.lock();
+			try {
+				connectionFailed = true;
+			} finally {
+				lock.unlock();
+			}
+			for (InvitationListener l : listeners) l.connectionFailed();
+		}
+	}
+
+	private Connector createAliceConnector(DuplexPlugin plugin,
+			LocalAuthor localAuthor) {
+		PseudoRandom random = crypto.getPseudoRandom(localInvitationCode,
+				remoteInvitationCode);
+		return new AliceConnector(crypto, bdfReaderFactory, bdfWriterFactory,
+				contactExchangeTask, this, plugin, localAuthor, random);
+	}
+
+	private Connector createBobConnector(DuplexPlugin plugin,
+			LocalAuthor localAuthor) {
+		PseudoRandom random = crypto.getPseudoRandom(remoteInvitationCode,
+				localInvitationCode);
+		return new BobConnector(crypto, bdfReaderFactory, bdfWriterFactory,
+				contactExchangeTask, this, plugin, localAuthor, random);
+	}
+
+	@Override
+	public void localConfirmationSucceeded() {
+		lock.lock();
+		try {
+			localCompared = true;
+			localMatched = true;
+		} finally {
+			lock.unlock();
+		}
+		localConfirmationLatch.countDown();
+	}
+
+	@Override
+	public void localConfirmationFailed() {
+		lock.lock();
+		try {
+			localCompared = true;
+			localMatched = false;
+		} finally {
+			lock.unlock();
+		}
+		localConfirmationLatch.countDown();
+	}
+
+	boolean getAndSetConnected() {
+		boolean redundant = connected.getAndSet(true);
+		if (!redundant)
+			for (InvitationListener l : listeners) l.connectionSucceeded();
+		return redundant;
+	}
+
+	void keyAgreementSucceeded(int localCode, int remoteCode) {
+		lock.lock();
+		try {
+			localConfirmationCode = localCode;
+			remoteConfirmationCode = remoteCode;
+		} finally {
+			lock.unlock();
+		}
+		for (InvitationListener l : listeners)
+			l.keyAgreementSucceeded(localCode, remoteCode);
+	}
+
+	void keyAgreementFailed() {
+		for (InvitationListener l : listeners) l.keyAgreementFailed();
+	}
+
+	boolean waitForLocalConfirmationResult() throws InterruptedException {
+		localConfirmationLatch.await(CONFIRMATION_TIMEOUT, MILLISECONDS);
+		lock.lock();
+		try {
+			return localMatched;
+		} finally {
+			lock.unlock();
+		}
+	}
+
+	void remoteConfirmationSucceeded() {
+		lock.lock();
+		try {
+			remoteCompared = true;
+			remoteMatched = true;
+		} finally {
+			lock.unlock();
+		}
+		for (InvitationListener l : listeners) l.remoteConfirmationSucceeded();
+	}
+
+	void remoteConfirmationFailed() {
+		lock.lock();
+		try {
+			remoteCompared = true;
+			remoteMatched = false;
+		} finally {
+			lock.unlock();
+		}
+		for (InvitationListener l : listeners) l.remoteConfirmationFailed();
+	}
+
+	@Override
+	public void contactExchangeSucceeded(Author remoteAuthor) {
+		String name = remoteAuthor.getName();
+		lock.lock();
+		try {
+			remoteName = name;
+		} finally {
+			lock.unlock();
+		}
+		for (InvitationListener l : listeners)
+			l.pseudonymExchangeSucceeded(name);
+	}
+
+	@Override
+	public void duplicateContact(Author remoteAuthor) {
+		// TODO differentiate
+		for (InvitationListener l : listeners) l.pseudonymExchangeFailed();
+	}
+
+	@Override
+	public void contactExchangeFailed() {
+		for (InvitationListener l : listeners) l.pseudonymExchangeFailed();
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/invitation/InvitationModule.java

@@ -0,0 +1,16 @@
+package org.briarproject.bramble.invitation;
+
+import org.briarproject.bramble.api.invitation.InvitationTaskFactory;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class InvitationModule {
+
+	@Provides
+	InvitationTaskFactory provideInvitationTaskFactory(
+			InvitationTaskFactoryImpl invitationTaskFactory) {
+		return invitationTaskFactory;
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/invitation/InvitationTaskFactoryImpl.java

@@ -0,0 +1,47 @@
+package org.briarproject.bramble.invitation;
+
+import org.briarproject.bramble.api.contact.ContactExchangeTask;
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.data.BdfReaderFactory;
+import org.briarproject.bramble.api.data.BdfWriterFactory;
+import org.briarproject.bramble.api.identity.IdentityManager;
+import org.briarproject.bramble.api.invitation.InvitationTask;
+import org.briarproject.bramble.api.invitation.InvitationTaskFactory;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.plugin.PluginManager;
+
+import javax.annotation.concurrent.Immutable;
+import javax.inject.Inject;
+
+@Immutable
+@NotNullByDefault
+class InvitationTaskFactoryImpl implements InvitationTaskFactory {
+
+	private final CryptoComponent crypto;
+	private final BdfReaderFactory bdfReaderFactory;
+	private final BdfWriterFactory bdfWriterFactory;
+	private final ContactExchangeTask contactExchangeTask;
+	private final IdentityManager identityManager;
+	private final PluginManager pluginManager;
+
+	@Inject
+	InvitationTaskFactoryImpl(CryptoComponent crypto,
+			BdfReaderFactory bdfReaderFactory,
+			BdfWriterFactory bdfWriterFactory,
+			ContactExchangeTask contactExchangeTask,
+			IdentityManager identityManager, PluginManager pluginManager) {
+		this.crypto = crypto;
+		this.bdfReaderFactory = bdfReaderFactory;
+		this.bdfWriterFactory = bdfWriterFactory;
+		this.contactExchangeTask = contactExchangeTask;
+		this.identityManager = identityManager;
+		this.pluginManager = pluginManager;
+	}
+
+	@Override
+	public InvitationTask createTask(int localCode, int remoteCode) {
+		return new ConnectorGroup(crypto, bdfReaderFactory, bdfWriterFactory,
+				contactExchangeTask, identityManager, pluginManager,
+				localCode, remoteCode);
+	}
+}

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

@@ -50,9 +50,10 @@ class KeyAgreementConnector {
 	private final PluginManager pluginManager;
 	private final CompletionService<KeyAgreementConnection> connect;
 
-	private final List<KeyAgreementListener> listeners = new ArrayList<>();
+	private final List<KeyAgreementListener> listeners =
+			new ArrayList<KeyAgreementListener>();
 	private final List<Future<KeyAgreementConnection>> pending =
-			new ArrayList<>();
+			new ArrayList<Future<KeyAgreementConnection>>();
 
 	private volatile boolean connecting = false;
 	private volatile boolean alice = false;
@@ -64,7 +65,8 @@ class KeyAgreementConnector {
 		this.clock = clock;
 		this.crypto = crypto;
 		this.pluginManager = pluginManager;
-		connect = new ExecutorCompletionService<>(ioExecutor);
+		connect = new ExecutorCompletionService<KeyAgreementConnection>(
+				ioExecutor);
 	}
 
 	public Payload listen(KeyPair localKeyPair) {
@@ -73,7 +75,8 @@ class KeyAgreementConnector {
 		byte[] commitment = crypto.deriveKeyCommitment(
 				localKeyPair.getPublic().getEncoded());
 		// Start all listeners and collect their descriptors
-		List<TransportDescriptor> descriptors = new ArrayList<>();
+		List<TransportDescriptor> descriptors =
+				new ArrayList<TransportDescriptor>();
 		for (DuplexPlugin plugin : pluginManager.getKeyAgreementPlugins()) {
 			KeyAgreementListener l =
 					plugin.createKeyAgreementListener(commitment);
@@ -129,7 +132,10 @@ class KeyAgreementConnector {
 			LOG.info("Interrupted while waiting for connection");
 			Thread.currentThread().interrupt();
 			return null;
-		} catch (ExecutionException | IOException e) {
+		} catch (ExecutionException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			return null;
+		} catch (IOException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			return null;
 		} finally {