Check whether first visible message ID is null before storing.

.gitlab-ci.yml

@@ -1,4 +1,4 @@
-image: registry.gitlab.com/fdroid/ci-images-base:latest
+image: registry.gitlab.com/fdroid/ci-images:client-latest
 
 cache:
   paths:
@@ -6,18 +6,9 @@ cache:
     - .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
+#  - export ANDROID_COMPILE_SDK=`sed -n 's,.*compileSdkVersion\s*\([0-9][0-9]*\).*,\1,p' app/build.gradle`
+#  - echo y | android --silent update sdk --no-ui --filter android-${ANDROID_COMPILE_SDK}
 
 test:
   script:

bramble-android/build.gradle

@@ -6,90 +6,99 @@ apply plugin: 'witness'
 apply plugin: 'de.undercouch.download'
 
 android {
-	compileSdkVersion 27
-	buildToolsVersion '26.0.2'
+	compileSdkVersion 23
+	buildToolsVersion "23.0.3"
 
 	defaultConfig {
 		minSdkVersion 14
-		targetSdkVersion 26
-		versionCode 1619
-		versionName "0.16.19"
+		targetSdkVersion 22
+		versionCode 14
+		versionName "0.14"
 		consumerProguardFiles 'proguard-rules.txt'
 	}
 
 	compileOptions {
-		sourceCompatibility JavaVersion.VERSION_1_8
-		targetCompatibility JavaVersion.VERSION_1_8
+		sourceCompatibility JavaVersion.VERSION_1_7
+		targetCompatibility JavaVersion.VERSION_1_7
 	}
 }
 
 dependencies {
-	implementation project(path: ':bramble-core', configuration: 'default')
-	implementation fileTree(dir: 'libs', include: '*.jar')
-
-	annotationProcessor 'com.google.dagger:dagger-compiler:2.0.2'
-
-	compileOnly 'javax.annotation:jsr250-api:1.0'
+	compile project(':bramble-core')
+	compile fileTree(dir: 'libs', include: ['*.jar'])
+	provided 'javax.annotation:jsr250-api:1.0'
 }
 
-dependencyVerification {
-	verify = [
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
-			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
-			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
-			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
-			'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
-			'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
-			'javax.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',
-	]
+def torBinaryDir = 'src/main/res/raw'
+
+task downloadTorGeoIp(type: Download) {
+	src 'https://briarproject.org/build/geoip-2015-12-01.zip'
+	dest "$torBinaryDir/geoip.zip"
+	onlyIfNewer true
 }
 
-ext.torBinaryDir = 'src/main/res/raw'
-ext.torVersion = '0.2.9.14'
-ext.geoipVersion = '2017-11-06'
-ext.torDownloadUrl = 'https://briarproject.org/build/'
-
-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}/${name}.zip"
-		onlyIfNewer true
-	}
+task downloadTorBinaryArm(type: Download) {
+	src 'https://briarproject.org/build/tor-0.2.7.6-arm.zip'
+	dest "$torBinaryDir/tor_arm.zip"
+	onlyIfNewer true
 }
 
-def verifyBinary(name, chksum) {
-	return tasks.create([
-			name     : "verifyBinary${name}",
-			type     : Verify,
-			dependsOn: downloadBinary(name)]) {
-		src "${torBinaryDir}/${name}.zip"
-		algorithm 'SHA-256'
-		checksum chksum
-	}
+task downloadTorBinaryArmPie(type: Download) {
+	src 'https://briarproject.org/build/tor-0.2.7.6-arm-pie.zip'
+	dest "$torBinaryDir/tor_arm_pie.zip"
+	onlyIfNewer true
+}
+
+task downloadTorBinaryX86(type: Download) {
+	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.add(verifyBinary(key, value))
+	preBuild.dependsOn {
+		[
+				'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

@@ -13,8 +13,7 @@ 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.bluetooth.AndroidBluetoothPluginFactory;
+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;
 
@@ -35,21 +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 AndroidBluetoothPluginFactory(ioExecutor, androidExecutor,
-						appContext, random, eventBus, backoffFactory);
-		DuplexPluginFactory tor = new TorPluginFactory(ioExecutor, scheduler,
-				appContext, locationUtils, reporter, eventBus,
-				torSocketFactory, backoffFactory);
+		DuplexPluginFactory bluetooth = new DroidtoothPluginFactory(ioExecutor,
+				androidExecutor, appContext, random, backoffFactory);
+		DuplexPluginFactory tor = new TorPluginFactory(ioExecutor, appContext,
+				locationUtils, reporter, eventBus, torSocketFactory,
+				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/bluetooth/AndroidBluetoothPlugin.java

@@ -1,206 +0,0 @@
-package org.briarproject.bramble.plugin.bluetooth;
-
-import android.bluetooth.BluetoothAdapter;
-import android.bluetooth.BluetoothDevice;
-import android.bluetooth.BluetoothServerSocket;
-import android.bluetooth.BluetoothSocket;
-import android.content.BroadcastReceiver;
-import android.content.Context;
-import android.content.Intent;
-import android.content.IntentFilter;
-
-import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
-import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
-import org.briarproject.bramble.api.plugin.Backoff;
-import org.briarproject.bramble.api.plugin.PluginException;
-import org.briarproject.bramble.api.plugin.duplex.DuplexPluginCallback;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.system.AndroidExecutor;
-import org.briarproject.bramble.util.AndroidUtils;
-
-import java.io.Closeable;
-import java.io.IOException;
-import java.security.SecureRandom;
-import java.util.UUID;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-
-import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
-import static android.bluetooth.BluetoothAdapter.ACTION_STATE_CHANGED;
-import static android.bluetooth.BluetoothAdapter.EXTRA_SCAN_MODE;
-import static android.bluetooth.BluetoothAdapter.EXTRA_STATE;
-import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE;
-import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
-import static android.bluetooth.BluetoothAdapter.SCAN_MODE_NONE;
-import static android.bluetooth.BluetoothAdapter.STATE_OFF;
-import static android.bluetooth.BluetoothAdapter.STATE_ON;
-import static java.util.logging.Level.WARNING;
-
-@MethodsNotNullByDefault
-@ParametersNotNullByDefault
-class AndroidBluetoothPlugin extends BluetoothPlugin<BluetoothServerSocket> {
-
-	private static final Logger LOG =
-			Logger.getLogger(AndroidBluetoothPlugin.class.getName());
-
-	private final AndroidExecutor androidExecutor;
-	private final Context appContext;
-
-	private volatile boolean wasEnabledByUs = false;
-	private volatile BluetoothStateReceiver receiver = null;
-
-	// Non-null if the plugin started successfully
-	private volatile BluetoothAdapter adapter = null;
-
-	AndroidBluetoothPlugin(Executor ioExecutor, AndroidExecutor androidExecutor,
-			Context appContext, SecureRandom secureRandom, Backoff backoff,
-			DuplexPluginCallback callback, int maxLatency) {
-		super(ioExecutor, secureRandom, backoff, callback, maxLatency);
-		this.androidExecutor = androidExecutor;
-		this.appContext = appContext;
-	}
-
-	@Override
-	public void start() throws PluginException {
-		super.start();
-		// Listen for changes to the Bluetooth state
-		IntentFilter filter = new IntentFilter();
-		filter.addAction(ACTION_STATE_CHANGED);
-		filter.addAction(ACTION_SCAN_MODE_CHANGED);
-		receiver = new BluetoothStateReceiver();
-		appContext.registerReceiver(receiver, filter);
-	}
-
-	@Override
-	public void stop() {
-		super.stop();
-		if (receiver != null) appContext.unregisterReceiver(receiver);
-	}
-
-	@Override
-	void initialiseAdapter() throws IOException {
-		// BluetoothAdapter.getDefaultAdapter() must be called on a thread
-		// with a message queue, so submit it to the AndroidExecutor
-		try {
-			adapter = androidExecutor.runOnBackgroundThread(
-					BluetoothAdapter::getDefaultAdapter).get();
-		} catch (InterruptedException | ExecutionException e) {
-			throw new IOException(e);
-		}
-		if (adapter == null)
-			throw new IOException("Bluetooth is not supported");
-	}
-
-	@Override
-	boolean isAdapterEnabled() {
-		return adapter != null && adapter.isEnabled();
-	}
-
-	@Override
-	void enableAdapter() {
-		if (adapter != null && !adapter.isEnabled()) {
-			if (adapter.enable()) {
-				LOG.info("Enabling Bluetooth");
-				wasEnabledByUs = true;
-			} else {
-				LOG.info("Could not enable Bluetooth");
-			}
-		}
-	}
-
-	@Override
-	void disableAdapterIfEnabledByUs() {
-		if (isAdapterEnabled() && wasEnabledByUs) {
-			if (adapter.disable()) LOG.info("Disabling Bluetooth");
-			else LOG.info("Could not disable Bluetooth");
-			wasEnabledByUs = false;
-		}
-	}
-
-	@Override
-	void setEnabledByUs() {
-		wasEnabledByUs = true;
-	}
-
-	@Override
-	@Nullable
-	String getBluetoothAddress() {
-		String address = AndroidUtils.getBluetoothAddress(appContext, adapter);
-		return address.isEmpty() ? null : address;
-	}
-
-	@Override
-	BluetoothServerSocket openServerSocket(String uuid) throws IOException {
-		return adapter.listenUsingInsecureRfcommWithServiceRecord(
-				"RFCOMM", UUID.fromString(uuid));
-	}
-
-	@Override
-	void tryToClose(@Nullable BluetoothServerSocket ss) {
-		try {
-			if (ss != null) ss.close();
-		} catch (IOException e) {
-			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-		}
-	}
-
-	@Override
-	DuplexTransportConnection acceptConnection(BluetoothServerSocket ss)
-			throws IOException {
-		return wrapSocket(ss.accept());
-	}
-
-	private DuplexTransportConnection wrapSocket(BluetoothSocket s) {
-		return new AndroidBluetoothTransportConnection(this, s);
-	}
-
-	@Override
-	boolean isValidAddress(String address) {
-		return BluetoothAdapter.checkBluetoothAddress(address);
-	}
-
-	@Override
-	DuplexTransportConnection connectTo(String address, String uuid)
-			throws IOException {
-		BluetoothDevice d = adapter.getRemoteDevice(address);
-		UUID u = UUID.fromString(uuid);
-		BluetoothSocket s = null;
-		try {
-			s = d.createInsecureRfcommSocketToServiceRecord(u);
-			s.connect();
-			return wrapSocket(s);
-		} catch (IOException e) {
-			tryToClose(s);
-			throw e;
-		}
-	}
-
-	private void tryToClose(@Nullable Closeable c) {
-		try {
-			if (c != null) c.close();
-		} catch (IOException e) {
-			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-		}
-	}
-
-	private class BluetoothStateReceiver extends BroadcastReceiver {
-
-		@Override
-		public void onReceive(Context ctx, Intent intent) {
-			int state = intent.getIntExtra(EXTRA_STATE, 0);
-			if (state == STATE_ON) onAdapterEnabled();
-			else if (state == STATE_OFF) onAdapterDisabled();
-			int scanMode = intent.getIntExtra(EXTRA_SCAN_MODE, 0);
-			if (scanMode == SCAN_MODE_NONE) {
-				LOG.info("Scan mode: None");
-			} else if (scanMode == SCAN_MODE_CONNECTABLE) {
-				LOG.info("Scan mode: Connectable");
-			} else if (scanMode == SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
-				LOG.info("Scan mode: Discoverable");
-			}
-		}
-	}
-}

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

@@ -0,0 +1,682 @@
+package org.briarproject.bramble.plugin.droidtooth;
+
+import android.bluetooth.BluetoothAdapter;
+import android.bluetooth.BluetoothDevice;
+import android.bluetooth.BluetoothServerSocket;
+import android.bluetooth.BluetoothSocket;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+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.keyagreement.KeyAgreementConnection;
+import org.briarproject.bramble.api.keyagreement.KeyAgreementListener;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.bramble.api.plugin.Backoff;
+import org.briarproject.bramble.api.plugin.PluginException;
+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.properties.TransportProperties;
+import org.briarproject.bramble.api.system.AndroidExecutor;
+import org.briarproject.bramble.util.AndroidUtils;
+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;
+
+import javax.annotation.Nullable;
+
+import static android.bluetooth.BluetoothAdapter.ACTION_SCAN_MODE_CHANGED;
+import static android.bluetooth.BluetoothAdapter.ACTION_STATE_CHANGED;
+import static android.bluetooth.BluetoothAdapter.EXTRA_SCAN_MODE;
+import static android.bluetooth.BluetoothAdapter.EXTRA_STATE;
+import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE;
+import static android.bluetooth.BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE;
+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;
+import static org.briarproject.bramble.util.PrivacyUtils.scrubMacAddress;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+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;
+	private final Context appContext;
+	private final SecureRandom secureRandom;
+	private final Backoff backoff;
+	private final DuplexPluginCallback callback;
+	private final int maxLatency;
+	private final AtomicBoolean used = new AtomicBoolean(false);
+
+	private volatile boolean running = false;
+	private volatile boolean wasEnabledByUs = false;
+	private volatile BluetoothStateReceiver receiver = null;
+	private volatile BluetoothServerSocket socket = null;
+
+	// Non-null if the plugin started successfully
+	private volatile BluetoothAdapter adapter = null;
+
+	DroidtoothPlugin(Executor ioExecutor, AndroidExecutor androidExecutor,
+			Context appContext, SecureRandom secureRandom, Backoff backoff,
+			DuplexPluginCallback callback, int maxLatency) {
+		this.ioExecutor = ioExecutor;
+		this.androidExecutor = androidExecutor;
+		this.appContext = appContext;
+		this.secureRandom = secureRandom;
+		this.backoff = backoff;
+		this.callback = callback;
+		this.maxLatency = maxLatency;
+	}
+
+	@Override
+	public TransportId getId() {
+		return ID;
+	}
+
+	@Override
+	public int getMaxLatency() {
+		return maxLatency;
+	}
+
+	@Override
+	public int getMaxIdleTime() {
+		// Bluetooth detects dead connections so we don't need keepalives
+		return Integer.MAX_VALUE;
+	}
+
+	@Override
+	public void start() throws PluginException {
+		if (used.getAndSet(true)) throw new IllegalStateException();
+		// BluetoothAdapter.getDefaultAdapter() must be called on a thread
+		// with a message queue, so submit it to the AndroidExecutor
+		try {
+			adapter = androidExecutor.runOnBackgroundThread(
+					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");
+			throw new PluginException(e);
+		} catch (ExecutionException e) {
+			throw new PluginException(e);
+		}
+		if (adapter == null) {
+			LOG.info("Bluetooth is not supported");
+			throw new PluginException();
+		}
+		running = true;
+		// Listen for changes to the Bluetooth state
+		IntentFilter filter = new IntentFilter();
+		filter.addAction(ACTION_STATE_CHANGED);
+		filter.addAction(ACTION_SCAN_MODE_CHANGED);
+		receiver = new BluetoothStateReceiver();
+		appContext.registerReceiver(receiver, filter);
+		// If Bluetooth is enabled, bind a socket
+		if (adapter.isEnabled()) {
+			bind();
+		} else {
+			// Enable Bluetooth if settings allow
+			if (callback.getSettings().getBoolean(PREF_BT_ENABLE, false)) {
+				wasEnabledByUs = true;
+				if (adapter.enable()) LOG.info("Enabling Bluetooth");
+				else LOG.info("Could not enable Bluetooth");
+			} else {
+				LOG.info("Not enabling Bluetooth");
+			}
+		}
+	}
+
+	private void bind() {
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				if (!isRunning()) return;
+				String address = AndroidUtils.getBluetoothAddress(appContext,
+						adapter);
+				if (LOG.isLoggable(INFO))
+					LOG.info("Local address " + scrubMacAddress(address));
+				if (!StringUtils.isNullOrEmpty(address)) {
+					// Advertise the Bluetooth address to contacts
+					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();
+			}
+		});
+	}
+
+	private UUID getUuid() {
+		String uuid = callback.getLocalProperties().get(PROP_UUID);
+		if (uuid == null) {
+			byte[] random = new byte[UUID_BYTES];
+			secureRandom.nextBytes(random);
+			uuid = UUID.nameUUIDFromBytes(random).toString();
+			TransportProperties p = new TransportProperties();
+			p.put(PROP_UUID, uuid);
+			callback.mergeLocalProperties(p);
+		}
+		return UUID.fromString(uuid);
+	}
+
+	private void tryToClose(@Nullable BluetoothServerSocket ss) {
+		try {
+			if (ss != null) ss.close();
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		} finally {
+			callback.transportDisabled();
+		}
+	}
+
+	private void acceptContactConnections() {
+		while (isRunning()) {
+			BluetoothSocket s;
+			try {
+				s = socket.accept();
+			} catch (IOException e) {
+				// This is expected when the socket is closed
+				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
+				return;
+			}
+			if (LOG.isLoggable(INFO)) {
+				String address = s.getRemoteDevice().getAddress();
+				LOG.info("Connection from " + scrubMacAddress(address));
+			}
+			backoff.reset();
+			callback.incomingConnectionCreated(wrapSocket(s));
+		}
+	}
+
+	private DuplexTransportConnection wrapSocket(BluetoothSocket s) {
+		return new DroidtoothTransportConnection(this, s);
+	}
+
+	@Override
+	public void stop() {
+		running = false;
+		if (receiver != null) appContext.unregisterReceiver(receiver);
+		tryToClose(socket);
+		// Disable Bluetooth if we enabled it and it's still enabled
+		if (wasEnabledByUs && adapter.isEnabled()) {
+			if (adapter.disable()) LOG.info("Disabling Bluetooth");
+			else LOG.info("Could not disable Bluetooth");
+		}
+	}
+
+	@Override
+	public boolean isRunning() {
+		return running && adapter != null && adapter.isEnabled();
+	}
+
+	@Override
+	public boolean shouldPoll() {
+		return true;
+	}
+
+	@Override
+	public int getPollingInterval() {
+		return backoff.getPollingInterval();
+	}
+
+	@Override
+	public void poll(Collection<ContactId> connected) {
+		if (!isRunning()) return;
+		backoff.increment();
+		// Try to connect to known devices in parallel
+		Map<ContactId, TransportProperties> remote =
+				callback.getRemoteProperties();
+		for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
+			final ContactId c = e.getKey();
+			if (connected.contains(c)) continue;
+			final String address = e.getValue().get(PROP_ADDRESS);
+			if (StringUtils.isNullOrEmpty(address)) continue;
+			final String uuid = e.getValue().get(PROP_UUID);
+			if (StringUtils.isNullOrEmpty(uuid)) continue;
+			ioExecutor.execute(new Runnable() {
+				@Override
+				public void run() {
+					if (!running) return;
+					BluetoothSocket s = connect(address, uuid);
+					if (s != null) {
+						backoff.reset();
+						callback.outgoingConnectionCreated(c, wrapSocket(s));
+					}
+				}
+			});
+		}
+	}
+
+	@Nullable
+	private BluetoothSocket connect(String address, String uuid) {
+		// Validate the address
+		if (!BluetoothAdapter.checkBluetoothAddress(address)) {
+			if (LOG.isLoggable(WARNING))
+				// not scrubbing here to be able to figure out the problem
+				LOG.warning("Invalid address " + address);
+			return null;
+		}
+		// Validate the UUID
+		UUID u;
+		try {
+			u = UUID.fromString(uuid);
+		} catch (IllegalArgumentException e) {
+			if (LOG.isLoggable(WARNING)) LOG.warning("Invalid UUID " + uuid);
+			return null;
+		}
+		// Try to connect
+		BluetoothDevice d = adapter.getRemoteDevice(address);
+		BluetoothSocket s = null;
+		try {
+			s = d.createInsecureRfcommSocketToServiceRecord(u);
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connecting to " + scrubMacAddress(address));
+			s.connect();
+			if (LOG.isLoggable(INFO))
+				LOG.info("Connected to " + scrubMacAddress(address));
+			return s;
+		} catch (IOException e) {
+			if (LOG.isLoggable(INFO)) {
+				LOG.info("Failed to connect to " + scrubMacAddress(address)
+						+ ": " + e);
+			}
+			tryToClose(s);
+			return null;
+		}
+	}
+
+	private void tryToClose(@Nullable Closeable c) {
+		try {
+			if (c != null) c.close();
+		} catch (IOException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		}
+	}
+
+	@Override
+	public DuplexTransportConnection createConnection(ContactId c) {
+		if (!isRunning()) return null;
+		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);
+		if (StringUtils.isNullOrEmpty(uuid)) return null;
+		BluetoothSocket s = connect(address, uuid);
+		if (s == null) return null;
+		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;
+	}
+
+	@Override
+	public KeyAgreementListener createKeyAgreementListener(byte[] commitment) {
+		if (!isRunning()) return null;
+		// There's no point listening if we can't discover our own address
+		String address = AndroidUtils.getBluetoothAddress(appContext, adapter);
+		if (address.isEmpty()) return null;
+		// 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 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;
+		}
+		BdfList descriptor = new BdfList();
+		descriptor.add(TRANSPORT_ID_BLUETOOTH);
+		descriptor.add(StringUtils.macToBytes(address));
+		return new BluetoothKeyAgreementListener(descriptor, ss);
+	}
+
+	@Override
+	public DuplexTransportConnection createKeyAgreementConnection(
+			byte[] commitment, BdfList descriptor, long timeout) {
+		if (!isRunning()) return null;
+		String address;
+		try {
+			address = parseAddress(descriptor);
+		} catch (FormatException e) {
+			LOG.info("Invalid address in key agreement descriptor");
+			return null;
+		}
+		// No truncation necessary because COMMIT_LENGTH = 16
+		UUID uuid = UUID.nameUUIDFromBytes(commitment);
+		if (LOG.isLoggable(INFO))
+			LOG.info("Connecting to key agreement UUID " + uuid);
+		BluetoothSocket s = connect(address, uuid.toString());
+		if (s == null) return null;
+		return new DroidtoothTransportConnection(this, s);
+	}
+
+	private String parseAddress(BdfList descriptor) throws FormatException {
+		byte[] mac = descriptor.getRaw(1);
+		if (mac.length != 6) throw new FormatException();
+		return StringUtils.macToString(mac);
+	}
+
+	private class BluetoothStateReceiver extends BroadcastReceiver {
+
+		@Override
+		public void onReceive(Context ctx, Intent intent) {
+			int state = intent.getIntExtra(EXTRA_STATE, 0);
+			if (state == STATE_ON) {
+				LOG.info("Bluetooth enabled");
+				bind();
+			} else if (state == STATE_OFF) {
+				LOG.info("Bluetooth disabled");
+				tryToClose(socket);
+			}
+			int scanMode = intent.getIntExtra(EXTRA_SCAN_MODE, 0);
+			if (scanMode == SCAN_MODE_NONE) {
+				LOG.info("Scan mode: None");
+			} else if (scanMode == SCAN_MODE_CONNECTABLE) {
+				LOG.info("Scan mode: Connectable");
+			} else if (scanMode == SCAN_MODE_CONNECTABLE_DISCOVERABLE) {
+				LOG.info("Scan mode: Discoverable");
+			}
+		}
+	}
+
+	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;
+
+		private BluetoothKeyAgreementListener(BdfList descriptor,
+				BluetoothServerSocket ss) {
+			super(descriptor);
+			this.ss = ss;
+		}
+
+		@Override
+		public Callable<KeyAgreementConnection> listen() {
+			return new Callable<KeyAgreementConnection>() {
+				@Override
+				public KeyAgreementConnection call() throws IOException {
+					BluetoothSocket s = ss.accept();
+					if (LOG.isLoggable(INFO))
+						LOG.info(ID.getString() + ": Incoming connection");
+					return new KeyAgreementConnection(
+							new DroidtoothTransportConnection(
+									DroidtoothPlugin.this, s), ID);
+				}
+			};
+		}
+
+		@Override
+		public void close() {
+			try {
+				ss.close();
+			} catch (IOException e) {
+				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+			}
+		}
+	}
+}

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

@@ -1,8 +1,7 @@
-package org.briarproject.bramble.plugin.bluetooth;
+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;
@@ -21,7 +20,7 @@ import static org.briarproject.bramble.api.plugin.BluetoothConstants.ID;
 
 @Immutable
 @NotNullByDefault
-public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
+public class DroidtoothPluginFactory implements DuplexPluginFactory {
 
 	private static final int MAX_LATENCY = 30 * 1000; // 30 seconds
 	private static final int MIN_POLLING_INTERVAL = 60 * 1000; // 1 minute
@@ -32,18 +31,15 @@ public class AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 	private final AndroidExecutor androidExecutor;
 	private final Context appContext;
 	private final SecureRandom secureRandom;
-	private final EventBus eventBus;
 	private final BackoffFactory backoffFactory;
 
-	public AndroidBluetoothPluginFactory(Executor ioExecutor,
+	public DroidtoothPluginFactory(Executor ioExecutor,
 			AndroidExecutor androidExecutor, Context appContext,
-			SecureRandom secureRandom, EventBus eventBus,
-			BackoffFactory backoffFactory) {
+			SecureRandom secureRandom, 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 AndroidBluetoothPluginFactory implements DuplexPluginFactory {
 	public DuplexPlugin createPlugin(DuplexPluginCallback callback) {
 		Backoff backoff = backoffFactory.createBackoff(MIN_POLLING_INTERVAL,
 				MAX_POLLING_INTERVAL, BACKOFF_BASE);
-		AndroidBluetoothPlugin plugin = new AndroidBluetoothPlugin(ioExecutor,
-				androidExecutor, appContext, secureRandom, backoff, callback,
-				MAX_LATENCY);
-		eventBus.addListener(plugin);
-		return plugin;
+		return new DroidtoothPlugin(ioExecutor, androidExecutor, appContext,
+				secureRandom, backoff, callback, MAX_LATENCY);
 	}
 }

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

@@ -1,4 +1,4 @@
-package org.briarproject.bramble.plugin.bluetooth;
+package org.briarproject.bramble.plugin.droidtooth;
 
 import android.bluetooth.BluetoothSocket;
 
@@ -11,12 +11,11 @@ import java.io.InputStream;
 import java.io.OutputStream;
 
 @NotNullByDefault
-class AndroidBluetoothTransportConnection
-		extends AbstractDuplexTransportConnection {
+class DroidtoothTransportConnection extends AbstractDuplexTransportConnection {
 
 	private final BluetoothSocket socket;
 
-	AndroidBluetoothTransportConnection(Plugin plugin, BluetoothSocket socket) {
+	DroidtoothTransportConnection(Plugin plugin, BluetoothSocket socket) {
 		super(plugin);
 		this.socket = socket;
 	}

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;
@@ -75,15 +70,10 @@ 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;
@@ -95,13 +85,13 @@ import static org.briarproject.bramble.api.plugin.TorConstants.PREF_TOR_NETWORK_
 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 +102,6 @@ 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 +114,6 @@ 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 +122,12 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	private volatile TorControlConnection controlConnection = null;
 	private volatile BroadcastReceiver networkStateReceiver = null;
 
-	TorPlugin(Executor ioExecutor, ScheduledExecutorService scheduler,
-			Context appContext, LocationUtils locationUtils,
-			DevReporter reporter, SocketFactory torSocketFactory,
-			Backoff backoff, DuplexPluginCallback callback,
-			String architecture, int maxLatency, int maxIdleTime) {
+	TorPlugin(Executor ioExecutor, Context appContext,
+			LocationUtils locationUtils, DevReporter reporter,
+			SocketFactory torSocketFactory, Backoff backoff,
+			DuplexPluginCallback callback, String architecture, int maxLatency,
+			int maxIdleTime) {
 		this.ioExecutor = ioExecutor;
-		this.scheduler = scheduler;
 		this.appContext = appContext;
 		this.locationUtils = locationUtils;
 		this.reporter = reporter;
@@ -164,10 +149,8 @@ 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, "LocationManagerService");
+		wakeLock = pm.newWakeLock(PARTIAL_WAKE_LOCK, "TorPlugin");
 		wakeLock.setReferenceCounted(false);
-		connectionStatusLock = new ReentrantLock();
 	}
 
 	@Override
@@ -220,11 +203,11 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		if (LOG.isLoggable(INFO)) {
 			Scanner stdout = new Scanner(torProcess.getInputStream());
 			Scanner stderr = new Scanner(torProcess.getErrorStream());
-			while (stdout.hasNextLine() || stderr.hasNextLine()) {
-				if (stdout.hasNextLine()) {
+			while (stdout.hasNextLine() || stderr.hasNextLine()){
+				if(stdout.hasNextLine()) {
 					LOG.info(stdout.nextLine());
 				}
-				if (stderr.hasNextLine()) {
+				if(stderr.hasNextLine()){
 					LOG.info(stderr.nextLine());
 				}
 			}
@@ -273,11 +256,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 		}
 		// Register to receive network status events
 		networkStateReceiver = new NetworkStateReceiver();
-		IntentFilter filter = new IntentFilter();
-		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);
+		IntentFilter filter = new IntentFilter(CONNECTIVITY_ACTION);
 		appContext.registerReceiver(networkStateReceiver, filter);
 		// Bind a server socket to receive incoming hidden service connections
 		bind();
@@ -390,45 +369,57 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void sendDevReports() {
-		ioExecutor.execute(() -> {
-			// TODO: Trigger this with a TransportEnabledEvent
-			File reportDir = AndroidUtils.getReportDir(appContext);
-			reporter.sendReports(reportDir);
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				// TODO: Trigger this with a TransportEnabledEvent
+				File reportDir = AndroidUtils.getReportDir(appContext);
+				reporter.sendReports(reportDir);
+			}
 		});
 	}
 
 	private void bind() {
-		ioExecutor.execute(() -> {
-			// If there's already a port number stored in config, reuse it
-			String portString = callback.getSettings().get(PREF_TOR_PORT);
-			int port;
-			if (StringUtils.isNullOrEmpty(portString)) port = 0;
-			else port = Integer.parseInt(portString);
-			// Bind a server socket to receive connections from Tor
-			ServerSocket ss = null;
-			try {
-				ss = new ServerSocket();
-				ss.bind(new InetSocketAddress("127.0.0.1", port));
-			} catch (IOException e) {
-				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-				tryToClose(ss);
-				return;
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				// If there's already a port number stored in config, reuse it
+				String portString = callback.getSettings().get(PREF_TOR_PORT);
+				int port;
+				if (StringUtils.isNullOrEmpty(portString)) port = 0;
+				else port = Integer.parseInt(portString);
+				// Bind a server socket to receive connections from Tor
+				ServerSocket ss = null;
+				try {
+					ss = new ServerSocket();
+					ss.bind(new InetSocketAddress("127.0.0.1", port));
+				} catch (IOException e) {
+					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(PREF_TOR_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 +539,20 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	public void poll(Collection<ContactId> connected) {
 		if (!isRunning()) return;
 		backoff.increment();
-		Map<ContactId, TransportProperties> remote =
-				callback.getRemoteProperties();
-		for (Entry<ContactId, TransportProperties> e : remote.entrySet()) {
-			ContactId c = e.getKey();
-			if (!connected.contains(c)) connectAndCallBack(c, e.getValue());
-		}
+		// TODO: Pass properties to connectAndCallBack()
+		for (ContactId c : callback.getRemoteProperties().keySet())
+			if (!connected.contains(c)) connectAndCallBack(c);
 	}
 
-	private void connectAndCallBack(ContactId c, TransportProperties p) {
-		ioExecutor.execute(() -> {
-			if (!isRunning()) return;
-			DuplexTransportConnection d = createConnection(p);
-			if (d != null) {
-				backoff.reset();
-				callback.outgoingConnectionCreated(c, d);
+	private void connectAndCallBack(final ContactId c) {
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				DuplexTransportConnection d = createConnection(c);
+				if (d != null) {
+					backoff.reset();
+					callback.outgoingConnectionCreated(c, d);
+				}
 			}
 		});
 	}
@@ -570,11 +560,8 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	@Override
 	public DuplexTransportConnection createConnection(ContactId c) {
 		if (!isRunning()) return null;
-		return createConnection(callback.getRemoteProperties(c));
-	}
-
-	@Nullable
-	private DuplexTransportConnection createConnection(TransportProperties p) {
+		TransportProperties p = callback.getRemoteProperties().get(c);
+		if (p == null) return null;
 		String onion = p.get(PROP_ONION);
 		if (StringUtils.isNullOrEmpty(onion)) return null;
 		if (!ONION.matcher(onion).matches()) {
@@ -602,6 +589,17 @@ 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;
@@ -614,7 +612,7 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 
 	@Override
 	public DuplexTransportConnection createKeyAgreementConnection(
-			byte[] commitment, BdfList descriptor) {
+			byte[] commitment, BdfList descriptor, long timeout) {
 		throw new UnsupportedOperationException();
 	}
 
@@ -638,8 +636,6 @@ 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 +675,7 @@ 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();
 		}
@@ -697,75 +693,60 @@ class TorPlugin implements DuplexPlugin, EventHandler, EventListener {
 	}
 
 	private void updateConnectionStatus() {
-		ioExecutor.execute(() -> {
-			if (!running) return;
-			try {
-				connectionStatusLock.lock();
-				updateConnectionStatusLocked();
-			} finally {
-				connectionStatusLock.unlock();
+		ioExecutor.execute(new Runnable() {
+			@Override
+			public void run() {
+				if (!running) return;
+
+				Object o = appContext.getSystemService(CONNECTIVITY_SERVICE);
+				ConnectivityManager cm = (ConnectivityManager) o;
+				NetworkInfo net = cm.getActiveNetworkInfo();
+				boolean online = net != null && net.isConnected();
+				boolean wifi = online && net.getType() == TYPE_WIFI;
+				String country = locationUtils.getCurrentCountry();
+				boolean blocked = TorNetworkMetadata.isTorProbablyBlocked(
+						country);
+				Settings s = callback.getSettings();
+				int network = s.getInt(PREF_TOR_NETWORK,
+						PREF_TOR_NETWORK_ALWAYS);
+
+				if (LOG.isLoggable(INFO)) {
+					LOG.info("Online: " + online + ", wifi: " + wifi);
+					if ("".equals(country)) LOG.info("Country code unknown");
+					else LOG.info("Country code: " + country);
+				}
+
+				try {
+					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);
+				}
 			}
 		});
 	}
 
-	// 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 (LOG.isLoggable(INFO)) LOG.info("Received broadcast " + action);
-			updateConnectionStatus();
-			if (ACTION_SCREEN_ON.equals(action)
-					|| ACTION_SCREEN_OFF.equals(action)) {
-				scheduleConnectionStatusUpdate();
+			if (CONNECTIVITY_ACTION.equals(i.getAction())) {
+				LOG.info("Detected connectivity change");
+				updateConnectionStatus();
 			}
 		}
 	}

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,
-			ScheduledExecutorService scheduler, Context appContext,
+	public TorPluginFactory(Executor ioExecutor, 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,
-				locationUtils, reporter, torSocketFactory, backoff, callback,
-				architecture, MAX_LATENCY, MAX_IDLE_TIME);
+		TorPlugin plugin = new TorPlugin(ioExecutor, appContext, locationUtils,
+				reporter, torSocketFactory, backoff, callback, architecture,
+				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 = () -> {
-			Looper.prepare();
-			backgroundHandler = new Handler();
-			startLatch.countDown();
-			Looper.loop();
+		loop = new Runnable() {
+			@Override
+			public void run() {
+				Looper.prepare();
+				backgroundHandler = new Handler();
+				startLatch.countDown();
+				Looper.loop();
+			}
 		};
 	}
 

bramble-api/build.gradle

@@ -1,39 +1,30 @@
-apply plugin: 'java-library'
-sourceCompatibility = 1.8
-targetCompatibility = 1.8
+apply plugin: 'java'
+sourceCompatibility = 1.6
+targetCompatibility = 1.6
 
 apply plugin: 'witness'
 
 dependencies {
-	implementation "com.google.dagger:dagger:2.0.2"
-	implementation 'com.google.code.findbugs:jsr305:3.0.2'
+	compile "com.google.dagger:dagger:2.0.2"
+	compile 'com.google.dagger:dagger-compiler:2.0.2'
+	compile 'com.google.code.findbugs:jsr305:3.0.1'
 
-	testImplementation 'junit:junit:4.12'
-	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"
+	testCompile 'junit:junit:4.12'
+	testCompile "org.jmock:jmock:2.8.1"
+	testCompile "org.jmock:jmock-junit4:2.8.1"
+	testCompile "org.jmock:jmock-legacy:2.8.1"
+	testCompile "org.hamcrest:hamcrest-library:1.3"
+	testCompile "org.hamcrest:hamcrest-core:1.3"
 }
 
 dependencyVerification {
 	verify = [
-			'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
-			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
-			'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.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',
+			'com.google.dagger:dagger:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
+			'com.google.dagger:dagger-compiler:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
+			'com.google.code.findbugs:jsr305:c885ce34249682bc0236b4a7d56efcc12048e6135a5baf7a9cde8ad8cda13fcd',
+			'javax.inject:javax.inject:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
+			'com.google.dagger:dagger-producers:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
+			'com.google.guava:guava:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
 	]
 }
 
@@ -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/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,
-			long streamNumber);
+	void encodeTag(byte[] tag, SecretKey tagKey, long streamNumber);
 
 	/**
 	 * Signs the given byte[] with the given PrivateKey.

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
-	 * stream.
+	 * Creates a {@link StreamDecrypter} for decrypting an invitation 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
-	 * stream.
+	 * Creates a {@link StreamEncrypter} for encrypting an invitation 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.TreeMap;
+import java.util.concurrent.ConcurrentSkipListMap;
 
 import javax.annotation.Nullable;
-import javax.annotation.concurrent.NotThreadSafe;
 
-@NotThreadSafe
-public class BdfDictionary extends TreeMap<String, Object> {
+public class BdfDictionary extends ConcurrentSkipListMap<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 ArrayList<Object> {
+public class BdfList extends Vector<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

@@ -37,13 +37,8 @@ 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(@Nullable MigrationListener listener) throws DbException;
+	boolean open() throws DbException;
 
 	/**
 	 * Waits for any open transactions to finish and closes the database.
@@ -127,9 +122,8 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/**
-	 * Deletes the message with the given ID. Unlike
-	 * {@link #removeMessage(Transaction, MessageId)}, the message ID and any
-	 * other associated data are not deleted.
+	 * Deletes the message with the given ID. The message ID and any other
+	 * associated data are not deleted.
 	 */
 	void deleteMessage(Transaction txn, MessageId m) throws DbException;
 
@@ -378,16 +372,6 @@ public interface DatabaseComponent {
 	MessageStatus getMessageStatus(Transaction txn, ContactId c, MessageId m)
 			throws DbException;
 
-	/*
-	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact. The returned value may
-	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE if
-	 * no messages are scheduled to be sent.
-	 * <p/>
-	 * Read-only.
-	 */
-	long getNextSendTime(Transaction txn, ContactId c) throws DbException;
-
 	/**
 	 * Returns all settings in the given namespace.
 	 * <p/>
@@ -468,11 +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
-public class Metadata extends TreeMap<String, byte[]> {
+@ThreadSafe
+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/MigrationListener.java

@@ -1,11 +0,0 @@
-package org.briarproject.bramble.api.db;
-
-public interface MigrationListener {
-
-	/**
-	 * This is called when a migration is started while opening the database.
-	 * It will be called once for each migration being applied.
-	 */
-	void onMigrationRun();
-
-}

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/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/keyagreement/KeyAgreementListener.java

@@ -2,7 +2,7 @@ package org.briarproject.bramble.api.keyagreement;
 
 import org.briarproject.bramble.api.data.BdfList;
 
-import java.io.IOException;
+import java.util.concurrent.Callable;
 
 /**
  * An class for managing a particular key agreement listener.
@@ -24,11 +24,11 @@ public abstract class KeyAgreementListener {
 	}
 
 	/**
-	 * Blocks until an incoming connection is received and returns it.
-	 *
-	 * @throws IOException if an error occurs or {@link #close()} is called.
+	 * Starts listening for incoming connections, and returns a Callable that
+	 * will return a KeyAgreementConnection when an incoming connection is
+	 * received.
 	 */
-	public abstract KeyAgreementConnection accept() throws IOException;
+	public abstract Callable<KeyAgreementConnection> listen();
 
 	/**
 	 * Closes the underlying server socket.

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

@@ -21,25 +21,7 @@ public interface LifecycleManager {
 	 * The result of calling {@link #startServices(String)}.
 	 */
 	enum StartResult {
-		ALREADY_RUNNING,
-		DB_ERROR,
-		DATA_TOO_OLD_ERROR,
-		DATA_TOO_NEW_ERROR,
-		SERVICE_ERROR,
-		SUCCESS
-	}
-
-	/**
-	 * The state the lifecycle can be in.
-	 * Returned by {@link #getLifecycleState()}
-	 */
-	enum LifecycleState {
-
-		STARTING, MIGRATING_DATABASE, STARTING_SERVICES, RUNNING, STOPPING;
-
-		public boolean isAfter(LifecycleState state) {
-			return ordinal() > state.ordinal();
-		}
+		ALREADY_RUNNING, DB_ERROR, SERVICE_ERROR, SUCCESS
 	}
 
 	/**
@@ -89,10 +71,4 @@ public interface LifecycleManager {
 	 * the {@link DatabaseComponent} to be closed before returning.
 	 */
 	void waitForShutdown() throws InterruptedException;
-
-	/**
-	 * Returns the current state of the lifecycle.
-	 */
-	LifecycleState getLifecycleState();
-
 }

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/event/LifecycleEvent.java

@@ -1,20 +0,0 @@
-package org.briarproject.bramble.api.lifecycle.event;
-
-import org.briarproject.bramble.api.event.Event;
-import org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState;
-
-/**
- * An event that is broadcast when the app enters a new lifecycle state.
- */
-public class LifecycleEvent extends Event {
-
-	private final LifecycleState state;
-
-	public LifecycleEvent(LifecycleState state) {
-		this.state = state;
-	}
-
-	public LifecycleState getLifecycleState() {
-		return state;
-	}
-}

bramble-api/src/main/java/org/briarproject/bramble/api/lifecycle/event/ShutdownEvent.java

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.lifecycle.event;
+
+import org.briarproject.bramble.api.event.Event;
+
+/**
+ * An event that is broadcast when the app is shutting down.
+ */
+public class ShutdownEvent extends Event {
+}

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

@@ -4,10 +4,5 @@ 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

@@ -4,8 +4,6 @@ public interface TorConstants {
 
 	TransportId ID = new TransportId("org.briarproject.bramble.tor");
 
-	String PROP_ONION = "onion";
-
 	int SOCKS_PORT = 59050;
 	int CONTROL_PORT = 59051;
 
@@ -18,5 +16,4 @@ public interface TorConstants {
 	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.
 	 */
@@ -36,9 +51,9 @@ public interface DuplexPlugin extends Plugin {
 
 	/**
 	 * Attempts to connect to the remote peer specified in the given descriptor.
-	 * Returns null if no connection can be established.
+	 * Returns null if no connection can be established within the given time.
 	 */
 	@Nullable
 	DuplexTransportConnection createKeyAgreementConnection(
-			byte[] remoteCommitment, BdfList descriptor);
+			byte[] remoteCommitment, BdfList descriptor, long timeout);
 }

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/event/BluetoothEnabledEvent.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 informs the Bluetooth plugin that we have enabled the
- * Bluetooth adapter.
- */
-@Immutable
-@NotNullByDefault
-public class BluetoothEnabledEvent extends Event {
-}

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 that 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/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
-	 * exchangestream.
+	 * Creates an {@link InputStream InputStream} for reading from an
+	 * 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
-	 * exchange stream.
+	 * Creates an {@link OutputStream OutputStream} for writing to an
+	 * 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
-			+ STREAM_HEADER_PLAINTEXT_LENGTH + MAC_LENGTH;
+	int STREAM_HEADER_LENGTH = STREAM_HEADER_IV_LENGTH + SecretKey.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/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;
@@ -126,10 +124,6 @@ public class StringUtils {
 		return toUtf8(s).length > maxLength;
 	}
 
-	public static boolean isValidMac(String mac) {
-		return MAC.matcher(mac).matches();
-	}
-
 	public static byte[] macToBytes(String mac) {
 		if (!MAC.matcher(mac).matches()) throw new IllegalArgumentException();
 		return fromHexString(mac.replaceAll(":", ""));
@@ -145,12 +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) -> {
-			throwable.printStackTrace();
-			fail();
+		UncaughtExceptionHandler fail = new UncaughtExceptionHandler() {
+			@Override
+			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'
-sourceCompatibility = 1.8
-targetCompatibility = 1.8
+plugins {
+	id "java"
+	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')
-	implementation 'com.madgag.spongycastle:core:1.58.0.0'
-	implementation 'com.h2database:h2:1.4.192' // This is the last version that supports Java 1.6
-	implementation 'org.bitlet:weupnp:0.1.4'
+	compile project(':bramble-api')
+	compile fileTree(dir: 'libs', include: '*.jar')
+	compile 'com.madgag.spongycastle:core:1.54.0.0'
+	compile 'com.h2database:h2:1.4.190'
 
-	apt 'com.google.dagger:dagger-compiler:2.0.2'
-
-	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'
+	testCompile project(path: ':bramble-api', configuration: 'testOutput')
 }
 
 dependencyVerification {
 	verify = [
-			'cglib:cglib:3.2.0:cglib-3.2.0.jar:adb13bab79712ad6bdf1bd59f2a3918018a8016e722e8a357065afb9e6690861',
-			'com.google.code.findbugs:jsr305:3.0.2:jsr305-3.0.2.jar:766ad2a0783f2687962c8ad74ceecc38a28b9f72a2d085ee438b7813e928d0c7',
-			'com.google.dagger:dagger-compiler:2.0.2:dagger-compiler-2.0.2.jar:b74bc9de063dd4c6400b232231f2ef5056145b8fbecbf5382012007dd1c071b3',
-			'com.google.dagger:dagger-producers:2.0-beta:dagger-producers-2.0-beta.jar:99ec15e8a0507ba569e7655bc1165ee5e5ca5aa914b3c8f7e2c2458f724edd6b',
-			'com.google.dagger:dagger:2.0.2:dagger-2.0.2.jar:84c0282ed8be73a29e0475d639da030b55dee72369e58dd35ae7d4fe6243dcf9',
-			'com.google.guava:guava:18.0:guava-18.0.jar:d664fbfc03d2e5ce9cab2a44fb01f1d0bf9dfebeccc1a473b1f9ea31f79f6f99',
-			'com.h2database:h2:1.4.192:h2-1.4.192.jar:225b22e9857235c46c93861410b60b8c81c10dc8985f4faf188985ba5445126c',
-			'com.madgag.spongycastle:core:1.58.0.0:core-1.58.0.0.jar:199617dd5698c5a9312b898c0a4cec7ce9dd8649d07f65d91629f58229d72728',
-			'javax.inject:javax.inject:1:javax.inject-1.jar:91c77044a50c481636c32d916fd89c9118a72195390452c81065080f957de7ff',
-			'junit:junit:4.12:junit-4.12.jar:59721f0805e223d84b90677887d9ff567dc534d7c502ca903c0c2b17f05c116a',
-			'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',
+			'com.madgag.spongycastle:core:1e7fa4b19ccccd1011364ab838d0b4702470c178bbbdd94c5c90b2d4d749ea1e',
+			'com.h2database:h2:23ba495a07bbbb3bd6c3084d10a96dad7a23741b8b6d64b213459a784195a98c'
 	]
 }
 
@@ -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

@@ -24,7 +24,7 @@ public class PoliteExecutor implements Executor {
 
 	private final Object lock = new Object();
 	@GuardedBy("lock")
-	private final Queue<Runnable> queue = new LinkedList<>();
+	private final Queue<Runnable> queue = new LinkedList<Runnable>();
 	private final Executor delegate;
 	private final int maxConcurrentTasks;
 	private final Logger log;
@@ -48,17 +48,20 @@ public class PoliteExecutor implements Executor {
 	}
 
 	@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();
+	public void execute(final Runnable r) {
+		final long submitted = System.currentTimeMillis();
+		Runnable wrapped = new Runnable() {
+			@Override
+			public void run() {
+				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) {

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

@@ -28,16 +28,19 @@ public class TimeLoggingExecutor extends ThreadPoolExecutor {
 	}
 
 	@Override
-	public void execute(Runnable r) {
+	public void execute(final 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");
+			final long submitted = System.currentTimeMillis();
+			super.execute(new Runnable() {
+				@Override
+				public void run() {
+					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<>();
-		removeHooks = new CopyOnWriteArrayList<>();
+		addHooks = new CopyOnWriteArrayList<AddContactHook>();
+		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/CryptoComponentImpl.java

@@ -4,6 +4,7 @@ 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;
@@ -40,13 +41,12 @@ 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 +66,9 @@ 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");
@@ -166,6 +169,14 @@ class CryptoComponentImpl implements CryptoComponent {
 		return new SecretKey(b);
 	}
 
+	@Override
+	public PseudoRandom getPseudoRandom(int seed1, int seed2) {
+		byte[] seed = new byte[INT_32_BYTES * 2];
+		ByteUtils.writeUint32(seed1, seed, 0);
+		ByteUtils.writeUint32(seed2, seed, INT_32_BYTES);
+		return new PseudoRandomImpl(seed);
+	}
+
 	@Override
 	public SecureRandom getSecureRandom() {
 		return secureRandom;
@@ -237,6 +248,20 @@ 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) {
@@ -387,11 +412,8 @@ class CryptoComponentImpl implements CryptoComponent {
 	}
 
 	@Override
-	public void encodeTag(byte[] tag, SecretKey tagKey, int protocolVersion,
-			long streamNumber) {
+	public void encodeTag(byte[] tag, SecretKey tagKey, 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 +421,10 @@ 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 stream number as a 64-bit integer
-		byte[] protocolVersionBytes = new byte[INT_16_BYTES];
-		ByteUtils.writeUint16(protocolVersion, protocolVersionBytes, 0);
-		prf.update(protocolVersionBytes, 0, protocolVersionBytes.length);
-		byte[] streamNumberBytes = new byte[INT_64_BYTES];
-		ByteUtils.writeUint64(streamNumber, streamNumberBytes, 0);
-		prf.update(streamNumberBytes, 0, streamNumberBytes.length);
+		// The input is the stream number as a 64-bit integer
+		byte[] input = new byte[INT_64_BYTES];
+		ByteUtils.writeUint64(streamNumber, input, 0);
+		prf.update(input, 0, input.length);
 		byte[] mac = new byte[macLength];
 		prf.doFinal(mac, 0);
 		// The output is the first TAG_LENGTH bytes of the MAC
@@ -602,8 +620,8 @@ class CryptoComponentImpl implements CryptoComponent {
 
 	// Package access for testing
 	int chooseIterationCount(int targetMillis) {
-		List<Long> quickSamples = new ArrayList<>(PBKDF_SAMPLES);
-		List<Long> slowSamples = new ArrayList<>(PBKDF_SAMPLES);
+		List<Long> quickSamples = new ArrayList<Long>(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

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

@@ -48,7 +48,7 @@ public class CryptoModule {
 
 	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();

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

@@ -16,7 +16,7 @@ class PasswordStrengthEstimatorImpl implements PasswordStrengthEstimator {
 
 	@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);

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.crypto;
 
+import org.briarproject.bramble.api.crypto.PseudoRandom;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.spongycastle.crypto.Digest;
 import org.spongycastle.crypto.engines.Salsa20Engine;
@@ -10,11 +11,11 @@ import javax.annotation.concurrent.NotThreadSafe;
 
 @NotThreadSafe
 @NotNullByDefault
-class PseudoRandom {
+class PseudoRandomImpl implements PseudoRandom {
 
 	private final Salsa20Engine cipher = new Salsa20Engine();
 
-	PseudoRandom(byte[] seed) {
+	PseudoRandomImpl(byte[] seed) {
 		// Hash the seed to produce a 32-byte key
 		byte[] key = new byte[32];
 		Digest digest = new Blake2sDigest();
@@ -25,7 +26,8 @@ class PseudoRandom {
 		cipher.init(true, new ParametersWithIV(new KeyParameter(key), nonce));
 	}
 
-	byte[] nextBytes(int length) {
+	@Override
+	public byte[] nextBytes(int length) {
 		byte[] in = new byte[length], out = new byte[length];
 		cipher.processBytes(in, 0, length, out, 0);
 		return out;

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,
-				STREAM_HEADER_NONCE_LENGTH);
+		ByteUtils.writeUint64(streamNumber, streamHeaderNonce, 0);
+		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_PLAINTEXT_LENGTH + MAC_LENGTH,
+					STREAM_HEADER_IV_LENGTH, SecretKey.LENGTH + MAC_LENGTH,
 					streamHeaderPlaintext, 0);
-			if (decrypted != STREAM_HEADER_PLAINTEXT_LENGTH)
-				throw new RuntimeException();
+			if (decrypted != SecretKey.LENGTH) throw new RuntimeException();
 		} catch (GeneralSecurityException e) {
 			throw new FormatException();
 		}
-		// Check the protocol version
-		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);
+		frameKey = new SecretKey(streamHeaderPlaintext);
 	}
 }

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_NONCE_LENGTH;
+import static org.briarproject.bramble.api.transport.TransportConstants.STREAM_HEADER_IV_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);
-		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
-		crypto.getSecureRandom().nextBytes(streamHeaderNonce);
+		crypto.encodeTag(tag, ctx.getTagKey(), streamNumber);
+		byte[] streamHeaderIv = new byte[STREAM_HEADER_IV_LENGTH];
+		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(
-			OutputStream out, SecretKey headerKey) {
+	public StreamEncrypter createInvitationStreamEncrypter(OutputStream out,
+			SecretKey headerKey) {
 		AuthenticatedCipher cipher = cipherProvider.get();
-		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
-		crypto.getSecureRandom().nextBytes(streamHeaderNonce);
+		byte[] streamHeaderIv = new byte[STREAM_HEADER_IV_LENGTH];
+		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];
@@ -116,23 +114,22 @@ class StreamEncrypterImpl implements StreamEncrypter {
 	}
 
 	private void writeStreamHeader() throws IOException {
-		// The header contains the protocol version, stream number and frame key
-		byte[] streamHeaderPlaintext = new byte[STREAM_HEADER_PLAINTEXT_LENGTH];
-		ByteUtils.writeUint16(PROTOCOL_VERSION, streamHeaderPlaintext, 0);
-		ByteUtils.writeUint64(streamNumber, streamHeaderPlaintext,
-				INT_16_BYTES);
-		System.arraycopy(frameKey.getBytes(), 0, streamHeaderPlaintext,
-				INT_16_BYTES + INT_64_BYTES, SecretKey.LENGTH);
+		// The nonce consists of the stream number followed by the IV
+		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
+		ByteUtils.writeUint64(streamNumber, streamHeaderNonce, 0);
+		System.arraycopy(streamHeaderIv, 0, streamHeaderNonce, INT_64_BYTES,
+				STREAM_HEADER_IV_LENGTH);
+		byte[] streamHeaderPlaintext = frameKey.getBytes();
 		byte[] streamHeaderCiphertext = new byte[STREAM_HEADER_LENGTH];
-		System.arraycopy(streamHeaderNonce, 0, streamHeaderCiphertext, 0,
-				STREAM_HEADER_NONCE_LENGTH);
-		// Encrypt and authenticate the stream header key
+		System.arraycopy(streamHeaderIv, 0, streamHeaderCiphertext, 0,
+				STREAM_HEADER_IV_LENGTH);
+		// Encrypt and authenticate the frame key
 		try {
 			cipher.init(true, streamHeaderKey, streamHeaderNonce);
 			int encrypted = cipher.process(streamHeaderPlaintext, 0,
-					STREAM_HEADER_PLAINTEXT_LENGTH, streamHeaderCiphertext,
-					STREAM_HEADER_NONCE_LENGTH);
-			if (encrypted != STREAM_HEADER_PLAINTEXT_LENGTH + MAC_LENGTH)
+					SecretKey.LENGTH, streamHeaderCiphertext,
+					STREAM_HEADER_IV_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

@@ -2,11 +2,8 @@ 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.db.MigrationListener;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.LocalAuthor;
@@ -40,13 +37,8 @@ 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(@Nullable MigrationListener listener) throws DbException;
+	boolean open() throws DbException;
 
 	/**
 	 * Prevents new transactions from starting, waits for all current
@@ -457,16 +449,6 @@ interface Database<T> {
 	Collection<MessageId> getMessagesToShare(T txn, ClientId c)
 			throws DbException;
 
-	/**
-	 * Returns the next time (in milliseconds since the Unix epoch) when a
-	 * message is due to be sent to the given contact. The returned value may
-	 * be zero if a message is due to be sent immediately, or Long.MAX_VALUE
-	 * if no messages are scheduled to be sent.
-	 * <p/>
-	 * Read-only.
-	 */
-	long getNextSendTime(T txn, ContactId c) throws DbException;
-
 	/**
 	 * Returns the message with the given ID, in serialised form, or null if
 	 * the message has been deleted.

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

@@ -10,7 +10,6 @@ import org.briarproject.bramble.api.db.ContactExistsException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Metadata;
-import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.db.NoSuchContactException;
 import org.briarproject.bramble.api.db.NoSuchGroupException;
 import org.briarproject.bramble.api.db.NoSuchLocalAuthorException;
@@ -91,6 +90,8 @@ 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) {
@@ -101,22 +102,27 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 	}
 
 	@Override
-	public boolean open(@Nullable MigrationListener listener)
-			throws DbException {
-		boolean reopened = db.open(listener);
-		shutdown.addShutdownHook(() -> {
-			try {
-				close();
-			} catch (DbException e) {
-				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+	public boolean open() throws DbException {
+		Runnable shutdownHook = new Runnable() {
+			@Override
+			public void run() {
+				try {
+					close();
+				} 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();
 	}
 
@@ -135,7 +141,11 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		}
 		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;
@@ -321,7 +331,7 @@ 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);
@@ -371,7 +381,7 @@ 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);
@@ -581,13 +591,6 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getMessageDependents(txn, m);
 	}
 
-	@Override
-	public long getNextSendTime(Transaction transaction, ContactId c)
-		throws DbException {
-		T txn = unbox(transaction);
-		return db.getNextSendTime(txn, c);
-	}
-
 	@Override
 	public Settings getSettings(Transaction transaction, String namespace)
 			throws DbException {
@@ -658,7 +661,7 @@ 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);
@@ -767,16 +770,6 @@ 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 {
@@ -893,7 +886,8 @@ 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

@@ -32,7 +32,7 @@ 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();

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,
-				shutdown);
+		return new DatabaseComponentImpl<Connection>(db, Connection.class,
+				eventBus, shutdown);
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/db/H2Database.java

@@ -3,7 +3,6 @@ package org.briarproject.bramble.db;
 import org.briarproject.bramble.api.crypto.SecretKey;
 import org.briarproject.bramble.api.db.DatabaseConfig;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.util.StringUtils;
@@ -14,7 +13,6 @@ import java.sql.DriverManager;
 import java.sql.SQLException;
 import java.util.Properties;
 
-import javax.annotation.Nullable;
 import javax.inject.Inject;
 
 /**
@@ -42,11 +40,10 @@ class H2Database extends JdbcDatabase {
 	}
 
 	@Override
-	public boolean open(@Nullable MigrationListener listener)
-			throws DbException {
+	public boolean open() throws DbException {
 		boolean reopen = config.databaseExists();
 		if (!reopen) config.getDatabaseDirectory().mkdirs();
-		super.open("org.h2.Driver", reopen, listener);
+		super.open("org.h2.Driver", reopen);
 		return reopen;
 	}
 

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

@@ -3,12 +3,9 @@ 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;
-import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.identity.Author;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.identity.LocalAuthor;
@@ -50,7 +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;
@@ -61,6 +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;
 
@@ -71,8 +68,8 @@ import static org.briarproject.bramble.db.ExponentialBackoff.calculateExpiry;
 @NotNullByDefault
 abstract class JdbcDatabase implements Database<Connection> {
 
-	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 31;
+	private static final int SCHEMA_VERSION = 30;
+	private static final int MIN_SCHEMA_VERSION = 30;
 
 	private static final String CREATE_SETTINGS =
 			"CREATE TABLE settings"
@@ -151,16 +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 =
@@ -240,18 +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());
 
@@ -259,8 +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 = new LinkedList<>();
+	private final LinkedList<Connection> connections =
+			new LinkedList<Connection>(); // Locking: connectionsLock
 
 	private int openConnections = 0; // Locking: connectionsLock
 	private boolean closed = false; // Locking: connectionsLock
@@ -280,24 +260,22 @@ abstract class JdbcDatabase implements Database<Connection> {
 		this.clock = clock;
 	}
 
-	protected void open(String driverClass, boolean reopen,
-			@Nullable MigrationListener listener) throws DbException {
+	protected void open(String driverClass, boolean reopen) throws DbException {
 		// Load the JDBC driver
 		try {
 			Class.forName(driverClass);
 		} 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, listener);
+				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);
@@ -305,51 +283,19 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	/**
-	 * 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,
-			@Nullable MigrationListener listener) throws DbException {
+	private boolean checkSchemaVersion(Connection txn) throws DbException {
 		Settings s = getSettings(txn, DB_SETTINGS_NAMESPACE);
-		int dataSchemaVersion = s.getInt(SCHEMA_VERSION_KEY, -1);
-		if (dataSchemaVersion == -1) throw new DbException();
-		if (dataSchemaVersion == CODE_SCHEMA_VERSION) return;
-		if (CODE_SCHEMA_VERSION < dataSchemaVersion)
-			throw new DataTooNewException();
-		// 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);
-				if (listener != null) listener.onMigrationRun();
-				// Apply the migration
-				m.migrate(txn);
-				// Store the new schema version
-				storeSchemaVersion(txn, end);
-				dataSchemaVersion = end;
-			}
-		}
-		if (dataSchemaVersion != CODE_SCHEMA_VERSION)
-			throw new DataTooOldException();
+		int schemaVersion = s.getInt(SCHEMA_VERSION_KEY, -1);
+		if (schemaVersion == SCHEMA_VERSION) return true;
+		if (schemaVersion < MIN_SCHEMA_VERSION) return false;
+		int minSchemaVersion = s.getInt(MIN_SCHEMA_VERSION_KEY, -1);
+		return SCHEMA_VERSION >= minSchemaVersion;
 	}
 
-	// Package access for testing
-	List<Migration<Connection>> getMigrations() {
-		return Collections.singletonList(new Migration30_31());
-	}
-
-	private void storeSchemaVersion(Connection txn, int version)
-			throws DbException {
+	private void storeSchemaVersion(Connection txn) 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);
 	}
 
@@ -394,20 +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);
@@ -526,8 +458,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			// Create a contact row
 			String sql = "INSERT INTO contacts"
-					+ " (authorId, name, publicKey, localAuthorId,"
-					+ " verified, active)"
+					+ " (authorId, name, publicKey, localAuthorId, verified, active)"
 					+ " VALUES (?, ?, ?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, remote.getId().getBytes());
@@ -1062,7 +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));
@@ -1096,7 +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();
@@ -1121,7 +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);
@@ -1177,7 +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);
@@ -1230,7 +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();
@@ -1282,7 +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);
@@ -1312,7 +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();
@@ -1335,7 +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();
@@ -1357,17 +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"
-					+ " WHERE groupId = ? AND state = ?"
+			String sql = "SELECT m.messageId"
+					+ " 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(2, DELIVERED.getValue());
+				ps.setInt(1, 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();
@@ -1391,20 +1325,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT messageId, key, value"
-					+ " FROM messageMetadata"
-					+ " WHERE groupId = ? AND state = ?";
+			String sql = "SELECT m.messageId, key, value"
+					+ " FROM messages AS m"
+					+ " 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(2, DELIVERED.getValue());
+			ps.setInt(1, 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 (metadata == null) {
+				if (lastMessageId == null || !messageId.equals(lastMessageId)) {
 					metadata = new Metadata();
 					all.put(messageId, metadata);
+					lastMessageId = messageId;
 				}
 				metadata.put(rs.getString(2), rs.getBytes(3));
 			}
@@ -1425,7 +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;
 	}
@@ -1459,8 +1399,10 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT key, value FROM messageMetadata"
-					+ " WHERE state = ? AND messageId = ?";
+			String sql = "SELECT key, value FROM messageMetadata AS md"
+					+ " 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());
@@ -1483,9 +1425,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			String sql = "SELECT key, value FROM messageMetadata"
-					+ " WHERE (state = ? OR state = ?)"
-					+ " AND messageId = ?";
+			String sql = "SELECT key, value FROM messageMetadata AS md"
+					+ " JOIN messages AS m"
+					+ " 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());
@@ -1519,7 +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);
@@ -1578,7 +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));
@@ -1616,7 +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));
@@ -1668,7 +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();
@@ -1704,7 +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();
@@ -1729,7 +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();
@@ -1764,7 +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);
@@ -1806,7 +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();
@@ -1836,7 +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();
@@ -1848,41 +1792,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	@Override
-	public long getNextSendTime(Connection txn, ContactId c)
-			throws DbException {
-		PreparedStatement ps = null;
-		ResultSet rs = null;
-		try {
-			String sql = "SELECT expiry FROM messages AS m"
-					+ " JOIN groupVisibilities AS gv"
-					+ " ON m.groupId = gv.groupId"
-					+ " JOIN statuses AS s"
-					+ " ON m.messageId = s.messageId"
-					+ " AND gv.contactId = s.contactId"
-					+ " WHERE gv.contactId = ? AND gv.shared = TRUE"
-					+ " AND state = ? AND m.shared = TRUE AND raw IS NOT NULL"
-					+ " AND seen = FALSE"
-					+ " ORDER BY expiry LIMIT 1";
-			ps = txn.prepareStatement(sql);
-			ps.setInt(1, c.getInt());
-			ps.setInt(2, DELIVERED.getValue());
-			rs = ps.executeQuery();
-			long nextSendTime = Long.MAX_VALUE;
-			if (rs.next()) {
-				nextSendTime = rs.getLong(1);
-				if (rs.next()) throw new AssertionError();
-			}
-			rs.close();
-			ps.close();
-			return nextSendTime;
-		} catch (SQLException e) {
-			tryToClose(rs);
-			tryToClose(ps);
-			throw new DbException(e);
-		}
-	}
-
 	@Override
 	@Nullable
 	public byte[] getRawMessage(Connection txn, MessageId m)
@@ -1930,7 +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);
@@ -1984,7 +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));
@@ -2004,7 +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();
@@ -2094,7 +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();
 			}
@@ -2108,92 +2018,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 	@Override
 	public void mergeGroupMetadata(Connection txn, GroupId g, Metadata meta)
 			throws DbException {
-		PreparedStatement ps = null;
-		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);
-		}
+		mergeMetadata(txn, g.getBytes(), meta, "groupMetadata", "groupId");
 	}
 
 	@Override
-	public void mergeMessageMetadata(Connection txn, MessageId m,
-			Metadata meta) throws DbException {
-		PreparedStatement ps = null;
-		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);
-		}
+	public void mergeMessageMetadata(Connection txn, MessageId m, Metadata meta)
+			throws DbException {
+		mergeMetadata(txn, m.getBytes(), meta, "messageMetadata", "messageId");
 	}
 
-	// Removes or updates any existing entries, returns any entries that
-	// need to be added
-	private Map<String, byte[]> removeOrUpdateMetadata(Connection txn,
-			byte[] id, Metadata meta, String tableName, String columnName)
-			throws DbException {
+	private void mergeMetadata(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<>();
-			Map<String, byte[]> notRemoved = new HashMap<>();
+			List<String> removed = new ArrayList<String>();
+			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()) {
@@ -2214,33 +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();
-			// Are there any keys that don't already exist?
-			Map<String, byte[]> added = new HashMap<>();
-			int updateIndex = 0;
-			for (Entry<String, byte[]> e : notRemoved.entrySet()) {
-				if (batchAffected[updateIndex++] == 0)
-					added.put(e.getKey(), e.getValue());
+			// Insert any keys that don't already exist
+			sql = "INSERT INTO " + tableName
+					+ " (" + columnName + ", key, value)"
+					+ " VALUES (?, ?, ?)";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, id);
+			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);
@@ -2593,8 +2448,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void setMessageShared(Connection txn, MessageId m)
-			throws DbException {
+	public void setMessageShared(Connection txn, MessageId m) throws DbException {
 		PreparedStatement ps = null;
 		try {
 			String sql = "UPDATE messages SET shared = TRUE"
@@ -2622,14 +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/ConnectionChooser.java

@@ -1,36 +0,0 @@
-package org.briarproject.bramble.keyagreement;
-
-import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
-
-import java.util.concurrent.Callable;
-
-import javax.annotation.Nullable;
-
-interface ConnectionChooser {
-
-	/**
-	 * Submits a connection task to the chooser.
-	 */
-	void submit(Callable<KeyAgreementConnection> task);
-
-	/**
-	 * Returns a connection returned by any of the tasks submitted to the
-	 * chooser, waiting up to the given amount of time for a connection if
-	 * necessary. Returns null if the time elapses without a connection
-	 * becoming available.
-	 *
-	 * @param timeout the timeout in milliseconds
-	 * @throws InterruptedException if the thread is interrupted while waiting
-	 * for a connection to become available
-	 */
-	@Nullable
-	KeyAgreementConnection poll(long timeout) throws InterruptedException;
-
-	/**
-	 * Stops the chooser. Any connections already returned to the chooser are
-	 * closed unless they have been removed from the chooser by calling
-	 * {@link #poll(long)}. Any connections subsequently returned to the
-	 * chooser will also be closed.
-	 */
-	void stop();
-}

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

@@ -1,112 +0,0 @@
-package org.briarproject.bramble.keyagreement;
-
-import org.briarproject.bramble.api.keyagreement.KeyAgreementConnection;
-import org.briarproject.bramble.api.lifecycle.IoExecutor;
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
-import org.briarproject.bramble.api.system.Clock;
-
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Queue;
-import java.util.concurrent.Callable;
-import java.util.concurrent.Executor;
-import java.util.logging.Logger;
-
-import javax.annotation.Nullable;
-import javax.annotation.concurrent.ThreadSafe;
-import javax.inject.Inject;
-
-import static java.util.logging.Level.INFO;
-
-@NotNullByDefault
-@ThreadSafe
-class ConnectionChooserImpl implements ConnectionChooser {
-
-	private static final Logger LOG =
-			Logger.getLogger(ConnectionChooserImpl.class.getName());
-
-	private final Clock clock;
-	private final Executor ioExecutor;
-	private final Object lock = new Object();
-
-	// The following are locking: lock
-	private boolean stopped = false;
-	private final Queue<KeyAgreementConnection> results = new LinkedList<>();
-
-	@Inject
-	ConnectionChooserImpl(Clock clock, @IoExecutor Executor ioExecutor) {
-		this.clock = clock;
-		this.ioExecutor = ioExecutor;
-	}
-
-	@Override
-	public void submit(Callable<KeyAgreementConnection> task) {
-		ioExecutor.execute(() -> {
-			try {
-				KeyAgreementConnection c = task.call();
-				if (c != null) addResult(c);
-			} catch (Exception e) {
-				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
-			}
-		});
-	}
-
-	@Nullable
-	@Override
-	public KeyAgreementConnection poll(long timeout)
-			throws InterruptedException {
-		long now = clock.currentTimeMillis();
-		long end = now + timeout;
-		synchronized (lock) {
-			while (!stopped && results.isEmpty() && now < end) {
-				lock.wait(end - now);
-				now = clock.currentTimeMillis();
-			}
-			return results.poll();
-		}
-	}
-
-	@Override
-	public void stop() {
-		List<KeyAgreementConnection> unused;
-		synchronized (lock) {
-			unused = new ArrayList<>(results);
-			results.clear();
-			stopped = true;
-			lock.notifyAll();
-		}
-		if (LOG.isLoggable(INFO))
-			LOG.info("Closing " + unused.size() + " unused connections");
-		for (KeyAgreementConnection c : unused) tryToClose(c.getConnection());
-	}
-
-	private void addResult(KeyAgreementConnection c) {
-		if (LOG.isLoggable(INFO))
-			LOG.info("Got connection for " + c.getTransportId());
-		boolean close = false;
-		synchronized (lock) {
-			if (stopped) {
-				close = true;
-			} else {
-				results.add(c);
-				lock.notifyAll();
-			}
-		}
-		if (close) {
-			LOG.info("Already stopped");
-			tryToClose(c.getConnection());
-		}
-	}
-
-	private void tryToClose(DuplexTransportConnection conn) {
-		try {
-			conn.getReader().dispose(false, true);
-			conn.getWriter().dispose(false);
-		} catch (IOException e) {
-			if (LOG.isLoggable(INFO)) LOG.info(e.toString());
-		}
-	}
-}

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

@@ -13,19 +13,23 @@ import org.briarproject.bramble.api.plugin.PluginManager;
 import org.briarproject.bramble.api.plugin.TransportId;
 import org.briarproject.bramble.api.plugin.duplex.DuplexPlugin;
 import org.briarproject.bramble.api.plugin.duplex.DuplexTransportConnection;
+import org.briarproject.bramble.api.system.Clock;
 
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.Callable;
-import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.CompletionService;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorCompletionService;
+import java.util.concurrent.Future;
 import java.util.logging.Logger;
 
 import javax.annotation.Nullable;
 
+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.CONNECTION_TIMEOUT;
@@ -41,42 +45,46 @@ class KeyAgreementConnector {
 			Logger.getLogger(KeyAgreementConnector.class.getName());
 
 	private final Callbacks callbacks;
+	private final Clock clock;
 	private final CryptoComponent crypto;
 	private final PluginManager pluginManager;
-	private final ConnectionChooser connectionChooser;
+	private final CompletionService<KeyAgreementConnection> connect;
 
 	private final List<KeyAgreementListener> listeners =
-			new CopyOnWriteArrayList<>();
-	private final CountDownLatch aliceLatch = new CountDownLatch(1);
-	private final AtomicBoolean waitingSent = new AtomicBoolean(false);
+			new ArrayList<KeyAgreementListener>();
+	private final List<Future<KeyAgreementConnection>> pending =
+			new ArrayList<Future<KeyAgreementConnection>>();
 
-	private volatile boolean alice = false, stopped = false;
+	private volatile boolean connecting = false;
+	private volatile boolean alice = false;
 
-	KeyAgreementConnector(Callbacks callbacks,
+	KeyAgreementConnector(Callbacks callbacks, Clock clock,
 			CryptoComponent crypto, PluginManager pluginManager,
-			ConnectionChooser connectionChooser) {
+			Executor ioExecutor) {
 		this.callbacks = callbacks;
+		this.clock = clock;
 		this.crypto = crypto;
 		this.pluginManager = pluginManager;
-		this.connectionChooser = connectionChooser;
+		connect = new ExecutorCompletionService<KeyAgreementConnection>(
+				ioExecutor);
 	}
 
-	Payload listen(KeyPair localKeyPair) {
+	public Payload listen(KeyPair localKeyPair) {
 		LOG.info("Starting BQP listeners");
 		// Derive commitment
 		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);
 			if (l != null) {
 				TransportId id = plugin.getId();
 				descriptors.add(new TransportDescriptor(id, l.getDescriptor()));
-				if (LOG.isLoggable(INFO)) LOG.info("Listening via " + id);
+				pending.add(connect.submit(new ReadableTask(l.listen())));
 				listeners.add(l);
-				connectionChooser.submit(new ReadableTask(l::accept));
 			}
 		}
 		return new Payload(commitment, descriptors);
@@ -84,92 +92,128 @@ class KeyAgreementConnector {
 
 	void stopListening() {
 		LOG.info("Stopping BQP listeners");
-		stopped = true;
-		aliceLatch.countDown();
-		for (KeyAgreementListener l : listeners) l.close();
-		connectionChooser.stop();
+		for (KeyAgreementListener l : listeners) {
+			l.close();
+		}
+		listeners.clear();
 	}
 
 	@Nullable
-	public KeyAgreementTransport connect(Payload remotePayload, boolean alice) {
-		// Let the ReadableTasks know if we are Alice
+	public KeyAgreementTransport connect(Payload remotePayload,
+			boolean alice) {
+		// Let the listeners know if we are Alice
+		this.connecting = true;
 		this.alice = alice;
-		aliceLatch.countDown();
+		long end = clock.currentTimeMillis() + CONNECTION_TIMEOUT;
 
 		// Start connecting over supported transports
-		if (LOG.isLoggable(INFO)) {
-			LOG.info("Starting outgoing BQP connections as "
-					+ (alice ? "Alice" : "Bob"));
-		}
+		LOG.info("Starting outgoing BQP connections");
 		for (TransportDescriptor d : remotePayload.getTransportDescriptors()) {
 			Plugin p = pluginManager.getPlugin(d.getId());
 			if (p instanceof DuplexPlugin) {
-				if (LOG.isLoggable(INFO))
-					LOG.info("Connecting via " + d.getId());
 				DuplexPlugin plugin = (DuplexPlugin) p;
-				byte[] commitment = remotePayload.getCommitment();
-				BdfList descriptor = d.getDescriptor();
-				connectionChooser.submit(new ReadableTask(
-						new ConnectorTask(plugin, commitment, descriptor)));
+				pending.add(connect.submit(new ReadableTask(
+						new ConnectorTask(plugin, remotePayload.getCommitment(),
+								d.getDescriptor(), end))));
 			}
 		}
 
 		// Get chosen connection
+		KeyAgreementConnection chosen = null;
 		try {
-			KeyAgreementConnection chosen =
-					connectionChooser.poll(CONNECTION_TIMEOUT);
-			if (chosen == null) return null;
+			long now = clock.currentTimeMillis();
+			Future<KeyAgreementConnection> f =
+					connect.poll(end - now, MILLISECONDS);
+			if (f == null)
+				return null; // No task completed within the timeout.
+			chosen = f.get();
 			return new KeyAgreementTransport(chosen);
 		} catch (InterruptedException e) {
 			LOG.info("Interrupted while waiting for connection");
 			Thread.currentThread().interrupt();
 			return null;
+		} 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 {
 			stopListening();
+			// Close all other connections
+			closePending(chosen);
 		}
 	}
 
-	private void waitingForAlice() {
-		if (!waitingSent.getAndSet(true)) callbacks.connectionWaiting();
+	private void closePending(@Nullable KeyAgreementConnection chosen) {
+		for (Future<KeyAgreementConnection> f : pending) {
+			try {
+				if (f.cancel(true)) {
+					LOG.info("Cancelled task");
+				} else if (!f.isCancelled()) {
+					KeyAgreementConnection c = f.get();
+					if (c != null && c != chosen)
+						tryToClose(c.getConnection(), false);
+				}
+			} catch (InterruptedException e) {
+				LOG.info("Interrupted while closing sockets");
+				Thread.currentThread().interrupt();
+				return;
+			} catch (ExecutionException e) {
+				if (LOG.isLoggable(INFO)) LOG.info(e.toString());
+			}
+		}
+	}
+
+	private void tryToClose(DuplexTransportConnection conn, boolean exception) {
+		try {
+			if (LOG.isLoggable(INFO))
+				LOG.info("Closing connection, exception: " + exception);
+			conn.getReader().dispose(exception, true);
+			conn.getWriter().dispose(exception);
+		} catch (IOException e) {
+			if (LOG.isLoggable(INFO)) LOG.info(e.toString());
+		}
 	}
 
 	private class ConnectorTask implements Callable<KeyAgreementConnection> {
 
 		private final byte[] commitment;
 		private final BdfList descriptor;
+		private final long end;
 		private final DuplexPlugin plugin;
 
 		private ConnectorTask(DuplexPlugin plugin, byte[] commitment,
-				BdfList descriptor) {
+				BdfList descriptor, long end) {
 			this.plugin = plugin;
 			this.commitment = commitment;
 			this.descriptor = descriptor;
+			this.end = end;
 		}
 
-		@Nullable
 		@Override
 		public KeyAgreementConnection call() throws Exception {
-			// Repeat attempts until we connect, get stopped, or get interrupted
-			while (!stopped) {
+			// Repeat attempts until we connect, get interrupted, or time out
+			while (true) {
+				long now = clock.currentTimeMillis();
+				if (now > end) throw new IOException();
 				DuplexTransportConnection conn =
 						plugin.createKeyAgreementConnection(commitment,
-								descriptor);
+								descriptor, end - now);
 				if (conn != null) {
 					if (LOG.isLoggable(INFO))
-						LOG.info(plugin.getId() + ": Outgoing connection");
+						LOG.info(plugin.getId().getString() +
+								": Outgoing connection");
 					return new KeyAgreementConnection(conn, plugin.getId());
 				}
 				// Wait 2s before retry (to circumvent transient failures)
 				Thread.sleep(2000);
 			}
-			return null;
 		}
 	}
 
-	private class ReadableTask implements Callable<KeyAgreementConnection> {
+	private class ReadableTask
+			implements Callable<KeyAgreementConnection> {
 
 		private final Callable<KeyAgreementConnection> connectionTask;
 
@@ -177,23 +221,24 @@ class KeyAgreementConnector {
 			this.connectionTask = connectionTask;
 		}
 
-		@Nullable
 		@Override
 		public KeyAgreementConnection call() throws Exception {
 			KeyAgreementConnection c = connectionTask.call();
-			if (c == null) return null;
-			aliceLatch.await();
-			if (alice || stopped) return c;
-			// Bob waits here for Alice to scan his QR code, determine her
-			// role, and send her key
 			InputStream in = c.getConnection().getReader().getInputStream();
-			while (!stopped && in.available() == 0) {
-				if (LOG.isLoggable(INFO))
-					LOG.info(c.getTransportId() + ": Waiting for data");
-				waitingForAlice();
-				Thread.sleep(500);
+			boolean waitingSent = false;
+			while (!alice && in.available() == 0) {
+				if (!waitingSent && connecting && !alice) {
+					// Bob waits here until Alice obtains his payload.
+					callbacks.connectionWaiting();
+					waitingSent = true;
+				}
+				if (LOG.isLoggable(INFO)) {
+					LOG.info(c.getTransportId().getString() +
+							": Waiting for connection");
+				}
+				Thread.sleep(1000);
 			}
-			if (!stopped && LOG.isLoggable(INFO))
+			if (!alice && LOG.isLoggable(INFO))
 				LOG.info(c.getTransportId().getString() + ": Data available");
 			return c;
 		}

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

@@ -1,10 +1,19 @@
 package org.briarproject.bramble.keyagreement;
 
+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.event.EventBus;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementTaskFactory;
 import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
 import org.briarproject.bramble.api.keyagreement.PayloadParser;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
+import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.system.Clock;
+
+import java.util.concurrent.Executor;
+
+import javax.inject.Singleton;
 
 import dagger.Module;
 import dagger.Provides;
@@ -13,9 +22,13 @@ import dagger.Provides;
 public class KeyAgreementModule {
 
 	@Provides
-	KeyAgreementTaskFactory provideKeyAgreementTaskFactory(
-			KeyAgreementTaskFactoryImpl keyAgreementTaskFactory) {
-		return keyAgreementTaskFactory;
+	@Singleton
+	KeyAgreementTaskFactory provideKeyAgreementTaskFactory(Clock clock,
+			CryptoComponent crypto, EventBus eventBus,
+			@IoExecutor Executor ioExecutor, PayloadEncoder payloadEncoder,
+			PluginManager pluginManager) {
+		return new KeyAgreementTaskFactoryImpl(clock, crypto, eventBus,
+				ioExecutor, payloadEncoder, pluginManager);
 	}
 
 	@Provides
@@ -27,10 +40,4 @@ public class KeyAgreementModule {
 	PayloadParser providePayloadParser(BdfReaderFactory bdfReaderFactory) {
 		return new PayloadParserImpl(bdfReaderFactory);
 	}
-
-	@Provides
-	ConnectionChooser provideConnectionChooser(
-			ConnectionChooserImpl connectionChooser) {
-		return connectionChooser;
-	}
 }

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

@@ -89,8 +89,7 @@ class KeyAgreementProtocol {
 			byte[] theirPublicKey;
 			if (alice) {
 				sendKey();
-				// Alice waits here for Bob to scan her QR code, determine his
-				// role, receive her key and respond with his key
+				// Alice waits here until Bob obtains her payload.
 				callbacks.connectionWaiting();
 				theirPublicKey = receiveKey();
 			} else {

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

@@ -5,37 +5,42 @@ import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementTaskFactory;
 import org.briarproject.bramble.api.keyagreement.PayloadEncoder;
+import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.system.Clock;
+
+import java.util.concurrent.Executor;
 
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
-import javax.inject.Provider;
 
 @Immutable
 @NotNullByDefault
 class KeyAgreementTaskFactoryImpl implements KeyAgreementTaskFactory {
 
+	private final Clock clock;
 	private final CryptoComponent crypto;
 	private final EventBus eventBus;
+	private final Executor ioExecutor;
 	private final PayloadEncoder payloadEncoder;
 	private final PluginManager pluginManager;
-	private final Provider<ConnectionChooser> connectionChooserProvider;
 
 	@Inject
-	KeyAgreementTaskFactoryImpl(CryptoComponent crypto, EventBus eventBus,
-			PayloadEncoder payloadEncoder, PluginManager pluginManager,
-			Provider<ConnectionChooser> connectionChooserProvider) {
+	KeyAgreementTaskFactoryImpl(Clock clock, CryptoComponent crypto,
+			EventBus eventBus, @IoExecutor Executor ioExecutor,
+			PayloadEncoder payloadEncoder, PluginManager pluginManager) {
+		this.clock = clock;
 		this.crypto = crypto;
 		this.eventBus = eventBus;
+		this.ioExecutor = ioExecutor;
 		this.payloadEncoder = payloadEncoder;
 		this.pluginManager = pluginManager;
-		this.connectionChooserProvider = connectionChooserProvider;
 	}
 
 	@Override
 	public KeyAgreementTask createTask() {
-		return new KeyAgreementTaskImpl(crypto, eventBus, payloadEncoder,
-				pluginManager, connectionChooserProvider.get());
+		return new KeyAgreementTaskImpl(clock, crypto, eventBus, payloadEncoder,
+				pluginManager, ioExecutor);
 	}
 }

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

@@ -17,16 +17,19 @@ import org.briarproject.bramble.api.keyagreement.event.KeyAgreementWaitingEvent;
 import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
 import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.bramble.api.plugin.PluginManager;
+import org.briarproject.bramble.api.system.Clock;
 
 import java.io.IOException;
+import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.WARNING;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
-class KeyAgreementTaskImpl extends Thread implements KeyAgreementTask,
-		KeyAgreementProtocol.Callbacks, KeyAgreementConnector.Callbacks {
+class KeyAgreementTaskImpl extends Thread implements
+		KeyAgreementTask, KeyAgreementConnector.Callbacks,
+		KeyAgreementProtocol.Callbacks {
 
 	private static final Logger LOG =
 			Logger.getLogger(KeyAgreementTaskImpl.class.getName());
@@ -40,15 +43,15 @@ class KeyAgreementTaskImpl extends Thread implements KeyAgreementTask,
 	private Payload localPayload;
 	private Payload remotePayload;
 
-	KeyAgreementTaskImpl(CryptoComponent crypto, EventBus eventBus,
-			PayloadEncoder payloadEncoder, PluginManager pluginManager,
-			ConnectionChooser connectionChooser) {
+	KeyAgreementTaskImpl(Clock clock, CryptoComponent crypto,
+			EventBus eventBus, PayloadEncoder payloadEncoder,
+			PluginManager pluginManager, Executor ioExecutor) {
 		this.crypto = crypto;
 		this.eventBus = eventBus;
 		this.payloadEncoder = payloadEncoder;
 		localKeyPair = crypto.generateAgreementKeyPair();
-		connector = new KeyAgreementConnector(this, crypto, pluginManager,
-				connectionChooser);
+		connector = new KeyAgreementConnector(this, clock, crypto,
+				pluginManager, ioExecutor);
 	}
 
 	@Override
@@ -62,8 +65,10 @@ class KeyAgreementTaskImpl extends Thread implements KeyAgreementTask,
 	@Override
 	public synchronized void stopListening() {
 		if (localPayload != null) {
-			if (remotePayload == null) connector.stopListening();
-			else interrupt();
+			if (remotePayload == null)
+				connector.stopListening();
+			else
+				interrupt();
 		}
 	}
 

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

@@ -51,7 +51,8 @@ class PayloadParserImpl implements PayloadParser {
 		byte[] commitment = payload.getRaw(1);
 		if (commitment.length != COMMIT_LENGTH) throw new FormatException();
 		// Remaining elements: transport descriptors
-		List<TransportDescriptor> recognised = new ArrayList<>();
+		List<TransportDescriptor> recognised =
+				new ArrayList<TransportDescriptor>();
 		for (int i = 2; i < payload.size(); i++) {
 			BdfList descriptor = payload.getList(i);
 			long transportId = descriptor.getLong(0);

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/LifecycleManagerImpl.java

@@ -2,11 +2,8 @@ package org.briarproject.bramble.lifecycle;
 
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyPair;
-import org.briarproject.bramble.api.db.DataTooNewException;
-import org.briarproject.bramble.api.db.DataTooOldException;
 import org.briarproject.bramble.api.db.DatabaseComponent;
 import org.briarproject.bramble.api.db.DbException;
-import org.briarproject.bramble.api.db.MigrationListener;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.identity.AuthorFactory;
@@ -15,7 +12,7 @@ import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.lifecycle.Service;
 import org.briarproject.bramble.api.lifecycle.ServiceException;
-import org.briarproject.bramble.api.lifecycle.event.LifecycleEvent;
+import org.briarproject.bramble.api.lifecycle.event.ShutdownEvent;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.Client;
 
@@ -32,21 +29,14 @@ import javax.inject.Inject;
 
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.MIGRATING_DATABASE;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.RUNNING;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STARTING_SERVICES;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.LifecycleState.STOPPING;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.ALREADY_RUNNING;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.DATA_TOO_NEW_ERROR;
-import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.DATA_TOO_OLD_ERROR;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.DB_ERROR;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.SERVICE_ERROR;
 import static org.briarproject.bramble.api.lifecycle.LifecycleManager.StartResult.SUCCESS;
 
 @ThreadSafe
 @NotNullByDefault
-class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
+class LifecycleManagerImpl implements LifecycleManager {
 
 	private static final Logger LOG =
 			Logger.getLogger(LifecycleManagerImpl.class.getName());
@@ -64,8 +54,6 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 	private final CountDownLatch startupLatch = new CountDownLatch(1);
 	private final CountDownLatch shutdownLatch = new CountDownLatch(1);
 
-	private volatile LifecycleState state = STARTING;
-
 	@Inject
 	LifecycleManagerImpl(DatabaseComponent db, EventBus eventBus,
 			CryptoComponent crypto, AuthorFactory authorFactory,
@@ -75,9 +63,9 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		this.crypto = crypto;
 		this.authorFactory = authorFactory;
 		this.identityManager = identityManager;
-		services = new CopyOnWriteArrayList<>();
-		clients = new CopyOnWriteArrayList<>();
-		executors = new CopyOnWriteArrayList<>();
+		services = new CopyOnWriteArrayList<Service>();
+		clients = new CopyOnWriteArrayList<Client>();
+		executors = new CopyOnWriteArrayList<ExecutorService>();
 	}
 
 	@Override
@@ -100,7 +88,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		executors.add(e);
 	}
 
-	private LocalAuthor createLocalAuthor(String nickname) {
+	private LocalAuthor createLocalAuthor(final String nickname) {
 		long now = System.currentTimeMillis();
 		KeyPair keyPair = crypto.generateSignatureKeyPair();
 		byte[] publicKey = keyPair.getPublic().getEncoded();
@@ -131,7 +119,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 			LOG.info("Starting services");
 			long start = System.currentTimeMillis();
 
-			boolean reopened = db.open(this);
+			boolean reopened = db.open();
 			long duration = System.currentTimeMillis() - start;
 			if (LOG.isLoggable(INFO)) {
 				if (reopened)
@@ -143,10 +131,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 				registerLocalAuthor(createLocalAuthor(nickname));
 			}
 
-			state = STARTING_SERVICES;
 			dbLatch.countDown();
-			eventBus.broadcast(new LifecycleEvent(STARTING_SERVICES));
-
 			Transaction txn = db.startTransaction(false);
 			try {
 				for (Client c : clients) {
@@ -172,17 +157,8 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 							+ " took " + duration + " ms");
 				}
 			}
-
-			state = RUNNING;
 			startupLatch.countDown();
-			eventBus.broadcast(new LifecycleEvent(RUNNING));
 			return SUCCESS;
-		} catch (DataTooOldException e) {
-			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-			return DATA_TOO_OLD_ERROR;
-		} catch (DataTooNewException e) {
-			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
-			return DATA_TOO_NEW_ERROR;
 		} catch (DbException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			return DB_ERROR;
@@ -194,12 +170,6 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		}
 	}
 
-	@Override
-	public void onMigrationRun() {
-		state = MIGRATING_DATABASE;
-		eventBus.broadcast(new LifecycleEvent(MIGRATING_DATABASE));
-	}
-
 	@Override
 	public void stopServices() {
 		try {
@@ -210,8 +180,7 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		}
 		try {
 			LOG.info("Stopping services");
-			state = STOPPING;
-			eventBus.broadcast(new LifecycleEvent(STOPPING));
+			eventBus.broadcast(new ShutdownEvent());
 			for (Service s : services) {
 				long start = System.currentTimeMillis();
 				s.stopService();
@@ -234,7 +203,9 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 			if (LOG.isLoggable(INFO))
 				LOG.info("Closing database took " + duration + " ms");
 			shutdownLatch.countDown();
-		} catch (DbException | ServiceException e) {
+		} catch (DbException e) {
+			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+		} catch (ServiceException e) {
 			if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 		} finally {
 			startStopSemaphore.release();
@@ -256,8 +227,4 @@ class LifecycleManagerImpl implements LifecycleManager, MigrationListener {
 		shutdownLatch.await();
 	}
 
-	@Override
-	public LifecycleState getLifecycleState() {
-		return state;
-	}
 }

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/LifecycleModule.java

@@ -37,7 +37,7 @@ public class LifecycleModule {
 
 	public LifecycleModule() {
 		// The thread pool is unbounded, so use direct handoff
-		BlockingQueue<Runnable> queue = new SynchronousQueue<>();
+		BlockingQueue<Runnable> queue = new SynchronousQueue<Runnable>();
 		// Discard tasks that are submitted during shutdown
 		RejectedExecutionHandler policy =
 				new ThreadPoolExecutor.DiscardPolicy();

bramble-core/src/main/java/org/briarproject/bramble/lifecycle/ShutdownManagerImpl.java

@@ -21,7 +21,7 @@ class ShutdownManagerImpl implements ShutdownManager {
 	private int nextHandle = 0;
 
 	ShutdownManagerImpl() {
-		hooks = new HashMap<>();
+		hooks = new HashMap<Integer, Thread>();
 	}
 
 	@Override

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

@@ -134,7 +134,11 @@ class ConnectionManagerImpl implements ConnectionManager {
 			try {
 				byte[] tag = readTag(reader);
 				ctx = keyManager.getStreamContext(transportId, tag);
-			} catch (IOException | DbException e) {
+			} catch (IOException e) {
+				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+				disposeReader(true, false);
+				return;
+			} catch (DbException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 				disposeReader(true, false);
 				return;
@@ -245,7 +249,11 @@ class ConnectionManagerImpl implements ConnectionManager {
 			try {
 				byte[] tag = readTag(reader);
 				ctx = keyManager.getStreamContext(transportId, tag);
-			} catch (IOException | DbException e) {
+			} catch (IOException e) {
+				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+				disposeReader(true, false);
+				return;
+			} catch (DbException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 				disposeReader(true, false);
 				return;
@@ -258,7 +266,12 @@ class ConnectionManagerImpl implements ConnectionManager {
 			contactId = ctx.getContactId();
 			connectionRegistry.registerConnection(contactId, transportId, true);
 			// Start the outgoing session on another thread
-			ioExecutor.execute(this::runOutgoingSession);
+			ioExecutor.execute(new Runnable() {
+				@Override
+				public void run() {
+					runOutgoingSession();
+				}
+			});
 			try {
 				// Create and run the incoming session
 				incomingSession = createIncomingSession(ctx, reader);
@@ -355,7 +368,12 @@ class ConnectionManagerImpl implements ConnectionManager {
 				return;
 			}
 			// Start the incoming session on another thread
-			ioExecutor.execute(this::runIncomingSession);
+			ioExecutor.execute(new Runnable() {
+				@Override
+				public void run() {
+					runIncomingSession();
+				}
+			});
 			try {
 				// Create and run the outgoing session
 				outgoingSession = createDuplexOutgoingSession(ctx, writer);
@@ -373,7 +391,11 @@ class ConnectionManagerImpl implements ConnectionManager {
 			try {
 				byte[] tag = readTag(reader);
 				ctx = keyManager.getStreamContext(transportId, tag);
-			} catch (IOException | DbException e) {
+			} catch (IOException e) {
+				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
+				disposeReader(true, false);
+				return;
+			} catch (DbException e) {
 				if (LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 				disposeReader(true, false);
 				return;

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

@@ -42,8 +42,8 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 	@Inject
 	ConnectionRegistryImpl(EventBus eventBus) {
 		this.eventBus = eventBus;
-		connections = new HashMap<>();
-		contactCounts = new HashMap<>();
+		connections = new HashMap<TransportId, Map<ContactId, Integer>>();
+		contactCounts = new HashMap<ContactId, Integer>();
 	}
 
 	@Override
@@ -58,7 +58,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 		try {
 			Map<ContactId, Integer> m = connections.get(t);
 			if (m == null) {
-				m = new HashMap<>();
+				m = new HashMap<ContactId, Integer>();
 				connections.put(t, m);
 			}
 			Integer count = m.get(c);
@@ -124,7 +124,7 @@ class ConnectionRegistryImpl implements ConnectionRegistry {
 		try {
 			Map<ContactId, Integer> m = connections.get(t);
 			if (m == null) return Collections.emptyList();
-			List<ContactId> ids = new ArrayList<>(m.keySet());
+			List<ContactId> ids = new ArrayList<ContactId>(m.keySet());
 			if (LOG.isLoggable(INFO))
 				LOG.info(ids.size() + " contacts connected");
 			return ids;