Add a bunch of tests highlighting implicit acks

Automatically decline incoming blog/forum invitations when they self-destruct

See merge request briar/briar!1392

.gitlab-ci.yml

@@ -2,6 +2,7 @@ image: briar/ci-image-android:latest
 
 stages:
 - test
+- optional_tests
 - check_reproducibility
 
 test:
@@ -31,3 +32,33 @@ test_reproducible:
     - "curl -X POST -F token=${RELEASE_CHECK_TOKEN} -F ref=master -F variables[RELEASE_TAG]=${CI_COMMIT_REF_NAME} https://code.briarproject.org/api/v4/projects/61/trigger/pipeline"
   only:
     - tags
+
+.optional_tests:
+  stage: optional_tests
+  before_script:
+    - set -e
+    - export GRADLE_USER_HOME=$PWD/.gradle
+
+  cache:
+    paths:
+      - .gradle/wrapper
+      - .gradle/caches
+
+  script:
+    - OPTIONAL_TESTS=org.briarproject.bramble.plugin.tor.BridgeTest ./gradlew --info bramble-java:test --tests BridgeTest
+
+  after_script:
+    # these file change every time but should not be cached
+    - rm -f $GRADLE_USER_HOME/caches/modules-2/modules-2.lock
+    - rm -fr $GRADLE_USER_HOME/caches/*/plugin-resolution/
+
+manual_tests:
+  extends: .optional_tests
+  when: manual
+  except:
+    - tags
+
+pre_release_tests:
+  extends: .optional_tests
+  only:
+    - tags

.idea/dictionaries/briar.xml

@@ -0,0 +1,15 @@
+<component name="ProjectDictionaryState">
+  <dictionary name="briar">
+    <words>
+      <w>briar</w>
+      <w>briarproject</w>
+      <w>emoji</w>
+      <w>encrypter</w>
+      <w>identicon</w>
+      <w>introducee</w>
+      <w>introducees</w>
+      <w>introducer</w>
+      <w>onboarding</w>
+    </words>
+  </dictionary>
+</component>

.idea/runConfigurations/BridgeTest.xml

@@ -0,0 +1,24 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="BridgeTest" type="AndroidJUnit" factoryName="Android JUnit" nameIsGenerated="true">
+    <module name="briar.bramble-java" />
+    <useClassPathOnly />
+    <extension name="coverage">
+      <pattern>
+        <option name="PATTERN" value="org.briarproject.bramble.plugin.tor.*" />
+        <option name="ENABLED" value="true" />
+      </pattern>
+    </extension>
+    <option name="PACKAGE_NAME" value="org.briarproject.bramble.plugin.tor" />
+    <option name="MAIN_CLASS_NAME" value="org.briarproject.bramble.plugin.tor.BridgeTest" />
+    <option name="METHOD_NAME" value="" />
+    <option name="TEST_OBJECT" value="class" />
+    <option name="PARAMETERS" value="" />
+    <option name="WORKING_DIRECTORY" value="$MODULE_DIR$" />
+    <envs>
+      <env name="OPTIONAL_TESTS" value="org.briarproject.bramble.plugin.tor.BridgeTest" />
+    </envs>
+    <method v="2">
+      <option name="Android.Gradle.BeforeRunTask" enabled="true" />
+    </method>
+  </configuration>
+</component>

bramble-android/build.gradle

@@ -11,8 +11,8 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 29
-		versionCode 10213
-		versionName "1.2.13"
+		versionCode 10216
+		versionName "1.2.16"
 		consumerProguardFiles 'proguard-rules.txt'
 
 		testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
@@ -38,8 +38,8 @@ configurations {
 
 dependencies {
 	implementation project(path: ':bramble-core', configuration: 'default')
-	tor 'org.briarproject:tor-android:0.3.5.12@zip'
-	tor 'org.briarproject:obfs4proxy-android:0.0.11-2@zip'
+	tor 'org.briarproject:tor-android:0.3.5.13@zip'
+	tor 'org.briarproject:obfs4proxy-android:0.0.12-dev-40245c4a@zip'
 
 	annotationProcessor 'com.google.dagger:dagger-compiler:2.24'
 

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

@@ -31,6 +31,7 @@ public class AndroidUtils {
 	private static final String FAKE_BLUETOOTH_ADDRESS = "02:00:00:00:00:00";
 
 	private static final String STORED_REPORTS = "dev-reports";
+	private static final String STORED_LOGCAT = "dev-logcat";
 
 	public static Collection<String> getSupportedArchitectures() {
 		List<String> abis = new ArrayList<>();
@@ -107,6 +108,10 @@ public class AndroidUtils {
 		return ctx.getDir(STORED_REPORTS, MODE_PRIVATE);
 	}
 
+	public static File getLogcatFile(Context ctx) {
+		return new File(ctx.getFilesDir(), STORED_LOGCAT);
+	}
+
 	/**
 	 * Returns an array of supported content types for image attachments.
 	 * GIFs can't be compressed on API < 24 so they're not supported.

bramble-android/witness.gradle

@@ -75,8 +75,8 @@ dependencyVerification {
         'org.beanshell:bsh:1.3.0:bsh-1.3.0.jar:9b04edc75d19db54f1b4e8b5355e9364384c6cf71eb0a1b9724c159d779879f8',
         'org.bouncycastle:bcpkix-jdk15on:1.56:bcpkix-jdk15on-1.56.jar:7043dee4e9e7175e93e0b36f45b1ec1ecb893c5f755667e8b916eb8dd201c6ca',
         'org.bouncycastle:bcprov-jdk15on:1.56:bcprov-jdk15on-1.56.jar:963e1ee14f808ffb99897d848ddcdb28fa91ddda867eb18d303e82728f878349',
-        'org.briarproject:obfs4proxy-android:0.0.11-2:obfs4proxy-android-0.0.11-2.zip:57e55cbe87aa2aac210fdbb6cd8cdeafe15f825406a08ebf77a8b787aa2c6a8a',
-        'org.briarproject:tor-android:0.3.5.12:tor-android-0.3.5.12.zip:db71fb3290acff79d572af0752570eaf6aad7c4d88c9b9aa0b4d5afe2b9ead9c',
+        'org.briarproject:obfs4proxy-android:0.0.12-dev-40245c4a:obfs4proxy-android-0.0.12-dev-40245c4a.zip:8ab05a8f8391be2cb5ab2b665c281a06d9e3a756bd0f95a40a36ca927866ea82',
+        'org.briarproject:tor-android:0.3.5.13:tor-android-0.3.5.13.zip:e0978db136731dae07774b722970cdae1e462fb5adc82845dd80a7e2d87f356c',
         'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.checkerframework:checker-qual:2.5.2:checker-qual-2.5.2.jar:64b02691c8b9d4e7700f8ee2e742dce7ea2c6e81e662b7522c9ee3bf568c040a',
         'org.checkerframework:checker-qual:2.8.1:checker-qual-2.8.1.jar:9103499008bcecd4e948da29b17864abb64304e15706444ae209d17ebe0575df',

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

@@ -9,4 +9,5 @@ public interface FeatureFlags {
 
 	boolean shouldEnableProfilePictures();
 
+	boolean shouldEnableDisappearingMessages();
 }

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

@@ -1,6 +0,0 @@
-package org.briarproject.bramble.api;
-
-public interface ThrowingRunnable<T extends Throwable> {
-
-	void run() throws T;
-}

bramble-api/src/main/java/org/briarproject/bramble/api/cleanup/CleanupHook.java

@@ -0,0 +1,29 @@
+package org.briarproject.bramble.api.cleanup;
+
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.MessageId;
+
+import java.util.Collection;
+
+/**
+ * An interface for registering a hook with the {@link CleanupManager}
+ * that will be called when a message's cleanup deadline is reached.
+ */
+@NotNullByDefault
+public interface CleanupHook {
+
+	/**
+	 * Called when the cleanup deadlines of one or more messages are reached.
+	 * <p>
+	 * The callee is not required to delete the messages, but the hook won't be
+	 * called again for these messages unless another cleanup timer is set (see
+	 * {@link DatabaseComponent#setCleanupTimerDuration(Transaction, MessageId, long)}
+	 * and {@link DatabaseComponent#startCleanupTimer(Transaction, MessageId)}).
+	 */
+	void deleteMessages(Transaction txn, GroupId g,
+			Collection<MessageId> messageIds) throws DbException;
+}

bramble-api/src/main/java/org/briarproject/bramble/api/cleanup/CleanupManager.java

@@ -0,0 +1,42 @@
+package org.briarproject.bramble.api.cleanup;
+
+import org.briarproject.bramble.api.cleanup.event.CleanupTimerStartedEvent;
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.ClientId;
+import org.briarproject.bramble.api.sync.MessageId;
+
+/**
+ * The CleanupManager is responsible for tracking the cleanup deadlines of
+ * messages and passing them to their respective
+ * {@link CleanupHook CleanupHooks} when the deadlines are reached.
+ * <p>
+ * The CleanupManager responds to
+ * {@link CleanupTimerStartedEvent CleanupTimerStartedEvents} broadcast by the
+ * {@link DatabaseComponent}.
+ * <p>
+ * See {@link DatabaseComponent#setCleanupTimerDuration(Transaction, MessageId, long)},
+ * {@link DatabaseComponent#startCleanupTimer(Transaction, MessageId)},
+ * {@link DatabaseComponent#stopCleanupTimer(Transaction, MessageId)}.
+ */
+@NotNullByDefault
+public interface CleanupManager {
+
+	/**
+	 * When scheduling a cleanup task we overshoot the deadline by this many
+	 * milliseconds to reduce the number of tasks that need to be scheduled
+	 * when messages have cleanup deadlines that are close together.
+	 */
+	long BATCH_DELAY_MS = 1000;
+
+	/**
+	 * Registers a hook to be called when messages are due for cleanup.
+	 * This method should be called before
+	 * {@link LifecycleManager#startServices(SecretKey)}.
+	 */
+	void registerCleanupHook(ClientId c, int majorVersion,
+			CleanupHook hook);
+}

bramble-api/src/main/java/org/briarproject/bramble/api/cleanup/event/CleanupTimerStartedEvent.java

@@ -0,0 +1,32 @@
+package org.briarproject.bramble.api.cleanup.event;
+
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when a message's cleanup timer is started.
+ */
+@Immutable
+@NotNullByDefault
+public class CleanupTimerStartedEvent extends Event {
+
+	private final MessageId messageId;
+	private final long cleanupDeadline;
+
+	public CleanupTimerStartedEvent(MessageId messageId,
+			long cleanupDeadline) {
+		this.messageId = messageId;
+		this.cleanupDeadline = cleanupDeadline;
+	}
+
+	public MessageId getMessageId() {
+		return messageId;
+	}
+
+	public long getCleanupDeadline() {
+		return cleanupDeadline;
+	}
+}

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

@@ -1,6 +1,7 @@
 package org.briarproject.bramble.api.client;
 
 import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.data.BdfDictionary;
@@ -16,6 +17,7 @@ import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 
 import java.security.GeneralSecurityException;
+import java.util.Collection;
 import java.util.Map;
 
 @NotNullByDefault
@@ -50,9 +52,11 @@ public interface ClientHelper {
 	BdfDictionary getGroupMetadataAsDictionary(Transaction txn, GroupId g)
 			throws DbException, FormatException;
 
+	Collection<MessageId> getMessageIds(Transaction txn, GroupId g,
+			BdfDictionary query) throws DbException, FormatException;
+
 	BdfDictionary getMessageMetadataAsDictionary(MessageId m)
-			throws DbException,
-			FormatException;
+			throws DbException, FormatException;
 
 	BdfDictionary getMessageMetadataAsDictionary(Transaction txn, MessageId m)
 			throws DbException, FormatException;
@@ -119,4 +123,17 @@ public interface ClientHelper {
 	Map<TransportId, TransportProperties> parseAndValidateTransportPropertiesMap(
 			BdfDictionary properties) throws FormatException;
 
+	/**
+	 * Retrieves the contact ID from the group metadata of the given contact
+	 * group.
+	 */
+	ContactId getContactId(Transaction txn, GroupId contactGroupId)
+			throws DbException, FormatException;
+
+	/**
+	 * Stores the given contact ID in the group metadata of the given contact
+	 * group.
+	 */
+	void setContactId(Transaction txn, GroupId contactGroupId, ContactId c)
+			throws DbException;
 }

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

@@ -0,0 +1,9 @@
+package org.briarproject.bramble.api.client;
+
+public interface ContactGroupConstants {
+
+	/**
+	 * Group metadata key for associating a contact ID with a contact group.
+	 */
+	String GROUP_KEY_CONTACT_ID = "contactId";
+}

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

@@ -19,4 +19,10 @@ public interface StreamDecrypterFactory {
 	 */
 	StreamDecrypter createContactExchangeStreamDecrypter(InputStream in,
 			SecretKey headerKey);
+
+	/**
+	 * Creates a {@link StreamDecrypter} for decrypting a log stream.
+	 */
+	StreamDecrypter createLogStreamDecrypter(InputStream in,
+			SecretKey headerKey);
 }

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

@@ -17,6 +17,12 @@ public interface StreamEncrypterFactory {
 	 * Creates a {@link StreamEncrypter} for encrypting a contact exchange
 	 * stream.
 	 */
-	StreamEncrypter createContactExchangeStreamDecrypter(OutputStream out,
+	StreamEncrypter createContactExchangeStreamEncrypter(OutputStream out,
+			SecretKey headerKey);
+
+	/**
+	 * Creates a {@link StreamEncrypter} for encrypting a log stream.
+	 */
+	StreamEncrypter createLogStreamEncrypter(OutputStream out,
 			SecretKey headerKey);
 }

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

@@ -41,6 +41,18 @@ import javax.annotation.Nullable;
 @NotNullByDefault
 public interface DatabaseComponent extends TransactionManager {
 
+	/**
+	 * Return value for {@link #getNextCleanupDeadline(Transaction)} if
+	 * no messages are scheduled to be deleted.
+	 */
+	long NO_CLEANUP_DEADLINE = -1;
+
+	/**
+	 * Return value for {@link #startCleanupTimer(Transaction, MessageId)}
+	 * if the cleanup timer was not started.
+	 */
+	long TIMER_NOT_STARTED = -1;
+
 	/**
 	 * Opens the database and returns true if the database already existed.
 	 *
@@ -288,6 +300,16 @@ public interface DatabaseComponent extends TransactionManager {
 	Collection<MessageId> getMessageIds(Transaction txn, GroupId g)
 			throws DbException;
 
+	/**
+	 * Returns the IDs of any delivered messages in the given group with
+	 * metadata that matches all entries in the given query. If the query is
+	 * empty, the IDs of all delivered messages are returned.
+	 * <p/>
+	 * Read-only.
+	 */
+	Collection<MessageId> getMessageIds(Transaction txn, GroupId g,
+			Metadata query) throws DbException;
+
 	/**
 	 * Returns the IDs of any messages that need to be validated.
 	 * <p/>
@@ -314,6 +336,15 @@ public interface DatabaseComponent extends TransactionManager {
 	Collection<MessageId> getMessagesToShare(Transaction txn)
 			throws DbException;
 
+	/**
+	 * Returns the IDs of any messages of any messages that are due for
+	 * deletion, along with their group IDs.
+	 * <p/>
+	 * Read-only.
+	 */
+	Map<GroupId, Collection<MessageId>> getMessagesToDelete(Transaction txn)
+			throws DbException;
+
 	/**
 	 * Returns the metadata for all delivered messages in the given group.
 	 * <p/>
@@ -395,6 +426,15 @@ public interface DatabaseComponent extends TransactionManager {
 	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 deleted, or {@link #NO_CLEANUP_DEADLINE}
+	 * if no messages are scheduled to be deleted.
+	 * <p/>
+	 * Read-only.
+	 */
+	long getNextCleanupDeadline(Transaction txn) 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
@@ -535,6 +575,13 @@ public interface DatabaseComponent extends TransactionManager {
 	void removeTransportKeys(Transaction txn, TransportId t, KeySetId k)
 			throws DbException;
 
+	/**
+	 * Sets the cleanup timer duration for the given message. This does not
+	 * start the message's cleanup timer.
+	 */
+	void setCleanupTimerDuration(Transaction txn, MessageId m, long duration)
+			throws DbException;
+
 	/**
 	 * Marks the given contact as verified.
 	 */
@@ -557,6 +604,12 @@ public interface DatabaseComponent extends TransactionManager {
 	 */
 	void setMessagePermanent(Transaction txn, MessageId m) throws DbException;
 
+	/**
+	 * Marks the given message as not shared. This method is only meant for
+	 * testing.
+	 */
+	void setMessageNotShared(Transaction txn, MessageId m) throws DbException;
+
 	/**
 	 * Marks the given message as shared.
 	 */
@@ -599,6 +652,22 @@ public interface DatabaseComponent extends TransactionManager {
 	void setTransportKeysActive(Transaction txn, TransportId t, KeySetId k)
 			throws DbException;
 
+	/**
+	 * Starts the cleanup timer for the given message, if a timer duration
+	 * has been set and the timer has not already been started.
+	 *
+	 * @return The cleanup deadline, or {@link #TIMER_NOT_STARTED} if no
+	 * timer duration has been set for this message or its timer has already
+	 * been started.
+	 */
+	long startCleanupTimer(Transaction txn, MessageId m) throws DbException;
+
+	/**
+	 * Stops the cleanup timer for the given message, if the timer has been
+	 * started.
+	 */
+	void stopCleanupTimer(Transaction txn, MessageId m) throws DbException;
+
 	/**
 	 * Stores the given transport keys, deleting any keys they have replaced.
 	 */

bramble-api/src/main/java/org/briarproject/bramble/api/reporting/DevConfig.java

@@ -13,4 +13,6 @@ public interface DevConfig {
 	String getDevOnionAddress();
 
 	File getReportDir();
+
+	File getLogcatFile();
 }

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

@@ -16,8 +16,13 @@ public interface StreamReaderFactory {
 
 	/**
 	 * Creates an {@link InputStream InputStream} for reading from a contact
-	 * exchangestream.
+	 * exchange stream.
 	 */
 	InputStream createContactExchangeStreamReader(InputStream in,
 			SecretKey headerKey);
+
+	/**
+	 * Creates an {@link InputStream} for reading from a log stream.
+	 */
+	InputStream createLogStreamReader(InputStream in, SecretKey headerKey);
 }

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

@@ -7,17 +7,19 @@ import java.io.OutputStream;
 
 @NotNullByDefault
 public interface StreamWriterFactory {
-
 	/**
-	 * Creates an {@link OutputStream OutputStream} for writing to a
-	 * transport stream
+	 * Creates a {@link StreamWriter} for writing to a transport stream.
 	 */
 	StreamWriter createStreamWriter(OutputStream out, StreamContext ctx);
 
 	/**
-	 * Creates an {@link OutputStream OutputStream} for writing to a contact
-	 * exchange stream.
+	 * Creates a {@link StreamWriter} for writing to a contact exchange stream.
 	 */
 	StreamWriter createContactExchangeStreamWriter(OutputStream out,
 			SecretKey headerKey);
+
+	/**
+	 * Creates a {@link StreamWriter} for writing to a log stream.
+	 */
+	StreamWriter createLogStreamWriter(OutputStream out, SecretKey headerKey);
 }

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

@@ -6,7 +6,9 @@ import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
 
+@Immutable
 @NotNullByDefault
 public class ValidationUtils {
 
@@ -64,4 +66,9 @@ public class ValidationUtils {
 		if (dictionary != null && dictionary.size() != size)
 			throw new FormatException();
 	}
+
+	public static void checkRange(@Nullable Long l, long min, long max)
+			throws FormatException {
+		if (l != null && (l < min || l > max)) throw new FormatException();
+	}
 }

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

@@ -0,0 +1,8 @@
+package org.briarproject.bramble.test;
+
+public interface TimeTravel {
+
+	void setCurrentTimeMillis(long now) throws InterruptedException;
+
+	void addCurrentTimeMillis(long add) throws InterruptedException;
+}

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble;
 
+import org.briarproject.bramble.cleanup.CleanupModule;
 import org.briarproject.bramble.contact.ContactModule;
 import org.briarproject.bramble.crypto.CryptoExecutorModule;
 import org.briarproject.bramble.db.DatabaseExecutorModule;
@@ -14,6 +15,8 @@ import org.briarproject.bramble.versioning.VersioningModule;
 
 public interface BrambleCoreEagerSingletons {
 
+	void inject(CleanupModule.EagerSingletons init);
+
 	void inject(ContactModule.EagerSingletons init);
 
 	void inject(CryptoExecutorModule.EagerSingletons init);
@@ -39,6 +42,7 @@ public interface BrambleCoreEagerSingletons {
 	class Helper {
 
 		public static void injectEagerSingletons(BrambleCoreEagerSingletons c) {
+			c.inject(new CleanupModule.EagerSingletons());
 			c.inject(new ContactModule.EagerSingletons());
 			c.inject(new CryptoExecutorModule.EagerSingletons());
 			c.inject(new DatabaseExecutorModule.EagerSingletons());

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble;
 
+import org.briarproject.bramble.cleanup.CleanupModule;
 import org.briarproject.bramble.client.ClientModule;
 import org.briarproject.bramble.connection.ConnectionModule;
 import org.briarproject.bramble.contact.ContactModule;
@@ -21,15 +22,14 @@ import org.briarproject.bramble.rendezvous.RendezvousModule;
 import org.briarproject.bramble.settings.SettingsModule;
 import org.briarproject.bramble.sync.SyncModule;
 import org.briarproject.bramble.sync.validation.ValidationModule;
-import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.bramble.transport.TransportModule;
 import org.briarproject.bramble.versioning.VersioningModule;
 
 import dagger.Module;
 
 @Module(includes = {
+		CleanupModule.class,
 		ClientModule.class,
-		ClockModule.class,
 		ConnectionModule.class,
 		ContactModule.class,
 		CryptoModule.class,

bramble-core/src/main/java/org/briarproject/bramble/cleanup/CleanupManagerImpl.java

@@ -0,0 +1,159 @@
+package org.briarproject.bramble.cleanup;
+
+import org.briarproject.bramble.api.cleanup.CleanupHook;
+import org.briarproject.bramble.api.cleanup.CleanupManager;
+import org.briarproject.bramble.api.cleanup.event.CleanupTimerStartedEvent;
+import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventListener;
+import org.briarproject.bramble.api.lifecycle.Service;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+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.MessageId;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.api.versioning.ClientMajorVersion;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Executor;
+import java.util.logging.Logger;
+
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+import javax.inject.Inject;
+
+import static java.lang.Math.max;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.logging.Level.INFO;
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.db.DatabaseComponent.NO_CLEANUP_DEADLINE;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@ThreadSafe
+@NotNullByDefault
+class CleanupManagerImpl implements CleanupManager, Service, EventListener {
+
+	private static final Logger LOG =
+			getLogger(CleanupManagerImpl.class.getName());
+
+	private final Executor dbExecutor;
+	private final DatabaseComponent db;
+	private final TaskScheduler taskScheduler;
+	private final Clock clock;
+	private final Map<ClientMajorVersion, CleanupHook> hooks =
+			new ConcurrentHashMap<>();
+	private final Object lock = new Object();
+
+	@GuardedBy("lock")
+	private final Set<CleanupTask> pending = new HashSet<>();
+
+	@Inject
+	CleanupManagerImpl(@DatabaseExecutor Executor dbExecutor,
+			DatabaseComponent db, TaskScheduler taskScheduler, Clock clock) {
+		this.dbExecutor = dbExecutor;
+		this.db = db;
+		this.taskScheduler = taskScheduler;
+		this.clock = clock;
+	}
+
+	@Override
+	public void registerCleanupHook(ClientId c, int majorVersion,
+			CleanupHook hook) {
+		hooks.put(new ClientMajorVersion(c, majorVersion), hook);
+	}
+
+	@Override
+	public void startService() {
+		maybeScheduleTask(clock.currentTimeMillis());
+	}
+
+	@Override
+	public void stopService() {
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof CleanupTimerStartedEvent) {
+			CleanupTimerStartedEvent a = (CleanupTimerStartedEvent) e;
+			maybeScheduleTask(a.getCleanupDeadline());
+		}
+	}
+
+	private void maybeScheduleTask(long deadline) {
+		synchronized (lock) {
+			for (CleanupTask task : pending) {
+				if (task.deadline <= deadline) return;
+			}
+			CleanupTask task = new CleanupTask(deadline);
+			pending.add(task);
+			scheduleTask(task);
+		}
+	}
+
+	private void scheduleTask(CleanupTask task) {
+		long now = clock.currentTimeMillis();
+		long delay = max(0, task.deadline - now + BATCH_DELAY_MS);
+		if (LOG.isLoggable(INFO)) {
+			LOG.info("Scheduling cleanup task in " + delay + " ms");
+		}
+		taskScheduler.schedule(() -> deleteMessagesAndScheduleNextTask(task),
+				dbExecutor, delay, MILLISECONDS);
+	}
+
+	private void deleteMessagesAndScheduleNextTask(CleanupTask task) {
+		try {
+			synchronized (lock) {
+				pending.remove(task);
+			}
+			long deadline = db.transactionWithResult(false, txn -> {
+				deleteMessages(txn);
+				return db.getNextCleanupDeadline(txn);
+			});
+			if (deadline != NO_CLEANUP_DEADLINE) {
+				maybeScheduleTask(deadline);
+			}
+		} catch (DbException e) {
+			logException(LOG, WARNING, e);
+		}
+	}
+
+	private void deleteMessages(Transaction txn) throws DbException {
+		Map<GroupId, Collection<MessageId>> ids = db.getMessagesToDelete(txn);
+		for (Entry<GroupId, Collection<MessageId>> e : ids.entrySet()) {
+			GroupId groupId = e.getKey();
+			Collection<MessageId> messageIds = e.getValue();
+			if (LOG.isLoggable(INFO)) {
+				LOG.info(messageIds.size() + " messages to delete");
+			}
+			for (MessageId m : messageIds) db.stopCleanupTimer(txn, m);
+			Group group = db.getGroup(txn, groupId);
+			ClientMajorVersion cv = new ClientMajorVersion(group.getClientId(),
+					group.getMajorVersion());
+			CleanupHook hook = hooks.get(cv);
+			if (hook == null) {
+				throw new IllegalStateException("No cleanup hook for " + cv);
+			}
+			hook.deleteMessages(txn, groupId, messageIds);
+		}
+	}
+
+	private static class CleanupTask {
+
+		private final long deadline;
+
+		private CleanupTask(long deadline) {
+			this.deadline = deadline;
+		}
+	}
+}

bramble-core/src/main/java/org/briarproject/bramble/cleanup/CleanupModule.java

@@ -0,0 +1,29 @@
+package org.briarproject.bramble.cleanup;
+
+import org.briarproject.bramble.api.cleanup.CleanupManager;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class CleanupModule {
+
+	public static class EagerSingletons {
+		@Inject
+		CleanupManager cleanupManager;
+	}
+
+	@Provides
+	@Singleton
+	CleanupManager provideCleanupManager(LifecycleManager lifecycleManager,
+			EventBus eventBus, CleanupManagerImpl cleanupManager) {
+		lifecycleManager.registerService(cleanupManager);
+		eventBus.addListener(cleanupManager);
+		return cleanupManager;
+	}
+}

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

@@ -2,11 +2,13 @@ package org.briarproject.bramble.client;
 
 import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.client.ClientHelper;
+import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.crypto.CryptoComponent;
 import org.briarproject.bramble.api.crypto.KeyParser;
 import org.briarproject.bramble.api.crypto.PrivateKey;
 import org.briarproject.bramble.api.crypto.PublicKey;
 import org.briarproject.bramble.api.data.BdfDictionary;
+import org.briarproject.bramble.api.data.BdfEntry;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.data.BdfReader;
 import org.briarproject.bramble.api.data.BdfReaderFactory;
@@ -32,6 +34,7 @@ import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.security.GeneralSecurityException;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -39,6 +42,7 @@ import java.util.Map.Entry;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.client.ContactGroupConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.bramble.api.identity.Author.FORMAT_VERSION;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_PUBLIC_KEY_LENGTH;
@@ -151,6 +155,12 @@ class ClientHelperImpl implements ClientHelper {
 		return metadataParser.parse(metadata);
 	}
 
+	@Override
+	public Collection<MessageId> getMessageIds(Transaction txn, GroupId g,
+			BdfDictionary query) throws DbException, FormatException {
+		return db.getMessageIds(txn, g, metadataEncoder.encode(query));
+	}
+
 	@Override
 	public BdfDictionary getMessageMetadataAsDictionary(MessageId m)
 			throws DbException, FormatException {
@@ -389,4 +399,27 @@ class ClientHelperImpl implements ClientHelper {
 		return tpMap;
 	}
 
+	@Override
+	public ContactId getContactId(Transaction txn, GroupId contactGroupId)
+			throws DbException {
+		try {
+			BdfDictionary meta =
+					getGroupMetadataAsDictionary(txn, contactGroupId);
+			return new ContactId(meta.getLong(GROUP_KEY_CONTACT_ID).intValue());
+		} catch (FormatException e) {
+			throw new DbException(e); // Invalid group metadata
+		}
+	}
+
+	@Override
+	public void setContactId(Transaction txn, GroupId contactGroupId,
+			ContactId c) throws DbException {
+		BdfDictionary meta = BdfDictionary.of(
+				new BdfEntry(GROUP_KEY_CONTACT_ID, c.getInt()));
+		try {
+			mergeGroupMetadata(txn, contactGroupId, meta);
+		} catch (FormatException e) {
+			throw new AssertionError(e);
+		}
+	}
 }

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

@@ -9,14 +9,16 @@ import java.util.logging.Logger;
 
 import javax.inject.Inject;
 
+import static java.lang.Math.min;
 import static java.util.logging.Level.INFO;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 class ScryptKdf implements PasswordBasedKdf {
 
 	private static final Logger LOG =
-			Logger.getLogger(ScryptKdf.class.getName());
+			getLogger(ScryptKdf.class.getName());
 
 	private static final int MIN_COST = 256; // Min parameter N
 	private static final int MAX_COST = 1024 * 1024; // Max parameter N
@@ -33,10 +35,20 @@ class ScryptKdf implements PasswordBasedKdf {
 
 	@Override
 	public int chooseCostParameter() {
+		// Scrypt uses at least 128 * N * r bytes of memory. Don't use more
+		// than half of the JVM's max heap size or we may run out of memory.
+		// https://blog.filippo.io/the-scrypt-parameters/
+		long maxMemory = Runtime.getRuntime().maxMemory();
+		long maxCost = min(MAX_COST, maxMemory / BLOCK_SIZE / 256);
+		if (LOG.isLoggable(INFO) && maxCost < MAX_COST) {
+			LOG.info("Max cost capped at " + maxCost
+					+ " due to max heap size " + maxMemory);
+		}
 		// Increase the cost from min to max while measuring performance
 		int cost = MIN_COST;
-		while (cost * 2 <= MAX_COST && measureDuration(cost) * 2 <= TARGET_MS)
+		while (cost * 2 <= maxCost && measureDuration(cost) * 2 <= TARGET_MS) {
 			cost *= 2;
+		}
 		if (LOG.isLoggable(INFO))
 			LOG.info("KDF cost parameter " + cost);
 		return cost;

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

@@ -36,4 +36,10 @@ class StreamDecrypterFactoryImpl implements StreamDecrypterFactory {
 			SecretKey headerKey) {
 		return new StreamDecrypterImpl(in, cipherProvider.get(), 0, headerKey);
 	}
+
+	@Override
+	public StreamDecrypter createLogStreamDecrypter(InputStream in,
+			SecretKey headerKey) {
+		return createContactExchangeStreamDecrypter(in, headerKey);
+	}
 }

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

@@ -51,7 +51,7 @@ class StreamEncrypterFactoryImpl implements StreamEncrypterFactory {
 	}
 
 	@Override
-	public StreamEncrypter createContactExchangeStreamDecrypter(
+	public StreamEncrypter createContactExchangeStreamEncrypter(
 			OutputStream out, SecretKey headerKey) {
 		AuthenticatedCipher cipher = cipherProvider.get();
 		byte[] streamHeaderNonce = new byte[STREAM_HEADER_NONCE_LENGTH];
@@ -60,4 +60,10 @@ class StreamEncrypterFactoryImpl implements StreamEncrypterFactory {
 		return new StreamEncrypterImpl(out, cipher, 0, null, streamHeaderNonce,
 				headerKey, frameKey);
 	}
+
+	@Override
+	public StreamEncrypter createLogStreamEncrypter(OutputStream out,
+			SecretKey headerKey) {
+		return createContactExchangeStreamEncrypter(out, headerKey);
+	}
 }

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

@@ -497,6 +497,25 @@ interface Database<T> {
 	 */
 	Collection<MessageId> getMessagesToShare(T txn) throws DbException;
 
+	/**
+	 * Returns the IDs of any messages of any messages that are due for
+	 * deletion, along with their group IDs.
+	 * <p/>
+	 * Read-only.
+	 */
+	Map<GroupId, Collection<MessageId>> getMessagesToDelete(T txn)
+			throws DbException;
+
+	/**
+	 * Returns the next time (in milliseconds since the Unix epoch) when a
+	 * message is due to be deleted, or
+	 * {@link DatabaseComponent#NO_CLEANUP_DEADLINE} if no messages are
+	 * scheduled to be deleted.
+	 * <p/>
+	 * Read-only.
+	 */
+	long getNextCleanupDeadline(T txn) 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
@@ -606,8 +625,10 @@ interface Database<T> {
 
 	/**
 	 * Marks a message as having been seen by the given contact.
+	 *
+	 * @return True if the message was not already marked as seen.
 	 */
-	void raiseSeenFlag(T txn, ContactId c, MessageId m) throws DbException;
+	boolean raiseSeenFlag(T txn, ContactId c, MessageId m) throws DbException;
 
 	/**
 	 * Removes a contact from the database.
@@ -671,6 +692,13 @@ interface Database<T> {
 	 */
 	void resetExpiryTime(T txn, ContactId c, MessageId m) throws DbException;
 
+	/**
+	 * Sets the cleanup timer duration for the given message. This does not
+	 * start the message's cleanup timer.
+	 */
+	void setCleanupTimerDuration(T txn, MessageId m, long duration)
+			throws DbException;
+
 	/**
 	 * Marks the given contact as verified.
 	 */
@@ -701,9 +729,10 @@ interface Database<T> {
 	void setMessagePermanent(T txn, MessageId m) throws DbException;
 
 	/**
-	 * Marks the given message as shared.
+	 * Marks the given message as shared or not.
 	 */
-	void setMessageShared(T txn, MessageId m) throws DbException;
+	void setMessageShared(T txn, MessageId m, boolean shared)
+			throws DbException;
 
 	/**
 	 * Sets the validation and delivery state of the given message.
@@ -730,6 +759,22 @@ interface Database<T> {
 	void setTransportKeysActive(T txn, TransportId t, KeySetId k)
 			throws DbException;
 
+	/**
+	 * Starts the cleanup timer for the given message, if a timer duration
+	 * has been set and the timer has not already been started.
+	 *
+	 * @return The cleanup deadline, or
+	 * {@link DatabaseComponent#TIMER_NOT_STARTED} if no timer duration has
+	 * been set for this message or its timer has already been started.
+	 */
+	long startCleanupTimer(T txn, MessageId m) throws DbException;
+
+	/**
+	 * Stops the cleanup timer for the given message, if the timer has been
+	 * started.
+	 */
+	void stopCleanupTimer(T txn, MessageId m) throws DbException;
+
 	/**
 	 * Updates the transmission count, expiry time and estimated time of arrival
 	 * of the given message with respect to the given contact, using the latency

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.db;
 
+import org.briarproject.bramble.api.cleanup.event.CleanupTimerStartedEvent;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.PendingContact;
@@ -576,6 +577,15 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getMessageIds(txn, g);
 	}
 
+	@Override
+	public Collection<MessageId> getMessageIds(Transaction transaction,
+			GroupId g, Metadata query) throws DbException {
+		T txn = unbox(transaction);
+		if (!db.containsGroup(txn, g))
+			throw new NoSuchGroupException();
+		return db.getMessageIds(txn, g, query);
+	}
+
 	@Override
 	public Collection<MessageId> getMessagesToValidate(Transaction transaction)
 			throws DbException {
@@ -597,6 +607,13 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getMessagesToShare(txn);
 	}
 
+	@Override
+	public Map<GroupId, Collection<MessageId>> getMessagesToDelete(
+			Transaction transaction) throws DbException {
+		T txn = unbox(transaction);
+		return db.getMessagesToDelete(txn);
+	}
+
 	@Override
 	public Map<MessageId, Metadata> getMessageMetadata(Transaction transaction,
 			GroupId g) throws DbException {
@@ -692,6 +709,13 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		return db.getMessageDependents(txn, m);
 	}
 
+	@Override
+	public long getNextCleanupDeadline(Transaction transaction)
+			throws DbException {
+		T txn = unbox(transaction);
+		return db.getNextCleanupDeadline(txn);
+	}
+
 	@Override
 	public long getNextSendTime(Transaction transaction, ContactId c)
 			throws DbException {
@@ -795,8 +819,17 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		Collection<MessageId> acked = new ArrayList<>();
 		for (MessageId m : a.getMessageIds()) {
 			if (db.containsVisibleMessage(txn, c, m)) {
-				db.raiseSeenFlag(txn, c, m);
-				acked.add(m);
+				if (db.raiseSeenFlag(txn, c, m)) {
+					// This is the first time the message has been acked by
+					// this contact. Start the cleanup timer (a no-op unless
+					// a cleanup deadline has been set for this message)
+					long deadline = db.startCleanupTimer(txn, m);
+					if (deadline != TIMER_NOT_STARTED) {
+						transaction.attach(new CleanupTimerStartedEvent(m,
+								deadline));
+					}
+					acked.add(m);
+				}
 			}
 		}
 		if (acked.size() > 0) {
@@ -952,6 +985,16 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		db.removeTransportKeys(txn, t, k);
 	}
 
+	@Override
+	public void setCleanupTimerDuration(Transaction transaction, MessageId m,
+			long duration) throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (!db.containsMessage(txn, m))
+			throw new NoSuchMessageException();
+		db.setCleanupTimerDuration(txn, m, duration);
+	}
+
 	@Override
 	public void setContactVerified(Transaction transaction, ContactId c)
 			throws DbException {
@@ -1001,6 +1044,16 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		db.setMessagePermanent(txn, m);
 	}
 
+	@Override
+	public void setMessageNotShared(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.setMessageShared(txn, m, false);
+	}
+
 	@Override
 	public void setMessageShared(Transaction transaction, MessageId m)
 			throws DbException {
@@ -1010,7 +1063,7 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 			throw new NoSuchMessageException();
 		if (db.getMessageState(txn, m) != DELIVERED)
 			throw new IllegalArgumentException("Shared undelivered message");
-		db.setMessageShared(txn, m);
+		db.setMessageShared(txn, m, true);
 		transaction.attach(new MessageSharedEvent(m));
 	}
 
@@ -1082,6 +1135,30 @@ class DatabaseComponentImpl<T> implements DatabaseComponent {
 		db.setTransportKeysActive(txn, t, k);
 	}
 
+	@Override
+	public long startCleanupTimer(Transaction transaction, MessageId m)
+			throws DbException {
+		if (transaction.isReadOnly()) throw new IllegalArgumentException();
+		T txn = unbox(transaction);
+		if (!db.containsMessage(txn, m))
+			throw new NoSuchMessageException();
+		long deadline = db.startCleanupTimer(txn, m);
+		if (deadline != TIMER_NOT_STARTED) {
+			transaction.attach(new CleanupTimerStartedEvent(m, deadline));
+		}
+		return deadline;
+	}
+
+	@Override
+	public void stopCleanupTimer(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.stopCleanupTimer(txn, m);
+	}
+
 	@Override
 	public void updateTransportKeys(Transaction transaction,
 			Collection<TransportKeySet> keys) throws DbException {

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

@@ -72,6 +72,8 @@ import static java.util.Arrays.asList;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.api.db.DatabaseComponent.NO_CLEANUP_DEADLINE;
+import static org.briarproject.bramble.api.db.DatabaseComponent.TIMER_NOT_STARTED;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
@@ -98,7 +100,7 @@ import static org.briarproject.bramble.util.LogUtils.now;
 abstract class JdbcDatabase implements Database<Connection> {
 
 	// Package access for testing
-	static final int CODE_SCHEMA_VERSION = 47;
+	static final int CODE_SCHEMA_VERSION = 48;
 
 	// Time period offsets for incoming transport keys
 	private static final int OFFSET_PREV = -1;
@@ -180,6 +182,11 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " state INT NOT NULL,"
 					+ " shared BOOLEAN NOT NULL,"
 					+ " temporary BOOLEAN NOT NULL,"
+					// Null if no timer duration has been set
+					+ " cleanupTimerDuration BIGINT,"
+					// Null if no timer duration has been set or the timer
+					// hasn't started
+					+ " cleanupDeadline BIGINT,"
 					+ " length INT NOT NULL,"
 					+ " raw BLOB," // Null if message has been deleted
 					+ " PRIMARY KEY (messageId),"
@@ -336,6 +343,10 @@ abstract class JdbcDatabase implements Database<Connection> {
 			"CREATE INDEX IF NOT EXISTS statusesByContactIdTimestamp"
 					+ " ON statuses (contactId, timestamp)";
 
+	private static final String INDEX_MESSAGES_BY_CLEANUP_DEADLINE =
+			"CREATE INDEX IF NOT EXISTS messagesByCleanupDeadline"
+					+ " ON messages (cleanupDeadline)";
+
 	private static final Logger LOG =
 			getLogger(JdbcDatabase.class.getName());
 
@@ -463,7 +474,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 				new Migration43_44(dbTypes),
 				new Migration44_45(),
 				new Migration45_46(),
-				new Migration46_47(dbTypes)
+				new Migration46_47(dbTypes),
+				new Migration47_48()
 		);
 	}
 
@@ -531,6 +543,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			s.executeUpdate(INDEX_MESSAGE_DEPENDENCIES_BY_DEPENDENCY_ID);
 			s.executeUpdate(INDEX_STATUSES_BY_CONTACT_ID_GROUP_ID);
 			s.executeUpdate(INDEX_STATUSES_BY_CONTACT_ID_TIMESTAMP);
+			s.executeUpdate(INDEX_MESSAGES_BY_CLEANUP_DEADLINE);
 			s.close();
 		} catch (SQLException e) {
 			tryToClose(s, LOG, WARNING);
@@ -1290,7 +1303,9 @@ abstract class JdbcDatabase implements Database<Connection> {
 	public void deleteMessage(Connection txn, MessageId m) throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql = "UPDATE messages SET raw = NULL WHERE messageId = ?";
+			String sql = "UPDATE messages"
+					+ " SET raw = NULL, cleanupDeadline = NULL"
+					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setBytes(1, m.getBytes());
 			int affected = ps.executeUpdate();
@@ -1769,7 +1784,6 @@ abstract class JdbcDatabase implements Database<Connection> {
 				// Return early if there are no matches
 				if (intersection.isEmpty()) return Collections.emptySet();
 			}
-			if (intersection == null) throw new AssertionError();
 			return intersection;
 		} catch (SQLException e) {
 			tryToClose(rs, LOG, WARNING);
@@ -2226,6 +2240,39 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public Map<GroupId, Collection<MessageId>> getMessagesToDelete(
+			Connection txn) throws DbException {
+		long now = clock.currentTimeMillis();
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT messageId, groupId FROM messages"
+					+ " WHERE cleanupDeadline <= ?";
+			ps = txn.prepareStatement(sql);
+			ps.setLong(1, now);
+			rs = ps.executeQuery();
+			Map<GroupId, Collection<MessageId>> ids = new HashMap<>();
+			while (rs.next()) {
+				MessageId m = new MessageId(rs.getBytes(1));
+				GroupId g = new GroupId(rs.getBytes(2));
+				Collection<MessageId> messageIds = ids.get(g);
+				if (messageIds == null) {
+					messageIds = new ArrayList<>();
+					ids.put(g, messageIds);
+				}
+				messageIds.add(m);
+			}
+			rs.close();
+			ps.close();
+			return ids;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public long getNextSendTime(Connection txn, ContactId c)
 			throws DbException {
@@ -2256,6 +2303,31 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public long getNextCleanupDeadline(Connection txn) throws DbException {
+		Statement s = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT cleanupDeadline FROM messages"
+					+ " WHERE cleanupDeadline IS NOT NULL"
+					+ " ORDER BY cleanupDeadline LIMIT 1";
+			s = txn.createStatement();
+			rs = s.executeQuery(sql);
+			long nextDeadline = NO_CLEANUP_DEADLINE;
+			if (rs.next()) {
+				nextDeadline = rs.getLong(1);
+				if (rs.next()) throw new AssertionError();
+			}
+			rs.close();
+			s.close();
+			return nextDeadline;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(s, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public PendingContact getPendingContact(Connection txn, PendingContactId p)
 			throws DbException {
@@ -2776,7 +2848,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void raiseSeenFlag(Connection txn, ContactId c, MessageId m)
+	public boolean raiseSeenFlag(Connection txn, ContactId c, MessageId m)
 			throws DbException {
 		PreparedStatement ps = null;
 		try {
@@ -2788,6 +2860,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			int affected = ps.executeUpdate();
 			if (affected < 0 || affected > 1) throw new DbStateException();
 			ps.close();
+			return affected == 1;
 		} catch (SQLException e) {
 			tryToClose(ps, LOG, WARNING);
 			throw new DbException(e);
@@ -3021,6 +3094,25 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public void setCleanupTimerDuration(Connection txn, MessageId m,
+			long duration) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE messages SET cleanupTimerDuration = ?"
+					+ " WHERE messageId = ? AND cleanupTimerDuration IS NULL";
+			ps = txn.prepareStatement(sql);
+			ps.setLong(1, duration);
+			ps.setBytes(2, m.getBytes());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void setContactVerified(Connection txn, ContactId c)
 			throws DbException {
@@ -3128,22 +3220,24 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	@Override
-	public void setMessageShared(Connection txn, MessageId m)
+	public void setMessageShared(Connection txn, MessageId m, boolean shared)
 			throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql = "UPDATE messages SET shared = TRUE"
+			String sql = "UPDATE messages SET shared = ?"
 					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
+			ps.setBoolean(1, shared);
+			ps.setBytes(2, m.getBytes());
 			int affected = ps.executeUpdate();
 			if (affected < 0 || affected > 1) throw new DbStateException();
 			ps.close();
 			// Update denormalised column in statuses
-			sql = "UPDATE statuses SET messageShared = TRUE"
+			sql = "UPDATE statuses SET messageShared = ?"
 					+ " WHERE messageId = ?";
 			ps = txn.prepareStatement(sql);
-			ps.setBytes(1, m.getBytes());
+			ps.setBoolean(1, shared);
+			ps.setBytes(2, m.getBytes());
 			affected = ps.executeUpdate();
 			if (affected < 0) throw new DbStateException();
 			ps.close();
@@ -3272,6 +3366,60 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	@Override
+	public long startCleanupTimer(Connection txn, MessageId m)
+			throws DbException {
+		long now = clock.currentTimeMillis();
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "UPDATE messages"
+					+ " SET cleanupDeadline = ? + cleanupTimerDuration"
+					+ " WHERE messageId = ?"
+					+ " AND cleanupTimerDuration IS NOT NULL"
+					+ " AND cleanupDeadline IS NULL";
+			ps = txn.prepareStatement(sql);
+			ps.setLong(1, now);
+			ps.setBytes(2, m.getBytes());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+			if (affected == 0) return TIMER_NOT_STARTED;
+			sql = "SELECT cleanupDeadline FROM messages WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			rs = ps.executeQuery();
+			if (!rs.next()) throw new DbStateException();
+			long deadline = rs.getLong(1);
+			if (rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
+			return deadline;
+		} catch (SQLException e) {
+			tryToClose(rs, LOG, WARNING);
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
+	@Override
+	public void stopCleanupTimer(Connection txn, MessageId m)
+			throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE messages SET cleanupDeadline = NULL"
+					+ " WHERE messageId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setBytes(1, m.getBytes());
+			int affected = ps.executeUpdate();
+			if (affected < 0 || affected > 1) throw new DbStateException();
+			ps.close();
+		} catch (SQLException e) {
+			tryToClose(ps, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void updateExpiryTimeAndEta(Connection txn, ContactId c, MessageId m,
 			int maxLatency) throws DbException {

bramble-core/src/main/java/org/briarproject/bramble/db/Migration47_48.java

@@ -0,0 +1,47 @@
+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 static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.db.JdbcUtils.tryToClose;
+
+class Migration47_48 implements Migration<Connection> {
+
+	private static final Logger LOG = getLogger(Migration47_48.class.getName());
+
+	@Override
+	public int getStartVersion() {
+		return 47;
+	}
+
+	@Override
+	public int getEndVersion() {
+		return 48;
+	}
+
+	@Override
+	public void migrate(Connection txn) throws DbException {
+		Statement s = null;
+		try {
+			s = txn.createStatement();
+			// Null if no timer duration has been set
+			s.execute("ALTER TABLE messages"
+					+ " ADD COLUMN cleanupTimerDuration BIGINT");
+			// Null if no timer duration has been set or the timer
+			// hasn't started
+			s.execute("ALTER TABLE messages"
+					+ " ADD COLUMN cleanupDeadline BIGINT");
+			s.execute("CREATE INDEX IF NOT EXISTS messagesByCleanupDeadline"
+					+ " ON messages (cleanupDeadline)");
+		} catch (SQLException e) {
+			tryToClose(s, LOG, WARNING);
+			throw new DbException(e);
+		}
+	}
+}

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

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.sync;
 
-import org.briarproject.bramble.api.ThrowingRunnable;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseComponent;

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

@@ -1,6 +1,5 @@
 package org.briarproject.bramble.sync;
 
-import org.briarproject.bramble.api.ThrowingRunnable;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.event.ContactRemovedEvent;
 import org.briarproject.bramble.api.db.DatabaseComponent;

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

@@ -0,0 +1,6 @@
+package org.briarproject.bramble.sync;
+
+interface ThrowingRunnable<T extends Throwable> {
+
+	void run() throws T;
+}

bramble-core/src/main/java/org/briarproject/bramble/transport/StreamReaderFactoryImpl.java

@@ -24,15 +24,21 @@ class StreamReaderFactoryImpl implements StreamReaderFactory {
 
 	@Override
 	public InputStream createStreamReader(InputStream in, StreamContext ctx) {
-		return new StreamReaderImpl(
-				streamDecrypterFactory.createStreamDecrypter(in, ctx));
+		return new StreamReaderImpl(streamDecrypterFactory
+				.createStreamDecrypter(in, ctx));
 	}
 
 	@Override
 	public InputStream createContactExchangeStreamReader(InputStream in,
 			SecretKey headerKey) {
-		return new StreamReaderImpl(
-				streamDecrypterFactory.createContactExchangeStreamDecrypter(in,
-						headerKey));
+		return new StreamReaderImpl(streamDecrypterFactory
+				.createContactExchangeStreamDecrypter(in, headerKey));
+	}
+
+	@Override
+	public InputStream createLogStreamReader(InputStream in,
+			SecretKey headerKey) {
+		return new StreamReaderImpl(streamDecrypterFactory
+				.createLogStreamDecrypter(in, headerKey));
 	}
 }

bramble-core/src/main/java/org/briarproject/bramble/transport/StreamWriterFactoryImpl.java

@@ -26,15 +26,21 @@ class StreamWriterFactoryImpl implements StreamWriterFactory {
 	@Override
 	public StreamWriter createStreamWriter(OutputStream out,
 			StreamContext ctx) {
-		return new StreamWriterImpl(
-				streamEncrypterFactory.createStreamEncrypter(out, ctx));
+		return new StreamWriterImpl(streamEncrypterFactory
+				.createStreamEncrypter(out, ctx));
 	}
 
 	@Override
 	public StreamWriter createContactExchangeStreamWriter(OutputStream out,
 			SecretKey headerKey) {
-		return new StreamWriterImpl(
-				streamEncrypterFactory.createContactExchangeStreamDecrypter(out,
-						headerKey));
+		return new StreamWriterImpl(streamEncrypterFactory
+				.createContactExchangeStreamEncrypter(out, headerKey));
 	}
-}
+
+	@Override
+	public StreamWriter createLogStreamWriter(OutputStream out,
+			SecretKey headerKey) {
+		return new StreamWriterImpl(streamEncrypterFactory
+				.createLogStreamEncrypter(out, headerKey));
+	}
+}

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

@@ -5,6 +5,5 @@ interface ClientVersioningConstants {
 	// Metadata keys
 	String MSG_KEY_UPDATE_VERSION = "version";
 	String MSG_KEY_LOCAL = "local";
-	String GROUP_KEY_CONTACT_ID = "contactId";
 }
 

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

@@ -50,7 +50,6 @@ import static java.util.Collections.emptyList;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
-import static org.briarproject.bramble.versioning.ClientVersioningConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
 
@@ -161,13 +160,7 @@ class ClientVersioningManagerImpl implements ClientVersioningManager,
 		db.addGroup(txn, g);
 		db.setGroupVisibility(txn, c.getId(), g.getId(), SHARED);
 		// Attach the contact ID to the group
-		BdfDictionary meta = new BdfDictionary();
-		meta.put(GROUP_KEY_CONTACT_ID, c.getId().getInt());
-		try {
-			clientHelper.mergeGroupMetadata(txn, g.getId(), meta);
-		} catch (FormatException e) {
-			throw new AssertionError(e);
-		}
+		clientHelper.setContactId(txn, g.getId(), c.getId());
 		// Create and store the first local update
 		List<ClientVersion> versions = new ArrayList<>(clients);
 		Collections.sort(versions);
@@ -229,7 +222,7 @@ class ClientVersioningManagerImpl implements ClientVersioningManager,
 			Map<ClientMajorVersion, Visibility> after =
 					getVisibilities(newLocalStates, newRemoteStates);
 			// Call hooks for any visibilities that have changed
-			ContactId c = getContactId(txn, m.getGroupId());
+			ContactId c = clientHelper.getContactId(txn, m.getGroupId());
 			if (!before.equals(after)) {
 				Contact contact = db.getContact(txn, c);
 				callVisibilityHooks(txn, contact, before, after);
@@ -521,17 +514,6 @@ class ClientVersioningManagerImpl implements ClientVersioningManager,
 		storeUpdate(txn, g, states, 1);
 	}
 
-	private ContactId getContactId(Transaction txn, GroupId g)
-			throws DbException {
-		try {
-			BdfDictionary meta =
-					clientHelper.getGroupMetadataAsDictionary(txn, g);
-			return new ContactId(meta.getLong(GROUP_KEY_CONTACT_ID).intValue());
-		} catch (FormatException e) {
-			throw new DbException(e);
-		}
-	}
-
 	private List<ClientState> updateStatesFromRemoteStates(
 			List<ClientState> oldLocalStates, List<ClientState> remoteStates) {
 		Set<ClientMajorVersion> remoteSet = new HashSet<>();

bramble-core/src/main/resources/bridges

@@ -1,5 +1,14 @@
+Bridge obfs4 192.95.36.142:443 CDF2E852BF539B82BD10E27E9115A31734E378C2 cert=qUVQ0srL1JI/vO6V6m/24anYXiJD3QP2HgzUKQtQ7GRqqUvs7P+tG43RtAqdhLOALP7DJQ iat-mode=1
+Bridge obfs4 38.229.1.78:80 C8CBDB2464FC9804A69531437BCF2BE31FDD2EE4 cert=Hmyfd2ev46gGY7NoVxA9ngrPF2zCZtzskRTzoWXbxNkzeVnGFPWmrTtILRyqCTjHR+s9dg iat-mode=1
+Bridge obfs4 37.218.245.14:38224 D9A82D2F9C2F65A18407B1D2B764F130847F8B5D cert=bjRaMrr1BRiAW8IE9U5z27fQaYgOhX1UCmOpg2pFpoMvo6ZgQMzLsaTzzQNTlm7hNcb+Sg iat-mode=0
+Bridge obfs4 85.31.186.98:443 011F2599C0E9B27EE74B353155E244813763C3E5 cert=ayq0XzCwhpdysn5o0EyDUbmSOx3X/oTEbzDMvczHOdBJKlvIdHHLJGkZARtT4dcBFArPPg iat-mode=0
+Bridge obfs4 85.31.186.26:443 91A6354697E6B02A386312F68D82CF86824D3606 cert=PBwr+S8JTVZo6MPdHnkTwXJPILWADLqfMGoVvhZClMq/Urndyd42BwX9YFJHZnBB3H0XCw iat-mode=0
+Bridge obfs4 193.11.166.194:27015 2D82C2E354D531A68469ADF7F878FA6060C6BACA cert=4TLQPJrTSaDffMK7Nbao6LC7G9OW/NHkUwIdjLSS3KYf0Nv4/nQiiI8dY2TcsQx01NniOg iat-mode=0
+Bridge obfs4 193.11.166.194:27020 86AC7B8D430DAC4117E9F42C9EAED18133863AAF cert=0LDeJH4JzMDtkJJrFphJCiPqKx7loozKN7VNfuukMGfHO0Z8OGdzHVkhVAOfo1mUdv9cMg iat-mode=0
+Bridge obfs4 193.11.166.194:27025 1AE2C08904527FEA90C4C4F8C1083EA59FBC6FAF cert=ItvYZzW5tn6v3G4UnQa6Qz04Npro6e81AP70YujmK/KXwDFPTs3aHXcHp4n8Vt6w/bv8cA iat-mode=0
+Bridge obfs4 209.148.46.65:443 74FAD13168806246602538555B5521A0383A1875 cert=ssH+9rP8dG2NLDN2XuFw63hIO/9MNNinLmxQDpVa+7kTOa9/m+tGWT1SmSYpQ9uTBGa6Hw iat-mode=0
+Bridge obfs4 146.57.248.225:22 10A6CD36A537FCE513A322361547444B393989F0 cert=K1gDtDAIcUfeLqbstggjIw2rtgIKqdIhUlHp82XRqNSq/mtAjp1BIC9vHKJ2FAEpGssTPw iat-mode=0
+Bridge obfs4 45.145.95.6:27015 C5B7CD6946FF10C5B3E89691A7D3F2C122D2117C cert=TD7PbUO0/0k6xYHMPW3vJxICfkMZNdkRrb63Zhl5j9dW3iRGiCx0A7mPhe5T2EDzQ35+Zw iat-mode=0
+Bridge obfs4 51.222.13.177:80 5EDAC3B810E12B01F6FD8050D2FD3E277B289A08 cert=2uplIpLQ0q9+0qMFrK5pkaYRDOe460LL9WHBvatgkuRr/SL31wBOEupaMMJ6koRE6Ld0ew iat-mode=0
 Bridge obfs4 78.46.188.239:37356 5A2D2F4158D0453E00C7C176978D3F41D69C45DB cert=3c0SwxpOisbohNxEc4tb875RVW8eOu1opRTVXJhafaKA/PNNtI7ElQIVOVZg1AdL5bxGCw iat-mode=0
-Bridge obfs4 52.15.78.72:9443 02069A3C5362476936B62BA6F5ACC41ABD573A9B cert=ijYG/OKc7kqu2YzKNFfeXN7/BG2BOgfEP2KyYEiGDQthnHbsOiTWHeIG0WJVW+BckzDgKw iat-mode=0
-Bridge obfs4 13.58.29.242:9443 0C58939A77DA6B6B29D4B5236A75865659607AE0 cert=OylWIEHb/ezpq1zWxW0sgKRn+9ARH2eOcQOZ8/Gew+4l+oKOhQ2jUX/Y+FSl61JorXZUWA iat-mode=0
-Bridge obfs4 45.33.37.112:9443 60A609BB4ABE8D46E634AE81ED29ADAB7776B399 cert=t5v19WmNv5Sc2YPNr8RQids365W7MY8zJwQVkOxBjUMFomMWARDzsbYpcWLLcw0J9Gm+BQ iat-mode=0
-Bridge meek_lite 0.0.2.0:2 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url=https://meek.azureedge.net/ front=ajax.aspnetcdn.com
+Bridge meek_lite 192.0.2.2:2 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url=https://meek.azureedge.net/ front=ajax.aspnetcdn.com

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

@@ -1,18 +1,18 @@
 package org.briarproject.bramble;
 
-import org.briarproject.bramble.system.DefaultTaskSchedulerModule;
+import org.briarproject.bramble.system.TimeTravelModule;
 
 public interface BrambleCoreIntegrationTestEagerSingletons
 		extends BrambleCoreEagerSingletons {
 
-	void inject(DefaultTaskSchedulerModule.EagerSingletons init);
+	void inject(TimeTravelModule.EagerSingletons init);
 
 	class Helper {
 
 		public static void injectEagerSingletons(
 				BrambleCoreIntegrationTestEagerSingletons c) {
 			BrambleCoreEagerSingletons.Helper.injectEagerSingletons(c);
-			c.inject(new DefaultTaskSchedulerModule.EagerSingletons());
+			c.inject(new TimeTravelModule.EagerSingletons());
 		}
 	}
 }

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

@@ -1,5 +1,6 @@
 package org.briarproject.bramble.db;
 
+import org.briarproject.bramble.api.cleanup.event.CleanupTimerStartedEvent;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.PendingContactId;
@@ -69,6 +70,8 @@ import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
+import static java.util.concurrent.TimeUnit.HOURS;
+import static org.briarproject.bramble.api.db.DatabaseComponent.TIMER_NOT_STARTED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.bramble.api.sync.Group.Visibility.VISIBLE;
@@ -510,11 +513,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the group is in the DB (which it's not)
-			exactly(8).of(database).startTransaction();
+			exactly(10).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(8).of(database).containsGroup(txn, groupId);
+			exactly(10).of(database).containsGroup(txn, groupId);
 			will(returnValue(false));
-			exactly(8).of(database).abortTransaction(txn);
+			exactly(10).of(database).abortTransaction(txn);
 			// Allow other checks to pass
 			allowing(database).containsContact(txn, contactId);
 			will(returnValue(true));
@@ -523,7 +526,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 				eventExecutor, shutdownManager);
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getGroup(transaction, groupId));
 			fail();
 		} catch (NoSuchGroupException expected) {
@@ -531,7 +534,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getGroupMetadata(transaction, groupId));
 			fail();
 		} catch (NoSuchGroupException expected) {
@@ -539,7 +542,23 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
+					db.getMessageIds(transaction, groupId));
+			fail();
+		} catch (NoSuchGroupException expected) {
+			// Expected
+		}
+
+		try {
+			db.transaction(true, transaction ->
+					db.getMessageIds(transaction, groupId, new Metadata()));
+			fail();
+		} catch (NoSuchGroupException expected) {
+			// Expected
+		}
+
+		try {
+			db.transaction(true, transaction ->
 					db.getMessageMetadata(transaction, groupId));
 			fail();
 		} catch (NoSuchGroupException expected) {
@@ -547,7 +566,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageMetadata(transaction, groupId,
 							new Metadata()));
 			fail();
@@ -556,7 +575,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageStatus(transaction, contactId, groupId));
 			fail();
 		} catch (NoSuchGroupException expected) {
@@ -594,11 +613,11 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			throws Exception {
 		context.checking(new Expectations() {{
 			// Check whether the message is in the DB (which it's not)
-			exactly(12).of(database).startTransaction();
+			exactly(15).of(database).startTransaction();
 			will(returnValue(txn));
-			exactly(12).of(database).containsMessage(txn, messageId);
+			exactly(15).of(database).containsMessage(txn, messageId);
 			will(returnValue(false));
-			exactly(12).of(database).abortTransaction(txn);
+			exactly(15).of(database).abortTransaction(txn);
 			// Allow other checks to pass
 			allowing(database).containsContact(txn, contactId);
 			will(returnValue(true));
@@ -623,7 +642,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessage(transaction, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
@@ -631,7 +650,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageMetadata(transaction, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
@@ -639,7 +658,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageState(transaction, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
@@ -647,7 +666,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageStatus(transaction, contactId, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
@@ -662,6 +681,15 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			// Expected
 		}
 
+		try {
+			db.transaction(false, transaction ->
+					db.setCleanupTimerDuration(transaction, message.getId(),
+							HOURS.toMillis(1)));
+			fail();
+		} catch (NoSuchMessageException expected) {
+			// Expected
+		}
+
 		try {
 			db.transaction(false, transaction ->
 					db.setMessagePermanent(transaction, message.getId()));
@@ -687,7 +715,7 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageDependencies(transaction, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
@@ -695,12 +723,28 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		}
 
 		try {
-			db.transaction(false, transaction ->
+			db.transaction(true, transaction ->
 					db.getMessageDependents(transaction, messageId));
 			fail();
 		} catch (NoSuchMessageException expected) {
 			// Expected
 		}
+
+		try {
+			db.transaction(false, transaction ->
+					db.startCleanupTimer(transaction, messageId));
+			fail();
+		} catch (NoSuchMessageException expected) {
+			// Expected
+		}
+
+		try {
+			db.transaction(false, transaction ->
+					db.stopCleanupTimer(transaction, messageId));
+			fail();
+		} catch (NoSuchMessageException expected) {
+			// Expected
+		}
 	}
 
 	@Test
@@ -981,6 +1025,9 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 			oneOf(database).containsVisibleMessage(txn, contactId, messageId);
 			will(returnValue(true));
 			oneOf(database).raiseSeenFlag(txn, contactId, messageId);
+			will(returnValue(true));
+			oneOf(database).startCleanupTimer(txn, messageId);
+			will(returnValue(TIMER_NOT_STARTED)); // No cleanup duration was set
 			oneOf(database).commitTransaction(txn);
 			oneOf(eventBus).broadcast(with(any(MessagesAckedEvent.class)));
 		}});
@@ -993,6 +1040,56 @@ public class DatabaseComponentImplTest extends BrambleMockTestCase {
 		});
 	}
 
+	@Test
+	public void testReceiveDuplicateAck() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(database).startTransaction();
+			will(returnValue(txn));
+			oneOf(database).containsContact(txn, contactId);
+			will(returnValue(true));
+			oneOf(database).containsVisibleMessage(txn, contactId, messageId);
+			will(returnValue(true));
+			oneOf(database).raiseSeenFlag(txn, contactId, messageId);
+			will(returnValue(false)); // Already acked
+			oneOf(database).commitTransaction(txn);
+		}});
+		DatabaseComponent db = createDatabaseComponent(database, eventBus,
+				eventExecutor, shutdownManager);
+
+		db.transaction(false, transaction -> {
+			Ack a = new Ack(singletonList(messageId));
+			db.receiveAck(transaction, contactId, a);
+		});
+	}
+
+	@Test
+	public void testReceiveAckWithCleanupTimer() throws Exception {
+		long deadline = System.currentTimeMillis();
+		context.checking(new Expectations() {{
+			oneOf(database).startTransaction();
+			will(returnValue(txn));
+			oneOf(database).containsContact(txn, contactId);
+			will(returnValue(true));
+			oneOf(database).containsVisibleMessage(txn, contactId, messageId);
+			will(returnValue(true));
+			oneOf(database).raiseSeenFlag(txn, contactId, messageId);
+			will(returnValue(true));
+			oneOf(database).startCleanupTimer(txn, messageId);
+			will(returnValue(deadline));
+			oneOf(database).commitTransaction(txn);
+			oneOf(eventBus).broadcast(with(any(
+					CleanupTimerStartedEvent.class)));
+			oneOf(eventBus).broadcast(with(any(MessagesAckedEvent.class)));
+		}});
+		DatabaseComponent db = createDatabaseComponent(database, eventBus,
+				eventExecutor, shutdownManager);
+
+		db.transaction(false, transaction -> {
+			Ack a = new Ack(singletonList(messageId));
+			db.receiveAck(transaction, contactId, a);
+		});
+	}
+
 	@Test
 	public void testReceiveMessage() throws Exception {
 		context.checking(new Expectations() {{

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

@@ -53,10 +53,11 @@ import java.util.concurrent.atomic.AtomicLong;
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.emptyList;
-import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static java.util.concurrent.TimeUnit.SECONDS;
+import static org.briarproject.bramble.api.db.DatabaseComponent.NO_CLEANUP_DEADLINE;
+import static org.briarproject.bramble.api.db.DatabaseComponent.TIMER_NOT_STARTED;
 import static org.briarproject.bramble.api.db.Metadata.REMOVE;
 import static org.briarproject.bramble.api.identity.AuthorConstants.MAX_AUTHOR_NAME_LENGTH;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
@@ -351,7 +352,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertTrue(ids.isEmpty());
 
 		// Sharing the message should make it sendable
-		db.setMessageShared(txn, messageId);
+		db.setMessageShared(txn, messageId, true);
 		ids = db.getMessagesToSend(txn, contactId, ONE_MEGABYTE, MAX_LATENCY);
 		assertEquals(singletonList(messageId), ids);
 		ids = db.getMessagesToOffer(txn, contactId, 100, MAX_LATENCY);
@@ -631,8 +632,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 
 		// The group should not be visible to the contact
 		assertEquals(INVISIBLE, db.getGroupVisibility(txn, contactId, groupId));
-		assertEquals(emptyMap(),
-				db.getGroupVisibility(txn, groupId));
+		assertTrue(db.getGroupVisibility(txn, groupId).isEmpty());
 
 		// Make the group visible to the contact
 		db.addGroupVisibility(txn, contactId, groupId, false);
@@ -655,8 +655,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		// Make the group invisible again
 		db.removeGroupVisibility(txn, contactId, groupId);
 		assertEquals(INVISIBLE, db.getGroupVisibility(txn, contactId, groupId));
-		assertEquals(emptyMap(),
-				db.getGroupVisibility(txn, groupId));
+		assertTrue(db.getGroupVisibility(txn, groupId).isEmpty());
 
 		db.commitTransaction(txn);
 		db.close();
@@ -2040,7 +2039,7 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		assertEquals(Long.MAX_VALUE, db.getNextSendTime(txn, contactId));
 
 		// Share the message - now it should be sendable immediately
-		db.setMessageShared(txn, messageId);
+		db.setMessageShared(txn, messageId, true);
 		assertEquals(0, db.getNextSendTime(txn, contactId));
 
 		// Mark the message as requested - it should still be sendable
@@ -2347,6 +2346,87 @@ public abstract class JdbcDatabaseTest extends BrambleTestCase {
 		db.close();
 	}
 
+	@Test
+	public void testCleanupTimer() throws Exception {
+		long duration = 60_000;
+		long now = System.currentTimeMillis();
+		AtomicLong time = new AtomicLong(now);
+		Database<Connection> db =
+				open(false, new TestMessageFactory(), new SettableClock(time));
+		Connection txn = db.startTransaction();
+
+		// No messages should be due or scheduled for deletion
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(NO_CLEANUP_DEADLINE, db.getNextCleanupDeadline(txn));
+
+		// Add a group and a message
+		db.addGroup(txn, group);
+		db.addMessage(txn, message, DELIVERED, false, false, null);
+
+		// No messages should be due or scheduled for deletion
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(NO_CLEANUP_DEADLINE, db.getNextCleanupDeadline(txn));
+
+		// Set the message's cleanup timer duration
+		db.setCleanupTimerDuration(txn, messageId, duration);
+
+		// No messages should be due or scheduled for deletion
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(NO_CLEANUP_DEADLINE, db.getNextCleanupDeadline(txn));
+
+		// Start the message's cleanup timer
+		assertEquals(now + duration, db.startCleanupTimer(txn, messageId));
+
+		// The timer can't be started again
+		assertEquals(TIMER_NOT_STARTED, db.startCleanupTimer(txn, messageId));
+
+		// No messages should be due for deletion, but the message should be
+		// scheduled for deletion
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(now + duration, db.getNextCleanupDeadline(txn));
+
+		// Stop the timer
+		db.stopCleanupTimer(txn, messageId);
+
+		// No messages should be due or scheduled for deletion
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(NO_CLEANUP_DEADLINE, db.getNextCleanupDeadline(txn));
+
+		// Start the timer again
+		assertEquals(now + duration, db.startCleanupTimer(txn, messageId));
+
+		// No messages should be due for deletion, but the message should be
+		// scheduled for deletion
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(now + duration, db.getNextCleanupDeadline(txn));
+
+		// 1 ms before the timer expires, no messages should be due for
+		// deletion but the message should be scheduled for deletion
+		time.set(now + duration - 1);
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(now + duration, db.getNextCleanupDeadline(txn));
+
+		// When the timer expires, the message should be due and scheduled for
+		// deletion
+		time.set(now + duration);
+		assertEquals(singletonMap(groupId, singletonList(messageId)),
+				db.getMessagesToDelete(txn));
+		assertEquals(now + duration, db.getNextCleanupDeadline(txn));
+
+		// 1 ms after the timer expires, the message should be due and
+		// scheduled for deletion
+		time.set(now + duration + 1);
+		assertEquals(singletonMap(groupId, singletonList(messageId)),
+				db.getMessagesToDelete(txn));
+		assertEquals(now + duration, db.getNextCleanupDeadline(txn));
+
+		// Once the message has been deleted, it should no longer be due
+		// or scheduled for deletion
+		db.deleteMessage(txn, messageId);
+		assertTrue(db.getMessagesToDelete(txn).isEmpty());
+		assertEquals(NO_CLEANUP_DEADLINE, db.getNextCleanupDeadline(txn));
+	}
+
 	private Database<Connection> open(boolean resume) throws Exception {
 		return open(resume, new TestMessageFactory(), new SystemClock());
 	}

bramble-core/src/test/java/org/briarproject/bramble/system/TestTaskScheduler.java

@@ -0,0 +1,122 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+
+import java.util.Queue;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Executor;
+import java.util.concurrent.PriorityBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static org.junit.Assert.fail;
+
+/**
+ * A {@link TaskScheduler} for use in tests. The scheduler keeps all scheduled
+ * tasks in a queue until {@link #runTasks()} is called.
+ */
+@NotNullByDefault
+class TestTaskScheduler implements TaskScheduler {
+
+	private final Queue<Task> queue = new PriorityBlockingQueue<>();
+	private final Clock clock;
+
+	TestTaskScheduler(Clock clock) {
+		this.clock = clock;
+	}
+
+	@Override
+	public Cancellable schedule(Runnable task, Executor executor, long delay,
+			TimeUnit unit) {
+		AtomicBoolean cancelled = new AtomicBoolean(false);
+		return schedule(task, executor, delay, unit, cancelled);
+	}
+
+	@Override
+	public Cancellable scheduleWithFixedDelay(Runnable task, Executor executor,
+			long delay, long interval, TimeUnit unit) {
+		AtomicBoolean cancelled = new AtomicBoolean(false);
+		return scheduleWithFixedDelay(task, executor, delay, interval, unit,
+				cancelled);
+	}
+
+	private Cancellable schedule(Runnable task, Executor executor, long delay,
+			TimeUnit unit, AtomicBoolean cancelled) {
+		long delayMillis = MILLISECONDS.convert(delay, unit);
+		long dueMillis = clock.currentTimeMillis() + delayMillis;
+		Task t = new Task(task, executor, dueMillis, cancelled);
+		queue.add(t);
+		return t;
+	}
+
+	private Cancellable scheduleWithFixedDelay(Runnable task, Executor executor,
+			long delay, long interval, TimeUnit unit, AtomicBoolean cancelled) {
+		// All executions of this periodic task share a cancelled flag
+		Runnable wrapped = () -> {
+			task.run();
+			scheduleWithFixedDelay(task, executor, interval, interval, unit,
+					cancelled);
+		};
+		return schedule(wrapped, executor, delay, unit, cancelled);
+	}
+
+	/**
+	 * Runs any scheduled tasks that are due.
+	 */
+	void runTasks() throws InterruptedException {
+		long now = clock.currentTimeMillis();
+		while (true) {
+			Task t = queue.peek();
+			if (t == null || t.dueMillis > now) return;
+			t = queue.poll();
+			// Submit the task to its executor and wait for it to finish
+			if (!t.run().await(1, MINUTES)) fail();
+		}
+	}
+
+	private static class Task
+			implements Cancellable, Comparable<Task> {
+
+		private final Runnable task;
+		private final Executor executor;
+		private final long dueMillis;
+		private final AtomicBoolean cancelled;
+
+		private Task(Runnable task, Executor executor, long dueMillis,
+				AtomicBoolean cancelled) {
+			this.task = task;
+			this.executor = executor;
+			this.dueMillis = dueMillis;
+			this.cancelled = cancelled;
+		}
+
+		@SuppressWarnings("UseCompareMethod") // Animal Sniffer
+		@Override
+		public int compareTo(Task task) {
+			return Long.valueOf(dueMillis).compareTo(task.dueMillis);
+		}
+
+		/**
+		 * Submits the task to its executor and returns a latch that will be
+		 * released when the task finishes.
+		 */
+		public CountDownLatch run() {
+			if (cancelled.get()) return new CountDownLatch(0);
+			CountDownLatch latch = new CountDownLatch(1);
+			executor.execute(() -> {
+				task.run();
+				latch.countDown();
+			});
+			return latch;
+		}
+
+		@Override
+		public void cancel() {
+			cancelled.set(true);
+		}
+	}
+}

bramble-core/src/test/java/org/briarproject/bramble/system/TimeTravelModule.java

@@ -0,0 +1,98 @@
+package org.briarproject.bramble.system;
+
+import org.briarproject.bramble.api.lifecycle.LifecycleManager;
+import org.briarproject.bramble.api.system.Clock;
+import org.briarproject.bramble.api.system.TaskScheduler;
+import org.briarproject.bramble.test.SettableClock;
+import org.briarproject.bramble.test.TimeTravel;
+
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.atomic.AtomicLong;
+
+import javax.inject.Inject;
+import javax.inject.Singleton;
+
+import dagger.Module;
+import dagger.Provides;
+
+@Module
+public class TimeTravelModule {
+
+	public static class EagerSingletons {
+		@Inject
+		TaskScheduler scheduler;
+	}
+
+	private final ScheduledExecutorService scheduledExecutorService;
+	private final Clock clock;
+	private final TaskScheduler taskScheduler;
+	private final TimeTravel timeTravel;
+
+	public TimeTravelModule() {
+		this(false);
+	}
+
+	public TimeTravelModule(boolean travel) {
+		// Discard tasks that are submitted during shutdown
+		RejectedExecutionHandler policy =
+				new ScheduledThreadPoolExecutor.DiscardPolicy();
+		scheduledExecutorService =
+				new ScheduledThreadPoolExecutor(1, policy);
+		if (travel) {
+			// Use a SettableClock and TestTaskScheduler to allow time travel
+			AtomicLong time = new AtomicLong(System.currentTimeMillis());
+			clock = new SettableClock(time);
+			TestTaskScheduler testTaskScheduler = new TestTaskScheduler(clock);
+			taskScheduler = testTaskScheduler;
+			timeTravel = new TimeTravel() {
+				@Override
+				public void setCurrentTimeMillis(long now)
+						throws InterruptedException {
+					time.set(now);
+					testTaskScheduler.runTasks();
+				}
+
+				@Override
+				public void addCurrentTimeMillis(long add)
+						throws InterruptedException {
+					time.addAndGet(add);
+					testTaskScheduler.runTasks();
+				}
+			};
+		} else {
+			// Use the default clock and task scheduler
+			clock = new SystemClock();
+			taskScheduler = new TaskSchedulerImpl(scheduledExecutorService);
+			timeTravel = new TimeTravel() {
+				@Override
+				public void setCurrentTimeMillis(long now) {
+					throw new UnsupportedOperationException();
+				}
+
+				@Override
+				public void addCurrentTimeMillis(long add) {
+					throw new UnsupportedOperationException();
+				}
+			};
+		}
+	}
+
+	@Provides
+	Clock provideClock() {
+		return clock;
+	}
+
+	@Provides
+	@Singleton
+	TaskScheduler provideTaskScheduler(LifecycleManager lifecycleManager) {
+		lifecycleManager.registerForShutdown(scheduledExecutorService);
+		return taskScheduler;
+	}
+
+	@Provides
+	TimeTravel provideTimeTravel() {
+		return timeTravel;
+	}
+}

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

@@ -3,8 +3,8 @@ package org.briarproject.bramble.test;
 import org.briarproject.bramble.api.FeatureFlags;
 import org.briarproject.bramble.battery.DefaultBatteryManagerModule;
 import org.briarproject.bramble.event.DefaultEventExecutorModule;
-import org.briarproject.bramble.system.DefaultTaskSchedulerModule;
 import org.briarproject.bramble.system.DefaultWakefulIoExecutorModule;
+import org.briarproject.bramble.system.TimeTravelModule;
 
 import dagger.Module;
 import dagger.Provides;
@@ -12,11 +12,11 @@ import dagger.Provides;
 @Module(includes = {
 		DefaultBatteryManagerModule.class,
 		DefaultEventExecutorModule.class,
-		DefaultTaskSchedulerModule.class,
 		DefaultWakefulIoExecutorModule.class,
 		TestDatabaseConfigModule.class,
 		TestPluginConfigModule.class,
-		TestSecureRandomModule.class
+		TestSecureRandomModule.class,
+		TimeTravelModule.class
 })
 public class BrambleCoreIntegrationTestModule {
 
@@ -33,6 +33,11 @@ public class BrambleCoreIntegrationTestModule {
 			public boolean shouldEnableProfilePictures() {
 				return true;
 			}
+
+			@Override
+			public boolean shouldEnableDisappearingMessages() {
+				return true;
+			}
 		};
 	}
 }

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

@@ -38,7 +38,6 @@ import static org.briarproject.bramble.test.TestUtils.getContact;
 import static org.briarproject.bramble.test.TestUtils.getGroup;
 import static org.briarproject.bramble.test.TestUtils.getMessage;
 import static org.briarproject.bramble.test.TestUtils.getRandomId;
-import static org.briarproject.bramble.versioning.ClientVersioningConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
 import static org.junit.Assert.assertEquals;
@@ -60,8 +59,6 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 	private final ClientId clientId = getClientId();
 	private final long now = System.currentTimeMillis();
 	private final Transaction txn = new Transaction(null, false);
-	private final BdfDictionary groupMeta = BdfDictionary.of(
-			new BdfEntry(GROUP_KEY_CONTACT_ID, contact.getId().getInt()));
 
 	private ClientVersioningManagerImpl createInstance() {
 		context.checking(new Expectations() {{
@@ -123,8 +120,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).addGroup(txn, contactGroup);
 			oneOf(db).setGroupVisibility(txn, contact.getId(),
 					contactGroup.getId(), SHARED);
-			oneOf(clientHelper).mergeGroupMetadata(txn, contactGroup.getId(),
-					groupMeta);
+			oneOf(clientHelper).setContactId(txn, contactGroup.getId(),
+					contact.getId());
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(now));
 			oneOf(clientHelper).createMessage(contactGroup.getId(), now,
@@ -460,9 +457,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).deleteMessage(txn, oldRemoteUpdateId);
 			oneOf(db).deleteMessageMetadata(txn, oldRemoteUpdateId);
 			// Get contact ID
-			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
-					contactGroup.getId());
-			will(returnValue(groupMeta));
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
+			will(returnValue(contact.getId()));
 			// No states or visibilities have changed
 		}});
 
@@ -492,10 +488,9 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			// Load the latest local update
 			oneOf(clientHelper).getMessageAsList(txn, oldLocalUpdateId);
 			will(returnValue(oldLocalUpdateBody));
-			// Get client ID
-			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
-					contactGroup.getId());
-			will(returnValue(groupMeta));
+			// Get contact ID
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
+			will(returnValue(contact.getId()));
 			// No states or visibilities have changed
 		}});
 
@@ -546,8 +541,6 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 		BdfDictionary newLocalUpdateMeta = BdfDictionary.of(
 				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
 				new BdfEntry(MSG_KEY_LOCAL, true));
-		BdfDictionary groupMeta = BdfDictionary.of(
-				new BdfEntry(GROUP_KEY_CONTACT_ID, contact.getId().getInt()));
 
 		context.checking(new Expectations() {{
 			oneOf(clientHelper).toList(newRemoteUpdate);
@@ -577,9 +570,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
 					newLocalUpdateMeta, true, false);
 			// The client's visibility has changed
-			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
-					contactGroup.getId());
-			will(returnValue(groupMeta));
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
+			will(returnValue(contact.getId()));
 			oneOf(db).getContact(txn, contact.getId());
 			will(returnValue(contact));
 			oneOf(hook).onClientVisibilityChanging(txn, contact, visibility);
@@ -619,8 +611,6 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 		BdfDictionary newLocalUpdateMeta = BdfDictionary.of(
 				new BdfEntry(MSG_KEY_UPDATE_VERSION, 2L),
 				new BdfEntry(MSG_KEY_LOCAL, true));
-		BdfDictionary groupMeta = BdfDictionary.of(
-				new BdfEntry(GROUP_KEY_CONTACT_ID, contact.getId().getInt()));
 
 		context.checking(new Expectations() {{
 			oneOf(clientHelper).toList(newRemoteUpdate);
@@ -650,9 +640,8 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 			oneOf(clientHelper).addLocalMessage(txn, newLocalUpdate,
 					newLocalUpdateMeta, true, false);
 			// The client's visibility has changed
-			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
-					contactGroup.getId());
-			will(returnValue(groupMeta));
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
+			will(returnValue(contact.getId()));
 			oneOf(db).getContact(txn, contact.getId());
 			will(returnValue(contact));
 			oneOf(hook).onClientVisibilityChanging(txn, contact, INVISIBLE);

bramble-java/build.gradle

@@ -16,8 +16,8 @@ dependencies {
 	implementation fileTree(dir: 'libs', include: '*.jar')
 	implementation 'net.java.dev.jna:jna:4.5.2'
 	implementation 'net.java.dev.jna:jna-platform:4.5.2'
-	tor 'org.briarproject:tor:0.3.5.12@zip'
-	tor 'org.briarproject:obfs4proxy:0.0.7@zip'
+	tor 'org.briarproject:tor:0.3.5.13@zip'
+	tor 'org.briarproject:obfs4proxy:0.0.12-dev-40245c4a@zip'
 
 	annotationProcessor 'com.google.dagger:dagger-compiler:2.24'
 

bramble-java/src/main/java/org/briarproject/bramble/BrambleJavaModule.java

@@ -8,9 +8,9 @@ import org.briarproject.bramble.system.JavaSystemModule;
 import dagger.Module;
 
 @Module(includes = {
+		CircumventionModule.class,
 		JavaNetworkModule.class,
 		JavaSystemModule.class,
-		CircumventionModule.class,
 		SocksModule.class
 })
 public class BrambleJavaModule {

bramble-java/src/test/java/org/briarproject/bramble/plugin/tor/BridgeTest.java

@@ -53,7 +53,7 @@ public class BridgeTest extends BrambleTestCase {
 		return component.getCircumventionProvider().getBridges(false);
 	}
 
-	private final static long TIMEOUT = SECONDS.toMillis(30);
+	private final static long TIMEOUT = SECONDS.toMillis(60);
 
 	private final static Logger LOG = getLogger(BridgeTest.class.getName());
 

bramble-java/witness.gradle

@@ -23,8 +23,8 @@ dependencyVerification {
         '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.briarproject:obfs4proxy:0.0.7:obfs4proxy-0.0.7.zip:5b2f693262ce43a7e130f7cc7d5d1617925330640a2eb6d71085e95df8ee0642',
-        'org.briarproject:tor:0.3.5.12:tor-0.3.5.12.zip:2f542c4befd216f2226bf7c76e3b8b2d99af6f146a8cb28bf727f42014587006',
+        'org.briarproject:obfs4proxy:0.0.12-dev-40245c4a:obfs4proxy-0.0.12-dev-40245c4a.zip:172029e7058b3a83ac93ac4991a44bf76e16ce8d46f558f5836d57da3cb3a766',
+        'org.briarproject:tor:0.3.5.13:tor-0.3.5.13.zip:1c5f0b821ee2aadb0ea04aa96caab3ca0a08370cce8de81c2dfe04d172f8a2a0',
         'org.checkerframework:checker-compat-qual:2.5.3:checker-compat-qual-2.5.3.jar:d76b9afea61c7c082908023f0cbc1427fab9abd2df915c8b8a3e7a509bccbc6d',
         'org.checkerframework:checker-qual:2.5.2:checker-qual-2.5.2.jar:64b02691c8b9d4e7700f8ee2e742dce7ea2c6e81e662b7522c9ee3bf568c040a',
         'org.codehaus.mojo:animal-sniffer-annotations:1.17:animal-sniffer-annotations-1.17.jar:92654f493ecfec52082e76354f0ebf87648dc3d5cec2e3c3cdb947c016747a53',

briar-android/artwork/notification_signout.svg

@@ -0,0 +1 @@
+<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="24" height="24" viewBox="0 0 24 24"><path d="M16,17V14H9V10H16V7L21,12L16,17M14,2A2,2 0 0,1 16,4V6H14V4H5V20H14V18H16V20A2,2 0 0,1 14,22H5A2,2 0 0,1 3,20V4A2,2 0 0,1 5,2H14Z" /></svg>

briar-android/build.gradle

@@ -22,9 +22,11 @@ android {
 	defaultConfig {
 		minSdkVersion 16
 		targetSdkVersion 29
-		versionCode 10213
-		versionName "1.2.13"
+		versionCode 10216
+		versionName "1.2.16"
 		applicationId "org.briarproject.briar.android"
+
+		vectorDrawables.useSupportLibrary = true
 		buildConfigField "String", "GitHash",
 				"\"${getStdout(['git', 'rev-parse', '--short=7', 'HEAD'], 'No commit hash')}\""
 		def now = (long) (System.currentTimeMillis() / 1000)
@@ -93,6 +95,7 @@ dependencies {
 	implementation project(path: ':bramble-core', configuration: 'default')
 	implementation project(':bramble-android')
 
+	implementation 'androidx.fragment:fragment:1.3.0'
 	implementation 'androidx.preference:preference:1.1.1'
 	implementation 'androidx.exifinterface:exifinterface:1.3.1'
 	implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'
@@ -134,6 +137,7 @@ dependencies {
 	testImplementation "org.jmock:jmock:$jmockVersion"
 	testImplementation "org.jmock:jmock-junit4:$jmockVersion"
 	testImplementation "org.jmock:jmock-legacy:$jmockVersion"
+	testAnnotationProcessor "com.google.dagger:dagger-compiler:2.24"
 
 	androidTestImplementation project(path: ':bramble-api', configuration: 'testOutput')
 	androidTestImplementation 'androidx.test.ext:junit:1.1.2'

briar-android/src/androidTestOfficial/java/org/briarproject/briar/android/BriarUiTestComponent.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android;
 import org.briarproject.bramble.BrambleAndroidModule;
 import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.account.BriarAccountModule;
+import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.briar.BriarCoreModule;
 import org.briarproject.briar.android.attachment.AttachmentModule;
 import org.briarproject.briar.android.attachment.media.MediaModule;
@@ -16,6 +17,7 @@ import dagger.Component;
 @Component(modules = {
 		AppModule.class,
 		AttachmentModule.class,
+		ClockModule.class,
 		MediaModule.class,
 		BriarCoreModule.class,
 		BrambleAndroidModule.class,

briar-android/src/androidTestScreenshot/java/org/briarproject/briar/android/BriarUiTestComponent.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android;
 import org.briarproject.bramble.BrambleAndroidModule;
 import org.briarproject.bramble.BrambleCoreModule;
 import org.briarproject.bramble.account.BriarAccountModule;
+import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.briar.BriarCoreModule;
 import org.briarproject.briar.android.attachment.AttachmentModule;
 import org.briarproject.briar.android.attachment.media.MediaModule;
@@ -17,6 +18,7 @@ import dagger.Component;
 @Component(modules = {
 		AppModule.class,
 		AttachmentModule.class,
+		ClockModule.class,
 		MediaModule.class,
 		BriarCoreModule.class,
 		BrambleAndroidModule.class,

briar-android/src/main/java/org/briarproject/briar/android/AndroidComponent.java

@@ -29,11 +29,13 @@ import org.briarproject.bramble.api.system.AndroidWakeLockManager;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.system.LocationUtils;
 import org.briarproject.bramble.plugin.tor.CircumventionProvider;
+import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.briar.BriarCoreEagerSingletons;
 import org.briarproject.briar.BriarCoreModule;
 import org.briarproject.briar.android.attachment.AttachmentModule;
 import org.briarproject.briar.android.attachment.media.MediaModule;
 import org.briarproject.briar.android.conversation.glide.BriarModelLoader;
+import org.briarproject.briar.android.logging.CachingLogHandler;
 import org.briarproject.briar.android.login.SignInReminderReceiver;
 import org.briarproject.briar.android.view.EmojiTextInputView;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
@@ -41,6 +43,7 @@ import org.briarproject.briar.api.android.DozeWatchdog;
 import org.briarproject.briar.api.android.LockManager;
 import org.briarproject.briar.api.android.ScreenFilterMonitor;
 import org.briarproject.briar.api.attachment.AttachmentReader;
+import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.blog.BlogManager;
 import org.briarproject.briar.api.blog.BlogPostFactory;
 import org.briarproject.briar.api.blog.BlogSharingManager;
@@ -75,6 +78,7 @@ import dagger.Component;
 		BriarAccountModule.class,
 		AppModule.class,
 		AttachmentModule.class,
+		ClockModule.class,
 		MediaModule.class
 })
 public interface AndroidComponent
@@ -179,6 +183,12 @@ public interface AndroidComponent
 
 	AndroidWakeLockManager wakeLockManager();
 
+	CachingLogHandler logHandler();
+
+	Thread.UncaughtExceptionHandler exceptionHandler();
+
+	AutoDeleteManager autoDeleteManager();
+
 	void inject(SignInReminderReceiver briarService);
 
 	void inject(BriarService briarService);

briar-android/src/main/java/org/briarproject/briar/android/AndroidNotificationManagerImpl.java

@@ -37,6 +37,7 @@ import org.briarproject.briar.android.splash.SplashScreenActivity;
 import org.briarproject.briar.android.util.BriarNotificationBuilder;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.blog.event.BlogPostAddedEvent;
+import org.briarproject.briar.api.conversation.ConversationResponse;
 import org.briarproject.briar.api.conversation.event.ConversationMessageReceivedEvent;
 import org.briarproject.briar.api.forum.event.ForumPostReceivedEvent;
 import org.briarproject.briar.api.privategroup.event.GroupMessageAddedEvent;
@@ -226,6 +227,12 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 		} else if (e instanceof ConversationMessageReceivedEvent) {
 			ConversationMessageReceivedEvent<?> p =
 					(ConversationMessageReceivedEvent<?>) e;
+			if (p.getMessageHeader() instanceof ConversationResponse) {
+				ConversationResponse r =
+						(ConversationResponse) p.getMessageHeader();
+				// don't show notification for own auto-decline responses
+				if (r.isAutoDecline()) return;
+			}
 			showContactNotification(p.getContactId());
 		} else if (e instanceof GroupMessageAddedEvent) {
 			GroupMessageAddedEvent g = (GroupMessageAddedEvent) e;
@@ -255,7 +262,7 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 				R.string.ongoing_notification_title;
 		int text = locked ? R.string.lock_tap_to_unlock :
 				R.string.ongoing_notification_text;
-		int icon = locked ? R.drawable.startup_lock :
+		int icon = locked ? R.drawable.notification_lock :
 				R.drawable.notification_ongoing;
 		// Ongoing foreground notification that shows BriarService is running
 		NotificationCompat.Builder b =
@@ -624,7 +631,7 @@ class AndroidNotificationManagerImpl implements AndroidNotificationManager,
 
 		NotificationCompat.Builder b =
 				new NotificationCompat.Builder(appContext, REMINDER_CHANNEL_ID);
-		b.setSmallIcon(R.drawable.ic_signout);
+		b.setSmallIcon(R.drawable.notification_signout);
 		b.setColor(getColor(appContext, R.color.briar_primary));
 		b.setContentTitle(
 				appContext.getText(R.string.reminder_notification_title));

briar-android/src/main/java/org/briarproject/briar/android/AppModule.java

@@ -33,12 +33,13 @@ import org.briarproject.briar.android.account.SetupModule;
 import org.briarproject.briar.android.contact.ContactListModule;
 import org.briarproject.briar.android.forum.ForumModule;
 import org.briarproject.briar.android.keyagreement.ContactExchangeModule;
+import org.briarproject.briar.android.logging.LoggingModule;
 import org.briarproject.briar.android.login.LoginModule;
 import org.briarproject.briar.android.navdrawer.NavDrawerModule;
 import org.briarproject.briar.android.privategroup.conversation.GroupConversationModule;
-import org.briarproject.briar.android.settings.SettingsModule;
 import org.briarproject.briar.android.privategroup.list.GroupListModule;
 import org.briarproject.briar.android.reporting.DevReportModule;
+import org.briarproject.briar.android.settings.SettingsModule;
 import org.briarproject.briar.android.sharing.SharingModule;
 import org.briarproject.briar.android.test.TestAvatarCreatorImpl;
 import org.briarproject.briar.android.viewmodel.ViewModelModule;
@@ -74,6 +75,7 @@ import static org.briarproject.briar.android.TestingConstants.IS_DEBUG_BUILD;
 		SetupModule.class,
 		DozeHelperModule.class,
 		ContactExchangeModule.class,
+		LoggingModule.class,
 		LoginModule.class,
 		NavDrawerModule.class,
 		ViewModelModule.class,
@@ -192,6 +194,11 @@ public class AppModule {
 			public File getReportDir() {
 				return AndroidUtils.getReportDir(app.getApplicationContext());
 			}
+
+			@Override
+			public File getLogcatFile() {
+				return AndroidUtils.getLogcatFile(app.getApplicationContext());
+			}
 		};
 		return devConfig;
 	}
@@ -276,6 +283,11 @@ public class AppModule {
 			public boolean shouldEnableProfilePictures() {
 				return IS_DEBUG_BUILD;
 			}
+
+			@Override
+			public boolean shouldEnableDisappearingMessages() {
+				return IS_DEBUG_BUILD;
+			}
 		};
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/BriarApplication.java

@@ -6,9 +6,6 @@ import android.content.SharedPreferences;
 import org.briarproject.bramble.BrambleApplication;
 import org.briarproject.briar.android.navdrawer.NavDrawerActivity;
 
-import java.util.Collection;
-import java.util.logging.LogRecord;
-
 /**
  * This exists so that the Application object will not necessarily be cast
  * directly to the Briar application object.
@@ -17,8 +14,6 @@ public interface BriarApplication extends BrambleApplication {
 
 	Class<? extends Activity> ENTRY_ACTIVITY = NavDrawerActivity.class;
 
-	Collection<LogRecord> getRecentLogRecords();
-
 	AndroidComponent getApplicationComponent();
 
 	SharedPreferences getDefaultSharedPreferences();

briar-android/src/main/java/org/briarproject/briar/android/BriarApplicationImpl.java

@@ -20,12 +20,10 @@ import org.briarproject.bramble.BrambleCoreEagerSingletons;
 import org.briarproject.briar.BriarCoreEagerSingletons;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.logging.CachingLogHandler;
-import org.briarproject.briar.android.reporting.BriarExceptionHandler;
 import org.briarproject.briar.android.util.UiUtils;
 
-import java.util.Collection;
+import java.lang.Thread.UncaughtExceptionHandler;
 import java.util.logging.Handler;
-import java.util.logging.LogRecord;
 import java.util.logging.Logger;
 
 import androidx.annotation.NonNull;
@@ -42,22 +40,18 @@ public class BriarApplicationImpl extends Application
 	private static final Logger LOG =
 			getLogger(BriarApplicationImpl.class.getName());
 
-	private final CachingLogHandler logHandler = new CachingLogHandler();
-	private final BriarExceptionHandler exceptionHandler =
-			new BriarExceptionHandler(this);
-
 	private AndroidComponent applicationComponent;
 	private volatile SharedPreferences prefs;
 
 	@Override
 	protected void attachBaseContext(Context base) {
-		Thread.setDefaultUncaughtExceptionHandler(exceptionHandler);
 		if (prefs == null)
 			prefs = PreferenceManager.getDefaultSharedPreferences(base);
 		// Loading the language needs to be done here.
 		Localizer.initialize(prefs);
 		super.attachBaseContext(
 				Localizer.getInstance().setLocale(base));
+		Localizer.getInstance().setLocale(this);
 		setTheme(base, prefs);
 	}
 
@@ -67,6 +61,11 @@ public class BriarApplicationImpl extends Application
 
 		if (IS_DEBUG_BUILD) enableStrictMode();
 
+		applicationComponent = createApplicationComponent();
+		UncaughtExceptionHandler exceptionHandler =
+				applicationComponent.exceptionHandler();
+		Thread.setDefaultUncaughtExceptionHandler(exceptionHandler);
+
 		Logger rootLogger = getLogger("");
 		Handler[] handlers = rootLogger.getHandlers();
 		// Disable the Android logger for release builds
@@ -78,12 +77,12 @@ public class BriarApplicationImpl extends Application
 			// Restore the default handlers after the level raising handler
 			for (Handler handler : handlers) rootLogger.addHandler(handler);
 		}
+		CachingLogHandler logHandler = applicationComponent.logHandler();
 		rootLogger.addHandler(logHandler);
 		rootLogger.setLevel(IS_DEBUG_BUILD ? FINE : INFO);
 
 		LOG.info("Created");
 
-		applicationComponent = createApplicationComponent();
 		EmojiManager.install(new GoogleEmojiProvider());
 	}
 
@@ -136,11 +135,6 @@ public class BriarApplicationImpl extends Application
 		return applicationComponent;
 	}
 
-	@Override
-	public Collection<LogRecord> getRecentLogRecords() {
-		return logHandler.getRecentLogRecords();
-	}
-
 	@Override
 	public AndroidComponent getApplicationComponent() {
 		return applicationComponent;

briar-android/src/main/java/org/briarproject/briar/android/BriarService.java

@@ -37,7 +37,7 @@ import javax.inject.Inject;
 import androidx.core.app.NotificationCompat;
 
 import static android.app.NotificationManager.IMPORTANCE_DEFAULT;
-import static android.app.NotificationManager.IMPORTANCE_NONE;
+import static android.app.NotificationManager.IMPORTANCE_LOW;
 import static android.app.PendingIntent.FLAG_UPDATE_CURRENT;
 import static android.content.Intent.ACTION_SHUTDOWN;
 import static android.content.Intent.FLAG_ACTIVITY_CLEAR_TASK;
@@ -46,6 +46,7 @@ import static android.content.Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS;
 import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
 import static android.content.Intent.FLAG_ACTIVITY_NO_ANIMATION;
 import static android.os.Build.VERSION.SDK_INT;
+import static android.os.Process.myPid;
 import static androidx.core.app.NotificationCompat.VISIBILITY_SECRET;
 import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
@@ -56,8 +57,10 @@ import static org.briarproject.briar.android.BriarApplication.ENTRY_ACTIVITY;
 import static org.briarproject.briar.api.android.AndroidNotificationManager.FAILURE_CHANNEL_ID;
 import static org.briarproject.briar.api.android.AndroidNotificationManager.FAILURE_NOTIFICATION_ID;
 import static org.briarproject.briar.api.android.AndroidNotificationManager.ONGOING_CHANNEL_ID;
+import static org.briarproject.briar.api.android.AndroidNotificationManager.ONGOING_CHANNEL_OLD_ID;
 import static org.briarproject.briar.api.android.AndroidNotificationManager.ONGOING_NOTIFICATION_ID;
 import static org.briarproject.briar.api.android.LockManager.ACTION_LOCK;
+import static org.briarproject.briar.api.android.LockManager.EXTRA_PID;
 
 public class BriarService extends Service {
 
@@ -120,11 +123,17 @@ public class BriarService extends Service {
 			if (SDK_INT >= 26) {
 				NotificationManager nm = (NotificationManager)
 						requireNonNull(getSystemService(NOTIFICATION_SERVICE));
+				// Delete the old notification channel, which had
+				// IMPORTANCE_NONE and showed a badge
+				nm.deleteNotificationChannel(ONGOING_CHANNEL_OLD_ID);
+				// Use IMPORTANCE_LOW so the system doesn't show its own
+				// notification on API 26-27
 				NotificationChannel ongoingChannel = new NotificationChannel(
 						ONGOING_CHANNEL_ID,
 						getString(R.string.ongoing_notification_title),
-						IMPORTANCE_NONE);
+						IMPORTANCE_LOW);
 				ongoingChannel.setLockscreenVisibility(VISIBILITY_SECRET);
+				ongoingChannel.setShowBadge(false);
 				nm.createNotificationChannel(ongoingChannel);
 				NotificationChannel failureChannel = new NotificationChannel(
 						FAILURE_CHANNEL_ID,
@@ -170,6 +179,7 @@ public class BriarService extends Service {
 	@Override
 	protected void attachBaseContext(Context base) {
 		super.attachBaseContext(Localizer.getInstance().setLocale(base));
+		Localizer.getInstance().setLocale(this);
 	}
 
 	private void showStartupFailureNotification(StartResult result) {
@@ -202,7 +212,12 @@ public class BriarService extends Service {
 	@Override
 	public int onStartCommand(Intent intent, int flags, int startId) {
 		if (ACTION_LOCK.equals(intent.getAction())) {
-			lockManager.setLocked(true);
+			int pid = intent.getIntExtra(EXTRA_PID, -1);
+			if (pid == myPid()) lockManager.setLocked(true);
+			else if (LOG.isLoggable(WARNING)) {
+				LOG.warning("Tried to lock process " + pid + " but this is " +
+						myPid());
+			}
 		}
 		return START_NOT_STICKY; // Don't restart automatically if killed
 	}

briar-android/src/main/java/org/briarproject/briar/android/Localizer.java

@@ -68,7 +68,21 @@ public class Localizer {
 			return new Locale(tag);
 	}
 
-	// Returns the localized version of context
+	/*
+	 * Apply localization to the specified context.
+	 *
+	 * It updates the configuration of the context's resources object but can
+	 * also return a new context derived from the context parameter. Hence
+	 * make sure to work with the return value of this method instead of
+	 * the context you passed as a parameter.
+	 *
+	 * This method also has side-effects as it calls Locale#setDefault().
+	 *
+	 * When using this in attachBaseContext() of Application, Service or
+	 * Activity subclasses, it is important to not only apply this method to the
+	 * base Context parameter received in that method, but also apply it on the
+	 * class itself which also extends Context.
+	 */
 	public Context setLocale(Context context) {
 		Resources res = context.getResources();
 		Configuration conf = res.getConfiguration();
@@ -82,7 +96,7 @@ public class Localizer {
 		Locale.setDefault(locale);
 		if (SDK_INT >= 17) {
 			conf.setLocale(locale);
-			context.createConfigurationContext(conf);
+			context = context.createConfigurationContext(conf);
 		} else
 			conf.locale = locale;
 		//noinspection deprecation

briar-android/src/main/java/org/briarproject/briar/android/account/LockManagerImpl.java

@@ -32,8 +32,10 @@ import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
 import static android.app.AlarmManager.ELAPSED_REALTIME;
+import static android.app.PendingIntent.FLAG_UPDATE_CURRENT;
 import static android.app.PendingIntent.getService;
 import static android.content.Context.ALARM_SERVICE;
+import static android.os.Process.myPid;
 import static android.os.SystemClock.elapsedRealtime;
 import static java.util.concurrent.TimeUnit.MINUTES;
 import static java.util.logging.Level.WARNING;
@@ -75,23 +77,25 @@ public class LockManagerImpl implements LockManager, Service, EventListener {
 	LockManagerImpl(Application app, SettingsManager settingsManager,
 			AndroidNotificationManager notificationManager,
 			@DatabaseExecutor Executor dbExecutor) {
-		this.appContext = app.getApplicationContext();
+		appContext = app.getApplicationContext();
 		this.settingsManager = settingsManager;
 		this.notificationManager = notificationManager;
 		this.dbExecutor = dbExecutor;
-		this.alarmManager =
+		alarmManager =
 				(AlarmManager) appContext.getSystemService(ALARM_SERVICE);
 		Intent i =
 				new Intent(ACTION_LOCK, null, appContext, BriarService.class);
-		this.lockIntent = getService(appContext, 0, i, 0);
-		this.timeoutNever = Integer.valueOf(
+		i.putExtra(EXTRA_PID, myPid());
+		// When not using FLAG_UPDATE_CURRENT, the intent might have no extras
+		lockIntent = getService(appContext, 0, i, FLAG_UPDATE_CURRENT);
+		timeoutNever = Integer.parseInt(
 				appContext.getString(R.string.pref_lock_timeout_value_never));
-		this.timeoutDefault = Integer.valueOf(
+		timeoutDefault = Integer.parseInt(
 				appContext.getString(R.string.pref_lock_timeout_value_default));
-		this.timeoutMinutes = timeoutNever;
+		timeoutMinutes = timeoutNever;
 
 		// setting this in the constructor makes #getValue() @NonNull
-		this.lockable.setValue(false);
+		lockable.setValue(false);
 	}
 
 	@Override
@@ -148,7 +152,7 @@ public class LockManagerImpl implements LockManager, Service, EventListener {
 		boolean oldValue = lockable.getValue();
 		boolean newValue = hasScreenLock(appContext) && lockableSetting;
 		if (oldValue != newValue) {
-			this.lockable.setValue(newValue);
+			lockable.setValue(newValue);
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/account/UnlockActivity.java

@@ -77,7 +77,7 @@ public class UnlockActivity extends BaseActivity {
 
 	@Override
 	protected void onActivityResult(int requestCode, int resultCode,
-			Intent data) {
+			@Nullable Intent data) {
 		super.onActivityResult(requestCode, resultCode, data);
 		if (requestCode == REQUEST_KEYGUARD_UNLOCK) {
 			if (resultCode == RESULT_OK) unlock();

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -27,6 +27,7 @@ import org.briarproject.briar.android.contact.add.remote.NicknameFragment;
 import org.briarproject.briar.android.contact.add.remote.PendingContactListActivity;
 import org.briarproject.briar.android.conversation.AliasDialogFragment;
 import org.briarproject.briar.android.conversation.ConversationActivity;
+import org.briarproject.briar.android.conversation.ConversationSettingsDialog;
 import org.briarproject.briar.android.conversation.ImageActivity;
 import org.briarproject.briar.android.conversation.ImageFragment;
 import org.briarproject.briar.android.forum.CreateForumActivity;
@@ -238,4 +239,6 @@ public interface ActivityComponent {
 
 	void inject(ConfirmAvatarDialogFragment fragment);
 
+	void inject(ConversationSettingsDialog dialog);
+
 }

briar-android/src/main/java/org/briarproject/briar/android/activity/BaseActivity.java

@@ -109,6 +109,7 @@ public abstract class BaseActivity extends AppCompatActivity
 	protected void attachBaseContext(Context base) {
 		super.attachBaseContext(
 				Localizer.getInstance().setLocale(base));
+		Localizer.getInstance().setLocale(this);
 	}
 
 	public ActivityComponent getActivityComponent() {

briar-android/src/main/java/org/briarproject/briar/android/blog/ReblogFragment.java

@@ -20,6 +20,7 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
+import org.briarproject.briar.android.view.TextSendController.SendState;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
 
 import java.util.List;
@@ -27,6 +28,9 @@ import java.util.List;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
 import static android.view.View.FOCUS_DOWN;
 import static android.view.View.GONE;
 import static android.view.View.INVISIBLE;
@@ -34,6 +38,7 @@ import static android.view.View.VISIBLE;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.activity.BriarActivity.GROUP_ID;
 import static org.briarproject.briar.android.blog.BasePostFragment.POST_ID;
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
 import static org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
@@ -121,8 +126,8 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+	public LiveData<SendState> onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers, long expectedAutoDeleteTimer) {
 		ui.input.hideSoftKeyboard();
 		feedController.repeatPost(item, text,
 				new UiExceptionHandler<DbException>(this) {
@@ -132,6 +137,7 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 					}
 				});
 		finish();
+		return new MutableLiveData<>(SENT);
 	}
 
 	private void showProgressBar() {

briar-android/src/main/java/org/briarproject/briar/android/blog/WriteBlogPostActivity.java

@@ -31,12 +31,16 @@ import java.util.logging.Logger;
 import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 
 import static android.view.View.GONE;
 import static android.view.View.VISIBLE;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
+import static org.briarproject.briar.android.view.TextSendController.SendState;
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
 import static org.briarproject.briar.api.blog.BlogConstants.MAX_BLOG_POST_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
@@ -112,8 +116,8 @@ public class WriteBlogPostActivity extends BriarActivity
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+	public LiveData<SendState> onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers, long expectedAutoDeleteTimer) {
 		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		// hide publish button, show progress bar
@@ -122,6 +126,7 @@ public class WriteBlogPostActivity extends BriarActivity
 		progressBar.setVisibility(VISIBLE);
 
 		storePost(text);
+		return new MutableLiveData<>(SENT);
 	}
 
 	private void storePost(String text) {

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListFragment.java

@@ -34,7 +34,6 @@ import io.github.kobakei.materialfabspeeddial.FabSpeedDial;
 import io.github.kobakei.materialfabspeeddial.FabSpeedDial.OnMenuItemClickListener;
 
 import static com.google.android.material.snackbar.BaseTransientBottomBar.LENGTH_INDEFINITE;
-import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
 
 @MethodsNotNullByDefault
@@ -102,7 +101,8 @@ public class ContactListFragment extends BaseFragment
 				.observe(getViewLifecycleOwner(), result -> {
 					result.onError(this::handleException).onSuccess(items -> {
 						adapter.submitList(items);
-						if (requireNonNull(items).size() == 0) list.showData();
+						// TODO remove when BriarRecyclerView was adapted
+						list.showData();
 					});
 				});
 		viewModel.getHasPendingContacts()

briar-android/src/main/java/org/briarproject/briar/android/contact/ContactListViewModel.java

@@ -45,8 +45,10 @@ import androidx.arch.core.util.Function;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
+import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 @NotNullByDefault
@@ -171,9 +173,14 @@ class ContactListViewModel extends DbViewModel implements EventListener {
 	}
 
 	void checkForPendingContacts() {
-		runOnDbThreadOrLogException(() -> {
-			boolean hasPending = !contactManager.getPendingContacts().isEmpty();
-			hasPendingContacts.postValue(hasPending);
+		runOnDbThread(() -> {
+			try {
+				boolean hasPending =
+						!contactManager.getPendingContacts().isEmpty();
+				hasPendingContacts.postValue(hasPending);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		});
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/AddContactViewModel.java

@@ -2,9 +2,12 @@ package org.briarproject.briar.android.contact.add.remote;
 
 import android.app.Application;
 
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.UnsupportedVersionException;
 import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.contact.PendingContact;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchPendingContactException;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
@@ -15,6 +18,7 @@ import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.LiveResult;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 
+import java.security.GeneralSecurityException;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -62,10 +66,15 @@ public class AddContactViewModel extends DbViewModel {
 	}
 
 	private void loadHandshakeLink() {
-		// If an exception is thrown the UI should stay disabled,
-		// leaving the user unable to proceed
-		runOnDbThreadOrLogException(() ->
-				handshakeLink.postValue(contactManager.getHandshakeLink()));
+		runOnDbThread(() -> {
+			try {
+				handshakeLink.postValue(contactManager.getHandshakeLink());
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				// the UI should stay disabled in this case,
+				// leaving the user unable to proceed
+			}
+		});
 	}
 
 	LiveData<String> getHandshakeLink() {
@@ -97,11 +106,17 @@ public class AddContactViewModel extends DbViewModel {
 	void addContact(String nickname) {
 		if (remoteHandshakeLink == null) throw new IllegalStateException();
 		runOnDbThread(() -> {
-			contactManager.addPendingContact(remoteHandshakeLink, nickname);
-			addContactResult.postValue(new LiveResult<>(true));
-		}, e -> {
-			logException(LOG, WARNING, e);
-			addContactResult.postValue(new LiveResult<>(e));
+			try {
+				contactManager.addPendingContact(remoteHandshakeLink, nickname);
+				addContactResult.postValue(new LiveResult<>(true));
+			} catch (UnsupportedVersionException e) {
+				logException(LOG, WARNING, e);
+				addContactResult.postValue(new LiveResult<>(e));
+			} catch (DbException | FormatException
+					| GeneralSecurityException e) {
+				logException(LOG, WARNING, e);
+				addContactResult.postValue(new LiveResult<>(e));
+			}
 		});
 	}
 
@@ -109,15 +124,15 @@ public class AddContactViewModel extends DbViewModel {
 		return addContactResult;
 	}
 
-	public void updatePendingContact(String name, PendingContact p) {
+	void updatePendingContact(String name, PendingContact p) {
 		runOnDbThread(() -> {
-			contactManager.removePendingContact(p.getId());
-			addContact(name);
-		}, e -> {
-			if (e instanceof NoSuchPendingContactException) {
+			try {
+				contactManager.removePendingContact(p.getId());
+				addContact(name);
+			} catch (NoSuchPendingContactException e) {
 				logException(LOG, WARNING, e);
 				// no error in UI as pending contact was converted into contact
-			} else {
+			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				addContactResult.postValue(new LiveResult<>(e));
 			}

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/NicknameFragment.java

@@ -29,11 +29,11 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import javax.annotation.Nullable;
 import javax.inject.Inject;
 
+import androidx.annotation.NonNull;
 import androidx.annotation.StringRes;
 import androidx.appcompat.app.AlertDialog.Builder;
 import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.ViewModelProvider;
-import androidx.lifecycle.ViewModelProviders;
 
 import static android.view.View.INVISIBLE;
 import static android.view.View.VISIBLE;
@@ -48,6 +48,7 @@ import static org.briarproject.briar.android.util.UiUtils.getDialogIcon;
 public class NicknameFragment extends BaseFragment {
 
 	private static final String TAG = NicknameFragment.class.getName();
+	private static final String SAVED_LINK = "savedLink";
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -67,6 +68,20 @@ public class NicknameFragment extends BaseFragment {
 	@Override
 	public void injectFragment(ActivityComponent component) {
 		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(AddContactViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		if (savedInstanceState != null) {
+			// When the activity (and the ViewModel) get destroyed,
+			// the link will not be available anymore and needs to be restored.
+			// TODO migrate to SavedStateViewModelFactory (once we can use it)
+			String savedLink = savedInstanceState.getString(SAVED_LINK);
+			if (savedLink != null) viewModel.setRemoteHandshakeLink(savedLink);
+		}
 	}
 
 	@Nullable
@@ -74,14 +89,9 @@ public class NicknameFragment extends BaseFragment {
 	public View onCreateView(LayoutInflater inflater,
 			@Nullable ViewGroup container,
 			@Nullable Bundle savedInstanceState) {
-		if (getActivity() == null || getContext() == null) return null;
-
 		View v = inflater.inflate(R.layout.fragment_nickname,
 				container, false);
 
-		viewModel = ViewModelProviders.of(getActivity(), viewModelFactory)
-				.get(AddContactViewModel.class);
-
 		contactNameLayout = v.findViewById(R.id.contactNameLayout);
 		contactNameInput = v.findViewById(R.id.contactNameInput);
 
@@ -93,6 +103,12 @@ public class NicknameFragment extends BaseFragment {
 		return v;
 	}
 
+	@Override
+	public void onSaveInstanceState(@NonNull Bundle outState) {
+		super.onSaveInstanceState(outState);
+		outState.putString(SAVED_LINK, viewModel.getRemoteHandshakeLink());
+	}
+
 	@Nullable
 	private String getNicknameOrNull() {
 		Editable text = contactNameInput.getText();

briar-android/src/main/java/org/briarproject/briar/android/contact/add/remote/PendingContactListViewModel.java

@@ -10,6 +10,7 @@ import org.briarproject.bramble.api.contact.PendingContactState;
 import org.briarproject.bramble.api.contact.event.PendingContactRemovedEvent;
 import org.briarproject.bramble.api.contact.event.PendingContactStateChangedEvent;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
@@ -32,8 +33,10 @@ import javax.inject.Inject;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
+import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.api.contact.PendingContactState.OFFLINE;
+import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
 public class PendingContactListViewModel extends DbViewModel
@@ -87,20 +90,24 @@ public class PendingContactListViewModel extends DbViewModel
 	}
 
 	private void loadPendingContacts() {
-		runOnDbThreadOrLogException(() -> {
-			Collection<Pair<PendingContact, PendingContactState>> pairs =
-					contactManager.getPendingContacts();
-			List<PendingContactItem> items = new ArrayList<>(pairs.size());
-			boolean online = pairs.isEmpty();
-			for (Pair<PendingContact, PendingContactState> pair : pairs) {
-				PendingContact p = pair.getFirst();
-				PendingContactState state = pair.getSecond();
-				long lastPoll = rendezvousPoller.getLastPollTime(p.getId());
-				items.add(new PendingContactItem(p, state, lastPoll));
-				online = online || state != OFFLINE;
+		runOnDbThread(() -> {
+			try {
+				Collection<Pair<PendingContact, PendingContactState>> pairs =
+						contactManager.getPendingContacts();
+				List<PendingContactItem> items = new ArrayList<>(pairs.size());
+				boolean online = pairs.isEmpty();
+				for (Pair<PendingContact, PendingContactState> pair : pairs) {
+					PendingContact p = pair.getFirst();
+					PendingContactState state = pair.getSecond();
+					long lastPoll = rendezvousPoller.getLastPollTime(p.getId());
+					items.add(new PendingContactItem(p, state, lastPoll));
+					online = online || state != OFFLINE;
+				}
+				pendingContacts.postValue(items);
+				hasInternetConnection.postValue(online);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
 			}
-			pendingContacts.postValue(items);
-			hasInternetConnection.postValue(online);
 		});
 	}
 
@@ -109,8 +116,13 @@ public class PendingContactListViewModel extends DbViewModel
 	}
 
 	void removePendingContact(PendingContactId id) {
-		runOnDbThreadOrLogException(() ->
-				contactManager.removePendingContact(id));
+		runOnDbThread(() -> {
+			try {
+				contactManager.removePendingContact(id);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
 	}
 
 	LiveData<Boolean> getHasInternetConnection() {

briar-android/src/main/java/org/briarproject/briar/android/conversation/AliasDialogFragment.java

@@ -31,6 +31,8 @@ import static org.briarproject.briar.android.util.UiUtils.showSoftKeyboard;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
+// TODO: we can probably switch to androidx DialogFragment here but need to
+//  test this properly
 public class AliasDialogFragment extends AppCompatDialogFragment {
 
 	final static String TAG = AliasDialogFragment.class.getName();

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.conversation;
 import android.annotation.SuppressLint;
 import android.content.DialogInterface;
 import android.content.Intent;
+import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.os.Parcelable;
 import android.transition.Slide;
@@ -49,6 +50,7 @@ import org.briarproject.briar.android.blog.BlogActivity;
 import org.briarproject.briar.android.conversation.ConversationVisitor.AttachmentCache;
 import org.briarproject.briar.android.conversation.ConversationVisitor.TextCache;
 import org.briarproject.briar.android.forum.ForumActivity;
+import org.briarproject.briar.android.fragment.BaseFragment.BaseFragmentListener;
 import org.briarproject.briar.android.introduction.IntroductionActivity;
 import org.briarproject.briar.android.privategroup.conversation.GroupActivity;
 import org.briarproject.briar.android.util.BriarSnackbarBuilder;
@@ -58,8 +60,10 @@ import org.briarproject.briar.android.view.TextAttachmentController;
 import org.briarproject.briar.android.view.TextAttachmentController.AttachmentListener;
 import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
+import org.briarproject.briar.android.view.TextSendController.SendState;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
+import org.briarproject.briar.api.autodelete.event.ConversationMessagesDeletedEvent;
 import org.briarproject.briar.api.blog.BlogSharingManager;
 import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
@@ -105,6 +109,7 @@ import androidx.recyclerview.selection.SelectionTracker.SelectionObserver;
 import androidx.recyclerview.selection.StorageStrategy;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
+import androidx.vectordrawable.graphics.drawable.VectorDrawableCompat;
 import de.hdodenhof.circleimageview.CircleImageView;
 import uk.co.samuelwall.materialtaptargetprompt.MaterialTapTargetPrompt;
 
@@ -136,12 +141,14 @@ import static org.briarproject.briar.android.util.UiUtils.observeOnce;
 import static org.briarproject.briar.android.view.AuthorView.setAvatar;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_ATTACHMENTS_PER_MESSAGE;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_PRIVATE_MESSAGE_TEXT_LENGTH;
+import static org.briarproject.briar.api.messaging.PrivateMessageFormat.TEXT_IMAGES_AUTO_DELETE;
+import static org.briarproject.briar.api.messaging.PrivateMessageFormat.TEXT_ONLY;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
 public class ConversationActivity extends BriarActivity
-		implements EventListener, ConversationListener, TextCache,
-		AttachmentCache, AttachmentListener, ActionMode.Callback {
+		implements BaseFragmentListener, EventListener, ConversationListener,
+		TextCache, AttachmentCache, AttachmentListener, ActionMode.Callback {
 
 	public static final String CONTACT_ID = "briar.CONTACT_ID";
 
@@ -266,15 +273,11 @@ public class ConversationActivity extends BriarActivity
 			ImagePreview imagePreview = findViewById(R.id.imagePreview);
 			sendController = new TextAttachmentController(textInputView,
 					imagePreview, this, viewModel);
-			viewModel.hasImageSupport().observe(this, new Observer<Boolean>() {
-				@Override
-				public void onChanged(@Nullable Boolean hasSupport) {
-					if (hasSupport != null && hasSupport) {
-						// TODO: remove cast when removing feature flag
-						((TextAttachmentController) sendController)
-								.setImagesSupported();
-						viewModel.hasImageSupport().removeObserver(this);
-					}
+			observeOnce(viewModel.getPrivateMessageFormat(), this, format -> {
+				if (format != TEXT_ONLY) {
+					// TODO: remove cast when removing feature flag
+					((TextAttachmentController) sendController)
+							.setImagesSupported();
 				}
 			});
 		} else {
@@ -284,6 +287,9 @@ public class ConversationActivity extends BriarActivity
 		textInputView.setMaxTextLength(MAX_PRIVATE_MESSAGE_TEXT_LENGTH);
 		textInputView.setReady(false);
 		textInputView.setOnKeyboardShownListener(this::scrollToBottom);
+
+		viewModel.getAutoDeleteTimer().observe(this, timer ->
+				sendController.setAutoDeleteTimer(timer));
 	}
 
 	private void scrollToBottom() {
@@ -367,6 +373,14 @@ public class ConversationActivity extends BriarActivity
 		// enable alias action if available
 		observeOnce(viewModel.getContactItem(), this, contact ->
 				menu.findItem(R.id.action_set_alias).setEnabled(true));
+		// Show auto-delete menu item if feature is enabled
+		if (featureFlags.shouldEnableDisappearingMessages()) {
+			MenuItem item = menu.findItem(R.id.action_conversation_settings);
+			item.setVisible(true);
+			// Enable menu item only if contact supports auto-delete
+			viewModel.getPrivateMessageFormat().observe(this, format ->
+					item.setEnabled(format == TEXT_IMAGES_AUTO_DELETE));
+		}
 
 		return super.onCreateOptionsMenu(menu);
 	}
@@ -388,6 +402,10 @@ public class ConversationActivity extends BriarActivity
 				AliasDialogFragment.newInstance().show(
 						getSupportFragmentManager(), AliasDialogFragment.TAG);
 				return true;
+			case R.id.action_conversation_settings:
+				if (contactId == null) return false;
+				onAutoDeleteTimerNoticeClicked();
+				return true;
 			case R.id.action_delete_all_messages:
 				askToDeleteAllMessages();
 				return true;
@@ -479,12 +497,10 @@ public class ConversationActivity extends BriarActivity
 	@UiThread
 	private void displayContactOnlineStatus() {
 		if (connectionRegistry.isConnected(contactId)) {
-			toolbarStatus.setImageDrawable(ContextCompat.getDrawable(
-					ConversationActivity.this, R.drawable.contact_online));
+			toolbarStatus.setImageResource(R.drawable.contact_online);
 			toolbarStatus.setContentDescription(getString(R.string.online));
 		} else {
-			toolbarStatus.setImageDrawable(ContextCompat.getDrawable(
-					ConversationActivity.this, R.drawable.contact_offline));
+			toolbarStatus.setImageResource(R.drawable.contact_offline);
 			toolbarStatus.setContentDescription(getString(R.string.offline));
 		}
 	}
@@ -559,7 +575,7 @@ public class ConversationActivity extends BriarActivity
 							this::showImageOnboarding);
 				}
 				List<ConversationItem> items = createItems(headers);
-				adapter.addAll(items);
+				adapter.replaceAll(items);
 				list.showData();
 				if (layoutManagerState == null) {
 					scrollToBottom();
@@ -640,8 +656,8 @@ public class ConversationActivity extends BriarActivity
 				supportFinishAfterTransition();
 			}
 		} else if (e instanceof ConversationMessageReceivedEvent) {
-			ConversationMessageReceivedEvent p =
-					(ConversationMessageReceivedEvent) e;
+			ConversationMessageReceivedEvent<?> p =
+					(ConversationMessageReceivedEvent<?>) e;
 			if (p.getContactId().equals(contactId)) {
 				LOG.info("Message received, adding");
 				onNewConversationMessage(p.getMessageHeader());
@@ -658,6 +674,13 @@ public class ConversationActivity extends BriarActivity
 				LOG.info("Messages acked");
 				markMessages(m.getMessageIds(), true, true);
 			}
+		} else if (e instanceof ConversationMessagesDeletedEvent) {
+			ConversationMessagesDeletedEvent m =
+					(ConversationMessagesDeletedEvent) e;
+			if (m.getContactId().equals(contactId)) {
+				LOG.info("Messages auto-deleted");
+				onConversationMessagesDeleted(m.getMessageIds());
+			}
 		} else if (e instanceof ContactConnectedEvent) {
 			ContactConnectedEvent c = (ContactConnectedEvent) e;
 			if (c.getContactId().equals(contactId)) {
@@ -705,6 +728,13 @@ public class ConversationActivity extends BriarActivity
 		}
 	}
 
+	@UiThread
+	private void onConversationMessagesDeleted(
+			Collection<MessageId> messageIds) {
+		adapter.incrementRevision();
+		adapter.removeItems(messageIds);
+	}
+
 	@UiThread
 	private void markMessages(Collection<MessageId> messageIds, boolean sent,
 			boolean seen) {
@@ -735,20 +765,13 @@ public class ConversationActivity extends BriarActivity
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text,
-			List<AttachmentHeader> attachmentHeaders) {
+	public LiveData<SendState> onSendClick(@Nullable String text,
+			List<AttachmentHeader> attachmentHeaders,
+			long expectedAutoDeleteTimer) {
 		if (isNullOrEmpty(text) && attachmentHeaders.isEmpty())
 			throw new AssertionError();
-		long timestamp = System.currentTimeMillis();
-		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
-		viewModel.sendMessage(text, attachmentHeaders, timestamp);
-		textInputView.clearText();
-	}
-
-	private long getMinTimestampForNewMessage() {
-		// Don't use an earlier timestamp than the newest message
-		ConversationItem item = adapter.getLastItem();
-		return item == null ? 0 : item.getTime() + 1;
+		return viewModel
+				.sendMessage(text, attachmentHeaders, expectedAutoDeleteTimer);
 	}
 
 	private void onAddedPrivateMessage(@Nullable PrivateMessageHeader h) {
@@ -823,10 +846,6 @@ public class ConversationActivity extends BriarActivity
 			fails.add(getString(
 					R.string.dialog_message_not_deleted_ongoing_invitations));
 		}
-		if (result.hasNotFullyDownloaded()) {
-			fails.add(getString(
-					R.string.dialog_message_not_deleted_partly_downloaded));
-		}
 		// add problems the user can resolve
 		if (result.hasNotAllIntroductionSelected() &&
 				result.hasNotAllInvitationSelected()) {
@@ -935,13 +954,16 @@ public class ConversationActivity extends BriarActivity
 			return;
 		}
 
+		int color =
+				ContextCompat.getColor(this, R.color.briar_primary);
+		Drawable drawable = VectorDrawableCompat
+				.create(getResources(), R.drawable.ic_more_vert_accent, null);
 		new MaterialTapTargetPrompt.Builder(ConversationActivity.this,
 				R.style.OnboardingDialogTheme).setTarget(target)
 				.setPrimaryText(R.string.introduction_onboarding_title)
 				.setSecondaryText(R.string.introduction_onboarding_text)
-				.setIcon(R.drawable.ic_more_vert_accent)
-				.setBackgroundColour(
-						ContextCompat.getColor(this, R.color.briar_primary))
+				.setIconDrawable(drawable)
+				.setBackgroundColour(color)
 				.show();
 	}
 
@@ -955,13 +977,11 @@ public class ConversationActivity extends BriarActivity
 			adapter.notifyItemChanged(position, item);
 		}
 		runOnDbThread(() -> {
-			long timestamp = System.currentTimeMillis();
-			timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
 			try {
 				switch (item.getRequestType()) {
 					case INTRODUCTION:
 						respondToIntroductionRequest(item.getSessionId(),
-								accept, timestamp);
+								accept);
 						break;
 					case FORUM:
 						respondToForumRequest(item.getSessionId(), accept);
@@ -1035,11 +1055,18 @@ public class ConversationActivity extends BriarActivity
 		ActivityCompat.startActivity(this, i, options.toBundle());
 	}
 
+	@Override
+	public void onAutoDeleteTimerNoticeClicked() {
+		ConversationSettingsDialog dialog =
+				ConversationSettingsDialog.newInstance(contactId);
+		dialog.show(getSupportFragmentManager(),
+				ConversationSettingsDialog.TAG);
+	}
+
 	@DatabaseExecutor
 	private void respondToIntroductionRequest(SessionId sessionId,
-			boolean accept, long time) throws DbException {
-		introductionManager.respondToIntroduction(contactId, sessionId, time,
-				accept);
+			boolean accept) throws DbException {
+		introductionManager.respondToIntroduction(contactId, sessionId, accept);
 	}
 
 	@DatabaseExecutor

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationAdapter.java

@@ -13,20 +13,26 @@ import org.briarproject.briar.R;
 import org.briarproject.briar.android.util.BriarAdapter;
 import org.briarproject.briar.android.util.ItemReturningAdapter;
 
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
 import androidx.annotation.LayoutRes;
 import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
 import androidx.recyclerview.selection.SelectionTracker;
 import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView.RecycledViewPool;
 
 import static androidx.recyclerview.widget.RecyclerView.NO_POSITION;
+import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
 
 @NotNullByDefault
 class ConversationAdapter
 		extends BriarAdapter<ConversationItem, ConversationItemViewHolder>
 		implements ItemReturningAdapter<ConversationItem> {
 
-	private ConversationListener listener;
+	private final ConversationListener listener;
 	private final RecycledViewPool imageViewPool;
 	private final ImageItemDecoration imageItemDecoration;
 	@Nullable
@@ -65,22 +71,20 @@ class ConversationAdapter
 			@LayoutRes int type) {
 		View v = LayoutInflater.from(viewGroup.getContext()).inflate(
 				type, viewGroup, false);
-		switch (type) {
-			case R.layout.list_item_conversation_msg_in:
-				return new ConversationMessageViewHolder(v, listener, true,
-						imageViewPool, imageItemDecoration);
-			case R.layout.list_item_conversation_msg_out:
-				return new ConversationMessageViewHolder(v, listener, false,
-						imageViewPool, imageItemDecoration);
-			case R.layout.list_item_conversation_notice_in:
-				return new ConversationNoticeViewHolder(v, listener, true);
-			case R.layout.list_item_conversation_notice_out:
-				return new ConversationNoticeViewHolder(v, listener, false);
-			case R.layout.list_item_conversation_request:
-				return new ConversationRequestViewHolder(v, listener, true);
-			default:
-				throw new IllegalArgumentException("Unknown ConversationItem");
+		if (type == R.layout.list_item_conversation_msg_in) {
+			return new ConversationMessageViewHolder(v, listener, true,
+					imageViewPool, imageItemDecoration);
+		} else if (type == R.layout.list_item_conversation_msg_out) {
+			return new ConversationMessageViewHolder(v, listener, false,
+					imageViewPool, imageItemDecoration);
+		} else if (type == R.layout.list_item_conversation_notice_in) {
+			return new ConversationNoticeViewHolder(v, listener, true);
+		} else if (type == R.layout.list_item_conversation_notice_out) {
+			return new ConversationNoticeViewHolder(v, listener, false);
+		} else if (type == R.layout.list_item_conversation_request) {
+			return new ConversationRequestViewHolder(v, listener, true);
 		}
+		throw new IllegalArgumentException("Unknown ConversationItem");
 	}
 
 	@Override
@@ -107,22 +111,65 @@ class ConversationAdapter
 		return c1.equals(c2);
 	}
 
+	@Override
+	public void add(ConversationItem item) {
+		items.beginBatchedUpdates();
+		items.add(item);
+		updateTimersInBatch();
+		items.endBatchedUpdates();
+	}
+
+	@Override
+	public void replaceAll(Collection<ConversationItem> itemsToReplace) {
+		items.beginBatchedUpdates();
+		// there can be items already in the adapter
+		// SortedList takes care of duplicates and detecting changed items
+		items.replaceAll(itemsToReplace);
+		updateTimersInBatch();
+		items.endBatchedUpdates();
+	}
+
+	@UiThread
+	void removeItems(Collection<MessageId> messageIds) {
+		// Collect all items to be deleted first
+		// and then delete them in one batched update.
+		// Deleting them right away would cause issues
+		// due to changing list positions.
+		List<ConversationItem> toRemove = new ArrayList<>(messageIds.size());
+		for (int i = 0; i < items.size(); i++) {
+			ConversationItem item = items.get(i);
+			if (messageIds.contains(item.getId())) toRemove.add(item);
+		}
+		items.beginBatchedUpdates();
+		for (ConversationItem item : toRemove) items.remove(item);
+		items.endBatchedUpdates();
+	}
+
+	private void updateTimersInBatch() {
+		long lastTimerIncoming = NO_AUTO_DELETE_TIMER;
+		long lastTimerOutgoing = NO_AUTO_DELETE_TIMER;
+		for (int i = 0; i < items.size(); i++) {
+			ConversationItem c = items.get(i);
+			boolean itemChanged;
+			boolean timerChanged;
+			if (c.isIncoming()) {
+				timerChanged = lastTimerIncoming != c.getAutoDeleteTimer();
+				lastTimerIncoming = c.getAutoDeleteTimer();
+			} else {
+				timerChanged = lastTimerOutgoing != c.getAutoDeleteTimer();
+				lastTimerOutgoing = c.getAutoDeleteTimer();
+			}
+			itemChanged = c.setTimerNoticeVisible(timerChanged);
+			if (itemChanged) items.updateItemAt(i, c);
+		}
+	}
+
 	void setSelectionTracker(SelectionTracker<String> tracker) {
 		this.tracker = tracker;
 	}
 
-	@Nullable
-	ConversationItem getLastItem() {
-		if (items.size() > 0) {
-			return items.get(items.size() - 1);
-		} else {
-			return null;
-		}
-	}
-
 	SparseArray<ConversationItem> getOutgoingMessages() {
 		SparseArray<ConversationItem> messages = new SparseArray<>();
-
 		for (int i = 0; i < items.size(); i++) {
 			ConversationItem item = items.get(i);
 			if (!item.isIncoming()) {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationItem.java

@@ -9,6 +9,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import androidx.annotation.LayoutRes;
+import androidx.lifecycle.LiveData;
 
 import static org.briarproject.bramble.util.StringUtils.toHexString;
 
@@ -22,20 +23,25 @@ abstract class ConversationItem {
 	protected String text;
 	private final MessageId id;
 	private final GroupId groupId;
-	private final long time;
+	private final long time, autoDeleteTimer;
 	private final boolean isIncoming;
-	private boolean read, sent, seen;
+	private final LiveData<String> contactName;
+	private boolean read, sent, seen, showTimerNotice;
 
-	ConversationItem(@LayoutRes int layoutRes, ConversationMessageHeader h) {
+	ConversationItem(@LayoutRes int layoutRes, ConversationMessageHeader h,
+			LiveData<String> contactName) {
 		this.layoutRes = layoutRes;
 		this.text = null;
 		this.id = h.getId();
 		this.groupId = h.getGroupId();
 		this.time = h.getTimestamp();
+		this.autoDeleteTimer = h.getAutoDeleteTimer();
 		this.read = h.isRead();
 		this.sent = h.isSent();
 		this.seen = h.isSeen();
 		this.isIncoming = !h.isLocal();
+		this.contactName = contactName;
+		this.showTimerNotice = false;
 	}
 
 	@LayoutRes
@@ -68,6 +74,10 @@ abstract class ConversationItem {
 		return time;
 	}
 
+	public long getAutoDeleteTimer() {
+		return autoDeleteTimer;
+	}
+
 	/**
 	 * Only useful for incoming messages.
 	 */
@@ -111,4 +121,25 @@ abstract class ConversationItem {
 		return isIncoming;
 	}
 
+	public LiveData<String> getContactName() {
+		return contactName;
+	}
+
+	/**
+	 * Set this to true when {@link #getAutoDeleteTimer()} has changed
+	 * since the last message from the same peer.
+	 *
+	 * @return true if the value was set, false if it was already set.
+	 */
+	boolean setTimerNoticeVisible(boolean visible) {
+		if (this.showTimerNotice != visible) {
+			this.showTimerNotice = visible;
+			return true;
+		}
+		return false;
+	}
+
+	boolean isTimerNoticeVisible() {
+		return showTimerNotice;
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationItemViewHolder.java

@@ -1,6 +1,8 @@
 package org.briarproject.briar.android.conversation;
 
+import android.content.Context;
 import android.view.View;
+import android.widget.ImageView;
 import android.widget.TextView;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
@@ -12,8 +14,12 @@ import androidx.annotation.UiThread;
 import androidx.constraintlayout.widget.ConstraintLayout;
 import androidx.recyclerview.widget.RecyclerView.ViewHolder;
 
+import static android.view.View.GONE;
+import static android.view.View.VISIBLE;
 import static org.briarproject.bramble.util.StringUtils.trim;
 import static org.briarproject.briar.android.util.UiUtils.formatDate;
+import static org.briarproject.briar.android.util.UiUtils.formatDuration;
+import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
 
 @UiThread
 @NotNullByDefault
@@ -24,8 +30,9 @@ abstract class ConversationItemViewHolder extends ViewHolder {
 	protected final ConstraintLayout layout;
 	@Nullable
 	private final OutItemViewHolder outViewHolder;
-	private final TextView text;
+	private final TextView topNotice, text;
 	protected final TextView time;
+	protected final ImageView bomb;
 	@Nullable
 	private String itemKey = null;
 
@@ -33,11 +40,13 @@ abstract class ConversationItemViewHolder extends ViewHolder {
 			boolean isIncoming) {
 		super(v);
 		this.listener = listener;
-		this.outViewHolder = isIncoming ? null : new OutItemViewHolder(v);
+		outViewHolder = isIncoming ? null : new OutItemViewHolder(v);
 		root = v;
+		topNotice = v.findViewById(R.id.topNotice);
 		layout = v.findViewById(R.id.layout);
 		text = v.findViewById(R.id.text);
 		time = v.findViewById(R.id.time);
+		bomb = v.findViewById(R.id.bomb);
 	}
 
 	@CallSuper
@@ -45,6 +54,8 @@ abstract class ConversationItemViewHolder extends ViewHolder {
 		itemKey = item.getKey();
 		root.setActivated(selected);
 
+		setTopNotice(item);
+
 		if (item.getText() != null) {
 			text.setText(trim(item.getText()));
 		}
@@ -52,6 +63,9 @@ abstract class ConversationItemViewHolder extends ViewHolder {
 		long timestamp = item.getTime();
 		time.setText(formatDate(time.getContext(), timestamp));
 
+		boolean showBomb = item.getAutoDeleteTimer() != NO_AUTO_DELETE_TIMER;
+		bomb.setVisibility(showBomb ? VISIBLE : GONE);
+
 		if (outViewHolder != null) outViewHolder.bind(item);
 	}
 
@@ -64,4 +78,35 @@ abstract class ConversationItemViewHolder extends ViewHolder {
 		return itemKey;
 	}
 
+	private void setTopNotice(ConversationItem item) {
+		if (item.isTimerNoticeVisible()) {
+			Context ctx = itemView.getContext();
+			topNotice.setVisibility(VISIBLE);
+			boolean enabled = item.getAutoDeleteTimer() != NO_AUTO_DELETE_TIMER;
+			String duration = enabled ?
+					formatDuration(ctx, item.getAutoDeleteTimer()) : "";
+			String tapToLearnMore = ctx.getString(R.string.tap_to_learn_more);
+			String text;
+			if (item.isIncoming()) {
+				String name = item.getContactName().getValue();
+				text = enabled ?
+						ctx.getString(R.string.auto_delete_msg_contact_enabled,
+								name, duration, tapToLearnMore) :
+						ctx.getString(R.string.auto_delete_msg_contact_disabled,
+								name, tapToLearnMore);
+			} else {
+				text = enabled ?
+						ctx.getString(R.string.auto_delete_msg_you_enabled,
+								duration, tapToLearnMore) :
+						ctx.getString(R.string.auto_delete_msg_you_disabled,
+								tapToLearnMore);
+			}
+			topNotice.setText(text);
+			topNotice.setOnClickListener(
+					v -> listener.onAutoDeleteTimerNoticeClicked());
+		} else {
+			topNotice.setVisibility(GONE);
+		}
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationListener.java

@@ -18,4 +18,6 @@ interface ConversationListener {
 	void onAttachmentClicked(View view, ConversationMessageItem messageItem,
 			AttachmentItem attachmentItem);
 
+	void onAutoDeleteTimerNoticeClicked();
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageItem.java

@@ -10,6 +10,7 @@ import javax.annotation.concurrent.NotThreadSafe;
 
 import androidx.annotation.LayoutRes;
 import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -18,8 +19,8 @@ class ConversationMessageItem extends ConversationItem {
 	private final List<AttachmentItem> attachments;
 
 	ConversationMessageItem(@LayoutRes int layoutRes, PrivateMessageHeader h,
-			List<AttachmentItem> attachments) {
-		super(layoutRes, h);
+			LiveData<String> contactName, List<AttachmentItem> attachments) {
+		super(layoutRes, h, contactName);
 		this.attachments = attachments;
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageViewHolder.java

@@ -1,5 +1,6 @@
 package org.briarproject.briar.android.conversation;
 
+import android.content.res.ColorStateList;
 import android.view.View;
 import android.view.ViewGroup;
 
@@ -14,6 +15,7 @@ import androidx.recyclerview.widget.RecyclerView.RecycledViewPool;
 
 import static androidx.constraintlayout.widget.ConstraintSet.WRAP_CONTENT;
 import static androidx.core.content.ContextCompat.getColor;
+import static androidx.core.widget.ImageViewCompat.setImageTintList;
 
 @UiThread
 @NotNullByDefault
@@ -84,6 +86,7 @@ class ConversationMessageViewHolder extends ConversationItemViewHolder {
 		if (item.getText() == null) {
 			statusLayout.setBackgroundResource(R.drawable.msg_status_bubble);
 			time.setTextColor(timeColorBubble);
+			setImageTintList(bomb, ColorStateList.valueOf(timeColorBubble));
 			constraintSet = imageConstraints;
 		} else {
 			resetStatusLayoutForText();
@@ -111,6 +114,7 @@ class ConversationMessageViewHolder extends ConversationItemViewHolder {
 		// also reset padding (the background drawable defines some)
 		statusLayout.setPadding(0, 0, 0, 0);
 		time.setTextColor(timeColor);
+		setImageTintList(bomb, ColorStateList.valueOf(timeColor));
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationNoticeItem.java

@@ -8,6 +8,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import androidx.annotation.LayoutRes;
+import androidx.lifecycle.LiveData;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -17,15 +18,15 @@ class ConversationNoticeItem extends ConversationItem {
 	private final String msgText;
 
 	ConversationNoticeItem(@LayoutRes int layoutRes, String text,
-			ConversationRequest r) {
-		super(layoutRes, r);
+			LiveData<String> contactName, ConversationRequest<?> r) {
+		super(layoutRes, r, contactName);
 		this.text = text;
 		this.msgText = r.getText();
 	}
 
 	ConversationNoticeItem(@LayoutRes int layoutRes, String text,
-			ConversationResponse r) {
-		super(layoutRes, r);
+			LiveData<String> contactName, ConversationResponse r) {
+		super(layoutRes, r, contactName);
 		this.text = text;
 		this.msgText = null;
 	}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationRequestItem.java

@@ -11,6 +11,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.NotThreadSafe;
 
 import androidx.annotation.LayoutRes;
+import androidx.lifecycle.LiveData;
 
 @NotThreadSafe
 @NotNullByDefault
@@ -26,14 +27,15 @@ class ConversationRequestItem extends ConversationNoticeItem {
 	private boolean answered;
 
 	ConversationRequestItem(@LayoutRes int layoutRes, String text,
-			RequestType type, ConversationRequest r) {
-		super(layoutRes, text, r);
+			LiveData<String> contactName, RequestType type,
+			ConversationRequest<?> r) {
+		super(layoutRes, text, contactName, r);
 		this.requestType = type;
 		this.sessionId = r.getSessionId();
 		this.answered = r.wasAnswered();
 		if (r instanceof InvitationRequest) {
 			this.requestedGroupId = ((Shareable) r.getNameable()).getId();
-			this.canBeOpened = ((InvitationRequest) r).canBeOpened();
+			this.canBeOpened = ((InvitationRequest<?>) r).canBeOpened();
 		} else {
 			this.requestedGroupId = null;
 			this.canBeOpened = false;

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationSettingsDialog.java

@@ -0,0 +1,123 @@
+package org.briarproject.briar.android.conversation;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.ActivityComponent;
+import org.briarproject.briar.android.fragment.BaseFragment;
+import org.briarproject.briar.android.widget.OnboardingFullDialogFragment;
+
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+import androidx.appcompat.widget.SwitchCompat;
+import androidx.appcompat.widget.Toolbar;
+import androidx.fragment.app.DialogFragment;
+import androidx.fragment.app.FragmentActivity;
+import androidx.lifecycle.ViewModelProvider;
+
+import static org.briarproject.briar.android.conversation.ConversationActivity.CONTACT_ID;
+import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
+
+@MethodsNotNullByDefault
+@ParametersNotNullByDefault
+public class ConversationSettingsDialog extends DialogFragment {
+
+	final static String TAG = ConversationSettingsDialog.class.getName();
+
+	private static final Logger LOG = Logger.getLogger(TAG);
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private ConversationViewModel viewModel;
+
+	static ConversationSettingsDialog newInstance(ContactId contactId) {
+		Bundle args = new Bundle();
+		args.putInt(CONTACT_ID, contactId.getInt());
+		ConversationSettingsDialog dialog = new ConversationSettingsDialog();
+		dialog.setArguments(args);
+		return dialog;
+	}
+
+	@Override
+	public void onAttach(Context context) {
+		super.onAttach(context);
+		injectFragment(((BaseFragment.BaseFragmentListener) context)
+				.getActivityComponent());
+	}
+
+	public void injectFragment(ActivityComponent component) {
+		component.inject(this);
+		viewModel = new ViewModelProvider(requireActivity(), viewModelFactory)
+				.get(ConversationViewModel.class);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setStyle(DialogFragment.STYLE_NO_FRAME,
+				R.style.BriarFullScreenDialogTheme);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_conversation_settings,
+				container, false);
+
+		Bundle args = requireArguments();
+		int id = args.getInt(CONTACT_ID, -1);
+		if (id == -1) throw new IllegalStateException();
+		ContactId contactId = new ContactId(id);
+
+		FragmentActivity activity = requireActivity();
+		viewModel = new ViewModelProvider(activity, viewModelFactory)
+				.get(ConversationViewModel.class);
+		viewModel.setContactId(contactId);
+
+		Toolbar toolbar = view.findViewById(R.id.toolbar);
+		toolbar.setNavigationOnClickListener(v -> dismiss());
+
+		SwitchCompat switchDisappearingMessages = view.findViewById(
+				R.id.switchDisappearingMessages);
+		switchDisappearingMessages.setOnCheckedChangeListener(
+				(button, value) -> viewModel.setAutoDeleteTimerEnabled(value));
+
+		Button buttonLearnMore =
+				view.findViewById(R.id.buttonLearnMore);
+		buttonLearnMore.setOnClickListener(e -> showLearnMoreDialog());
+
+		viewModel.getAutoDeleteTimer()
+				.observe(getViewLifecycleOwner(), timer -> {
+					LOG.info("Received auto delete timer: " + timer);
+					boolean disappearingMessages =
+							timer != NO_AUTO_DELETE_TIMER;
+					switchDisappearingMessages
+							.setChecked(disappearingMessages);
+					switchDisappearingMessages.setEnabled(true);
+				});
+
+		return view;
+	}
+
+	private void showLearnMoreDialog() {
+		OnboardingFullDialogFragment.newInstance(
+				R.string.disappearing_messages_title,
+				R.string.disappearing_messages_explanation_long
+		).show(getChildFragmentManager(), OnboardingFullDialogFragment.TAG);
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -10,6 +10,7 @@ import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
+import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
@@ -28,16 +29,22 @@ import org.briarproject.briar.android.attachment.AttachmentResult;
 import org.briarproject.briar.android.attachment.AttachmentRetriever;
 import org.briarproject.briar.android.contact.ContactItem;
 import org.briarproject.briar.android.util.UiUtils;
+import org.briarproject.briar.android.view.TextSendController.SendState;
 import org.briarproject.briar.android.viewmodel.DbViewModel;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
+import org.briarproject.briar.api.autodelete.AutoDeleteManager;
+import org.briarproject.briar.api.autodelete.UnexpectedTimerException;
+import org.briarproject.briar.api.autodelete.event.AutoDeleteTimerMirroredEvent;
 import org.briarproject.briar.api.avatar.event.AvatarUpdatedEvent;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.identity.AuthorInfo;
 import org.briarproject.briar.api.identity.AuthorManager;
 import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessage;
 import org.briarproject.briar.api.messaging.PrivateMessageFactory;
+import org.briarproject.briar.api.messaging.PrivateMessageFormat;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 import org.briarproject.briar.api.messaging.event.AttachmentReceivedEvent;
 
@@ -55,6 +62,7 @@ import androidx.lifecycle.MutableLiveData;
 
 import static androidx.lifecycle.Transformations.map;
 import static java.util.Objects.requireNonNull;
+import static java.util.logging.Level.INFO;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
@@ -62,6 +70,13 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
 import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
+import static org.briarproject.briar.android.view.TextSendController.SendState.ERROR;
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
+import static org.briarproject.briar.android.view.TextSendController.SendState.UNEXPECTED_TIMER;
+import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
+import static org.briarproject.briar.api.autodelete.AutoDeleteManager.DEFAULT_TIMER_DURATION;
+import static org.briarproject.briar.api.messaging.PrivateMessageFormat.TEXT_IMAGES;
+import static org.briarproject.briar.api.messaging.PrivateMessageFormat.TEXT_ONLY;
 
 @NotNullByDefault
 public class ConversationViewModel extends DbViewModel
@@ -84,6 +99,8 @@ public class ConversationViewModel extends DbViewModel
 	private final PrivateMessageFactory privateMessageFactory;
 	private final AttachmentRetriever attachmentRetriever;
 	private final AttachmentCreator attachmentCreator;
+	private final AutoDeleteManager autoDeleteManager;
+	private final ConversationManager conversationManager;
 
 	@Nullable
 	private ContactId contactId = null;
@@ -92,7 +109,7 @@ public class ConversationViewModel extends DbViewModel
 	private final LiveData<String> contactName = map(contactItem, c ->
 			UiUtils.getContactDisplayName(c.getContact()));
 	private final LiveData<GroupId> messagingGroupId;
-	private final MutableLiveData<Boolean> imageSupport =
+	private final MutableLiveData<PrivateMessageFormat> privateMessageFormat =
 			new MutableLiveData<>();
 	private final MutableLiveEvent<Boolean> showImageOnboarding =
 			new MutableLiveEvent<>();
@@ -100,8 +117,10 @@ public class ConversationViewModel extends DbViewModel
 			new MutableLiveEvent<>();
 	private final MutableLiveData<Boolean> showIntroductionAction =
 			new MutableLiveData<>();
-	private final MutableLiveData<Boolean> contactDeleted =
+	private final MutableLiveData<Long> autoDeleteTimer =
 			new MutableLiveData<>();
+	private final MutableLiveData<Boolean> contactDeleted =
+			new MutableLiveData<>(false);
 	private final MutableLiveEvent<PrivateMessageHeader> addedHeader =
 			new MutableLiveEvent<>();
 
@@ -118,7 +137,9 @@ public class ConversationViewModel extends DbViewModel
 			SettingsManager settingsManager,
 			PrivateMessageFactory privateMessageFactory,
 			AttachmentRetriever attachmentRetriever,
-			AttachmentCreator attachmentCreator) {
+			AttachmentCreator attachmentCreator,
+			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager) {
 		super(application, dbExecutor, lifecycleManager, db, androidExecutor);
 		this.db = db;
 		this.eventBus = eventBus;
@@ -129,10 +150,10 @@ public class ConversationViewModel extends DbViewModel
 		this.privateMessageFactory = privateMessageFactory;
 		this.attachmentRetriever = attachmentRetriever;
 		this.attachmentCreator = attachmentCreator;
+		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		messagingGroupId = map(contactItem, c ->
 				messagingManager.getContactGroup(c.getContact()).getId());
-		contactDeleted.setValue(false);
-
 		eventBus.addListener(this);
 	}
 
@@ -149,9 +170,14 @@ public class ConversationViewModel extends DbViewModel
 			AttachmentReceivedEvent a = (AttachmentReceivedEvent) e;
 			if (a.getContactId().equals(contactId)) {
 				LOG.info("Attachment received");
-				runOnDbThreadOrLogException(() -> attachmentRetriever
+				runOnDbThread(() -> attachmentRetriever
 						.loadAttachmentItem(a.getMessageId()));
 			}
+		} else if (e instanceof AutoDeleteTimerMirroredEvent) {
+			AutoDeleteTimerMirroredEvent a = (AutoDeleteTimerMirroredEvent) e;
+			if (a.getContactId().equals(contactId)) {
+				autoDeleteTimer.postValue(a.getNewTimer());
+			}
 		} else if (e instanceof AvatarUpdatedEvent) {
 			AvatarUpdatedEvent a = (AvatarUpdatedEvent) e;
 			if (a.getContactId().equals(contactId)) {
@@ -194,50 +220,49 @@ public class ConversationViewModel extends DbViewModel
 
 	private void loadContact(ContactId contactId) {
 		runOnDbThread(() -> {
-			long start = now();
-			Contact c = contactManager.getContact(contactId);
-			AuthorInfo authorInfo = authorManager.getAuthorInfo(c);
-			contactItem.postValue(new ContactItem(c, authorInfo));
-			logDuration(LOG, "Loading contact", start);
-			start = now();
-			checkFeaturesAndOnboarding(contactId);
-			logDuration(LOG, "Checking for image support", start);
-		}, e -> {
-			if (e instanceof NoSuchContactException) {
+			try {
+				long start = now();
+				Contact c = contactManager.getContact(contactId);
+				AuthorInfo authorInfo = authorManager.getAuthorInfo(c);
+				contactItem.postValue(new ContactItem(c, authorInfo));
+				logDuration(LOG, "Loading contact", start);
+				start = now();
+				long timer = db.transactionWithResult(true, txn ->
+						autoDeleteManager.getAutoDeleteTimer(txn, contactId));
+				autoDeleteTimer.postValue(timer);
+				logDuration(LOG, "Getting auto-delete timer", start);
+				start = now();
+				checkFeaturesAndOnboarding(contactId);
+				logDuration(LOG, "Checking for image support", start);
+			} catch (NoSuchContactException e) {
 				contactDeleted.postValue(true);
-			} else {
+			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 			}
 		});
 	}
 
 	void markMessageRead(GroupId g, MessageId m) {
-		runOnDbThreadOrLogException(() -> {
-			long start = now();
-			messagingManager.setReadFlag(g, m, true);
-			logDuration(LOG, "Marking read", start);
+		runOnDbThread(() -> {
+			try {
+				long start = now();
+				messagingManager.setReadFlag(g, m, true);
+				logDuration(LOG, "Marking read", start);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		});
 	}
 
 	void setContactAlias(String alias) {
-		runOnDbThreadOrLogException(() -> {
-			contactManager.setContactAlias(requireNonNull(contactId),
-					alias.isEmpty() ? null : alias);
-			loadContact(contactId);
-		});
-	}
-
-	@UiThread
-	void sendMessage(@Nullable String text,
-			List<AttachmentHeader> headers, long timestamp) {
-		// messagingGroupId is loaded with the contact
-		observeForeverOnce(messagingGroupId, groupId -> {
-			requireNonNull(groupId);
-			observeForeverOnce(imageSupport, hasImageSupport -> {
-				requireNonNull(hasImageSupport);
-				createMessage(groupId, text, headers, timestamp,
-						hasImageSupport);
-			});
+		runOnDbThread(() -> {
+			try {
+				contactManager.setContactAlias(requireNonNull(contactId),
+						alias.isEmpty() ? null : alias);
+				loadContact(contactId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		});
 	}
 
@@ -267,10 +292,12 @@ public class ConversationViewModel extends DbViewModel
 
 	@DatabaseExecutor
 	private void checkFeaturesAndOnboarding(ContactId c) throws DbException {
-		// check if images are supported
-		boolean imagesSupported = db.transactionWithResult(true, txn ->
-				messagingManager.contactSupportsImages(txn, c));
-		imageSupport.postValue(imagesSupported);
+		// check if images and auto-deletion are supported
+		PrivateMessageFormat format = db.transactionWithResult(true, txn ->
+				messagingManager.getContactMessageFormat(txn, c));
+		if (LOG.isLoggable(INFO))
+			LOG.info("PrivateMessageFormat loaded: " + format.name());
+		privateMessageFormat.postValue(format);
 
 		// check if introductions are supported
 		Collection<Contact> contacts = contactManager.getContacts();
@@ -279,7 +306,7 @@ public class ConversationViewModel extends DbViewModel
 
 		// we only show one onboarding dialog at a time
 		Settings settings = settingsManager.getSettings(SETTINGS_NAMESPACE);
-		if (imagesSupported &&
+		if (format != TEXT_ONLY &&
 				settings.getBoolean(SHOW_ONBOARDING_IMAGE, true)) {
 			onOnboardingShown(SHOW_ONBOARDING_IMAGE);
 			showImageOnboarding.postEvent(true);
@@ -298,38 +325,85 @@ public class ConversationViewModel extends DbViewModel
 	}
 
 	@UiThread
-	private void createMessage(GroupId groupId, @Nullable String text,
-			List<AttachmentHeader> headers, long timestamp,
-			boolean hasImageSupport) {
+	LiveData<SendState> sendMessage(@Nullable String text,
+			List<AttachmentHeader> headers, long expectedTimer) {
+		MutableLiveData<SendState> liveData = new MutableLiveData<>();
+		runOnDbThread(() -> {
+			try {
+				db.transaction(false, txn -> {
+					long start = now();
+					PrivateMessage m = createMessage(txn, text, headers,
+							expectedTimer);
+					messagingManager.addLocalMessage(txn, m);
+					logDuration(LOG, "Storing message", start);
+					Message message = m.getMessage();
+					PrivateMessageHeader h = new PrivateMessageHeader(
+							message.getId(), message.getGroupId(),
+							message.getTimestamp(), true, true, false, false,
+							m.hasText(), m.getAttachmentHeaders(),
+							m.getAutoDeleteTimer());
+					// TODO add text to cache when available here
+					MessageId id = message.getId();
+					txn.attach(() -> {
+						attachmentCreator.onAttachmentsSent(id);
+						liveData.setValue(SENT);
+						addedHeader.setEvent(h);
+					});
+				});
+			} catch (UnexpectedTimerException e) {
+				liveData.postValue(UNEXPECTED_TIMER);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				liveData.postValue(ERROR);
+			}
+		});
+		return liveData;
+	}
+
+	private PrivateMessage createMessage(Transaction txn, @Nullable String text,
+			List<AttachmentHeader> headers, long expectedTimer)
+			throws DbException {
+		// Sending is only possible (setReady(true)) after loading all messages
+		// which happens after the contact has been loaded.
+		// privateMessageFormat is loaded together with contact
+		Contact contact = requireNonNull(contactItem.getValue()).getContact();
+		GroupId groupId = messagingManager.getContactGroup(contact).getId();
+		PrivateMessageFormat format =
+				requireNonNull(privateMessageFormat.getValue());
+		long timestamp = conversationManager
+				.getTimestampForOutgoingMessage(txn, requireNonNull(contactId));
 		try {
-			PrivateMessage pm;
-			if (hasImageSupport) {
-				pm = privateMessageFactory.createPrivateMessage(groupId,
+			if (format == TEXT_ONLY) {
+				return privateMessageFactory.createLegacyPrivateMessage(
+						groupId, timestamp, requireNonNull(text));
+			} else if (format == TEXT_IMAGES) {
+				return privateMessageFactory.createPrivateMessage(groupId,
 						timestamp, text, headers);
 			} else {
-				pm = privateMessageFactory.createLegacyPrivateMessage(
-						groupId, timestamp, requireNonNull(text));
+				long timer = autoDeleteManager
+						.getAutoDeleteTimer(txn, contactId, timestamp);
+				if (timer != expectedTimer)
+					throw new UnexpectedTimerException();
+				return privateMessageFactory.createPrivateMessage(groupId,
+						timestamp, text, headers, timer);
 			}
-			storeMessage(pm);
 		} catch (FormatException e) {
 			throw new AssertionError(e);
 		}
 	}
 
-	@UiThread
-	private void storeMessage(PrivateMessage m) {
-		attachmentCreator.onAttachmentsSent(m.getMessage().getId());
-		runOnDbThreadOrLogException(() -> {
-			long start = now();
-			messagingManager.addLocalMessage(m);
-			logDuration(LOG, "Storing message", start);
-			Message message = m.getMessage();
-			PrivateMessageHeader h = new PrivateMessageHeader(
-					message.getId(), message.getGroupId(),
-					message.getTimestamp(), true, true, false, false,
-					m.hasText(), m.getAttachmentHeaders());
-			// TODO add text to cache when available here
-			addedHeader.postEvent(h);
+	void setAutoDeleteTimerEnabled(boolean enabled) {
+		long timer = enabled ? DEFAULT_TIMER_DURATION : NO_AUTO_DELETE_TIMER;
+		// ContactId is set before menu gets inflated and UI interaction
+		final ContactId c = requireNonNull(contactId);
+		runOnDbThread(() -> {
+			try {
+				db.transaction(false, txn ->
+						autoDeleteManager.setAutoDeleteTimer(txn, c, timer));
+				autoDeleteTimer.postValue(timer);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		});
 	}
 
@@ -345,8 +419,8 @@ public class ConversationViewModel extends DbViewModel
 		return contactName;
 	}
 
-	LiveData<Boolean> hasImageSupport() {
-		return imageSupport;
+	LiveData<PrivateMessageFormat> getPrivateMessageFormat() {
+		return privateMessageFormat;
 	}
 
 	LiveEvent<Boolean> showImageOnboarding() {
@@ -361,6 +435,10 @@ public class ConversationViewModel extends DbViewModel
 		return showIntroductionAction;
 	}
 
+	LiveData<Long> getAutoDeleteTimer() {
+		return autoDeleteTimer;
+	}
+
 	LiveData<Boolean> isContactDeleted() {
 		return contactDeleted;
 	}
@@ -371,7 +449,12 @@ public class ConversationViewModel extends DbViewModel
 
 	@UiThread
 	void recheckFeaturesAndOnboarding(ContactId contactId) {
-		runOnDbThreadOrLogException(() ->
-				checkFeaturesAndOnboarding(contactId));
+		runOnDbThread(() -> {
+			try {
+				checkFeaturesAndOnboarding(contactId);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationVisitor.java

@@ -60,10 +60,12 @@ class ConversationVisitor implements
 		}
 		if (h.isLocal()) {
 			item = new ConversationMessageItem(
-					R.layout.list_item_conversation_msg_out, h, attachments);
+					R.layout.list_item_conversation_msg_out, h, contactName,
+					attachments);
 		} else {
 			item = new ConversationMessageItem(
-					R.layout.list_item_conversation_msg_in, h, attachments);
+					R.layout.list_item_conversation_msg_in, h, contactName,
+					attachments);
 		}
 		if (h.hasText()) {
 			String text = textCache.getText(h.getId());
@@ -79,13 +81,15 @@ class ConversationVisitor implements
 			String text = ctx.getString(R.string.blogs_sharing_invitation_sent,
 					r.getName(), contactName.getValue());
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text = ctx.getString(
 					R.string.blogs_sharing_invitation_received,
 					contactName.getValue(), r.getName());
 			return new ConversationRequestItem(
-					R.layout.list_item_conversation_request, text, BLOG, r);
+					R.layout.list_item_conversation_request, text, contactName,
+					BLOG, r);
 		}
 	}
 
@@ -98,13 +102,18 @@ class ConversationVisitor implements
 				text = ctx.getString(
 						R.string.blogs_sharing_response_accepted_sent,
 						contactName.getValue());
+			} else if (r.isAutoDecline()) {
+				text = ctx.getString(
+						R.string.blogs_sharing_response_declined_auto,
+						contactName.getValue());
 			} else {
 				text = ctx.getString(
 						R.string.blogs_sharing_response_declined_sent,
 						contactName.getValue());
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text;
 			if (r.wasAccepted()) {
@@ -117,7 +126,8 @@ class ConversationVisitor implements
 						contactName.getValue());
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_in, text, r);
+					R.layout.list_item_conversation_notice_in, text,
+					contactName, r);
 		}
 	}
 
@@ -128,13 +138,15 @@ class ConversationVisitor implements
 			String text = ctx.getString(R.string.forum_invitation_sent,
 					r.getName(), contactName.getValue());
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text = ctx.getString(
 					R.string.forum_invitation_received,
 					contactName.getValue(), r.getName());
 			return new ConversationRequestItem(
-					R.layout.list_item_conversation_request, text, FORUM, r);
+					R.layout.list_item_conversation_request, text, contactName,
+					FORUM, r);
 		}
 	}
 
@@ -147,13 +159,18 @@ class ConversationVisitor implements
 				text = ctx.getString(
 						R.string.forum_invitation_response_accepted_sent,
 						contactName.getValue());
+			} else if (r.isAutoDecline()) {
+				text = ctx.getString(
+						R.string.forum_invitation_response_declined_auto,
+						contactName.getValue());
 			} else {
 				text = ctx.getString(
 						R.string.forum_invitation_response_declined_sent,
 						contactName.getValue());
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text;
 			if (r.wasAccepted()) {
@@ -166,7 +183,8 @@ class ConversationVisitor implements
 						contactName.getValue());
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_in, text, r);
+					R.layout.list_item_conversation_notice_in, text,
+					contactName, r);
 		}
 	}
 
@@ -178,13 +196,15 @@ class ConversationVisitor implements
 					R.string.groups_invitations_invitation_sent,
 					contactName.getValue(), r.getName());
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text = ctx.getString(
 					R.string.groups_invitations_invitation_received,
 					contactName.getValue(), r.getName());
 			return new ConversationRequestItem(
-					R.layout.list_item_conversation_request, text, GROUP, r);
+					R.layout.list_item_conversation_request, text, contactName,
+					GROUP, r);
 		}
 	}
 
@@ -197,13 +217,18 @@ class ConversationVisitor implements
 				text = ctx.getString(
 						R.string.groups_invitations_response_accepted_sent,
 						contactName.getValue());
+			} else if (r.isAutoDecline()) {
+				text = ctx.getString(
+						R.string.groups_invitations_response_declined_auto,
+						contactName.getValue());
 			} else {
 				text = ctx.getString(
 						R.string.groups_invitations_response_declined_sent,
 						contactName.getValue());
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text;
 			if (r.wasAccepted()) {
@@ -216,7 +241,8 @@ class ConversationVisitor implements
 						contactName.getValue());
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_in, text, r);
+					R.layout.list_item_conversation_notice_in, text,
+					contactName, r);
 		}
 	}
 
@@ -227,7 +253,8 @@ class ConversationVisitor implements
 			String text = ctx.getString(R.string.introduction_request_sent,
 					contactName.getValue(), name);
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text;
 			if (r.wasAnswered()) {
@@ -243,7 +270,7 @@ class ConversationVisitor implements
 						contactName.getValue(), name);
 			}
 			return new ConversationRequestItem(
-					R.layout.list_item_conversation_request, text,
+					R.layout.list_item_conversation_request, text, contactName,
 					INTRODUCTION, r);
 		}
 	}
@@ -262,13 +289,18 @@ class ConversationVisitor implements
 				text = ctx.getString(
 						R.string.introduction_response_accepted_sent,
 						introducedAuthor) + suffix;
+			} else if (r.isAutoDecline()) {
+				text = ctx.getString(
+						R.string.introduction_response_declined_auto,
+						introducedAuthor);
 			} else {
 				text = ctx.getString(
 						R.string.introduction_response_declined_sent,
 						introducedAuthor);
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_out, text, r);
+					R.layout.list_item_conversation_notice_out, text,
+					contactName, r);
 		} else {
 			String text;
 			if (r.wasAccepted()) {
@@ -288,7 +320,8 @@ class ConversationVisitor implements
 						introducedAuthor);
 			}
 			return new ConversationNoticeItem(
-					R.layout.list_item_conversation_notice_in, text, r);
+					R.layout.list_item_conversation_notice_in, text,
+					contactName, r);
 		}
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewModel.java

@@ -6,6 +6,7 @@ import android.net.Uri;
 import android.view.View;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.Event;
 import org.briarproject.bramble.api.event.EventBus;
@@ -197,12 +198,14 @@ public class ImageViewModel extends DbViewModel implements EventListener {
 	private void saveImage(AttachmentItem attachment, OutputStreamProvider osp,
 			@Nullable Runnable afterCopy) {
 		runOnDbThread(() -> {
-			Attachment a =
-					attachmentReader.getAttachment(attachment.getHeader());
-			copyImageFromDb(a, osp, afterCopy);
-		}, e -> {
-			logException(LOG, WARNING, e);
-			saveState.postEvent(true);
+			try {
+				Attachment a =
+						attachmentReader.getAttachment(attachment.getHeader());
+				copyImageFromDb(a, osp, afterCopy);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+				saveState.postEvent(true);
+			}
 		});
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumActivity.java

@@ -79,12 +79,6 @@ public class ForumActivity extends
 		}
 	}
 
-	@Override
-	public void onStart() {
-		super.onStart();
-		viewModel.clearForumPostNotification();
-	}
-
 	@Override
 	protected void onActivityResult(int request, int result,
 			@Nullable Intent data) {
@@ -109,16 +103,16 @@ public class ForumActivity extends
 		// Handle presses on the action bar items
 		int itemId = item.getItemId();
 		if (itemId == R.id.action_forum_share) {
-			Intent i2 = new Intent(this, ShareForumActivity.class);
-			i2.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-			i2.putExtra(GROUP_ID, groupId.getBytes());
-			startActivityForResult(i2, REQUEST_SHARE_FORUM);
+			Intent i = new Intent(this, ShareForumActivity.class);
+			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			i.putExtra(GROUP_ID, groupId.getBytes());
+			startActivityForResult(i, REQUEST_SHARE_FORUM);
 			return true;
 		} else if (itemId == R.id.action_forum_sharing_status) {
-			Intent i3 = new Intent(this, ForumSharingStatusActivity.class);
-			i3.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
-			i3.putExtra(GROUP_ID, groupId.getBytes());
-			startActivity(i3);
+			Intent i = new Intent(this, ForumSharingStatusActivity.class);
+			i.setFlags(FLAG_ACTIVITY_CLEAR_TOP);
+			i.putExtra(GROUP_ID, groupId.getBytes());
+			startActivity(i);
 			return true;
 		} else if (itemId == R.id.action_forum_delete) {
 			showUnsubscribeDialog();

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumListViewModel.java

@@ -40,8 +40,10 @@ import androidx.annotation.UiThread;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 
+import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 import static org.briarproject.briar.api.forum.ForumManager.CLIENT_ID;
 
@@ -162,11 +164,15 @@ class ForumListViewModel extends DbViewModel implements EventListener {
 	}
 
 	void loadForumInvitations() {
-		runOnDbThreadOrLogException(() -> {
-			long start = now();
-			int available = forumSharingManager.getInvitations().size();
-			logDuration(LOG, "Loading available", start);
-			numInvitations.postValue(available);
+		runOnDbThread(() -> {
+			try {
+				long start = now();
+				int available = forumSharingManager.getInvitations().size();
+				logDuration(LOG, "Loading available", start);
+				numInvitations.postValue(available);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		});
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/forum/ForumViewModel.java

@@ -26,7 +26,6 @@ import org.briarproject.briar.android.threaded.ThreadListViewModel;
 import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.MessageTracker.GroupCount;
-import org.briarproject.briar.api.client.PostHeader;
 import org.briarproject.briar.api.forum.Forum;
 import org.briarproject.briar.api.forum.ForumInvitationResponse;
 import org.briarproject.briar.api.forum.ForumManager;
@@ -51,8 +50,10 @@ import androidx.lifecycle.MutableLiveData;
 
 import static android.widget.Toast.LENGTH_SHORT;
 import static java.lang.Math.max;
+import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
+import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
 
 @MethodsNotNullByDefault
@@ -92,8 +93,9 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 			ForumPostReceivedEvent f = (ForumPostReceivedEvent) e;
 			if (f.getGroupId().equals(groupId)) {
 				LOG.info("Forum post received, adding...");
-				ForumPostItem item = buildItem(f.getHeader(), f.getText());
-				addItem(item);
+				ForumPostItem item =
+						new ForumPostItem(f.getHeader(), f.getText());
+				addItem(item, false);
 			}
 		} else if (e instanceof ForumInvitationResponseReceivedEvent) {
 			ForumInvitationResponseReceivedEvent f =
@@ -114,14 +116,20 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 		}
 	}
 
-	void clearForumPostNotification() {
+	protected void clearNotifications() {
 		notificationManager.clearForumPostNotification(groupId);
 	}
 
 	LiveData<Forum> loadForum() {
 		MutableLiveData<Forum> forum = new MutableLiveData<>();
-		runOnDbThreadOrLogException(() ->
-				forum.postValue(forumManager.getForum(groupId)));
+		runOnDbThread(() -> {
+			try {
+				Forum f = forumManager.getForum(groupId);
+				forum.postValue(f);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
 		return forum;
 	}
 
@@ -132,19 +140,35 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 			List<ForumPostHeader> headers =
 					forumManager.getPostHeaders(txn, groupId);
 			logDuration(LOG, "Loading headers", start);
-			return createItems(txn, headers, this::buildItem);
+			start = now();
+			List<ForumPostItem> items = new ArrayList<>();
+			for (ForumPostHeader header : headers) {
+				items.add(loadItem(txn, header));
+			}
+			logDuration(LOG, "Loading bodies and creating items", start);
+			return items;
 		}, this::setItems);
 	}
 
+	private ForumPostItem loadItem(Transaction txn, ForumPostHeader header)
+			throws DbException {
+		String text = forumManager.getPostText(txn, header.getId());
+		return new ForumPostItem(header, text);
+	}
+
 	@Override
 	public void createAndStoreMessage(String text,
 			@Nullable MessageId parentId) {
-		runOnDbThreadOrLogException(() -> {
-			LocalAuthor author = identityManager.getLocalAuthor();
-			GroupCount count = forumManager.getGroupCount(groupId);
-			long timestamp = max(count.getLatestMsgTime() + 1,
-					clock.currentTimeMillis());
-			createMessage(text, timestamp, parentId, author);
+		runOnDbThread(() -> {
+			try {
+				LocalAuthor author = identityManager.getLocalAuthor();
+				GroupCount count = forumManager.getGroupCount(groupId);
+				long timestamp = max(count.getLatestMsgTime() + 1,
+						clock.currentTimeMillis());
+				createMessage(text, timestamp, parentId, author);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
 		});
 	}
 
@@ -159,43 +183,47 @@ class ForumViewModel extends ThreadListViewModel<ForumPostItem> {
 	}
 
 	private void storePost(ForumPost msg, String text) {
-		runOnDbThreadOrLogException(() -> {
+		runOnDbThread(false, txn -> {
 			long start = now();
-			ForumPostHeader header = forumManager.addLocalPost(msg);
-			addItemAsync(buildItem(header, text));
+			ForumPostHeader header = forumManager.addLocalPost(txn, msg);
 			logDuration(LOG, "Storing forum post", start);
-		});
-	}
-
-	private ForumPostItem buildItem(ForumPostHeader header, String text) {
-		return new ForumPostItem(header, text);
-	}
-
-	@Override
-	protected String loadMessageText(Transaction txn, PostHeader header)
-			throws DbException {
-		return forumManager.getPostText(txn, header.getId());
+			txn.attach(() -> {
+				ForumPostItem item = new ForumPostItem(header, text);
+				addItem(item, true);
+			});
+		}, e -> logException(LOG, WARNING, e));
 	}
 
 	@Override
 	protected void markItemRead(ForumPostItem item) {
-		runOnDbThreadOrLogException(() ->
-				forumManager.setReadFlag(groupId, item.getId(), true));
+		runOnDbThread(() -> {
+			try {
+				forumManager.setReadFlag(groupId, item.getId(), true);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
 	}
 
 	public void loadSharingContacts() {
-		runOnDbThreadOrLogException(true, txn -> {
+		runOnDbThread(true, txn -> {
 			Collection<Contact> contacts =
 					forumSharingManager.getSharedWith(txn, groupId);
 			Collection<ContactId> contactIds = new ArrayList<>(contacts.size());
 			for (Contact c : contacts) contactIds.add(c.getId());
 			txn.attach(() -> sharingController.addAll(contactIds));
-		});
+		}, e -> logException(LOG, WARNING, e));
 	}
 
 	void deleteForum() {
-		runOnDbThreadOrLogException(() ->
-				forumManager.removeForum(forumManager.getForum(groupId)));
+		runOnDbThread(() -> {
+			try {
+				Forum f = forumManager.getForum(groupId);
+				forumManager.removeForum(f);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
 		Toast.makeText(getApplication(), R.string.forum_left_toast,
 				LENGTH_SHORT).show();
 	}

briar-android/src/main/java/org/briarproject/briar/android/fragment/BaseFragment.java

@@ -10,9 +10,8 @@ import org.briarproject.bramble.api.nullsafety.ParametersNotNullByDefault;
 import org.briarproject.briar.android.DestroyableContext;
 import org.briarproject.briar.android.activity.ActivityComponent;
 
-import javax.annotation.Nullable;
-
 import androidx.annotation.CallSuper;
+import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentActivity;
@@ -47,13 +46,11 @@ public abstract class BaseFragment extends Fragment
 
 	@Override
 	public boolean onOptionsItemSelected(MenuItem item) {
-		switch (item.getItemId()) {
-			case android.R.id.home:
-				listener.onBackPressed();
-				return true;
-			default:
-				return super.onOptionsItemSelected(item);
+		if (item.getItemId() == android.R.id.home) {
+			requireActivity().onBackPressed();
+			return true;
 		}
+		return super.onOptionsItemSelected(item);
 	}
 
 	@UiThread
@@ -79,6 +76,7 @@ public abstract class BaseFragment extends Fragment
 		void handleException(Exception e);
 	}
 
+	@Deprecated
 	@CallSuper
 	@Override
 	public void runOnUiThreadUnlessDestroyed(Runnable r) {

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -35,6 +35,8 @@ import javax.inject.Inject;
 
 import androidx.annotation.Nullable;
 import androidx.appcompat.app.ActionBar;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 import de.hdodenhof.circleimageview.CircleImageView;
 
 import static android.app.Activity.RESULT_OK;
@@ -46,6 +48,8 @@ import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.briar.android.util.UiUtils.getContactDisplayName;
 import static org.briarproject.briar.android.util.UiUtils.hideSoftKeyboard;
 import static org.briarproject.briar.android.view.AuthorView.setAvatar;
+import static org.briarproject.briar.android.view.TextSendController.SendState;
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
 import static org.briarproject.briar.api.introduction.IntroductionConstants.MAX_INTRODUCTION_TEXT_LENGTH;
 
 @MethodsNotNullByDefault
@@ -201,8 +205,8 @@ public class IntroductionMessageFragment extends BaseFragment
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+	public LiveData<SendState> onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers, long expectedAutoDeleteTimer) {
 		// disable button to prevent accidental double invitations
 		ui.message.setReady(false);
 
@@ -212,6 +216,7 @@ public class IntroductionMessageFragment extends BaseFragment
 		hideSoftKeyboard(ui.message);
 		introductionActivity.setResult(RESULT_OK);
 		introductionActivity.supportFinishAfterTransition();
+		return new MutableLiveData<>(SENT);
 	}
 
 	private void makeIntroduction(Contact c1, Contact c2,
@@ -219,8 +224,7 @@ public class IntroductionMessageFragment extends BaseFragment
 		introductionActivity.runOnDbThread(() -> {
 			// actually make the introduction
 			try {
-				long timestamp = System.currentTimeMillis();
-				introductionManager.makeIntroduction(c1, c2, text, timestamp);
+				introductionManager.makeIntroduction(c1, c2, text);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				introductionError();

briar-android/src/main/java/org/briarproject/briar/android/keyagreement/KeyAgreementActivity.java

@@ -411,6 +411,8 @@ public abstract class KeyAgreementActivity extends BriarActivity implements
 	@UiThread
 	public void onRequestPermissionsResult(int requestCode,
 			String[] permissions, int[] grantResults) {
+		super.onRequestPermissionsResult(requestCode, permissions,
+				grantResults);
 		if (requestCode != REQUEST_PERMISSION_CAMERA_LOCATION)
 			throw new AssertionError();
 		if (gotPermission(CAMERA, permissions, grantResults)) {

briar-android/src/main/java/org/briarproject/briar/android/logging/BriefLogFormatter.java

@@ -4,6 +4,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
+import java.util.Collection;
 import java.util.Date;
 import java.util.TimeZone;
 import java.util.logging.Formatter;
@@ -17,6 +18,16 @@ import static java.util.Locale.US;
 @NotNullByDefault
 public class BriefLogFormatter extends Formatter {
 
+	public static String formatLog(Formatter formatter,
+			Collection<LogRecord> logRecords) {
+		StringBuilder sb = new StringBuilder();
+		for (LogRecord record : logRecords) {
+			String formatted = formatter.format(record);
+			sb.append(formatted).append('\n');
+		}
+		return sb.toString();
+	}
+
 	private final Object lock = new Object();
 	private final DateFormat dateFormat; // Locking: lock
 	private final Date date; // Locking: lock

briar-android/src/main/java/org/briarproject/briar/android/logging/CachingLogHandler.java

@@ -21,6 +21,10 @@ public class CachingLogHandler extends Handler {
 	// Locking: lock
 	private final Queue<LogRecord> recent = new LinkedList<>();
 
+	// package-private constructor
+	CachingLogHandler() {
+	}
+
 	@Override
 	public void publish(LogRecord record) {
 		synchronized (lock) {

briar-android/src/main/java/org/briarproject/briar/android/logging/LogDecrypter.java

@@ -0,0 +1,16 @@
+package org.briarproject.briar.android.logging;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.AndroidUtils;
+
+import androidx.annotation.Nullable;
+
+@NotNullByDefault
+public interface LogDecrypter {
+	/**
+	 * Returns decrypted log records from {@link AndroidUtils#getLogcatFile}
+	 * or null if there was an error reading the logs.
+	 */
+	@Nullable
+	String decryptLogs(@Nullable byte[] logKey);
+}

briar-android/src/main/java/org/briarproject/briar/android/logging/LogDecrypterImpl.java

@@ -0,0 +1,61 @@
+package org.briarproject.briar.android.logging;
+
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.reporting.DevConfig;
+import org.briarproject.bramble.api.transport.StreamReaderFactory;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Scanner;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@NotNullByDefault
+class LogDecrypterImpl implements LogDecrypter {
+
+	private static final Logger LOG =
+			getLogger(LogDecrypterImpl.class.getName());
+
+	private final DevConfig devConfig;
+	private final StreamReaderFactory streamReaderFactory;
+
+	@Inject
+	LogDecrypterImpl(DevConfig devConfig,
+			StreamReaderFactory streamReaderFactory) {
+		this.devConfig = devConfig;
+		this.streamReaderFactory = streamReaderFactory;
+	}
+
+	@Nullable
+	@Override
+	public String decryptLogs(@Nullable byte[] logKey) {
+		if (logKey == null) return null;
+		SecretKey key = new SecretKey(logKey);
+		File logFile = devConfig.getLogcatFile();
+		try (InputStream in = new FileInputStream(logFile)) {
+			InputStream reader =
+					streamReaderFactory.createLogStreamReader(in, key);
+			Scanner s = new Scanner(reader);
+			StringBuilder sb = new StringBuilder();
+			while (s.hasNextLine()) sb.append(s.nextLine()).append("\n");
+			s.close();
+			return sb.toString();
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			return null;
+		} finally {
+			//noinspection ResultOfMethodCallIgnored
+			logFile.delete();
+		}
+	}
+}

briar-android/src/main/java/org/briarproject/briar/android/logging/LogEncrypter.java

@@ -0,0 +1,16 @@
+package org.briarproject.briar.android.logging;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.util.AndroidUtils;
+
+import androidx.annotation.Nullable;
+
+@NotNullByDefault
+public interface LogEncrypter {
+	/**
+	 * Writes encrypted log records to {@link AndroidUtils#getLogcatFile}
+	 * and returns the encryption key if everything went fine.
+	 */
+	@Nullable
+	byte[] encryptLogs();
+}

briar-android/src/main/java/org/briarproject/briar/android/logging/LogEncrypterImpl.java

@@ -0,0 +1,77 @@
+package org.briarproject.briar.android.logging;
+
+import org.briarproject.bramble.api.crypto.CryptoComponent;
+import org.briarproject.bramble.api.crypto.SecretKey;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.reporting.DevConfig;
+import org.briarproject.bramble.api.transport.StreamWriter;
+import org.briarproject.bramble.api.transport.StreamWriterFactory;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
+import java.util.logging.Formatter;
+import java.util.logging.LogRecord;
+import java.util.logging.Logger;
+
+import javax.inject.Inject;
+
+import androidx.annotation.Nullable;
+
+import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.LogUtils.logException;
+
+@NotNullByDefault
+class LogEncrypterImpl implements LogEncrypter {
+
+	private static final Logger LOG =
+			getLogger(LogEncrypterImpl.class.getName());
+
+	private final DevConfig devConfig;
+	private final CachingLogHandler logHandler;
+	private final CryptoComponent crypto;
+	private final StreamWriterFactory streamWriterFactory;
+
+	@Inject
+	LogEncrypterImpl(DevConfig devConfig,
+			CachingLogHandler logHandler,
+			CryptoComponent crypto,
+			StreamWriterFactory streamWriterFactory) {
+		this.devConfig = devConfig;
+		this.logHandler = logHandler;
+		this.crypto = crypto;
+		this.streamWriterFactory = streamWriterFactory;
+	}
+
+	@Nullable
+	@Override
+	public byte[] encryptLogs() {
+		SecretKey logKey = crypto.generateSecretKey();
+		File logFile = devConfig.getLogcatFile();
+		try (OutputStream out = new FileOutputStream(logFile)) {
+			StreamWriter streamWriter =
+					streamWriterFactory.createLogStreamWriter(out, logKey);
+			Writer writer =
+					new OutputStreamWriter(streamWriter.getOutputStream());
+			writeLogString(writer);
+			writer.close();
+			return logKey.getBytes();
+		} catch (IOException e) {
+			logException(LOG, WARNING, e);
+			return null;
+		}
+	}
+
+	private void writeLogString(Writer writer) throws IOException {
+		Formatter formatter = new BriefLogFormatter();
+		for (LogRecord record : logHandler.getRecentLogRecords()) {
+			String formatted = formatter.format(record);
+			writer.append(formatted).append('\n');
+		}
+	}
+
+}