Add a bunch of tests highlighting implicit acks

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

See merge request briar/briar!1392

.idea/dictionaries/briar.xml

@@ -7,6 +7,7 @@
       <w>encrypter</w>
       <w>identicon</w>
       <w>introducee</w>
+      <w>introducees</w>
       <w>introducer</w>
       <w>onboarding</w>
     </words>

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/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,
+			throws DbException, FormatException;
-			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/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/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/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 {
@@ -795,10 +819,19 @@ 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);
+				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) {
 			transaction.attach(new MessagesAckedEvent(c, acked));
 		}
@@ -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/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();
+		clientHelper.setContactId(txn, g.getId(), c.getId());
-		meta.put(GROUP_KEY_CONTACT_ID, c.getId().getInt());
-		try {
-			clientHelper.mergeGroupMetadata(txn, g.getId(), meta);
-		} catch (FormatException e) {
-			throw new AssertionError(e);
-		}
 		// Create and store the first local update
 		List<ClientVersion> versions = new ArrayList<>(clients);
 		Collections.sort(versions);
@@ -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/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(),
+		assertTrue(db.getGroupVisibility(txn, groupId).isEmpty());
-				db.getGroupVisibility(txn, groupId));
 
 		// 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(),
+		assertTrue(db.getGroupVisibility(txn, groupId).isEmpty());
-				db.getGroupVisibility(txn, groupId));
 
 		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(),
+			oneOf(clientHelper).setContactId(txn, contactGroup.getId(),
-					groupMeta);
+					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,
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
-					contactGroup.getId());
+			will(returnValue(contact.getId()));
-			will(returnValue(groupMeta));
 			// 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
+			// Get contact ID
-			oneOf(clientHelper).getGroupMetadataAsDictionary(txn,
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
-					contactGroup.getId());
+			will(returnValue(contact.getId()));
-			will(returnValue(groupMeta));
 			// 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,
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
-					contactGroup.getId());
+			will(returnValue(contact.getId()));
-			will(returnValue(groupMeta));
 			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,
+			oneOf(clientHelper).getContactId(txn, contactGroup.getId());
-					contactGroup.getId());
+			will(returnValue(contact.getId()));
-			will(returnValue(groupMeta));
 			oneOf(db).getContact(txn, contact.getId());
 			will(returnValue(contact));
 			oneOf(hook).onClientVisibilityChanging(txn, contact, INVISIBLE);

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 {

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

@@ -29,6 +29,7 @@ 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;
@@ -42,6 +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;
@@ -76,6 +78,7 @@ import dagger.Component;
 		BriarAccountModule.class,
 		AppModule.class,
 		AttachmentModule.class,
+		ClockModule.class,
 		MediaModule.class
 })
 public interface AndroidComponent
@@ -184,6 +187,8 @@ public interface AndroidComponent
 
 	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;

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

@@ -283,6 +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/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/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,
+	public LiveData<SendState> onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+			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,
+	public LiveData<SendState> onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+			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/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

@@ -50,6 +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;
@@ -59,8 +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;
@@ -138,12 +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,
+		implements BaseFragmentListener, EventListener, ConversationListener,
-		AttachmentCache, AttachmentListener, ActionMode.Callback {
+		TextCache, AttachmentCache, AttachmentListener, ActionMode.Callback {
 
 	public static final String CONTACT_ID = "briar.CONTACT_ID";
 
@@ -268,15 +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>() {
+			observeOnce(viewModel.getPrivateMessageFormat(), this, format -> {
-				@Override
+				if (format != TEXT_ONLY) {
-				public void onChanged(@Nullable Boolean hasSupport) {
-					if (hasSupport != null && hasSupport) {
 					// TODO: remove cast when removing feature flag
 					((TextAttachmentController) sendController)
 							.setImagesSupported();
-						viewModel.hasImageSupport().removeObserver(this);
-					}
 				}
 			});
 		} else {
@@ -286,6 +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() {
@@ -369,6 +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);
 	}
@@ -390,6 +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;
@@ -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<?> p =
-					(ConversationMessageReceivedEvent) e;
+					(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,
+	public LiveData<SendState> onSendClick(@Nullable String text,
-			List<AttachmentHeader> attachmentHeaders) {
+			List<AttachmentHeader> attachmentHeaders,
+			long expectedAutoDeleteTimer) {
 		if (isNullOrEmpty(text) && attachmentHeaders.isEmpty())
 			throw new AssertionError();
-		long timestamp = System.currentTimeMillis();
+		return viewModel
-		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
+				.sendMessage(text, attachmentHeaders, expectedAutoDeleteTimer);
-		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;
 	}
 
 	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()) {
@@ -958,13 +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);
@@ -1038,11 +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 {
+			boolean accept) throws DbException {
-		introductionManager.respondToIntroduction(contactId, sessionId, time,
+		introductionManager.respondToIntroduction(contactId, sessionId, accept);
-				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) {
+		if (type == R.layout.list_item_conversation_msg_in) {
-			case R.layout.list_item_conversation_msg_in:
 			return new ConversationMessageViewHolder(v, listener, true,
 					imageViewPool, imageItemDecoration);
-			case R.layout.list_item_conversation_msg_out:
+		} else if (type == R.layout.list_item_conversation_msg_out) {
 			return new ConversationMessageViewHolder(v, listener, false,
 					imageViewPool, imageItemDecoration);
-			case R.layout.list_item_conversation_notice_in:
+		} else if (type == R.layout.list_item_conversation_notice_in) {
 			return new ConversationNoticeViewHolder(v, listener, true);
-			case R.layout.list_item_conversation_notice_out:
+		} else if (type == R.layout.list_item_conversation_notice_out) {
 			return new ConversationNoticeViewHolder(v, listener, false);
-			case R.layout.list_item_conversation_request:
+		} else if (type == R.layout.list_item_conversation_request) {
 			return new ConversationRequestViewHolder(v, listener, true);
-			default:
-				throw new IllegalArgumentException("Unknown ConversationItem");
 		}
+		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) {
+			LiveData<String> contactName, List<AttachmentItem> attachments) {
-		super(layoutRes, h);
+		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) {
+			LiveData<String> contactName, ConversationRequest<?> r) {
-		super(layoutRes, r);
+		super(layoutRes, r, contactName);
 		this.text = text;
 		this.msgText = r.getText();
 	}
 
 	ConversationNoticeItem(@LayoutRes int layoutRes, String text,
-			ConversationResponse r) {
+			LiveData<String> contactName, ConversationResponse r) {
-		super(layoutRes, 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) {
+			LiveData<String> contactName, RequestType type,
-		super(layoutRes, text, r);
+			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);
 	}
 
@@ -152,6 +173,11 @@ public class ConversationViewModel extends DbViewModel
 				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)) {
@@ -201,6 +227,11 @@ public class ConversationViewModel extends DbViewModel
 				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) {
@@ -235,20 +266,6 @@ public class ConversationViewModel extends DbViewModel
 		});
 	}
 
-	@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);
-			});
-		});
-	}
-
 	@Override
 	@UiThread
 	public LiveData<AttachmentResult> storeAttachments(Collection<Uri> uris,
@@ -275,10 +292,12 @@ public class ConversationViewModel extends DbViewModel
 
 	@DatabaseExecutor
 	private void checkFeaturesAndOnboarding(ContactId c) throws DbException {
-		// check if images are supported
+		// check if images and auto-deletion are supported
-		boolean imagesSupported = db.transactionWithResult(true, txn ->
+		PrivateMessageFormat format = db.transactionWithResult(true, txn ->
-				messagingManager.contactSupportsImages(txn, c));
+				messagingManager.getContactMessageFormat(txn, c));
-		imageSupport.postValue(imagesSupported);
+		if (LOG.isLoggable(INFO))
+			LOG.info("PrivateMessageFormat loaded: " + format.name());
+		privateMessageFormat.postValue(format);
 
 		// check if introductions are supported
 		Collection<Contact> contacts = contactManager.getContacts();
@@ -287,7 +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);
@@ -306,39 +325,82 @@ public class ConversationViewModel extends DbViewModel
 	}
 
 	@UiThread
-	private void createMessage(GroupId groupId, @Nullable String text,
+	LiveData<SendState> sendMessage(@Nullable String text,
-			List<AttachmentHeader> headers, long timestamp,
+			List<AttachmentHeader> headers, long expectedTimer) {
-			boolean hasImageSupport) {
+		MutableLiveData<SendState> liveData = new MutableLiveData<>();
-		try {
-			PrivateMessage pm;
-			if (hasImageSupport) {
-				pm = privateMessageFactory.createPrivateMessage(groupId,
-						timestamp, text, headers);
-			} else {
-				pm = privateMessageFactory.createLegacyPrivateMessage(
-						groupId, timestamp, requireNonNull(text));
-			}
-			storeMessage(pm);
-		} catch (FormatException e) {
-			throw new AssertionError(e);
-		}
-	}
-
-	@UiThread
-	private void storeMessage(PrivateMessage m) {
-		attachmentCreator.onAttachmentsSent(m.getMessage().getId());
 		runOnDbThread(() -> {
 			try {
+				db.transaction(false, txn -> {
 					long start = now();
-				messagingManager.addLocalMessage(m);
+					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.hasText(), m.getAttachmentHeaders(),
+							m.getAutoDeleteTimer());
 					// TODO add text to cache when available here
-				addedHeader.postEvent(h);
+					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 {
+			if (format == TEXT_ONLY) {
+				return privateMessageFactory.createLegacyPrivateMessage(
+						groupId, timestamp, requireNonNull(text));
+			} else if (format == TEXT_IMAGES) {
+				return privateMessageFactory.createPrivateMessage(groupId,
+						timestamp, text, headers);
+			} else {
+				long timer = autoDeleteManager
+						.getAutoDeleteTimer(txn, contactId, timestamp);
+				if (timer != expectedTimer)
+					throw new UnexpectedTimerException();
+				return privateMessageFactory.createPrivateMessage(groupId,
+						timestamp, text, headers, timer);
+			}
+		} catch (FormatException e) {
+			throw new AssertionError(e);
+		}
+	}
+
+	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);
 			}
@@ -357,8 +419,8 @@ public class ConversationViewModel extends DbViewModel
 		return contactName;
 	}
 
-	LiveData<Boolean> hasImageSupport() {
+	LiveData<PrivateMessageFormat> getPrivateMessageFormat() {
-		return imageSupport;
+		return privateMessageFormat;
 	}
 
 	LiveEvent<Boolean> showImageOnboarding() {
@@ -373,6 +435,10 @@ public class ConversationViewModel extends DbViewModel
 		return showIntroductionAction;
 	}
 
+	LiveData<Long> getAutoDeleteTimer() {
+		return autoDeleteTimer;
+	}
+
 	LiveData<Boolean> isContactDeleted() {
 		return contactDeleted;
 	}

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/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,
+	public LiveData<SendState> onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+			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);
-				introductionManager.makeIntroduction(c1, c2, text, timestamp);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				introductionError();

briar-android/src/main/java/org/briarproject/briar/android/privategroup/creation/CreateGroupControllerImpl.java

@@ -7,6 +7,8 @@ import org.briarproject.bramble.api.crypto.CryptoExecutor;
 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.identity.IdentityManager;
 import org.briarproject.bramble.api.identity.LocalAuthor;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
@@ -15,6 +17,8 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.android.contactselection.ContactSelectorControllerImpl;
 import org.briarproject.briar.android.controller.handler.ResultExceptionHandler;
+import org.briarproject.briar.api.autodelete.AutoDeleteManager;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.identity.AuthorManager;
 import org.briarproject.briar.api.privategroup.GroupMessage;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
@@ -36,6 +40,8 @@ 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.api.nullsafety.NullSafety.requireNonNull;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @Immutable
@@ -44,9 +50,12 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 		implements CreateGroupController {
 
 	private static final Logger LOG =
-			Logger.getLogger(CreateGroupControllerImpl.class.getName());
+			getLogger(CreateGroupControllerImpl.class.getName());
 
 	private final Executor cryptoExecutor;
+	private final TransactionManager db;
+	private final AutoDeleteManager autoDeleteManager;
+	private final ConversationManager conversationManager;
 	private final ContactManager contactManager;
 	private final IdentityManager identityManager;
 	private final PrivateGroupFactory groupFactory;
@@ -57,17 +66,27 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 	private final Clock clock;
 
 	@Inject
-	CreateGroupControllerImpl(@DatabaseExecutor Executor dbExecutor,
+	CreateGroupControllerImpl(
+			@DatabaseExecutor Executor dbExecutor,
 			@CryptoExecutor Executor cryptoExecutor,
-			LifecycleManager lifecycleManager, ContactManager contactManager,
+			TransactionManager db,
-			AuthorManager authorManager, IdentityManager identityManager,
+			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
+			LifecycleManager lifecycleManager,
+			ContactManager contactManager,
+			AuthorManager authorManager,
+			IdentityManager identityManager,
 			PrivateGroupFactory groupFactory,
 			GroupMessageFactory groupMessageFactory,
 			PrivateGroupManager groupManager,
 			GroupInvitationFactory groupInvitationFactory,
-			GroupInvitationManager groupInvitationManager, Clock clock) {
+			GroupInvitationManager groupInvitationManager,
+			Clock clock) {
 		super(dbExecutor, lifecycleManager, contactManager, authorManager);
 		this.cryptoExecutor = cryptoExecutor;
+		this.db = db;
+		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		this.contactManager = contactManager;
 		this.identityManager = identityManager;
 		this.groupFactory = groupFactory;
@@ -131,16 +150,14 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 			ResultExceptionHandler<Void, DbException> handler) {
 		runOnDbThread(() -> {
 			try {
-				LocalAuthor localAuthor = identityManager.getLocalAuthor();
+				db.transaction(false, txn -> {
-				List<Contact> contacts = new ArrayList<>();
+					LocalAuthor localAuthor =
-				for (ContactId c : contactIds) {
+							identityManager.getLocalAuthor(txn);
-					try {
+					List<InvitationContext> contexts =
-						contacts.add(contactManager.getContact(c));
+							createInvitationContexts(txn, contactIds);
-					} catch (NoSuchContactException e) {
+					txn.attach(() -> signInvitations(g, localAuthor, contexts,
-						// Continue
+							text, handler));
-					}
+				});
-				}
-				signInvitations(g, localAuthor, contacts, text, handler);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
 				handler.onException(e);
@@ -148,17 +165,32 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 		});
 	}
 
+	private List<InvitationContext> createInvitationContexts(Transaction txn,
+			Collection<ContactId> contactIds) throws DbException {
+		List<InvitationContext> contexts = new ArrayList<>();
+		for (ContactId c : contactIds) {
+			try {
+				Contact contact = contactManager.getContact(txn, c);
+				long timestamp = conversationManager
+						.getTimestampForOutgoingMessage(txn, c);
+				long timer = autoDeleteManager.getAutoDeleteTimer(txn, c,
+						timestamp);
+				contexts.add(new InvitationContext(contact, timestamp, timer));
+			} catch (NoSuchContactException e) {
+				// Continue
+			}
+		}
+		return contexts;
+	}
+
 	private void signInvitations(GroupId g, LocalAuthor localAuthor,
-			Collection<Contact> contacts, @Nullable String text,
+			List<InvitationContext> contexts, @Nullable String text,
 			ResultExceptionHandler<Void, DbException> handler) {
 		cryptoExecutor.execute(() -> {
-			long timestamp = clock.currentTimeMillis();
+			for (InvitationContext ctx : contexts) {
-			List<InvitationContext> contexts = new ArrayList<>();
+				ctx.signature = groupInvitationFactory.signInvitation(
-			for (Contact c : contacts) {
+						ctx.contact, g, ctx.timestamp,
-				byte[] signature = groupInvitationFactory.signInvitation(c, g,
+						localAuthor.getPrivateKey());
-						timestamp, localAuthor.getPrivateKey());
-				contexts.add(new InvitationContext(c.getId(), timestamp,
-						signature));
 			}
 			sendInvitations(g, contexts, text, handler);
 		});
@@ -169,11 +201,12 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 			ResultExceptionHandler<Void, DbException> handler) {
 		runOnDbThread(() -> {
 			try {
-				for (InvitationContext context : contexts) {
+				for (InvitationContext ctx : contexts) {
 					try {
 						groupInvitationManager.sendInvitation(g,
-								context.contactId, text, context.timestamp,
+								ctx.contact.getId(), text, ctx.timestamp,
-								context.signature);
+								requireNonNull(ctx.signature),
+								ctx.autoDeleteTimer);
 					} catch (NoSuchContactException e) {
 						// Continue
 					}
@@ -188,15 +221,16 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 
 	private static class InvitationContext {
 
-		private final ContactId contactId;
+		private final Contact contact;
-		private final long timestamp;
+		private final long timestamp, autoDeleteTimer;
-		private final byte[] signature;
+		@Nullable
+		private byte[] signature = null;
 
-		private InvitationContext(ContactId contactId, long timestamp,
+		private InvitationContext(Contact contact, long timestamp,
-				byte[] signature) {
+				long autoDeleteTimer) {
-			this.contactId = contactId;
+			this.contact = contact;
 			this.timestamp = timestamp;
-			this.signature = signature;
+			this.autoDeleteTimer = autoDeleteTimer;
 		}
 	}
 }

briar-android/src/main/java/org/briarproject/briar/android/sharing/BaseMessageFragment.java

@@ -15,6 +15,7 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.LargeTextInputView;
 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;
@@ -22,6 +23,10 @@ import java.util.List;
 import androidx.annotation.Nullable;
 import androidx.annotation.StringRes;
 import androidx.annotation.UiThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -79,13 +84,14 @@ public abstract class BaseMessageFragment extends BaseFragment
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text,
+	public LiveData<SendState> onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+			List<AttachmentHeader> headers, long expectedAutoDeleteTimer) {
 		// disable button to prevent accidental double actions
 		sendController.setReady(false);
 		message.hideSoftKeyboard();
 
 		listener.onButtonClick(text);
+		return new MutableLiveData<>(SENT);
 	}
 
 	@UiThread

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareBlogControllerImpl.java

@@ -10,11 +10,9 @@ import org.briarproject.bramble.api.db.NoSuchGroupException;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.android.contactselection.ContactSelectorControllerImpl;
 import org.briarproject.briar.android.controller.handler.ExceptionHandler;
 import org.briarproject.briar.api.blog.BlogSharingManager;
-import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.identity.AuthorManager;
 
 import java.util.Collection;
@@ -26,6 +24,7 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @Immutable
@@ -34,22 +33,17 @@ class ShareBlogControllerImpl extends ContactSelectorControllerImpl
 		implements ShareBlogController {
 
 	private final static Logger LOG =
-			Logger.getLogger(ShareBlogControllerImpl.class.getName());
+			getLogger(ShareBlogControllerImpl.class.getName());
 
-	private final ConversationManager conversationManager;
 	private final BlogSharingManager blogSharingManager;
-	private final Clock clock;
 
 	@Inject
 	ShareBlogControllerImpl(@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager, ContactManager contactManager,
 			AuthorManager authorManager,
-			ConversationManager conversationManager,
+			BlogSharingManager blogSharingManager) {
-			BlogSharingManager blogSharingManager, Clock clock) {
 		super(dbExecutor, lifecycleManager, contactManager, authorManager);
-		this.conversationManager = conversationManager;
 		this.blogSharingManager = blogSharingManager;
-		this.clock = clock;
 	}
 
 	@Override
@@ -64,10 +58,7 @@ class ShareBlogControllerImpl extends ContactSelectorControllerImpl
 			try {
 				for (ContactId c : contacts) {
 					try {
-						long time = Math.max(clock.currentTimeMillis(),
+						blogSharingManager.sendInvitation(g, c, text);
-								conversationManager.getGroupCount(c)
-										.getLatestMsgTime() + 1);
-						blogSharingManager.sendInvitation(g, c, text, time);
 					} catch (NoSuchContactException | NoSuchGroupException e) {
 						logException(LOG, WARNING, e);
 					}

briar-android/src/main/java/org/briarproject/briar/android/sharing/ShareForumControllerImpl.java

@@ -10,10 +10,8 @@ import org.briarproject.bramble.api.db.NoSuchGroupException;
 import org.briarproject.bramble.api.lifecycle.LifecycleManager;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.android.contactselection.ContactSelectorControllerImpl;
 import org.briarproject.briar.android.controller.handler.ExceptionHandler;
-import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.forum.ForumSharingManager;
 import org.briarproject.briar.api.identity.AuthorManager;
 
@@ -26,6 +24,7 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.logging.Level.WARNING;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @Immutable
@@ -34,22 +33,17 @@ class ShareForumControllerImpl extends ContactSelectorControllerImpl
 		implements ShareForumController {
 
 	private final static Logger LOG =
-			Logger.getLogger(ShareForumControllerImpl.class.getName());
+			getLogger(ShareForumControllerImpl.class.getName());
 
-	private final ConversationManager conversationManager;
 	private final ForumSharingManager forumSharingManager;
-	private final Clock clock;
 
 	@Inject
 	ShareForumControllerImpl(@DatabaseExecutor Executor dbExecutor,
 			LifecycleManager lifecycleManager, ContactManager contactManager,
 			AuthorManager authorManager,
-			ConversationManager conversationManager,
+			ForumSharingManager forumSharingManager) {
-			ForumSharingManager forumSharingManager, Clock clock) {
 		super(dbExecutor, lifecycleManager, contactManager, authorManager);
-		this.conversationManager = conversationManager;
 		this.forumSharingManager = forumSharingManager;
-		this.clock = clock;
 	}
 
 	@Override
@@ -64,10 +58,7 @@ class ShareForumControllerImpl extends ContactSelectorControllerImpl
 			try {
 				for (ContactId c : contacts) {
 					try {
-						long time = Math.max(clock.currentTimeMillis(),
+						forumSharingManager.sendInvitation(g, c, text);
-								conversationManager.getGroupCount(c)
-										.getLatestMsgTime() + 1);
-						forumSharingManager.sendInvitation(g, c, text, time);
 					} catch (NoSuchContactException | NoSuchGroupException e) {
 						logException(LOG, WARNING, e);
 					}

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListActivity.java

@@ -19,6 +19,7 @@ import org.briarproject.briar.android.view.BriarRecyclerView;
 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.android.view.UnreadMessageButton;
 import org.briarproject.briar.api.attachment.AttachmentHeader;
 
@@ -29,10 +30,13 @@ import javax.annotation.Nullable;
 import androidx.annotation.CallSuper;
 import androidx.annotation.StringRes;
 import androidx.appcompat.app.ActionBar;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
 import androidx.recyclerview.widget.LinearLayoutManager;
 
 import static androidx.recyclerview.widget.RecyclerView.NO_POSITION;
 import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
 
 @MethodsNotNullByDefault
 @ParametersNotNullByDefault
@@ -231,8 +235,8 @@ public abstract class ThreadListActivity<I extends ThreadItem, A extends ThreadI
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text,
+	public LiveData<SendState> onSendClick(@Nullable String text,
-			List<AttachmentHeader> headers) {
+			List<AttachmentHeader> headers, long expectedAutoDeleteTimer) {
 		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		MessageId replyId = getViewModel().getReplyId();
@@ -241,6 +245,7 @@ public abstract class ThreadListActivity<I extends ThreadItem, A extends ThreadI
 		textInput.clearText();
 		getViewModel().setReplyId(null);
 		updateTextInput();
+		return new MutableLiveData<>(SENT);
 	}
 
 	protected abstract int getMaxTextLength();

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -6,6 +6,7 @@ import android.app.KeyguardManager;
 import android.content.Context;
 import android.content.DialogInterface.OnClickListener;
 import android.content.Intent;
+import android.content.res.Resources;
 import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.os.PowerManager;
@@ -76,6 +77,7 @@ import static android.text.format.DateUtils.FORMAT_ABBREV_TIME;
 import static android.text.format.DateUtils.FORMAT_SHOW_DATE;
 import static android.text.format.DateUtils.FORMAT_SHOW_TIME;
 import static android.text.format.DateUtils.FORMAT_SHOW_YEAR;
+import static android.text.format.DateUtils.HOUR_IN_MILLIS;
 import static android.text.format.DateUtils.MINUTE_IN_MILLIS;
 import static android.text.format.DateUtils.WEEK_IN_MILLIS;
 import static android.text.format.DateUtils.YEAR_IN_MILLIS;
@@ -167,6 +169,37 @@ public class UiUtils {
 		return DateUtils.formatDateTime(ctx, time, flags);
 	}
 
+	/**
+	 * Returns the given duration in a human-friendly format. For example,
+	 * "7 days" or "1 hour". Returns only the largest meaningful unit of time,
+	 * from days up to minutes.
+	 */
+	public static String formatDuration(Context ctx, long millis) {
+		Resources r = ctx.getResources();
+		if (millis >= DAY_IN_MILLIS) {
+			int days = (int) (millis / DAY_IN_MILLIS);
+			int rest = (int) (millis % DAY_IN_MILLIS);
+			String dayStr =
+					r.getQuantityString(R.plurals.duration_days, days, days);
+			if (rest < HOUR_IN_MILLIS / 2) return dayStr;
+			else return dayStr + " " + formatDuration(ctx, rest);
+		} else if (millis >= HOUR_IN_MILLIS) {
+			int hours = (int) (millis / HOUR_IN_MILLIS);
+			int rest = (int) (millis % HOUR_IN_MILLIS);
+			String hourStr =
+					r.getQuantityString(R.plurals.duration_hours, hours, hours);
+			if (rest < MINUTE_IN_MILLIS / 2) return hourStr;
+			else return hourStr + " " + formatDuration(ctx, rest);
+		} else {
+			int minutes =
+					(int) ((millis + MINUTE_IN_MILLIS / 2) / MINUTE_IN_MILLIS);
+			// anything less than one minute is shown as one minute
+			if (minutes < 1) minutes = 1;
+			return r.getQuantityString(R.plurals.duration_minutes, minutes,
+					minutes);
+		}
+	}
+
 	public static long getDaysUntilExpiry() {
 		long now = System.currentTimeMillis();
 		return (EXPIRY_DATE - now) / DAYS.toMillis(1);

briar-android/src/main/java/org/briarproject/briar/android/view/CompositeSendButton.java

@@ -5,6 +5,7 @@ import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.widget.FrameLayout;
+import android.widget.ImageView;
 import android.widget.ProgressBar;
 
 import org.briarproject.briar.R;
@@ -19,6 +20,7 @@ import static java.util.Objects.requireNonNull;
 public class CompositeSendButton extends FrameLayout {
 
 	private final AppCompatImageButton sendButton, imageButton;
+	private final ImageView bombBadge;
 	private final ProgressBar progressBar;
 
 	private boolean hasImageSupport = false;
@@ -32,6 +34,7 @@ public class CompositeSendButton extends FrameLayout {
 
 		sendButton = findViewById(R.id.sendButton);
 		imageButton = findViewById(R.id.imageButton);
+		bombBadge = findViewById(R.id.bombBadge);
 		progressBar = findViewById(R.id.progressBar);
 	}
 
@@ -71,6 +74,10 @@ public class CompositeSendButton extends FrameLayout {
 		return hasImageSupport;
 	}
 
+	public void setBombVisible(boolean visible) {
+		bombBadge.setVisibility(visible ? VISIBLE : INVISIBLE);
+	}
+
 	public void showImageButton(boolean showImageButton, boolean sendEnabled) {
 		if (showImageButton) {
 			imageButton.setVisibility(VISIBLE);

briar-android/src/main/java/org/briarproject/briar/android/view/TextAttachmentController.java

@@ -26,7 +26,6 @@ import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
 import androidx.appcompat.app.AlertDialog.Builder;
 import androidx.customview.view.AbsSavedState;
-import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.Observer;
 import androidx.vectordrawable.graphics.drawable.VectorDrawableCompat;
@@ -39,6 +38,7 @@ import static androidx.core.content.ContextCompat.getColor;
 import static androidx.customview.view.AbsSavedState.EMPTY_STATE;
 import static androidx.lifecycle.Lifecycle.State.DESTROYED;
 import static org.briarproject.briar.android.util.UiUtils.resolveColorAttribute;
+import static org.briarproject.briar.android.view.TextSendController.SendState.SENT;
 import static org.briarproject.briar.api.messaging.MessagingConstants.MAX_ATTACHMENTS_PER_MESSAGE;
 
 @UiThread
@@ -52,7 +52,6 @@ public class TextAttachmentController extends TextSendController
 	private final AttachmentManager attachmentManager;
 
 	private final List<Uri> imageUris = new ArrayList<>();
-	private final CharSequence textHint;
 	private boolean loadingUris = false;
 
 	public TextAttachmentController(TextInputView v, ImagePreview imagePreview,
@@ -66,23 +65,44 @@ public class TextAttachmentController extends TextSendController
 
 		sendButton = (CompositeSendButton) compositeSendButton;
 		sendButton.setOnImageClickListener(view -> onImageButtonClicked());
-
-		textHint = textInput.getHint();
 	}
 
 	@Override
 	protected void updateViewState() {
-		textInput.setEnabled(ready && !loadingUris);
+		super.updateViewState();
-		boolean sendEnabled = ready && !loadingUris &&
-				(!textIsEmpty || canSendEmptyText());
 		if (loadingUris) {
 			sendButton.showProgress(true);
 		} else if (imageUris.isEmpty()) {
 			sendButton.showProgress(false);
-			sendButton.showImageButton(textIsEmpty, sendEnabled);
+			sendButton.showImageButton(textIsEmpty, isSendButtonEnabled());
 		} else {
 			sendButton.showProgress(false);
-			sendButton.showImageButton(false, sendEnabled);
+			sendButton.showImageButton(false, isSendButtonEnabled());
+		}
+	}
+
+	@Override
+	protected boolean isTextInputEnabled() {
+		return super.isTextInputEnabled() && !loadingUris;
+	}
+
+	@Override
+	protected boolean isSendButtonEnabled() {
+		return super.isSendButtonEnabled() && !loadingUris;
+	}
+
+	@Override
+	protected boolean isBombVisible() {
+		return super.isBombVisible() && (!textIsEmpty || !imageUris.isEmpty());
+	}
+
+	@Override
+	protected CharSequence getCurrentTextHint() {
+		if (imageUris.isEmpty()) {
+			return super.getCurrentTextHint();
+		} else {
+			Context ctx = textInput.getContext();
+			return ctx.getString(R.string.image_caption_hint);
 		}
 	}
 
@@ -91,11 +111,17 @@ public class TextAttachmentController extends TextSendController
 		if (canSend()) {
 			if (loadingUris) throw new AssertionError();
 			listener.onSendClick(textInput.getText(),
-					attachmentManager.getAttachmentHeadersForSending());
+					attachmentManager.getAttachmentHeadersForSending(),
-			reset();
+					expectedTimer).observe(listener, this::onSendStateChanged);
 		}
 	}
 
+	@Override
+	protected void onSendStateChanged(SendState sendState) {
+		super.onSendStateChanged(sendState);
+		if (sendState == SENT) reset();
+	}
+
 	@Override
 	protected boolean canSendEmptyText() {
 		return !imageUris.isEmpty();
@@ -154,6 +180,7 @@ public class TextAttachmentController extends TextSendController
 	private void onNewUris(boolean restart, List<Uri> newUris) {
 		if (newUris.isEmpty()) return;
 		if (loadingUris) throw new AssertionError();
+		if (textIsEmpty) onStartingMessage();
 		loadingUris = true;
 		if (newUris.size() > MAX_ATTACHMENTS_PER_MESSAGE) {
 			newUris = newUris.subList(0, MAX_ATTACHMENTS_PER_MESSAGE);
@@ -161,7 +188,6 @@ public class TextAttachmentController extends TextSendController
 		}
 		imageUris.addAll(newUris);
 		updateViewState();
-		textInput.setHint(R.string.image_caption_hint);
 		List<ImagePreviewItem> items = ImagePreviewItem.fromUris(imageUris);
 		imagePreview.showPreview(items);
 		// store attachments and show preview when successful
@@ -207,8 +233,6 @@ public class TextAttachmentController extends TextSendController
 	}
 
 	private void reset() {
-		// restore hint
-		textInput.setHint(textHint);
 		// hide image layout
 		imagePreview.setVisibility(GONE);
 		// reset image URIs
@@ -303,7 +327,7 @@ public class TextAttachmentController extends TextSendController
 	}
 
 	@UiThread
-	public interface AttachmentListener extends SendListener, LifecycleOwner {
+	public interface AttachmentListener extends SendListener {
 
 		void onAttachImage(Intent intent);
 

briar-android/src/main/java/org/briarproject/briar/android/view/TextSendController.java

@@ -1,7 +1,9 @@
 package org.briarproject.briar.android.view;
 
+import android.content.Context;
 import android.os.Parcelable;
 import android.view.View;
+import android.widget.Toast;
 
 import com.google.android.material.snackbar.Snackbar;
 
@@ -12,11 +14,20 @@ import org.briarproject.briar.api.attachment.AttachmentHeader;
 
 import java.util.List;
 
+import androidx.annotation.CallSuper;
 import androidx.annotation.Nullable;
 import androidx.annotation.UiThread;
+import androidx.appcompat.app.AlertDialog;
+import androidx.lifecycle.LifecycleOwner;
+import androidx.lifecycle.LiveData;
 
+import static android.widget.Toast.LENGTH_LONG;
 import static com.google.android.material.snackbar.Snackbar.LENGTH_SHORT;
 import static java.util.Collections.emptyList;
+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;
 
 @UiThread
 @NotNullByDefault
@@ -26,8 +37,12 @@ public class TextSendController implements TextInputListener {
 	protected final View compositeSendButton;
 	protected final SendListener listener;
 
-	protected boolean ready = true, textIsEmpty = true;
+	protected boolean textIsEmpty = true;
+	private boolean ready = true;
+	private long currentTimer = NO_AUTO_DELETE_TIMER;
+	protected long expectedTimer = NO_AUTO_DELETE_TIMER;
 
+	private final CharSequence defaultHint;
 	private final boolean allowEmptyText;
 
 	public TextSendController(TextInputView v, SendListener listener,
@@ -36,31 +51,91 @@ public class TextSendController implements TextInputListener {
 		this.compositeSendButton.setOnClickListener(view -> onSendEvent());
 		this.listener = listener;
 		this.textInput = v.getEmojiTextInputView();
+		this.defaultHint = textInput.getHint();
 		this.allowEmptyText = allowEmptyText;
 	}
 
 	@Override
 	public void onTextIsEmptyChanged(boolean isEmpty) {
 		textIsEmpty = isEmpty;
+		if (!isEmpty) onStartingMessage();
 		updateViewState();
 	}
 
 	@Override
 	public void onSendEvent() {
 		if (canSend()) {
-			listener.onSendClick(textInput.getText(), emptyList());
+			listener.onSendClick(textInput.getText(), emptyList(),
+					expectedTimer).observe(listener, this::onSendStateChanged);
 		}
 	}
 
+	@CallSuper
+	protected void onSendStateChanged(SendState sendState) {
+		if (sendState == SENT) {
+			textInput.clearText();
+		} else if (sendState == UNEXPECTED_TIMER) {
+			boolean enabled = expectedTimer == NO_AUTO_DELETE_TIMER;
+			showTimerChangedDialog(enabled);
+		} else if (sendState == ERROR) {
+			Toast.makeText(textInput.getContext(), R.string.message_error,
+					LENGTH_LONG).show();
+		}
+	}
+
+	/**
+	 * Call whenever the user starts a new message,
+	 * either by entering text or adding an attachment.
+	 * This updates the expected auto-delete timer to the current value.
+	 */
+	protected void onStartingMessage() {
+		expectedTimer = currentTimer;
+	}
+
 	public void setReady(boolean ready) {
 		this.ready = ready;
 		updateViewState();
 	}
 
+	/**
+	 * Sets the current auto delete timer and updates the UI accordingly.
+	 */
+	public void setAutoDeleteTimer(long timer) {
+		currentTimer = timer;
+		updateViewState();
+	}
+
+	@CallSuper
 	protected void updateViewState() {
-		textInput.setEnabled(ready);
+		textInput.setEnabled(isTextInputEnabled());
-		compositeSendButton
+		textInput.setHint(getCurrentTextHint());
-				.setEnabled(ready && (!textIsEmpty || canSendEmptyText()));
+		compositeSendButton.setEnabled(isSendButtonEnabled());
+		if (compositeSendButton instanceof CompositeSendButton) {
+			CompositeSendButton sendButton =
+					(CompositeSendButton) compositeSendButton;
+			sendButton.setBombVisible(isBombVisible());
+		}
+	}
+
+	protected boolean isTextInputEnabled() {
+		return ready;
+	}
+
+	protected boolean isSendButtonEnabled() {
+		return ready && (!textIsEmpty || canSendEmptyText());
+	}
+
+	protected boolean isBombVisible() {
+		return currentTimer != NO_AUTO_DELETE_TIMER;
+	}
+
+	protected CharSequence getCurrentTextHint() {
+		if (currentTimer == NO_AUTO_DELETE_TIMER) {
+			return defaultHint;
+		} else {
+			Context ctx = textInput.getContext();
+			return ctx.getString(R.string.message_hint_auto_delete);
+		}
 	}
 
 	protected final boolean canSend() {
@@ -76,6 +151,23 @@ public class TextSendController implements TextInputListener {
 		return allowEmptyText;
 	}
 
+	private void showTimerChangedDialog(boolean enabled) {
+		Context ctx = textInput.getContext();
+		int message =
+				enabled ? R.string.auto_delete_changed_warning_message_enabled :
+						R.string.auto_delete_changed_warning_message_disabled;
+		new AlertDialog.Builder(ctx, R.style.BriarDialogTheme)
+				.setTitle(R.string.auto_delete_changed_warning_title)
+				.setMessage(message)
+				.setPositiveButton(R.string.auto_delete_changed_warning_send,
+						(dialog, which) -> {
+							expectedTimer = currentTimer;
+							onSendEvent();
+						})
+				.setNegativeButton(R.string.cancel, null)
+				.show();
+	}
+
 	@Nullable
 	public Parcelable onSaveInstanceState(@Nullable Parcelable superState) {
 		return superState;
@@ -86,9 +178,11 @@ public class TextSendController implements TextInputListener {
 		return state;
 	}
 
-	@UiThread
+	public enum SendState {SENT, ERROR, UNEXPECTED_TIMER}
-	public interface SendListener {
+
-		void onSendClick(@Nullable String text, List<AttachmentHeader> headers);
+	public interface SendListener extends LifecycleOwner {
+		LiveData<SendState> onSendClick(@Nullable String text,
+				List<AttachmentHeader> headers, long expectedAutoDeleteTimer);
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/widget/OnboardingFullDialogFragment.java

@@ -0,0 +1,66 @@
+package org.briarproject.briar.android.widget;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.TextView;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.StringRes;
+import androidx.appcompat.widget.Toolbar;
+import androidx.fragment.app.DialogFragment;
+
+@NotNullByDefault
+public class OnboardingFullDialogFragment extends DialogFragment {
+
+	public final static String TAG =
+			OnboardingFullDialogFragment.class.getName();
+
+	private final static String RES_TITLE = "resTitle";
+	private final static String RES_CONTENT = "resContent";
+
+	public static OnboardingFullDialogFragment newInstance(@StringRes int title,
+			@StringRes int content) {
+		Bundle args = new Bundle();
+		args.putInt(RES_TITLE, title);
+		args.putInt(RES_CONTENT, content);
+		OnboardingFullDialogFragment f = new OnboardingFullDialogFragment();
+		f.setArguments(args);
+		return f;
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		setStyle(DialogFragment.STYLE_NORMAL,
+				R.style.BriarFullScreenDialogTheme);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(@NonNull LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View view = inflater.inflate(R.layout.fragment_onboarding_full,
+				container, false);
+
+		Bundle args = requireArguments();
+
+		Toolbar toolbar = view.findViewById(R.id.toolbar);
+		toolbar.setNavigationOnClickListener(v -> dismiss());
+		toolbar.setTitle(args.getInt(RES_TITLE));
+
+		TextView contentView = view.findViewById(R.id.contentView);
+		contentView.setText(args.getInt(RES_CONTENT));
+
+		view.findViewById(R.id.button).setOnClickListener(v -> dismiss());
+
+		return view;
+	}
+
+}

briar-android/src/main/res/drawable/ic_bomb.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="16dp"
+	android:height="16dp"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<path
+		android:fillColor="#FFFFFF"
+		android:pathData="M11.25,6A3.25,3.25 0 0,1 14.5,2.75A3.25,3.25 0 0,1 17.75,6C17.75,6.42 18.08,6.75 18.5,6.75C18.92,6.75 19.25,6.42 19.25,6V5.25H20.75V6A2.25,2.25 0 0,1 18.5,8.25A2.25,2.25 0 0,1 16.25,6A1.75,1.75 0 0,0 14.5,4.25A1.75,1.75 0 0,0 12.75,6H14V7.29C16.89,8.15 19,10.83 19,14A7,7 0 0,1 12,21A7,7 0 0,1 5,14C5,10.83 7.11,8.15 10,7.29V6H11.25M22,6H24V7H22V6M19,4V2H20V4H19M20.91,4.38L22.33,2.96L23.04,3.67L21.62,5.09L20.91,4.38Z" />
+</vector>

briar-android/src/main/res/layout/fragment_conversation_settings.xml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		style="@style/BriarToolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent"
+		app:navigationIcon="@drawable/abc_ic_ab_back_material"
+		app:title="@string/disappearing_messages_title" />
+
+	<ScrollView
+		android:layout_width="match_parent"
+		android:layout_height="0dp"
+		app:layout_constraintBottom_toBottomOf="parent"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toBottomOf="@id/toolbar">
+
+		<androidx.constraintlayout.widget.ConstraintLayout
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content">
+
+			<ImageView
+				android:id="@+id/imageViewBomb"
+				android:layout_width="64dp"
+				android:layout_height="64dp"
+				android:layout_marginTop="16dp"
+				app:layout_constraintEnd_toEndOf="parent"
+				app:layout_constraintStart_toStartOf="parent"
+				app:layout_constraintTop_toTopOf="parent"
+				app:srcCompat="@drawable/ic_bomb"
+				app:tint="?attr/colorControlNormal"
+				tools:ignore="ContentDescription" />
+
+			<androidx.appcompat.widget.SwitchCompat
+				android:id="@+id/switchDisappearingMessages"
+				android:layout_width="0dp"
+				android:layout_height="wrap_content"
+				android:layout_margin="16dp"
+				android:enabled="false"
+				android:text="@string/disappearing_messages_summary"
+				app:layout_constraintEnd_toEndOf="parent"
+				app:layout_constraintStart_toStartOf="parent"
+				app:layout_constraintTop_toBottomOf="@+id/imageViewBomb"
+				tools:enabled="true" />
+
+			<Button
+				android:id="@+id/buttonLearnMore"
+				style="@style/BriarButtonFlat.Positive"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:padding="16dp"
+				android:text="@string/learn_more"
+				android:textAllCaps="false"
+				android:textSize="14sp"
+				app:layout_constraintStart_toStartOf="parent"
+				app:layout_constraintTop_toBottomOf="@+id/switchDisappearingMessages" />
+
+		</androidx.constraintlayout.widget.ConstraintLayout>
+
+	</ScrollView>
+
+</androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/fragment_onboarding_full.xml

@@ -0,0 +1,69 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:orientation="vertical">
+
+	<androidx.appcompat.widget.Toolbar
+		android:id="@+id/toolbar"
+		style="@style/BriarToolbar"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:elevation="4dp"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent"
+		app:navigationIcon="@drawable/abc_ic_ab_back_material"
+		tools:title="Onboarding Fullscreen Dialog" />
+
+	<ScrollView
+		android:layout_width="match_parent"
+		android:layout_height="match_parent"
+		android:background="@color/briar_primary"
+		android:fillViewport="true">
+
+		<androidx.constraintlayout.widget.ConstraintLayout
+			android:layout_width="match_parent"
+			android:layout_height="wrap_content">
+
+			<ImageView
+				android:id="@+id/imageView"
+				android:layout_width="64dp"
+				android:layout_height="64dp"
+				android:layout_margin="16dp"
+				app:layout_constraintEnd_toEndOf="parent"
+				app:layout_constraintStart_toStartOf="parent"
+				app:layout_constraintTop_toTopOf="parent"
+				app:srcCompat="@drawable/ic_info_white"
+				app:tint="@color/briar_text_secondary_inverse"
+				tools:ignore="ContentDescription" />
+
+			<TextView
+				android:id="@+id/contentView"
+				android:layout_width="0dp"
+				android:layout_height="wrap_content"
+				android:layout_margin="16dp"
+				android:textColor="@color/briar_text_secondary_inverse"
+				app:layout_constraintBottom_toTopOf="@+id/button"
+				app:layout_constraintEnd_toEndOf="parent"
+				app:layout_constraintStart_toStartOf="parent"
+				app:layout_constraintTop_toBottomOf="@+id/imageView"
+				app:layout_constraintVertical_bias="0.0"
+				tools:text="@tools:sample/lorem/random" />
+
+			<Button
+				android:id="@+id/button"
+				style="@style/BriarButtonFlat.Positive"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:text="@string/got_it"
+				app:layout_constraintBottom_toBottomOf="parent"
+				app:layout_constraintEnd_toEndOf="parent" />
+
+		</androidx.constraintlayout.widget.ConstraintLayout>
+
+	</ScrollView>
+
+</LinearLayout>

briar-android/src/main/res/layout/list_item_conversation_msg_image.xml

@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
+
+<!-- This layout is only used indirectly by cloning and setting its ConstraintSet -->
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	xmlns:app="http://schemas.android.com/apk/res-auto"
 	xmlns:tools="http://schemas.android.com/tools"
@@ -68,6 +70,16 @@
 			android:layout_height="wrap_content"
 			tools:text="Dec 24, 13:37" />
 
+		<ImageView
+			android:id="@+id/bomb"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="4dp"
+			android:layout_marginEnd="4dp"
+			app:srcCompat="@drawable/ic_bomb"
+			app:tint="?android:attr/textColorSecondary"
+			tools:ignore="ContentDescription" />
+
 	</LinearLayout>
 
 </androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/list_item_conversation_msg_image_text.xml

@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
+
+<!-- This layout is only used indirectly by cloning and setting its ConstraintSet -->
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	xmlns:app="http://schemas.android.com/apk/res-auto"
 	xmlns:tools="http://schemas.android.com/tools"
@@ -58,7 +60,8 @@
 		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintHorizontal_bias="1.0"
 		app:layout_constraintStart_toStartOf="parent"
-		app:layout_constraintTop_toBottomOf="@+id/text">
+		app:layout_constraintTop_toBottomOf="@+id/text"
+		tools:ignore="UseCompoundDrawables">
 
 		<TextView
 			android:id="@+id/time"
@@ -67,6 +70,16 @@
 			android:layout_height="wrap_content"
 			tools:text="Dec 24, 13:37" />
 
+		<ImageView
+			android:id="@+id/bomb"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="4dp"
+			android:layout_marginEnd="4dp"
+			app:srcCompat="@drawable/ic_bomb"
+			app:tint="?android:attr/textColorSecondary"
+			tools:ignore="ContentDescription" />
+
 	</LinearLayout>
 
 </androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/list_item_conversation_msg_in.xml

@@ -1,14 +1,19 @@
 <?xml version="1.0" encoding="utf-8"?>
-<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	android:layout_width="match_parent"
 	android:layout_height="wrap_content"
-	android:background="@drawable/list_item_background_selectable">
+	android:background="@drawable/list_item_background_selectable"
+	android:orientation="vertical">
 
 	<!--
-	We need to wrap the actual layout, because
+	We need to wrap the actual layout, because we want to
-	* we want to clone the ConstraintLayout's constraints in the ViewHolder
+	* clone the ConstraintLayout's constraints in the ViewHolder
-	* we want to have a selectable frame around the message bubble
+	* have a selectable frame around the message bubble
+	* insert a top notice with its own independent width
 	-->
+
+	<include layout="@layout/list_item_conversation_top_notice_in" />
+
 	<include layout="@layout/list_item_conversation_msg_in_content" />
 
-</FrameLayout>
+</LinearLayout>

briar-android/src/main/res/layout/list_item_conversation_msg_in_content.xml

@@ -1,4 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
+
+<!-- This layout gets wrapped in *_msg_in.xml -->
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	xmlns:app="http://schemas.android.com/apk/res-auto"
 	xmlns:tools="http://schemas.android.com/tools"
@@ -68,6 +70,17 @@
 			android:layout_height="wrap_content"
 			tools:text="Dec 24, 13:37" />
 
+		<ImageView
+			android:id="@+id/bomb"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="4dp"
+			android:layout_marginLeft="4dp"
+			app:srcCompat="@drawable/ic_bomb"
+			app:tint="?android:attr/textColorSecondary"
+			tools:ignore="ContentDescription"
+			tools:visibility="visible" />
+
 	</LinearLayout>
 
 </androidx.constraintlayout.widget.ConstraintLayout>

briar-android/src/main/res/layout/list_item_conversation_msg_out.xml

@@ -1,10 +1,14 @@
 <?xml version="1.0" encoding="utf-8"?>
-<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 	xmlns:app="http://schemas.android.com/apk/res-auto"
 	xmlns:tools="http://schemas.android.com/tools"
 	android:layout_width="match_parent"
 	android:layout_height="wrap_content"
-	android:background="@drawable/list_item_background_selectable">
+	android:background="@drawable/list_item_background_selectable"
+	android:orientation="vertical"
+	android:paddingTop="@dimen/message_bubble_margin">
+
+	<include layout="@layout/list_item_conversation_top_notice_out" />
 
 	<androidx.constraintlayout.widget.ConstraintLayout
 		android:id="@+id/layout"
@@ -73,15 +77,26 @@
 				style="@style/TextMessage.Timestamp"
 				android:layout_width="wrap_content"
 				android:layout_height="wrap_content"
-				android:layout_marginEnd="6dp"
+				android:layout_marginEnd="4dp"
-				android:layout_marginRight="6dp"
+				android:layout_marginRight="4dp"
 				android:textColor="@color/private_message_date_inverse"
 				tools:text="Dec 24, 13:37" />
 
+			<ImageView
+				android:id="@+id/bomb"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:layout_marginEnd="4dp"
+				android:layout_marginRight="4dp"
+				app:srcCompat="@drawable/ic_bomb"
+				app:tint="@color/private_message_date_inverse"
+				tools:ignore="ContentDescription" />
+
 			<ImageView
 				android:id="@+id/status"
 				android:layout_width="wrap_content"
 				android:layout_height="wrap_content"
+				app:tint="@color/private_message_date_inverse"
 				tools:ignore="ContentDescription"
 				tools:src="@drawable/message_delivered" />
 
@@ -89,4 +104,4 @@
 
 	</androidx.constraintlayout.widget.ConstraintLayout>
 
-</FrameLayout>
+</LinearLayout>

briar-android/src/main/res/layout/list_item_conversation_notice_in.xml

@@ -5,8 +5,9 @@
 	android:layout_width="match_parent"
 	android:layout_height="wrap_content"
 	android:background="@drawable/list_item_background_selectable"
-	android:orientation="vertical"
+	android:orientation="vertical">
-	android:paddingTop="@dimen/message_bubble_margin">
+
+	<include layout="@layout/list_item_conversation_top_notice_in" />
 
 	<com.vanniktech.emoji.EmojiTextView
 		android:id="@+id/msgText"
@@ -15,11 +16,13 @@
 		android:layout_height="wrap_content"
 		android:layout_marginStart="@dimen/message_bubble_margin_tail"
 		android:layout_marginLeft="@dimen/message_bubble_margin_tail"
+		android:layout_marginTop="@dimen/message_bubble_margin"
 		android:layout_marginEnd="@dimen/message_bubble_margin_non_tail"
 		android:layout_marginRight="@dimen/message_bubble_margin_non_tail"
 		android:background="@drawable/msg_in_top"
 		android:elevation="@dimen/message_bubble_elevation"
-		tools:text="Short message" />
+		tools:text="Short message"
+		tools:visibility="visible" />
 
 	<androidx.constraintlayout.widget.ConstraintLayout
 		android:id="@+id/layout"
@@ -48,10 +51,28 @@
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
 			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
-			app:layout_constraintEnd_toEndOf="@+id/text"
+			app:layout_constraintEnd_toStartOf="@+id/bomb"
+			app:layout_constraintHorizontal_bias="1.0"
+			app:layout_constraintHorizontal_chainStyle="packed"
+			app:layout_constraintStart_toStartOf="parent"
 			app:layout_constraintTop_toBottomOf="@+id/text"
 			tools:text="Dec 24, 13:37" />
 
+		<ImageView
+			android:id="@+id/bomb"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="4dp"
+			android:layout_marginLeft="4dp"
+			android:layout_marginTop="@dimen/message_bubble_timestamp_margin"
+			app:layout_constraintEnd_toEndOf="@+id/text"
+			app:layout_constraintStart_toEndOf="@+id/time"
+			app:layout_constraintTop_toBottomOf="@+id/text"
+			app:srcCompat="@drawable/ic_bomb"
+			app:tint="?android:attr/textColorSecondary"
+			tools:ignore="ContentDescription"
+			tools:visibility="visible" />
+
 	</androidx.constraintlayout.widget.ConstraintLayout>
 
 </LinearLayout>

briar-android/src/main/res/layout/list_item_conversation_notice_out.xml

@@ -8,6 +8,8 @@
 	android:orientation="vertical"
 	android:paddingTop="@dimen/message_bubble_margin">
 
+	<include layout="@layout/list_item_conversation_top_notice_out" />
+
 	<com.vanniktech.emoji.EmojiTextView
 		android:id="@+id/msgText"
 		style="@style/TextMessage"
@@ -15,12 +17,14 @@
 		android:layout_height="wrap_content"
 		android:layout_marginStart="@dimen/message_bubble_margin_non_tail"
 		android:layout_marginLeft="@dimen/message_bubble_margin_non_tail"
+		android:layout_marginTop="@dimen/message_bubble_margin"
 		android:layout_marginEnd="@dimen/message_bubble_margin_tail"
 		android:layout_marginRight="@dimen/message_bubble_margin_tail"
 		android:background="@drawable/msg_out_top"
 		android:elevation="@dimen/message_bubble_elevation"
 		android:textColor="@color/briar_text_primary_inverse"
-		tools:text="This is a long long long message that spans over several lines.\n\nIt ends here." />
+		tools:text="This is a long long long message that spans over several lines.\n\nIt ends here."
+		tools:visibility="visible" />
 
 	<androidx.constraintlayout.widget.ConstraintLayout
 		android:id="@+id/layout"
@@ -56,14 +60,28 @@
 			tools:text="Dec 24, 13:37" />
 
 		<ImageView
-			android:id="@+id/status"
+			android:id="@+id/bomb"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
-			android:layout_marginStart="@dimen/margin_medium"
+			android:layout_marginStart="4dp"
-			android:layout_marginLeft="@dimen/margin_medium"
+			android:layout_marginLeft="4dp"
 			app:layout_constraintBottom_toBottomOf="@+id/time"
 			app:layout_constraintStart_toEndOf="@+id/time"
 			app:layout_constraintTop_toTopOf="@+id/time"
+			app:srcCompat="@drawable/ic_bomb"
+			app:tint="@color/private_message_date_inverse"
+			tools:ignore="ContentDescription" />
+
+		<ImageView
+			android:id="@+id/status"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="4dp"
+			android:layout_marginLeft="4dp"
+			app:layout_constraintBottom_toBottomOf="@+id/time"
+			app:layout_constraintStart_toEndOf="@+id/bomb"
+			app:layout_constraintTop_toTopOf="@+id/time"
+			app:tint="@color/private_message_date_inverse"
 			tools:ignore="ContentDescription"
 			tools:src="@drawable/message_delivered" />
 

briar-android/src/main/res/layout/list_item_conversation_request.xml

@@ -5,8 +5,9 @@
 	android:layout_width="match_parent"
 	android:layout_height="wrap_content"
 	android:background="@drawable/list_item_background_selectable"
-	android:orientation="vertical"
+	android:orientation="vertical">
-	android:paddingTop="@dimen/message_bubble_margin">
+
+	<include layout="@layout/list_item_conversation_top_notice_in" />
 
 	<com.vanniktech.emoji.EmojiTextView
 		android:id="@+id/msgText"
@@ -15,6 +16,7 @@
 		android:layout_height="wrap_content"
 		android:layout_marginStart="@dimen/message_bubble_margin_tail"
 		android:layout_marginLeft="@dimen/message_bubble_margin_tail"
+		android:layout_marginTop="@dimen/message_bubble_margin"
 		android:layout_marginEnd="@dimen/message_bubble_margin_non_tail"
 		android:layout_marginRight="@dimen/message_bubble_margin_non_tail"
 		android:background="@drawable/msg_in_top"
@@ -68,10 +70,27 @@
 			style="@style/TextMessage.Timestamp"
 			android:layout_width="wrap_content"
 			android:layout_height="wrap_content"
-			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintEnd_toStartOf="@+id/bomb"
+			app:layout_constraintHorizontal_bias="1.0"
+			app:layout_constraintHorizontal_chainStyle="packed"
+			app:layout_constraintStart_toStartOf="parent"
 			app:layout_constraintTop_toBottomOf="@+id/acceptButton"
 			tools:text="Dec 24, 13:37" />
 
+		<ImageView
+			android:id="@+id/bomb"
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_marginStart="4dp"
+			android:layout_marginLeft="4dp"
+			app:layout_constraintEnd_toEndOf="parent"
+			app:layout_constraintStart_toEndOf="@+id/time"
+			app:layout_constraintTop_toBottomOf="@+id/acceptButton"
+			app:srcCompat="@drawable/ic_bomb"
+			app:tint="?android:attr/textColorSecondary"
+			tools:ignore="ContentDescription"
+			tools:visibility="visible" />
+
 	</androidx.constraintlayout.widget.ConstraintLayout>
 
 </LinearLayout>

briar-android/src/main/res/layout/list_item_conversation_top_notice_in.xml

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.vanniktech.emoji.EmojiTextView xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/topNotice"
+	style="@style/TextMessage.Notice"
+	android:layout_width="wrap_content"
+	android:layout_height="wrap_content"
+	android:layout_marginStart="@dimen/message_bubble_margin_tail"
+	android:layout_marginLeft="@dimen/message_bubble_margin_tail"
+	android:layout_marginTop="@dimen/message_bubble_margin"
+	android:layout_marginEnd="@dimen/message_bubble_margin_non_tail"
+	android:layout_marginRight="@dimen/message_bubble_margin_non_tail"
+	android:layout_marginBottom="@dimen/message_bubble_margin"
+	android:background="@drawable/notice_in"
+	android:elevation="@dimen/message_bubble_elevation"
+	android:paddingBottom="@dimen/message_bubble_padding_top"
+	android:textIsSelectable="false"
+	android:visibility="gone"
+	tools:text="@string/auto_delete_msg_contact_enabled"
+	tools:visibility="visible" />

briar-android/src/main/res/layout/list_item_conversation_top_notice_out.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.vanniktech.emoji.EmojiTextView xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:id="@+id/topNotice"
+	style="@style/TextMessage.Notice"
+	android:layout_width="wrap_content"
+	android:layout_height="wrap_content"
+	android:layout_gravity="end|right"
+	android:layout_marginStart="@dimen/message_bubble_margin_non_tail"
+	android:layout_marginLeft="@dimen/message_bubble_margin_non_tail"
+	android:layout_marginEnd="@dimen/message_bubble_margin_tail"
+	android:layout_marginRight="@dimen/message_bubble_margin_tail"
+	android:layout_marginBottom="@dimen/message_bubble_margin"
+	android:background="@drawable/notice_out"
+	android:elevation="@dimen/message_bubble_elevation"
+	android:paddingBottom="@dimen/message_bubble_padding_top"
+	android:textColor="@color/private_message_date_inverse"
+	android:textIsSelectable="false"
+	android:visibility="gone"
+	tools:showIn="@layout/list_item_conversation_msg_out"
+	tools:text="@string/auto_delete_msg_you_enabled"
+	tools:visibility="visible" />

briar-android/src/main/res/layout/view_composite_send_button.xml

@@ -37,6 +37,18 @@
 		app:srcCompat="@drawable/social_send_now_white"
 		app:tint="@color/briar_accent" />
 
+	<ImageView
+		android:id="@+id/bombBadge"
+		android:layout_width="wrap_content"
+		android:layout_height="wrap_content"
+		android:layout_gravity="end|bottom"
+		android:layout_margin="3dp"
+		android:contentDescription="@string/auto_delete_msg_contact_enabled"
+		android:visibility="invisible"
+		app:srcCompat="@drawable/ic_bomb"
+		app:tint="@color/briar_accent"
+		tools:visibility="visible" />
+
 	<ProgressBar
 		android:id="@+id/progressBar"
 		android:layout_width="@dimen/text_input_height"

briar-android/src/main/res/menu/conversation_actions.xml

@@ -1,21 +1,28 @@
 <?xml version="1.0" encoding="utf-8"?>
-<menu
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
-	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
-	xmlns:app="http://schemas.android.com/apk/res-auto">
+	xmlns:tools="http://schemas.android.com/tools">
 
 	<item
 		android:id="@+id/action_introduction"
+		android:enabled="false"
 		android:icon="@drawable/introduction_white"
 		android:title="@string/introduction_menu_item"
-		android:enabled="false"
 		app:showAsAction="never" />
 
 	<item
 		android:id="@+id/action_set_alias"
-		android:title="@string/set_contact_alias"
 		android:enabled="false"
+		android:title="@string/set_contact_alias"
 		app:showAsAction="never" />
 
+	<item
+		android:id="@+id/action_conversation_settings"
+		android:title="@string/menu_item_disappearing_messages"
+		android:visible="false"
+		app:showAsAction="never"
+		tools:visible="true" />
+
 	<item
 		android:id="@+id/action_delete_all_messages"
 		android:title="@string/delete_all_messages"

briar-android/src/main/res/values/strings.xml

@@ -157,7 +157,9 @@
 	<string name="no_contacts_action">Tap the + icon to add a contact</string>
 	<string name="date_no_private_messages">No messages.</string>
 	<string name="no_private_messages">No messages to show</string>
-	<string name="message_hint">Type message</string>
+	<string name="message_hint">New message</string>
+	<string name="message_hint_auto_delete">New disappearing message</string>
+	<string name="message_error">Error sending message</string>
 	<string name="image_caption_hint">Add a caption (optional)</string>
 	<string name="image_attach">Attach image</string>
 	<string name="image_attach_error">Could not attach image(s)</string>
@@ -165,6 +167,32 @@
 	<string name="image_attach_error_invalid_mime_type">Image format unsupported: %s</string>
 	<string name="set_contact_alias">Change contact name</string>
 	<string name="set_contact_alias_hint">Contact name</string>
+	<string name="menu_item_disappearing_messages">Disappearing messages</string>
+	<!-- The first placeholder will show a duration like "7 days". The second placeholder at the end will add "Tap to learn more." -->
+	<string name="auto_delete_msg_you_enabled">Your messages will disappear after %1$s. %2$s</string>
+	<!-- The placeholder at the end will add "Tap to learn more." -->
+	<string name="auto_delete_msg_you_disabled">Your messages will not disappear. %1$s</string>
+	<!-- The second placeholder will show a duration like "7 days". The third placeholder at the end will add "Tap to learn more." -->
+	<string name="auto_delete_msg_contact_enabled">%1$s\'s messages will disappear after %2$s. %3$s</string>
+	<plurals name="duration_minutes">
+		<item quantity="one">%d minute</item>
+		<item quantity="other">%d minutes</item>
+	</plurals>
+	<plurals name="duration_hours">
+		<item quantity="one">%d hour</item>
+		<item quantity="other">%d hours</item>
+	</plurals>
+	<plurals name="duration_days">
+		<item quantity="one">%d day</item>
+		<item quantity="other">%d days</item>
+	</plurals>
+	<!-- The second placeholder at the end will add "Tap to learn more." -->
+	<string name="auto_delete_msg_contact_disabled">%1$s\'s messages will not disappear. %2$s</string>
+	<string name="tap_to_learn_more">Tap to learn more.</string>
+	<string name="auto_delete_changed_warning_title">Disappearing messages changed</string>
+	<string name="auto_delete_changed_warning_message_enabled">Since you started composing your message, disappearing messages have been enabled.</string>
+	<string name="auto_delete_changed_warning_message_disabled">Since you started composing your message, disappearing messages have been disabled.</string>
+	<string name="auto_delete_changed_warning_send">Send anyway</string>
 	<string name="delete_all_messages">Delete all messages</string>
 	<string name="dialog_title_delete_all_messages">Confirm Message Deletion</string>
 	<string name="dialog_message_delete_all_messages">Are you sure that you want to delete all messages?</string>
@@ -172,7 +200,6 @@
 	<string name="dialog_message_not_deleted_ongoing_both">Messages related to ongoing invitations and introductions cannot be deleted until they conclude.</string>
 	<string name="dialog_message_not_deleted_ongoing_introductions">Messages related to ongoing introductions cannot be deleted until they conclude.</string>
 	<string name="dialog_message_not_deleted_ongoing_invitations">Messages related to ongoing invitations cannot be deleted until they conclude.</string>
-	<string name="dialog_message_not_deleted_partly_downloaded">Partly downloaded messages cannot be deleted until they have finished downloading.</string>
 	<string name="dialog_message_not_deleted_not_all_selected_both">To delete an invitation or introduction, you need to select the request and the response.</string>
 	<string name="dialog_message_not_deleted_not_all_selected_introductions">To delete an introduction, you need to select the request and the response.</string>
 	<string name="dialog_message_not_deleted_not_all_selected_invitations">To delete an invitation, you need to select the request and the response.</string>
@@ -290,6 +317,7 @@
 	<string name="introduction_response_accepted_sent">You accepted the introduction to %1$s.</string>
 	<string name="introduction_response_accepted_sent_info">Before %1$s gets added to your contacts, they need to accept the introduction as well. This might take some time.</string>
 	<string name="introduction_response_declined_sent">You declined the introduction to %1$s.</string>
+	<string name="introduction_response_declined_auto">The introduction to %1$s was automatically declined.</string>
 	<string name="introduction_response_accepted_received">%1$s accepted the introduction to %2$s.</string>
 	<string name="introduction_response_declined_received">%1$s declined the introduction to %2$s.</string>
 	<string name="introduction_response_declined_received_by_introducee">%1$s says that %2$s declined the introduction.</string>
@@ -338,6 +366,7 @@
 	</plurals>
 	<string name="groups_invitations_response_accepted_sent">You accepted the group invitation from %s.</string>
 	<string name="groups_invitations_response_declined_sent">You declined the group invitation from %s.</string>
+	<string name="groups_invitations_response_declined_auto">The group invitation from %s was automatically declined.</string>
 	<string name="groups_invitations_response_accepted_received">%s accepted the group invitation.</string>
 	<string name="groups_invitations_response_declined_received">%s declined the group invitation.</string>
 	<string name="sharing_status_groups">Only the creator can invite new members to the group. Below are all current members of the group.</string>
@@ -391,6 +420,7 @@
 	<string name="forum_invitation_already_sharing">Already sharing</string>
 	<string name="forum_invitation_response_accepted_sent">You accepted the forum invitation from %s.</string>
 	<string name="forum_invitation_response_declined_sent">You declined the forum invitation from %s.</string>
+	<string name="forum_invitation_response_declined_auto">The forum invitation from %s was automatically declined.</string>
 	<string name="forum_invitation_response_accepted_received">%s accepted the forum invitation.</string>
 	<string name="forum_invitation_response_declined_received">%s declined the forum invitation.</string>
 
@@ -428,6 +458,7 @@
 	<string name="blogs_sharing_snackbar">Blog shared with chosen contacts</string>
 	<string name="blogs_sharing_response_accepted_sent">You accepted the blog invitation from %s.</string>
 	<string name="blogs_sharing_response_declined_sent">You declined the blog invitation from %s.</string>
+	<string name="blogs_sharing_response_declined_auto">The blog invitation from %s was automatically declined.</string>
 	<string name="blogs_sharing_response_accepted_received">%s accepted the blog invitation.</string>
 	<string name="blogs_sharing_response_declined_received">%s declined the blog invitation.</string>
 	<string name="blogs_sharing_invitation_received">%1$s has shared the blog \"%2$s\" with you.</string>
@@ -551,6 +582,20 @@
 	<string name="choose_ringtone_title">Choose ringtone</string>
 	<string name="cannot_load_ringtone">Cannot load ringtone</string>
 
+	<!-- Conversation Settings -->
+	<string name="disappearing_messages_title">Disappearing messages</string>
+	<string name="disappearing_messages_explanation_long">Turning on this setting will make new
+		messages in this conversation automatically disappear after 7\u00A0days.
+		\n\nThe countdown for the sender\'s copy of the message starts after it has been delivered.
+		The countdown starts for the recipient after they have read the message.
+		\n\nMessages that will disappear are marked with a bomb icon.
+		\n\nKeep in mind that recipients can still make copies of the messages you send.
+		\n\nIf you change this setting, it will apply to your new messages immediately and to your
+		contact\'s messages once they receive your next message.
+		Your contact can also change this setting for the both of you.</string>
+	<string name="learn_more">Learn more</string>
+	<string name="disappearing_messages_summary">Make future messages in this conversation automatically disappear after 7\u00A0days.</string>
+
 	<!-- Settings Feedback -->
 	<string name="feedback_settings_title">Feedback</string>
 	<string name="send_feedback">Send feedback</string>

briar-android/src/main/res/values/themes.xml

@@ -43,6 +43,16 @@
 		<item name="android:filterTouchesWhenObscured">true</item>
 	</style>
 
+	<style name="BriarFullScreenDialogTheme" parent="BriarDialogTheme">
+		<item name="android:windowIsFloating">false</item>
+		<item name="android:windowAnimationStyle">@style/FullScreenDialogAnimation</item>
+	</style>
+
+	<style name="FullScreenDialogAnimation" parent="@android:style/Animation.Activity">
+		<item name="android:windowEnterAnimation">@anim/step_next_in</item>
+		<item name="android:windowExitAnimation">@anim/step_next_out</item>
+	</style>
+
 	<!-- Use this with care. Only used for the screen filter warning dialog -->
 	<style name="BriarDialogThemeNoFilter" parent="BriarDialogTheme">
 		<item name="android:filterTouchesWhenObscured">false</item>

briar-android/src/test/java/org/briarproject/briar/android/logging/LoggingComponent.java

@@ -1,6 +1,7 @@
 package org.briarproject.briar.android.logging;
 
 import org.briarproject.bramble.BrambleCoreModule;
+import org.briarproject.bramble.system.ClockModule;
 import org.briarproject.bramble.test.TestSecureRandomModule;
 
 import java.security.SecureRandom;
@@ -11,6 +12,7 @@ import dagger.Component;
 
 @Singleton
 @Component(modules = {
+		ClockModule.class,
 		BrambleCoreModule.class,
 		TestSecureRandomModule.class,
 		LoggingModule.class,

briar-android/src/test/java/org/briarproject/briar/android/util/UiUtilsFormatDurationTest.java

@@ -0,0 +1,168 @@
+package org.briarproject.briar.android.util;
+
+import android.content.Context;
+import android.content.res.Resources;
+
+import org.briarproject.bramble.test.BrambleMockTestCase;
+import org.briarproject.briar.R;
+import org.jmock.Expectations;
+import org.jmock.lib.legacy.ClassImposteriser;
+import org.junit.Test;
+
+import static java.util.concurrent.TimeUnit.DAYS;
+import static java.util.concurrent.TimeUnit.HOURS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+import static java.util.concurrent.TimeUnit.SECONDS;
+import static org.briarproject.briar.android.util.UiUtils.formatDuration;
+
+public class UiUtilsFormatDurationTest extends BrambleMockTestCase {
+
+	private final Context ctx;
+	private final Resources r;
+	private final int strMinutes = R.plurals.duration_minutes;
+	private final int strHours = R.plurals.duration_hours;
+	private final int strDays = R.plurals.duration_days;
+
+	public UiUtilsFormatDurationTest() {
+		context.setImposteriser(ClassImposteriser.INSTANCE);
+		ctx = context.mock(Context.class);
+		r = context.mock(Resources.class);
+	}
+
+	@Test
+	public void testOneMinute() {
+		expectMinuteString(1);
+		formatDuration(ctx, MINUTES.toMillis(1));
+	}
+
+	@Test
+	public void testOneHour() {
+		expectHourString(1);
+		formatDuration(ctx, HOURS.toMillis(1));
+	}
+
+	@Test
+	public void testOneDay() {
+		expectDayString(1);
+		formatDuration(ctx, DAYS.toMillis(1));
+	}
+
+	@Test
+	public void test10Seconds() {
+		// capped to 1min
+		expectMinuteString(1);
+		formatDuration(ctx, SECONDS.toMillis(10));
+	}
+
+	@Test
+	public void test100Seconds() {
+		expectMinuteString(2);
+		formatDuration(ctx, SECONDS.toMillis(100));
+	}
+
+	@Test
+	public void test2Minutes() {
+		expectMinuteString(2);
+		formatDuration(ctx, MINUTES.toMillis(2));
+	}
+
+	@Test
+	public void test10Minutes() {
+		expectMinuteString(10);
+		formatDuration(ctx, MINUTES.toMillis(10));
+	}
+
+	@Test
+	public void test130Minutes() {
+		expectHourString(2);
+		expectMinuteString(10);
+		formatDuration(ctx, MINUTES.toMillis(130));
+	}
+
+	@Test
+	public void test13Hours() {
+		expectHourString(13);
+		formatDuration(ctx, HOURS.toMillis(13));
+	}
+
+	@Test
+	public void testSevenDays() {
+		expectDayString(7);
+		formatDuration(ctx, DAYS.toMillis(7));
+	}
+
+	@Test
+	public void testSevenDays2Hours() {
+		expectDayString(7);
+		expectHourString(2);
+		formatDuration(ctx, DAYS.toMillis(7) + HOURS.toMillis(2));
+	}
+
+	@Test
+	public void testSevenDays20Minutes() {
+		expectDayString(7);
+		formatDuration(ctx, DAYS.toMillis(7) + MINUTES.toMillis(20));
+	}
+
+	@Test
+	public void testSevenDays40Minutes() {
+		expectDayString(7);
+		expectMinuteString(40);
+		formatDuration(ctx, DAYS.toMillis(7) + MINUTES.toMillis(40));
+	}
+
+	@Test
+	public void testTwoDays11Hours() {
+		expectDayString(2);
+		expectHourString(11);
+		formatDuration(ctx, DAYS.toMillis(2) + HOURS.toMillis(11));
+	}
+
+	@Test
+	public void testTwoDays12Hours() {
+		expectDayString(2);
+		expectHourString(12);
+		formatDuration(ctx, DAYS.toMillis(2) + HOURS.toMillis(12));
+	}
+
+	@Test
+	public void testTwoDays13Hours() {
+		expectDayString(2);
+		expectHourString(13);
+		formatDuration(ctx, DAYS.toMillis(2) + HOURS.toMillis(13));
+	}
+
+	@Test
+	public void test7Days23Hours55Minutes() {
+		expectDayString(7);
+		expectHourString(23);
+		expectMinuteString(55);
+		formatDuration(ctx,
+				DAYS.toMillis(7) + HOURS.toMillis(23) + MINUTES.toMillis(55));
+	}
+
+	private void expectMinuteString(int minutes) {
+		context.checking(new Expectations() {{
+			oneOf(ctx).getResources();
+			will(returnValue(r));
+			oneOf(r).getQuantityString(strMinutes, minutes, minutes);
+		}});
+	}
+
+	private void expectHourString(int hours) {
+		context.checking(new Expectations() {{
+			oneOf(ctx).getResources();
+			will(returnValue(r));
+			oneOf(r).getQuantityString(strHours, hours, hours);
+		}});
+	}
+
+	private void expectDayString(int days) {
+		context.checking(new Expectations() {{
+			oneOf(ctx).getResources();
+			will(returnValue(r));
+			oneOf(r).getQuantityString(strDays, days, days);
+		}});
+	}
+
+}

briar-api/src/main/java/org/briarproject/briar/api/autodelete/AutoDeleteConstants.java

@@ -0,0 +1,23 @@
+package org.briarproject.briar.api.autodelete;
+
+import static java.util.concurrent.TimeUnit.DAYS;
+import static java.util.concurrent.TimeUnit.MINUTES;
+
+public interface AutoDeleteConstants {
+
+	/**
+	 * The minimum valid auto-delete timer duration in milliseconds.
+	 */
+	long MIN_AUTO_DELETE_TIMER_MS = MINUTES.toMillis(1);
+
+	/**
+	 * The maximum valid auto-delete timer duration in milliseconds.
+	 */
+	long MAX_AUTO_DELETE_TIMER_MS = DAYS.toMillis(365);
+
+	/**
+	 * Placeholder value indicating that a message has no auto-delete timer.
+	 * This value should not be sent over the wire - send null instead.
+	 */
+	long NO_AUTO_DELETE_TIMER = -1;
+}

briar-api/src/main/java/org/briarproject/briar/api/autodelete/AutoDeleteManager.java

@@ -0,0 +1,64 @@
+package org.briarproject.briar.api.autodelete;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.db.Transaction;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.ClientId;
+
+import static java.util.concurrent.TimeUnit.MINUTES;
+
+@NotNullByDefault
+public interface AutoDeleteManager {
+
+	/**
+	 * The unique ID of the auto-delete client.
+	 */
+	ClientId CLIENT_ID = new ClientId("org.briarproject.briar.autodelete");
+
+	/**
+	 * The current major version of the auto-delete client.
+	 */
+	int MAJOR_VERSION = 0;
+
+	/**
+	 * The current minor version of the auto-delete client.
+	 */
+	int MINOR_VERSION = 0;
+
+	/**
+	 * The default auto-delete timer duration.
+	 * TODO: Change this to one week before release
+	 */
+	long DEFAULT_TIMER_DURATION = MINUTES.toMillis(1);
+
+	/**
+	 * Returns the auto-delete timer duration for the given contact. Use
+	 * {@link #getAutoDeleteTimer(Transaction, ContactId, long)} if the timer
+	 * will be used in an outgoing message.
+	 */
+	long getAutoDeleteTimer(Transaction txn, ContactId c) throws DbException;
+
+	/**
+	 * Returns the auto-delete timer duration for the given contact, for use in
+	 * a message with the given timestamp. The timestamp is stored.
+	 */
+	long getAutoDeleteTimer(Transaction txn, ContactId c, long timestamp)
+			throws DbException;
+
+	/**
+	 * Sets the auto-delete timer duration for the given contact.
+	 */
+	void setAutoDeleteTimer(Transaction txn, ContactId c, long timer)
+			throws DbException;
+
+	/**
+	 * Receives an auto-delete timer duration from the given contact, carried
+	 * in a message with the given timestamp. The local timer is set to the
+	 * same duration unless it has been
+	 * {@link #setAutoDeleteTimer(Transaction, ContactId, long) changed} more
+	 * recently than the remote timer.
+	 */
+	void receiveAutoDeleteTimer(Transaction txn, ContactId c, long timer,
+			long timestamp) throws DbException;
+}

briar-api/src/main/java/org/briarproject/briar/api/autodelete/UnexpectedTimerException.java

@@ -0,0 +1,12 @@
+package org.briarproject.briar.api.autodelete;
+
+import org.briarproject.bramble.api.db.DbException;
+
+/**
+ * Thrown when a database operation is attempted as part of message storing
+ * and the operation is expecting a different timer state. This
+ * exception may occur due to concurrent updates and does not indicate a
+ * database error.
+ */
+public class UnexpectedTimerException extends DbException {
+}

briar-api/src/main/java/org/briarproject/briar/api/autodelete/event/AutoDeleteTimerMirroredEvent.java

@@ -0,0 +1,28 @@
+package org.briarproject.briar.api.autodelete.event;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class AutoDeleteTimerMirroredEvent extends Event {
+
+	private final ContactId contactId;
+	private final long newTimer;
+
+	public AutoDeleteTimerMirroredEvent(ContactId contactId, long newTimer) {
+		this.contactId = contactId;
+		this.newTimer = newTimer;
+	}
+
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	public long getNewTimer() {
+		return newTimer;
+	}
+}

briar-api/src/main/java/org/briarproject/briar/api/autodelete/event/ConversationMessagesDeletedEvent.java

@@ -0,0 +1,36 @@
+package org.briarproject.briar.api.autodelete.event;
+
+import org.briarproject.bramble.api.contact.ContactId;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
+
+import java.util.Collection;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * An event that is broadcast when one or more messages
+ * in the private conversation with a contact have been deleted.
+ */
+@Immutable
+@NotNullByDefault
+public class ConversationMessagesDeletedEvent extends Event {
+
+	private final ContactId contactId;
+	private final Collection<MessageId> messageIds;
+
+	public ConversationMessagesDeletedEvent(ContactId contactId,
+			Collection<MessageId> messageIds) {
+		this.contactId = contactId;
+		this.messageIds = messageIds;
+	}
+
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	public Collection<MessageId> getMessageIds() {
+		return messageIds;
+	}
+}

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogInvitationRequest.java

@@ -15,9 +15,9 @@ public class BlogInvitationRequest extends InvitationRequest<Blog> {
 	public BlogInvitationRequest(MessageId id, GroupId groupId, long time,
 			boolean local, boolean read, boolean sent, boolean seen,
 			SessionId sessionId, Blog blog, @Nullable String text,
-			boolean available, boolean canBeOpened) {
+			boolean available, boolean canBeOpened, long autoDeleteTimer) {
 		super(id, groupId, time, local, read, sent, seen, sessionId, blog,
-				text, available, canBeOpened);
+				text, available, canBeOpened, autoDeleteTimer);
 	}
 
 	@Override

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogInvitationResponse.java

@@ -12,9 +12,10 @@ public class BlogInvitationResponse extends InvitationResponse {
 
 	public BlogInvitationResponse(MessageId id, GroupId groupId, long time,
 			boolean local, boolean read, boolean sent, boolean seen,
-			SessionId sessionId, boolean accept, GroupId shareableId) {
+			SessionId sessionId, boolean accept, GroupId shareableId,
+			long autoDeleteTimer, boolean isAutoDecline) {
 		super(id, groupId, time, local, read, sent, seen, sessionId,
-				accept, shareableId);
+				accept, shareableId, autoDeleteTimer, isAutoDecline);
 	}
 
 	@Override

briar-api/src/main/java/org/briarproject/briar/api/blog/BlogSharingManager.java

@@ -18,5 +18,5 @@ public interface BlogSharingManager extends SharingManager<Blog> {
 	/**
 	 * The current minor version of the blog sharing client.
 	 */
-	int MINOR_VERSION = 0;
+	int MINOR_VERSION = 1;
 }

briar-api/src/main/java/org/briarproject/briar/api/client/MessageTracker.java

@@ -61,8 +61,11 @@ public interface MessageTracker {
 
 	/**
 	 * Marks a message as read or unread and updates the group count.
+	 *
+	 * @return True if the message was previously marked as read
 	 */
-	void setReadFlag(GroupId g, MessageId m, boolean read) throws DbException;
+	boolean setReadFlag(Transaction txn, GroupId g, MessageId m, boolean read)
+			throws DbException;
 
 	/**
 	 * Resets the {@link GroupCount} to the given msgCount and unreadCount.

briar-api/src/main/java/org/briarproject/briar/api/conversation/ConversationManager.java

@@ -21,7 +21,6 @@ public interface ConversationManager {
 	int DELETE_SESSION_INVITATION_INCOMPLETE = 1 << 1;
 	int DELETE_SESSION_INTRODUCTION_IN_PROGRESS = 1 << 2;
 	int DELETE_SESSION_INVITATION_IN_PROGRESS = 1 << 3;
-	int DELETE_NOT_DOWNLOADED = 1 << 4;
 
 	/**
 	 * Clients that present messages in a private conversation need to
@@ -48,6 +47,13 @@ public interface ConversationManager {
 	 */
 	GroupCount getGroupCount(Transaction txn, ContactId c) throws DbException;
 
+	/**
+	 * Returns a timestamp for an outgoing message, which is later than the
+	 * timestamp of any message in the conversation with the given contact.
+	 */
+	long getTimestampForOutgoingMessage(Transaction txn, ContactId c)
+			throws DbException;
+
 	/**
 	 * Deletes all messages exchanged with the given contact.
 	 */

briar-api/src/main/java/org/briarproject/briar/api/conversation/ConversationMessageHeader.java

@@ -12,18 +12,20 @@ public abstract class ConversationMessageHeader {
 
 	private final MessageId id;
 	private final GroupId groupId;
-	private final long timestamp;
+	private final long timestamp, autoDeleteTimer;
-	private final boolean local, sent, seen, read;
+	private final boolean local, read, sent, seen;
 
-	public ConversationMessageHeader(MessageId id, GroupId groupId, long timestamp,
+	public ConversationMessageHeader(MessageId id, GroupId groupId,
-			boolean local, boolean read, boolean sent, boolean seen) {
+			long timestamp, boolean local, boolean read, boolean sent,
+			boolean seen, long autoDeleteTimer) {
 		this.id = id;
 		this.groupId = groupId;
 		this.timestamp = timestamp;
 		this.local = local;
+		this.read = read;
 		this.sent = sent;
 		this.seen = seen;
-		this.read = read;
+		this.autoDeleteTimer = autoDeleteTimer;
 	}
 
 	public MessageId getId() {
@@ -55,4 +57,8 @@ public abstract class ConversationMessageHeader {
 	}
 
 	public abstract <T> T accept(ConversationMessageVisitor<T> v);
+
+	public long getAutoDeleteTimer() {
+		return autoDeleteTimer;
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/conversation/ConversationRequest.java

@@ -20,11 +20,12 @@ public abstract class ConversationRequest<N extends Nameable>
 	private final String text;
 	private final boolean answered;
 
-	public ConversationRequest(MessageId messageId, GroupId groupId, long time,
+	public ConversationRequest(MessageId messageId, GroupId groupId,
-			boolean local, boolean read, boolean sent, boolean seen,
+			long timestamp, boolean local, boolean read, boolean sent,
-			SessionId sessionId, N nameable, @Nullable String text,
+			boolean seen, SessionId sessionId, N nameable,
-			boolean answered) {
+			@Nullable String text, boolean answered, long autoDeleteTimer) {
-		super(messageId, groupId, time, local, read, sent, seen);
+		super(messageId, groupId, timestamp, local, read, sent, seen,
+				autoDeleteTimer);
 		this.sessionId = sessionId;
 		this.nameable = nameable;
 		this.text = text;

briar-api/src/main/java/org/briarproject/briar/api/conversation/ConversationResponse.java

@@ -12,14 +12,16 @@ import javax.annotation.concurrent.Immutable;
 public abstract class ConversationResponse extends ConversationMessageHeader {
 
 	private final SessionId sessionId;
-	private final boolean accepted;
+	private final boolean accepted, isAutoDecline;
 
 	public ConversationResponse(MessageId id, GroupId groupId, long time,
 			boolean local, boolean read, boolean sent, boolean seen,
-			SessionId sessionId, boolean accepted) {
+			SessionId sessionId, boolean accepted, long autoDeleteTimer,
-		super(id, groupId, time, local, read, sent, seen);
+			boolean isAutoDecline) {
+		super(id, groupId, time, local, read, sent, seen, autoDeleteTimer);
 		this.sessionId = sessionId;
 		this.accepted = accepted;
+		this.isAutoDecline = isAutoDecline;
 	}
 
 	public SessionId getSessionId() {
@@ -30,4 +32,7 @@ public abstract class ConversationResponse extends ConversationMessageHeader {
 		return accepted;
 	}
 
+	public boolean isAutoDecline() {
+		return isAutoDecline;
+	}
 }

briar-api/src/main/java/org/briarproject/briar/api/conversation/DeletionResult.java

@@ -4,7 +4,6 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 
 import javax.annotation.concurrent.NotThreadSafe;
 
-import static org.briarproject.briar.api.conversation.ConversationManager.DELETE_NOT_DOWNLOADED;
 import static org.briarproject.briar.api.conversation.ConversationManager.DELETE_SESSION_INTRODUCTION_INCOMPLETE;
 import static org.briarproject.briar.api.conversation.ConversationManager.DELETE_SESSION_INTRODUCTION_IN_PROGRESS;
 import static org.briarproject.briar.api.conversation.ConversationManager.DELETE_SESSION_INVITATION_INCOMPLETE;
@@ -36,10 +35,6 @@ public class DeletionResult {
 		result |= DELETE_SESSION_INTRODUCTION_IN_PROGRESS;
 	}
 
-	public void addNotFullyDownloaded() {
-		result |= DELETE_NOT_DOWNLOADED;
-	}
-
 	public boolean allDeleted() {
 		return result == 0;
 	}
@@ -59,9 +54,4 @@ public class DeletionResult {
 	public boolean hasNotAllInvitationSelected() {
 		return (result & DELETE_SESSION_INVITATION_INCOMPLETE) != 0;
 	}
-
-	public boolean hasNotFullyDownloaded() {
-		return (result & DELETE_NOT_DOWNLOADED) != 0;
-	}
-
 }

briar-api/src/main/java/org/briarproject/briar/api/forum/ForumInvitationRequest.java

@@ -17,9 +17,9 @@ public class ForumInvitationRequest extends InvitationRequest<Forum> {
 	public ForumInvitationRequest(MessageId id, GroupId groupId, long time,
 			boolean local, boolean read, boolean sent, boolean seen,
 			SessionId sessionId, Forum forum, @Nullable String text,
-			boolean available, boolean canBeOpened) {
+			boolean available, boolean canBeOpened, long autoDeleteTimer) {
 		super(id, groupId, time, local, read, sent, seen, sessionId, forum,
-				text, available, canBeOpened);
+				text, available, canBeOpened, autoDeleteTimer);
 	}
 
 	@Override

briar-api/src/main/java/org/briarproject/briar/api/forum/ForumInvitationResponse.java

@@ -15,9 +15,10 @@ public class ForumInvitationResponse extends InvitationResponse {
 
 	public ForumInvitationResponse(MessageId id, GroupId groupId, long time,
 			boolean local, boolean read, boolean sent, boolean seen,
-			SessionId sessionId, boolean accept, GroupId shareableId) {
+			SessionId sessionId, boolean accept, GroupId shareableId,
+			long autoDeleteTimer, boolean isAutoDecline) {
 		super(id, groupId, time, local, read, sent, seen, sessionId,
-				accept, shareableId);
+				accept, shareableId, autoDeleteTimer, isAutoDecline);
 	}
 
 	@Override

briar-api/src/main/java/org/briarproject/briar/api/forum/ForumSharingManager.java

@@ -18,5 +18,5 @@ public interface ForumSharingManager extends SharingManager<Forum> {
 	/**
 	 * The current minor version of the forum sharing client.
 	 */
-	int MINOR_VERSION = 0;
+	int MINOR_VERSION = 1;
 }

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionManager.java

@@ -31,18 +31,18 @@ public interface IntroductionManager extends ConversationClient {
 	/**
 	 * The current minor version of the introduction client.
 	 */
-	int MINOR_VERSION = 0;
+	int MINOR_VERSION = 1;
 
 	/**
 	 * Sends two initial introduction messages.
 	 */
-	void makeIntroduction(Contact c1, Contact c2, @Nullable String text,
+	void makeIntroduction(Contact c1, Contact c2, @Nullable String text)
-			long timestamp) throws DbException;
+			throws DbException;
 
 	/**
 	 * Responds to an introduction.
 	 */
 	void respondToIntroduction(ContactId contactId, SessionId sessionId,
-			long timestamp, boolean accept) throws DbException;
+			boolean accept) throws DbException;
 
 }

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionRequest.java

@@ -18,12 +18,12 @@ public class IntroductionRequest extends ConversationRequest<Author> {
 
 	private final AuthorInfo authorInfo;
 
-	public IntroductionRequest(MessageId messageId, GroupId groupId,
+	public IntroductionRequest(MessageId messageId, GroupId groupId, long time,
-			long time, boolean local, boolean read, boolean sent, boolean seen,
+			boolean local, boolean read, boolean sent, boolean seen,
 			SessionId sessionId, Author author, @Nullable String text,
-			boolean answered, AuthorInfo authorInfo) {
+			boolean answered, AuthorInfo authorInfo, long autoDeleteTimer) {
 		super(messageId, groupId, time, local, read, sent, seen, sessionId,
-				author, text, answered);
+				author, text, answered, autoDeleteTimer);
 		this.authorInfo = authorInfo;
 	}
 

briar-api/src/main/java/org/briarproject/briar/api/introduction/IntroductionResponse.java

@@ -1,13 +1,13 @@
 package org.briarproject.briar.api.introduction;
 
 import org.briarproject.bramble.api.identity.Author;
-import org.briarproject.briar.api.identity.AuthorInfo;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.client.SessionId;
 import org.briarproject.briar.api.conversation.ConversationMessageVisitor;
 import org.briarproject.briar.api.conversation.ConversationResponse;
+import org.briarproject.briar.api.identity.AuthorInfo;
 
 import javax.annotation.concurrent.Immutable;
 
@@ -25,9 +25,10 @@ public class IntroductionResponse extends ConversationResponse {
 	public IntroductionResponse(MessageId messageId, GroupId groupId, long time,
 			boolean local, boolean read, boolean sent, boolean seen,
 			SessionId sessionId, boolean accepted, Author author,
-			AuthorInfo introducedAuthorInfo, Role role, boolean canSucceed) {
+			AuthorInfo introducedAuthorInfo, Role role, boolean canSucceed,
+			long autoDeleteTimer, boolean isAutoDecline) {
 		super(messageId, groupId, time, local, read, sent, seen, sessionId,
-				accepted);
+				accepted, autoDeleteTimer, isAutoDecline);
 		this.introducedAuthor = author;
 		this.introducedAuthorInfo = introducedAuthorInfo;
 		this.ourRole = role;