Merge branch '1832-use-conversation-timestamp' into '804-self-destructing-messages'

Use latest conversation timestamp for all invitation/introduction messages

See merge request briar/briar!1310

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

@@ -14,6 +14,7 @@ import org.briarproject.bramble.api.contact.ContactManager;
 import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.crypto.PasswordStrengthEstimator;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
+import org.briarproject.bramble.api.db.TransactionManager;
 import org.briarproject.bramble.api.event.EventBus;
 import org.briarproject.bramble.api.identity.IdentityManager;
 import org.briarproject.bramble.api.keyagreement.KeyAgreementTask;
@@ -39,6 +40,7 @@ import org.briarproject.briar.api.android.AndroidNotificationManager;
 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.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.blog.BlogManager;
 import org.briarproject.briar.api.blog.BlogPostFactory;
 import org.briarproject.briar.api.blog.BlogSharingManager;
@@ -169,6 +171,10 @@ public interface AndroidComponent
 
 	AndroidWakeLockManager wakeLockManager();
 
+	TransactionManager transactionManager();
+
+	AutoDeleteManager autoDeleteManager();
+
 	void inject(SignInReminderReceiver briarService);
 
 	void inject(BriarService briarService);

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

@@ -753,18 +753,10 @@ public class ConversationActivity extends BriarActivity
 			List<AttachmentHeader> attachmentHeaders) {
 		if (isNullOrEmpty(text) && attachmentHeaders.isEmpty())
 			throw new AssertionError();
-		long timestamp = System.currentTimeMillis();
+		viewModel.sendMessage(text, attachmentHeaders);
-		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
-		viewModel.sendMessage(text, attachmentHeaders, timestamp);
 		textInputView.clearText();
 	}
 
-	private long getMinTimestampForNewMessage() {
-		// Don't use an earlier timestamp than the newest message
-		ConversationItem item = adapter.getLastItem();
-		return item == null ? 0 : item.getTime() + 1;
-	}
-
 	private void onAddedPrivateMessage(@Nullable PrivateMessageHeader h) {
 		if (h == null) return;
 		addConversationItem(h.accept(visitor));
@@ -969,13 +961,11 @@ 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);
@@ -1051,9 +1041,8 @@ public class ConversationActivity extends BriarActivity
 
 	@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/ConversationViewModel.java

@@ -30,6 +30,7 @@ import org.briarproject.briar.android.util.UiUtils;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
 import org.briarproject.briar.api.messaging.PrivateMessage;
@@ -86,6 +87,7 @@ public class ConversationViewModel extends AndroidViewModel
 	private final AttachmentRetriever attachmentRetriever;
 	private final AttachmentCreator attachmentCreator;
 	private final AutoDeleteManager autoDeleteManager;
+	private final ConversationManager conversationManager;
 
 	@Nullable
 	private ContactId contactId = null;
@@ -119,7 +121,8 @@ public class ConversationViewModel extends AndroidViewModel
 			PrivateMessageFactory privateMessageFactory,
 			AttachmentRetriever attachmentRetriever,
 			AttachmentCreator attachmentCreator,
-			AutoDeleteManager autoDeleteManager) {
+			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager) {
 		super(application);
 		this.dbExecutor = dbExecutor;
 		this.db = db;
@@ -131,6 +134,7 @@ public class ConversationViewModel extends AndroidViewModel
 		this.attachmentRetriever = attachmentRetriever;
 		this.attachmentCreator = attachmentCreator;
 		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		messagingGroupId = Transformations
 				.map(contact, c -> messagingManager.getContactGroup(c).getId());
 		contactDeleted.setValue(false);
@@ -213,14 +217,13 @@ public class ConversationViewModel extends AndroidViewModel
 	}
 
 	@UiThread
-	void sendMessage(@Nullable String text,
+	void sendMessage(@Nullable String text, List<AttachmentHeader> headers) {
-			List<AttachmentHeader> headers, long timestamp) {
 		// messagingGroupId is loaded with the contact
 		observeForeverOnce(messagingGroupId, groupId -> {
 			requireNonNull(groupId);
 			observeForeverOnce(privateMessageFormat, format ->
 					storeMessage(requireNonNull(contactId), groupId, text,
-							headers, timestamp, format));
+							headers, format));
 		});
 	}
 
@@ -282,8 +285,10 @@ public class ConversationViewModel extends AndroidViewModel
 
 	private PrivateMessage createMessage(Transaction txn, ContactId c,
 			GroupId groupId, @Nullable String text,
-			List<AttachmentHeader> headers, long timestamp,
+			List<AttachmentHeader> headers, PrivateMessageFormat format)
-			PrivateMessageFormat format) throws DbException {
+			throws DbException {
+		long timestamp =
+				conversationManager.getTimestampForOutgoingMessage(txn, c);
 		try {
 			if (format == TEXT_ONLY) {
 				return privateMessageFactory.createLegacyPrivateMessage(
@@ -304,13 +309,13 @@ public class ConversationViewModel extends AndroidViewModel
 	@UiThread
 	private void storeMessage(ContactId c, GroupId groupId,
 			@Nullable String text, List<AttachmentHeader> headers,
-			long timestamp, PrivateMessageFormat format) {
+			PrivateMessageFormat format) {
 		dbExecutor.execute(() -> {
 			try {
 				db.transaction(false, txn -> {
 					long start = now();
 					PrivateMessage m = createMessage(txn, c, groupId, text,
-							headers, timestamp, format);
+							headers, format);
 					messagingManager.addLocalMessage(txn, m);
 					logDuration(LOG, "Storing message", start);
 					Message message = m.getMessage();

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

@@ -211,8 +211,7 @@ 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.privategroup.GroupMessage;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroup;
@@ -35,6 +39,8 @@ 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
@@ -43,9 +49,12 @@ 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;
@@ -56,16 +65,26 @@ 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,
-			IdentityManager identityManager, PrivateGroupFactory groupFactory,
+			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
+			LifecycleManager lifecycleManager,
+			ContactManager contactManager,
+			IdentityManager identityManager,
+			PrivateGroupFactory groupFactory,
 			GroupMessageFactory groupMessageFactory,
 			PrivateGroupManager groupManager,
 			GroupInvitationFactory groupInvitationFactory,
-			GroupInvitationManager groupInvitationManager, Clock clock) {
+			GroupInvitationManager groupInvitationManager,
+			Clock clock) {
 		super(dbExecutor, lifecycleManager, contactManager);
 		this.cryptoExecutor = cryptoExecutor;
+		this.db = db;
+		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		this.contactManager = contactManager;
 		this.identityManager = identityManager;
 		this.groupFactory = groupFactory;
@@ -129,16 +148,14 @@ class CreateGroupControllerImpl extends ContactSelectorControllerImpl
 			ResultExceptionHandler<Void, DbException> handler) {
 		runOnDbThread(() -> {
 			try {
-				LocalAuthor localAuthor = identityManager.getLocalAuthor();
+				db.transaction(true, 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);
@@ -146,17 +163,31 @@ 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);
+				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);
 		});
@@ -167,16 +198,16 @@ 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
 					}
 				}
-				//noinspection ConstantConditions
 				handler.onResult(null);
 			} catch (DbException e) {
 				logException(LOG, WARNING, e);
@@ -187,15 +218,16 @@ 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/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 java.util.Collection;
 import java.util.concurrent.Executor;
@@ -25,6 +23,7 @@ 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
@@ -33,21 +32,16 @@ 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,
-			ConversationManager conversationManager,
+			BlogSharingManager blogSharingManager) {
-			BlogSharingManager blogSharingManager, Clock clock) {
 		super(dbExecutor, lifecycleManager, contactManager);
-		this.conversationManager = conversationManager;
 		this.blogSharingManager = blogSharingManager;
-		this.clock = clock;
 	}
 
 	@Override
@@ -62,10 +56,7 @@ 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 java.util.Collection;
@@ -25,6 +23,7 @@ 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
@@ -33,21 +32,16 @@ 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,
-			ConversationManager conversationManager,
+			ForumSharingManager forumSharingManager) {
-			ForumSharingManager forumSharingManager, Clock clock) {
 		super(dbExecutor, lifecycleManager, contactManager);
-		this.conversationManager = conversationManager;
 		this.forumSharingManager = forumSharingManager;
-		this.clock = clock;
 	}
 
 	@Override
@@ -62,10 +56,7 @@ 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-api/src/main/java/org/briarproject/briar/api/conversation/ConversationManager.java

@@ -43,6 +43,18 @@ public interface ConversationManager {
 	 */
 	GroupCount getGroupCount(ContactId c) throws DbException;
 
+	/**
+	 * Returns the unified group count for all private conversation messages.
+	 */
+	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/introduction/IntroductionManager.java

@@ -36,13 +36,13 @@ public interface IntroductionManager extends ConversationClient {
 	/**
 	 * 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/privategroup/invitation/GroupInvitationManager.java

@@ -43,7 +43,8 @@ public interface GroupInvitationManager extends ConversationClient {
 	 * pending.
 	 */
 	void sendInvitation(GroupId g, ContactId c, @Nullable String text,
-			long timestamp, byte[] signature) throws DbException;
+			long timestamp, byte[] signature, long autoDeleteTimer)
+			throws DbException;
 
 	/**
 	 * Responds to a pending private group invitation from the given contact.

briar-api/src/main/java/org/briarproject/briar/api/sharing/SharingManager.java

@@ -21,7 +21,7 @@ public interface SharingManager<S extends Shareable>
 	 * including optional text.
 	 */
 	void sendInvitation(GroupId shareableId, ContactId contactId,
-			@Nullable String text, long timestamp) throws DbException;
+			@Nullable String text) throws DbException;
 
 	/**
 	 * Responds to a pending group invitation

briar-core/src/main/java/org/briarproject/briar/introduction/AbstractProtocolEngine.java

@@ -26,6 +26,7 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.introduction.IntroductionResponse;
 import org.briarproject.briar.api.introduction.event.IntroductionResponseReceivedEvent;
 
@@ -59,6 +60,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 	protected final MessageEncoder messageEncoder;
 	protected final ClientVersioningManager clientVersioningManager;
 	protected final AutoDeleteManager autoDeleteManager;
+	protected final ConversationManager conversationManager;
 	protected final Clock clock;
 
 	AbstractProtocolEngine(
@@ -72,6 +74,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 			MessageEncoder messageEncoder,
 			ClientVersioningManager clientVersioningManager,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		this.db = db;
 		this.clientHelper = clientHelper;
@@ -83,6 +86,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 		this.messageEncoder = messageEncoder;
 		this.clientVersioningManager = clientVersioningManager;
 		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		this.clock = clock;
 	}
 
@@ -227,14 +231,10 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 		return !dependency.equals(lastRemoteMessageId);
 	}
 
-	long getLocalTimestamp(long localTimestamp, long requestTimestamp) {
+	long getTimestampForOutgoingMessage(Transaction txn, GroupId contactGroupId)
-		return Math.max(
+			throws DbException {
-				clock.currentTimeMillis(),
+		ContactId c = getContactId(txn, contactGroupId);
-				Math.max(
+		return conversationManager.getTimestampForOutgoingMessage(txn, c);
-						localTimestamp,
-						requestTimestamp
-				) + 1
-		);
 	}
 
 	private ContactId getContactId(Transaction txn, GroupId contactGroupId)

briar-core/src/main/java/org/briarproject/briar/introduction/IntroduceeProtocolEngine.java

@@ -31,6 +31,7 @@ import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.introduction.IntroductionRequest;
 import org.briarproject.briar.api.introduction.event.IntroductionAbortedEvent;
 import org.briarproject.briar.api.introduction.event.IntroductionRequestReceivedEvent;
@@ -43,6 +44,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static java.lang.Math.max;
 import static java.util.logging.Level.WARNING;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.briar.introduction.IntroduceeState.AWAIT_AUTH;
@@ -75,15 +77,17 @@ class IntroduceeProtocolEngine
 			IdentityManager identityManager,
 			MessageParser messageParser,
 			MessageEncoder messageEncoder,
-			Clock clock,
 			IntroductionCrypto crypto,
 			KeyManager keyManager,
 			TransportPropertyManager transportPropertyManager,
 			ClientVersioningManager clientVersioningManager,
-			AutoDeleteManager autoDeleteManager) {
+			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
+			Clock clock) {
 		super(db, clientHelper, contactManager, contactGroupFactory,
 				messageTracker, identityManager, messageParser, messageEncoder,
-				clientVersioningManager, autoDeleteManager, clock);
+				clientVersioningManager, autoDeleteManager,
+				conversationManager, clock);
 		this.crypto = crypto;
 		this.keyManager = keyManager;
 		this.transportPropertyManager = transportPropertyManager;
@@ -91,18 +95,18 @@ class IntroduceeProtocolEngine
 
 	@Override
 	public IntroduceeSession onRequestAction(Transaction txn,
-			IntroduceeSession session, @Nullable String text, long timestamp) {
+			IntroduceeSession session, @Nullable String text) {
 		throw new UnsupportedOperationException(); // Invalid in this role
 	}
 
 	@Override
 	public IntroduceeSession onAcceptAction(Transaction txn,
-			IntroduceeSession session, long timestamp) throws DbException {
+			IntroduceeSession session) throws DbException {
 		switch (session.getState()) {
 			case AWAIT_RESPONSES:
 			case REMOTE_DECLINED:
 			case REMOTE_ACCEPTED:
-				return onLocalAccept(txn, session, timestamp);
+				return onLocalAccept(txn, session);
 			case START:
 			case LOCAL_DECLINED:
 			case LOCAL_ACCEPTED:
@@ -116,12 +120,12 @@ class IntroduceeProtocolEngine
 
 	@Override
 	public IntroduceeSession onDeclineAction(Transaction txn,
-			IntroduceeSession session, long timestamp) throws DbException {
+			IntroduceeSession session) throws DbException {
 		switch (session.getState()) {
 			case AWAIT_RESPONSES:
 			case REMOTE_DECLINED:
 			case REMOTE_ACCEPTED:
-				return onLocalDecline(txn, session, timestamp);
+				return onLocalDecline(txn, session);
 			case START:
 			case LOCAL_DECLINED:
 			case LOCAL_ACCEPTED:
@@ -272,7 +276,7 @@ class IntroduceeProtocolEngine
 	}
 
 	private IntroduceeSession onLocalAccept(Transaction txn,
-			IntroduceeSession s, long timestamp) throws DbException {
+			IntroduceeSession s) throws DbException {
 		// Mark the request message unavailable to answer
 		markRequestsUnavailableToAnswer(txn, s);
 
@@ -283,8 +287,8 @@ class IntroduceeProtocolEngine
 		Map<TransportId, TransportProperties> transportProperties =
 				transportPropertyManager.getLocalProperties(txn);
 
-		// Send a ACCEPT message
+		// Send an ACCEPT message
-		long localTimestamp = Math.max(timestamp + 1, getLocalTimestamp(s));
+		long localTimestamp = getTimestampForVisibleMessage(txn, s);
 		Message sent = sendAcceptMessage(txn, s, localTimestamp, publicKey,
 				localTimestamp, transportProperties, true);
 		// Track the message
@@ -309,12 +313,12 @@ class IntroduceeProtocolEngine
 	}
 
 	private IntroduceeSession onLocalDecline(Transaction txn,
-			IntroduceeSession s, long timestamp) throws DbException {
+			IntroduceeSession s) throws DbException {
 		// Mark the request message unavailable to answer
 		markRequestsUnavailableToAnswer(txn, s);
 
 		// Send a DECLINE message
-		long localTimestamp = Math.max(timestamp + 1, getLocalTimestamp(s));
+		long localTimestamp = getTimestampForVisibleMessage(txn, s);
 		Message sent = sendDeclineMessage(txn, s, localTimestamp, true);
 
 		// Track the message
@@ -412,8 +416,8 @@ class IntroduceeProtocolEngine
 			return abort(txn, s);
 		}
 		if (s.getState() != AWAIT_AUTH) throw new AssertionError();
-		Message sent = sendAuthMessage(txn, s, getLocalTimestamp(s), mac,
+		long localTimestamp = getTimestampForInvisibleMessage(s);
-				signature);
+		Message sent = sendAuthMessage(txn, s, localTimestamp, mac, signature);
 		return IntroduceeSession.addLocalAuth(s, AWAIT_AUTH, sent, masterKey,
 				aliceMacKey, bobMacKey);
 	}
@@ -464,7 +468,8 @@ class IntroduceeProtocolEngine
 
 		// send ACTIVATE message with a MAC
 		byte[] mac = crypto.activateMac(s);
-		Message sent = sendActivateMessage(txn, s, getLocalTimestamp(s), mac);
+		long localTimestamp = getTimestampForInvisibleMessage(s);
+		Message sent = sendActivateMessage(txn, s, localTimestamp, mac);
 
 		// Move to AWAIT_ACTIVATE state and clear key material from session
 		return IntroduceeSession.awaitActivate(s, m, sent, keys);
@@ -515,7 +520,8 @@ class IntroduceeProtocolEngine
 		markRequestsUnavailableToAnswer(txn, s);
 
 		// Send an ABORT message
-		Message sent = sendAbortMessage(txn, s, getLocalTimestamp(s));
+		long localTimestamp = getTimestampForInvisibleMessage(s);
+		Message sent = sendAbortMessage(txn, s, localTimestamp);
 
 		// Broadcast abort event for testing
 		txn.attach(new IntroductionAbortedEvent(s.getSessionId()));
@@ -530,9 +536,34 @@ class IntroduceeProtocolEngine
 		return isInvalidDependency(s.getLastRemoteMessageId(), dependency);
 	}
 
-	private long getLocalTimestamp(IntroduceeSession s) {
+	/**
-		return getLocalTimestamp(s.getLocalTimestamp(),
+	 * Returns a timestamp for a visible outgoing message. The timestamp is
-				s.getRequestTimestamp());
+	 * later than the timestamp of any message sent or received so far in the
+	 * conversation, and later than the {@link
+	 * #getSessionTimestamp(IntroduceeSession) session timestamp}.
+	 */
+	private long getTimestampForVisibleMessage(Transaction txn,
+			IntroduceeSession s) throws DbException {
+		long conversationTimestamp =
+				getTimestampForOutgoingMessage(txn, s.getContactGroupId());
+		return max(conversationTimestamp, getSessionTimestamp(s) + 1);
+	}
+
+	/**
+	 * Returns a timestamp for an invisible outgoing message. The timestamp is
+	 * later than the {@link #getSessionTimestamp(IntroduceeSession) session
+	 * timestamp}.
+	 */
+	private long getTimestampForInvisibleMessage(IntroduceeSession s) {
+		return max(clock.currentTimeMillis(), getSessionTimestamp(s) + 1);
+	}
+
+	/**
+	 * Returns the latest timestamp of any message sent so far in the session,
+	 * and any request message received so far in the session.
+	 */
+	private long getSessionTimestamp(IntroduceeSession s) {
+		return max(s.getLocalTimestamp(), s.getRequestTimestamp());
 	}
 
 	private void addSessionId(Transaction txn, MessageId m, SessionId sessionId)

briar-core/src/main/java/org/briarproject/briar/introduction/IntroducerProtocolEngine.java

@@ -17,6 +17,7 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.ProtocolStateException;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.introduction.event.IntroductionAbortedEvent;
 import org.briarproject.briar.introduction.IntroducerSession.Introducee;
 
@@ -24,6 +25,7 @@ import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static java.lang.Math.max;
 import static org.briarproject.briar.introduction.IntroducerState.AWAIT_ACTIVATES;
 import static org.briarproject.briar.introduction.IntroducerState.AWAIT_ACTIVATE_A;
 import static org.briarproject.briar.introduction.IntroducerState.AWAIT_ACTIVATE_B;
@@ -54,19 +56,21 @@ class IntroducerProtocolEngine
 			MessageEncoder messageEncoder,
 			ClientVersioningManager clientVersioningManager,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		super(db, clientHelper, contactManager, contactGroupFactory,
 				messageTracker, identityManager, messageParser, messageEncoder,
-				clientVersioningManager, autoDeleteManager, clock);
+				clientVersioningManager, autoDeleteManager,
+				conversationManager, clock);
 	}
 
 	@Override
 	public IntroducerSession onRequestAction(Transaction txn,
-			IntroducerSession s, @Nullable String text, long timestamp)
+			IntroducerSession s, @Nullable String text)
 			throws DbException {
 		switch (s.getState()) {
 			case START:
-				return onLocalRequest(txn, s, text, timestamp);
+				return onLocalRequest(txn, s, text);
 			case AWAIT_RESPONSES:
 			case AWAIT_RESPONSE_A:
 			case AWAIT_RESPONSE_B:
@@ -86,37 +90,24 @@ class IntroducerProtocolEngine
 
 	@Override
 	public IntroducerSession onAcceptAction(Transaction txn,
-			IntroducerSession s, long timestamp) {
+			IntroducerSession s) {
 		throw new UnsupportedOperationException(); // Invalid in this role
 	}
 
 	@Override
 	public IntroducerSession onDeclineAction(Transaction txn,
-			IntroducerSession s, long timestamp) {
+			IntroducerSession s) {
 		throw new UnsupportedOperationException(); // Invalid in this role
 	}
 
 	IntroducerSession onIntroduceeRemoved(Transaction txn,
 			Introducee remainingIntroducee, IntroducerSession session)
 			throws DbException {
-		// abort session
+		// abort session with remaining introducee
-		IntroducerSession s = abort(txn, session);
+		IntroducerSession s = abort(txn, session, remainingIntroducee);
-		// reset information for introducee that was removed
-		Introducee introduceeA, introduceeB;
-		if (remainingIntroducee.author.equals(s.getIntroduceeA().author)) {
-			introduceeA = s.getIntroduceeA();
-			introduceeB =
-					new Introducee(s.getSessionId(), s.getIntroduceeB().groupId,
-							s.getIntroduceeB().author);
-		} else if (remainingIntroducee.author
-				.equals(s.getIntroduceeB().author)) {
-			introduceeA =
-					new Introducee(s.getSessionId(), s.getIntroduceeA().groupId,
-							s.getIntroduceeA().author);
-			introduceeB = s.getIntroduceeB();
-		} else throw new DbException();
 		return new IntroducerSession(s.getSessionId(), s.getState(),
-				s.getRequestTimestamp(), introduceeA, introduceeB);
+				s.getRequestTimestamp(), s.getIntroduceeA(),
+				s.getIntroduceeB());
 	}
 
 	@Override
@@ -226,13 +217,13 @@ class IntroducerProtocolEngine
 	}
 
 	private IntroducerSession onLocalRequest(Transaction txn,
-			IntroducerSession s, @Nullable String text, long timestamp)
+			IntroducerSession s, @Nullable String text) throws DbException {
-			throws DbException {
 		// Send REQUEST messages
-		long maxIntroduceeTimestamp =
+		long timestampA =
-				Math.max(getLocalTimestamp(s, s.getIntroduceeA()),
+				getTimestampForVisibleMessage(txn, s, s.getIntroduceeA());
-						getLocalTimestamp(s, s.getIntroduceeB()));
+		long timestampB =
-		long localTimestamp = Math.max(timestamp, maxIntroduceeTimestamp);
+				getTimestampForVisibleMessage(txn, s, s.getIntroduceeB());
+		long localTimestamp = max(timestampA, timestampB);
 		Message sentA = sendRequestMessage(txn, s.getIntroduceeA(),
 				localTimestamp, s.getIntroduceeB().author, text);
 		Message sentB = sendRequestMessage(txn, s.getIntroduceeB(),
@@ -272,11 +263,11 @@ class IntroducerProtocolEngine
 
 		// Forward ACCEPT message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		long timestamp = getLocalTimestamp(s, i);
+		// The forwarded message will not be visible to the introducee
-		Message sent =
+		long localTimestamp = getTimestampForInvisibleMessage(s, i);
-				sendAcceptMessage(txn, i, timestamp, m.getEphemeralPublicKey(),
+		Message sent = sendAcceptMessage(txn, i, localTimestamp,
-						m.getAcceptTimestamp(), m.getTransportProperties(),
+				m.getEphemeralPublicKey(), m.getAcceptTimestamp(),
-						false);
+				m.getTransportProperties(), false);
 
 		// Create the next state
 		IntroducerState state = AWAIT_AUTHS;
@@ -333,7 +324,9 @@ class IntroducerProtocolEngine
 
 		// Forward ACCEPT message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		Message sent = sendAcceptMessage(txn, i, getLocalTimestamp(s, i),
+		// The forwarded message will not be visible to the introducee
+		long localTimestamp = getTimestampForInvisibleMessage(s, i);
+		Message sent = sendAcceptMessage(txn, i, localTimestamp,
 				m.getEphemeralPublicKey(), m.getAcceptTimestamp(),
 				m.getTransportProperties(), false);
 
@@ -384,8 +377,9 @@ class IntroducerProtocolEngine
 
 		// Forward DECLINE message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		long timestamp = getLocalTimestamp(s, i);
+		// The forwarded message will be visible to the introducee
-		Message sent = sendDeclineMessage(txn, i, timestamp, false);
+		long localTimestamp = getTimestampForVisibleMessage(txn, s, i);
+		Message sent = sendDeclineMessage(txn, i, localTimestamp, false);
 
 		// Create the next state
 		IntroducerState state = START;
@@ -436,8 +430,9 @@ class IntroducerProtocolEngine
 
 		// Forward DECLINE message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		long timestamp = getLocalTimestamp(s, i);
+		// The forwarded message will be visible to the introducee
-		Message sent = sendDeclineMessage(txn, i, timestamp, false);
+		long localTimestamp = getTimestampForVisibleMessage(txn, s, i);
+		Message sent = sendDeclineMessage(txn, i, localTimestamp, false);
 
 		Introducee introduceeA, introduceeB;
 		Author sender, other;
@@ -477,8 +472,8 @@ class IntroducerProtocolEngine
 
 		// Forward AUTH message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		long timestamp = getLocalTimestamp(s, i);
+		long localTimestamp = getTimestampForInvisibleMessage(s, i);
-		Message sent = sendAuthMessage(txn, i, timestamp, m.getMac(),
+		Message sent = sendAuthMessage(txn, i, localTimestamp, m.getMac(),
 				m.getSignature());
 
 		// Move to the next state
@@ -513,8 +508,8 @@ class IntroducerProtocolEngine
 
 		// Forward ACTIVATE message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		long timestamp = getLocalTimestamp(s, i);
+		long localTimestamp = getTimestampForInvisibleMessage(s, i);
-		Message sent = sendActivateMessage(txn, i, timestamp, m.getMac());
+		Message sent = sendActivateMessage(txn, i, localTimestamp, m.getMac());
 
 		// Move to the next state
 		IntroducerState state = START;
@@ -536,8 +531,8 @@ class IntroducerProtocolEngine
 			IntroducerSession s, AbortMessage m) throws DbException {
 		// Forward ABORT message
 		Introducee i = getOtherIntroducee(s, m.getGroupId());
-		long timestamp = getLocalTimestamp(s, i);
+		long localTimestamp = getTimestampForInvisibleMessage(s, i);
-		Message sent = sendAbortMessage(txn, i, timestamp);
+		Message sent = sendAbortMessage(txn, i, localTimestamp);
 
 		// Broadcast abort event for testing
 		txn.attach(new IntroductionAbortedEvent(s.getSessionId()));
@@ -555,15 +550,45 @@ class IntroducerProtocolEngine
 				s.getRequestTimestamp(), introduceeA, introduceeB);
 	}
 
-	private IntroducerSession abort(Transaction txn,
+	private IntroducerSession abort(Transaction txn, IntroducerSession s,
-			IntroducerSession s) throws DbException {
+			Introducee remainingIntroducee) throws DbException {
+		// Broadcast abort event for testing
+		txn.attach(new IntroductionAbortedEvent(s.getSessionId()));
+
+		// Send an ABORT message to the remaining introducee
+		long localTimestamp =
+				getTimestampForInvisibleMessage(s, remainingIntroducee);
+		Message sent =
+				sendAbortMessage(txn, remainingIntroducee, localTimestamp);
+		// Reset the session back to initial state
+		Introducee introduceeA = s.getIntroduceeA();
+		Introducee introduceeB = s.getIntroduceeB();
+		if (remainingIntroducee.author.equals(introduceeA.author)) {
+			introduceeA = new Introducee(introduceeA, sent);
+			introduceeB = new Introducee(s.getSessionId(), introduceeB.groupId,
+					introduceeB.author);
+		} else if (remainingIntroducee.author.equals(introduceeB.author)) {
+			introduceeA = new Introducee(s.getSessionId(), introduceeA.groupId,
+					introduceeA.author);
+			introduceeB = new Introducee(introduceeB, sent);
+		} else {
+			throw new DbException();
+		}
+		return new IntroducerSession(s.getSessionId(), START,
+				s.getRequestTimestamp(), introduceeA, introduceeB);
+	}
+
+	private IntroducerSession abort(Transaction txn, IntroducerSession s)
+			throws DbException {
 		// Broadcast abort event for testing
 		txn.attach(new IntroductionAbortedEvent(s.getSessionId()));
 
 		// Send an ABORT message to both introducees
-		long timestampA = getLocalTimestamp(s, s.getIntroduceeA());
+		long timestampA =
+				getTimestampForInvisibleMessage(s, s.getIntroduceeA());
 		Message sentA = sendAbortMessage(txn, s.getIntroduceeA(), timestampA);
-		long timestampB = getLocalTimestamp(s, s.getIntroduceeB());
+		long timestampB =
+				getTimestampForInvisibleMessage(s, s.getIntroduceeB());
 		Message sentB = sendAbortMessage(txn, s.getIntroduceeB(), timestampB);
 		// Reset the session back to initial state
 		Introducee introduceeA = new Introducee(s.getIntroduceeA(), sentA);
@@ -593,9 +618,33 @@ class IntroducerProtocolEngine
 		return isInvalidDependency(expected, dependency);
 	}
 
-	private long getLocalTimestamp(IntroducerSession s, PeerSession p) {
+	/**
-		return getLocalTimestamp(p.getLocalTimestamp(),
+	 * Returns a timestamp for a visible outgoing message. The timestamp is
-				s.getRequestTimestamp());
+	 * later than the timestamp of any message sent or received so far in the
+	 * conversation, and later than the {@link
+	 * #getSessionTimestamp(IntroducerSession, PeerSession) session timestamp}.
+	 */
+	private long getTimestampForVisibleMessage(Transaction txn,
+			IntroducerSession s, PeerSession p) throws DbException {
+		long conversationTimestamp =
+				getTimestampForOutgoingMessage(txn, p.getContactGroupId());
+		return max(conversationTimestamp, getSessionTimestamp(s, p) + 1);
 	}
 
+	/**
+	 * Returns a timestamp for an invisible outgoing message. The timestamp is
+	 * later than the {@link #getSessionTimestamp(IntroducerSession, PeerSession)
+	 * session timestamp}.
+	 */
+	private long getTimestampForInvisibleMessage(IntroducerSession s,
+			PeerSession p) {
+		return max(clock.currentTimeMillis(), getSessionTimestamp(s, p) + 1);
+	}
+
+	/**
+	 * Returns the latest timestamp of any message sent so far in the session.
+	 */
+	private long getSessionTimestamp(IntroducerSession s, PeerSession p) {
+		return max(p.getLocalTimestamp(), s.getRequestTimestamp());
+	}
 }

briar-core/src/main/java/org/briarproject/briar/introduction/IntroductionManagerImpl.java

@@ -311,8 +311,8 @@ class IntroductionManagerImpl extends ConversationClientImpl
 	}
 
 	@Override
-	public void makeIntroduction(Contact c1, Contact c2, @Nullable String text,
+	public void makeIntroduction(Contact c1, Contact c2, @Nullable String text)
-			long timestamp) throws DbException {
+			throws DbException {
 		Transaction txn = db.startTransaction(false);
 		try {
 			// Look up the session, if there is one
@@ -344,8 +344,7 @@ class IntroductionManagerImpl extends ConversationClientImpl
 				storageId = ss.storageId;
 			}
 			// Handle the request action
-			session = introducerEngine
+			session = introducerEngine.onRequestAction(txn, session, text);
-					.onRequestAction(txn, session, text, timestamp);
 			// Store the updated session
 			storeSession(txn, storageId, session);
 			db.commitTransaction(txn);
@@ -358,7 +357,7 @@ class IntroductionManagerImpl extends ConversationClientImpl
 
 	@Override
 	public void respondToIntroduction(ContactId contactId, SessionId sessionId,
-			long timestamp, boolean accept) throws DbException {
+			boolean accept) throws DbException {
 		Transaction txn = db.startTransaction(false);
 		try {
 			// Look up the session
@@ -376,11 +375,9 @@ class IntroductionManagerImpl extends ConversationClientImpl
 					.parseIntroduceeSession(contactGroupId, ss.bdfSession);
 			// Handle the join or leave action
 			if (accept) {
-				session = introduceeEngine
+				session = introduceeEngine.onAcceptAction(txn, session);
-						.onAcceptAction(txn, session, timestamp);
 			} else {
-				session = introduceeEngine
+				session = introduceeEngine.onDeclineAction(txn, session);
-						.onDeclineAction(txn, session, timestamp);
 			}
 			// Store the updated session
 			storeSession(txn, ss.storageId, session);

briar-core/src/main/java/org/briarproject/briar/introduction/ProtocolEngine.java

@@ -8,16 +8,14 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import javax.annotation.Nullable;
 
 @NotNullByDefault
-interface ProtocolEngine<S extends Session> {
+interface ProtocolEngine<S extends Session<?>> {
 
-	S onRequestAction(Transaction txn, S session, @Nullable String text,
+	S onRequestAction(Transaction txn, S session, @Nullable String text)
-			long timestamp) throws DbException;
-
-	S onAcceptAction(Transaction txn, S session, long timestamp)
 			throws DbException;
 
-	S onDeclineAction(Transaction txn, S session, long timestamp)
+	S onAcceptAction(Transaction txn, S session) throws DbException;
-			throws DbException;
+
+	S onDeclineAction(Transaction txn, S session) throws DbException;
 
 	S onRequestMessage(Transaction txn, S session, RequestMessage m)
 			throws DbException, FormatException;

briar-core/src/main/java/org/briarproject/briar/messaging/ConversationManagerImpl.java

@@ -6,6 +6,7 @@ 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.MessageId;
+import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.briar.api.client.MessageTracker.GroupCount;
 import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.conversation.ConversationMessageHeader;
@@ -20,16 +21,20 @@ import java.util.concurrent.CopyOnWriteArraySet;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
+import static java.lang.Math.max;
+
 @ThreadSafe
 @NotNullByDefault
 class ConversationManagerImpl implements ConversationManager {
 
 	private final DatabaseComponent db;
+	private final Clock clock;
 	private final Set<ConversationClient> clients;
 
 	@Inject
-	ConversationManagerImpl(DatabaseComponent db) {
+	ConversationManagerImpl(DatabaseComponent db, Clock clock) {
 		this.db = db;
+		this.clock = clock;
 		clients = new CopyOnWriteArraySet<>();
 	}
 
@@ -57,24 +62,33 @@ class ConversationManagerImpl implements ConversationManager {
 
 	@Override
 	public GroupCount getGroupCount(ContactId contactId) throws DbException {
+		return db.transactionWithResult(true, txn ->
+				getGroupCount(txn, contactId));
+	}
+
+	@Override
+	public GroupCount getGroupCount(Transaction txn, ContactId contactId)
+			throws DbException {
 		int msgCount = 0, unreadCount = 0;
 		long latestTime = 0;
-		Transaction txn = db.startTransaction(true);
+		for (ConversationClient client : clients) {
-		try {
+			GroupCount count = client.getGroupCount(txn, contactId);
-			for (ConversationClient client : clients) {
+			msgCount += count.getMsgCount();
-				GroupCount count = client.getGroupCount(txn, contactId);
+			unreadCount += count.getUnreadCount();
-				msgCount += count.getMsgCount();
+			if (count.getLatestMsgTime() > latestTime)
-				unreadCount += count.getUnreadCount();
+				latestTime = count.getLatestMsgTime();
-				if (count.getLatestMsgTime() > latestTime)
-					latestTime = count.getLatestMsgTime();
-			}
-			db.commitTransaction(txn);
-		} finally {
-			db.endTransaction(txn);
 		}
 		return new GroupCount(msgCount, unreadCount, latestTime);
 	}
 
+	@Override
+	public long getTimestampForOutgoingMessage(Transaction txn, ContactId c)
+			throws DbException {
+		long now = clock.currentTimeMillis();
+		GroupCount gc = getGroupCount(txn, c);
+		return max(now, gc.getLatestMsgTime() + 1);
+	}
+
 	@Override
 	public DeletionResult deleteAllMessages(ContactId c) throws DbException {
 		return db.transactionWithResult(false, txn -> {
@@ -87,8 +101,8 @@ class ConversationManagerImpl implements ConversationManager {
 	}
 
 	@Override
-	public DeletionResult deleteMessages(ContactId c, Collection<MessageId> toDelete)
+	public DeletionResult deleteMessages(ContactId c,
-			throws DbException {
+			Collection<MessageId> toDelete) throws DbException {
 		return db.transactionWithResult(false, txn -> {
 			DeletionResult result = new DeletionResult();
 			for (ConversationClient client : clients) {

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/AbstractProtocolEngine.java

@@ -19,6 +19,7 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.privategroup.GroupMessage;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroup;
@@ -31,6 +32,7 @@ import java.util.Map;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
+import static java.lang.Math.max;
 import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
 import static org.briarproject.briar.privategroup.invitation.MessageType.ABORT;
 import static org.briarproject.briar.privategroup.invitation.MessageType.INVITE;
@@ -54,6 +56,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 	private final MessageParser messageParser;
 	private final MessageEncoder messageEncoder;
 	private final AutoDeleteManager autoDeleteManager;
+	private final ConversationManager conversationManager;
 	private final Clock clock;
 
 	AbstractProtocolEngine(
@@ -68,6 +71,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 			MessageEncoder messageEncoder,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		this.db = db;
 		this.clientHelper = clientHelper;
@@ -80,6 +84,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 		this.messageEncoder = messageEncoder;
 		this.messageTracker = messageTracker;
 		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		this.clock = clock;
 	}
 
@@ -110,8 +115,8 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 	}
 
 	Message sendInviteMessage(Transaction txn, S s,
-			@Nullable String text, long timestamp, byte[] signature)
+			@Nullable String text, long timestamp, byte[] signature,
-			throws DbException {
+			long timer) throws DbException {
 		Group g = db.getGroup(txn, s.getPrivateGroupId());
 		PrivateGroup privateGroup;
 		try {
@@ -122,7 +127,6 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 		Message m;
 		ContactId c = getContactId(txn, s.getContactGroupId());
 		if (contactSupportsAutoDeletion(txn, c)) {
-			long timer = autoDeleteManager.getAutoDeleteTimer(txn, c);
 			m = messageEncoder.encodeInviteMessage(s.getContactGroupId(),
 					privateGroup.getId(), timestamp, privateGroup.getName(),
 					privateGroup.getCreator(), privateGroup.getSalt(), text,
@@ -142,6 +146,9 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 	Message sendJoinMessage(Transaction txn, S s, boolean visibleInUi)
 			throws DbException {
 		Message m;
+		long localTimestamp = visibleInUi
+				? getTimestampForVisibleMessage(txn, s)
+				: getTimestampForInvisibleMessage(s);
 		ContactId c = getContactId(txn, s.getContactGroupId());
 		if (contactSupportsAutoDeletion(txn, c)) {
 			// Set auto-delete timer if manually accepting an invitation
@@ -149,13 +156,13 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 					? autoDeleteManager.getAutoDeleteTimer(txn, c)
 					: NO_AUTO_DELETE_TIMER;
 			m = messageEncoder.encodeJoinMessage(s.getContactGroupId(),
-					s.getPrivateGroupId(), getLocalTimestamp(s),
+					s.getPrivateGroupId(), localTimestamp,
 					s.getLastLocalMessageId(), timer);
 			sendMessage(txn, m, JOIN, s.getPrivateGroupId(), visibleInUi,
 					timer);
 		} else {
 			m = messageEncoder.encodeJoinMessage(s.getContactGroupId(),
-					s.getPrivateGroupId(), getLocalTimestamp(s),
+					s.getPrivateGroupId(), localTimestamp,
 					s.getLastLocalMessageId());
 			sendMessage(txn, m, JOIN, s.getPrivateGroupId(), visibleInUi,
 					NO_AUTO_DELETE_TIMER);
@@ -166,6 +173,9 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 	Message sendLeaveMessage(Transaction txn, S s, boolean visibleInUi)
 			throws DbException {
 		Message m;
+		long localTimestamp = visibleInUi
+				? getTimestampForVisibleMessage(txn, s)
+				: getTimestampForInvisibleMessage(s);
 		ContactId c = getContactId(txn, s.getContactGroupId());
 		if (contactSupportsAutoDeletion(txn, c)) {
 			// Set auto-delete timer if manually accepting an invitation
@@ -173,13 +183,13 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 					? autoDeleteManager.getAutoDeleteTimer(txn, c)
 					: NO_AUTO_DELETE_TIMER;
 			m = messageEncoder.encodeLeaveMessage(s.getContactGroupId(),
-					s.getPrivateGroupId(), getLocalTimestamp(s),
+					s.getPrivateGroupId(), localTimestamp,
 					s.getLastLocalMessageId(), timer);
 			sendMessage(txn, m, LEAVE, s.getPrivateGroupId(), visibleInUi,
 					timer);
 		} else {
 			m = messageEncoder.encodeLeaveMessage(s.getContactGroupId(),
-					s.getPrivateGroupId(), getLocalTimestamp(s),
+					s.getPrivateGroupId(), localTimestamp,
 					s.getLastLocalMessageId());
 			sendMessage(txn, m, LEAVE, s.getPrivateGroupId(), visibleInUi,
 					NO_AUTO_DELETE_TIMER);
@@ -190,7 +200,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 	Message sendAbortMessage(Transaction txn, S session) throws DbException {
 		Message m = messageEncoder.encodeAbortMessage(
 				session.getContactGroupId(), session.getPrivateGroupId(),
-				getLocalTimestamp(session));
+				getTimestampForInvisibleMessage(session));
 		sendMessage(txn, m, ABORT, session.getPrivateGroupId(), false,
 				NO_AUTO_DELETE_TIMER);
 		return m;
@@ -246,7 +256,7 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 		PrivateGroup privateGroup = privateGroupFactory.createPrivateGroup(
 				invite.getGroupName(), invite.getCreator(), invite.getSalt());
 		long timestamp =
-				Math.max(clock.currentTimeMillis(), invite.getTimestamp() + 1);
+				max(clock.currentTimeMillis(), invite.getTimestamp() + 1);
 		// TODO: Create the join message on the crypto executor
 		LocalAuthor member = identityManager.getLocalAuthor(txn);
 		GroupMessage joinMessage = groupMessageFactory.createJoinMessage(
@@ -256,10 +266,34 @@ abstract class AbstractProtocolEngine<S extends Session<?>>
 				.addPrivateGroup(txn, privateGroup, joinMessage, false);
 	}
 
-	long getLocalTimestamp(S session) {
+	/**
-		return Math.max(clock.currentTimeMillis(),
+	 * Returns a timestamp for a visible outgoing message. The timestamp is
-				Math.max(session.getLocalTimestamp(),
+	 * later than the timestamp of any message sent or received so far in the
-						session.getInviteTimestamp()) + 1);
+	 * conversation, and later than the {@link #getSessionTimestamp(Session)
+	 * session timestamp}.
+	 */
+	long getTimestampForVisibleMessage(Transaction txn, S s)
+			throws DbException {
+		ContactId c = getContactId(txn, s.getContactGroupId());
+		long conversationTimestamp =
+				conversationManager.getTimestampForOutgoingMessage(txn, c);
+		return max(conversationTimestamp, getSessionTimestamp(s) + 1);
+	}
+
+	/**
+	 * Returns a timestamp for an invisible outgoing message. The timestamp is
+	 * later than the {@link #getSessionTimestamp(Session) session timestamp}.
+	 */
+	long getTimestampForInvisibleMessage(S s) {
+		return max(clock.currentTimeMillis(), getSessionTimestamp(s) + 1);
+	}
+
+	/**
+	 * Returns the latest timestamp of any message sent so far in the session,
+	 * and any invite message sent or received so far in the session.
+	 */
+	private long getSessionTimestamp(S s) {
+		return max(s.getLocalTimestamp(), s.getInviteTimestamp());
 	}
 
 	private void sendMessage(Transaction txn, Message m, MessageType type,

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/CreatorProtocolEngine.java

@@ -15,6 +15,7 @@ import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
@@ -24,6 +25,7 @@ import org.briarproject.briar.api.privategroup.invitation.GroupInvitationRespons
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
+import static java.lang.Math.max;
 import static org.briarproject.bramble.api.sync.Group.Visibility.INVISIBLE;
 import static org.briarproject.bramble.api.sync.Group.Visibility.SHARED;
 import static org.briarproject.briar.privategroup.invitation.CreatorState.DISSOLVED;
@@ -49,20 +51,22 @@ class CreatorProtocolEngine extends AbstractProtocolEngine<CreatorSession> {
 			MessageEncoder messageEncoder,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		super(db, clientHelper, clientVersioningManager, privateGroupManager,
 				privateGroupFactory, groupMessageFactory, identityManager,
 				messageParser, messageEncoder, messageTracker,
-				autoDeleteManager, clock);
+				autoDeleteManager, conversationManager, clock);
 	}
 
 	@Override
 	public CreatorSession onInviteAction(Transaction txn, CreatorSession s,
-			@Nullable String text, long timestamp, byte[] signature)
+			@Nullable String text, long timestamp, byte[] signature,
-			throws DbException {
+			long autoDeleteTimer) throws DbException {
 		switch (s.getState()) {
 			case START:
-				return onLocalInvite(txn, s, text, timestamp, signature);
+				return onLocalInvite(txn, s, text, timestamp, signature,
+						autoDeleteTimer);
 			case INVITED:
 			case JOINED:
 			case LEFT:
@@ -152,14 +156,16 @@ class CreatorProtocolEngine extends AbstractProtocolEngine<CreatorSession> {
 	}
 
 	private CreatorSession onLocalInvite(Transaction txn, CreatorSession s,
-			@Nullable String text, long timestamp, byte[] signature)
+			@Nullable String text, long timestamp, byte[] signature,
-			throws DbException {
+			long autoDeleteTimer) throws DbException {
 		// Send an INVITE message
-		Message sent = sendInviteMessage(txn, s, text, timestamp, signature);
+		Message sent = sendInviteMessage(txn, s, text, timestamp, signature,
+				autoDeleteTimer);
 		// Track the message
 		messageTracker.trackOutgoingMessage(txn, sent);
 		// Move to the INVITED state
-		long localTimestamp = Math.max(timestamp, getLocalTimestamp(s));
+		long localTimestamp =
+				max(timestamp, getTimestampForVisibleMessage(txn, s));
 		return new CreatorSession(s.getContactGroupId(), s.getPrivateGroupId(),
 				sent.getId(), s.getLastRemoteMessageId(), localTimestamp,
 				timestamp, INVITED);

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/GroupInvitationManagerImpl.java

@@ -257,8 +257,8 @@ class GroupInvitationManagerImpl extends ConversationClientImpl
 
 	@Override
 	public void sendInvitation(GroupId privateGroupId, ContactId c,
-			@Nullable String text, long timestamp, byte[] signature)
+			@Nullable String text, long timestamp, byte[] signature,
-			throws DbException {
+			long autoDeleteTimer) throws DbException {
 		SessionId sessionId = getSessionId(privateGroupId);
 		Transaction txn = db.startTransaction(false);
 		try {
@@ -281,7 +281,7 @@ class GroupInvitationManagerImpl extends ConversationClientImpl
 			}
 			// Handle the invite action
 			session = creatorEngine.onInviteAction(txn, session, text,
-					timestamp, signature);
+					timestamp, signature, autoDeleteTimer);
 			// Store the updated session
 			storeSession(txn, storageId, session);
 			db.commitTransaction(txn);

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/InviteeProtocolEngine.java

@@ -17,6 +17,7 @@ import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.ProtocolStateException;
 import org.briarproject.briar.api.client.SessionId;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
@@ -42,7 +43,8 @@ import static org.briarproject.briar.privategroup.invitation.InviteeState.START;
 @NotNullByDefault
 class InviteeProtocolEngine extends AbstractProtocolEngine<InviteeSession> {
 
-	InviteeProtocolEngine(DatabaseComponent db,
+	InviteeProtocolEngine(
+			DatabaseComponent db,
 			ClientHelper clientHelper,
 			ClientVersioningManager clientVersioningManager,
 			PrivateGroupManager privateGroupManager,
@@ -53,16 +55,18 @@ class InviteeProtocolEngine extends AbstractProtocolEngine<InviteeSession> {
 			MessageEncoder messageEncoder,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		super(db, clientHelper, clientVersioningManager, privateGroupManager,
 				privateGroupFactory, groupMessageFactory, identityManager,
 				messageParser, messageEncoder, messageTracker,
-				autoDeleteManager, clock);
+				autoDeleteManager, conversationManager, clock);
 	}
 
 	@Override
 	public InviteeSession onInviteAction(Transaction txn, InviteeSession s,
-			@Nullable String text, long timestamp, byte[] signature) {
+			@Nullable String text, long timestamp, byte[] signature,
+			long autoDeleteTimer) {
 		throw new UnsupportedOperationException(); // Invalid in this role
 	}
 

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/PeerProtocolEngine.java

@@ -15,6 +15,7 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.ProtocolStateException;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
@@ -49,16 +50,18 @@ class PeerProtocolEngine extends AbstractProtocolEngine<PeerSession> {
 			MessageEncoder messageEncoder,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		super(db, clientHelper, clientVersioningManager, privateGroupManager,
 				privateGroupFactory, groupMessageFactory, identityManager,
 				messageParser, messageEncoder, messageTracker,
-				autoDeleteManager, clock);
+				autoDeleteManager, conversationManager, clock);
 	}
 
 	@Override
 	public PeerSession onInviteAction(Transaction txn, PeerSession s,
-			@Nullable String text, long timestamp, byte[] signature) {
+			@Nullable String text, long timestamp, byte[] signature,
+			long autoDeleteTimer) {
 		throw new UnsupportedOperationException(); // Invalid in this role
 	}
 

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/ProtocolEngine.java

@@ -8,10 +8,11 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import javax.annotation.Nullable;
 
 @NotNullByDefault
-interface ProtocolEngine<S extends Session> {
+interface ProtocolEngine<S extends Session<?>> {
 
 	S onInviteAction(Transaction txn, S session, @Nullable String text,
-			long timestamp, byte[] signature) throws DbException;
+			long timestamp, byte[] signature, long autoDeleteTimer)
+			throws DbException;
 
 	S onJoinAction(Transaction txn, S session) throws DbException;
 

briar-core/src/main/java/org/briarproject/briar/privategroup/invitation/ProtocolEngineFactoryImpl.java

@@ -8,6 +8,7 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroupManager;
@@ -30,6 +31,7 @@ class ProtocolEngineFactoryImpl implements ProtocolEngineFactory {
 	private final MessageEncoder messageEncoder;
 	private final MessageTracker messageTracker;
 	private final AutoDeleteManager autoDeleteManager;
+	private final ConversationManager conversationManager;
 	private final Clock clock;
 
 	@Inject
@@ -45,6 +47,7 @@ class ProtocolEngineFactoryImpl implements ProtocolEngineFactory {
 			MessageEncoder messageEncoder,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock) {
 		this.db = db;
 		this.clientHelper = clientHelper;
@@ -57,6 +60,7 @@ class ProtocolEngineFactoryImpl implements ProtocolEngineFactory {
 		this.messageEncoder = messageEncoder;
 		this.messageTracker = messageTracker;
 		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		this.clock = clock;
 	}
 
@@ -66,7 +70,7 @@ class ProtocolEngineFactoryImpl implements ProtocolEngineFactory {
 				clientVersioningManager, privateGroupManager,
 				privateGroupFactory, groupMessageFactory, identityManager,
 				messageParser, messageEncoder, messageTracker,
-				autoDeleteManager, clock);
+				autoDeleteManager, conversationManager, clock);
 	}
 
 	@Override
@@ -75,7 +79,7 @@ class ProtocolEngineFactoryImpl implements ProtocolEngineFactory {
 				clientVersioningManager, privateGroupManager,
 				privateGroupFactory, groupMessageFactory, identityManager,
 				messageParser, messageEncoder, messageTracker,
-				autoDeleteManager, clock);
+				autoDeleteManager, conversationManager, clock);
 	}
 
 	@Override
@@ -84,6 +88,6 @@ class ProtocolEngineFactoryImpl implements ProtocolEngineFactory {
 				clientVersioningManager, privateGroupManager,
 				privateGroupFactory, groupMessageFactory, identityManager,
 				messageParser, messageEncoder, messageTracker,
-				autoDeleteManager, clock);
+				autoDeleteManager, conversationManager, clock);
 	}
 }

briar-core/src/main/java/org/briarproject/briar/sharing/BlogProtocolEngineImpl.java

@@ -19,6 +19,7 @@ import org.briarproject.briar.api.blog.BlogSharingManager;
 import org.briarproject.briar.api.blog.event.BlogInvitationRequestReceivedEvent;
 import org.briarproject.briar.api.blog.event.BlogInvitationResponseReceivedEvent;
 import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.conversation.ConversationRequest;
 
 import javax.annotation.concurrent.Immutable;
@@ -41,13 +42,15 @@ class BlogProtocolEngineImpl extends ProtocolEngineImpl<Blog> {
 			MessageParser<Blog> messageParser,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock,
 			BlogManager blogManager,
 			InvitationFactory<Blog, BlogInvitationResponse> invitationFactory) {
 		super(db, clientHelper, clientVersioningManager, messageEncoder,
-				messageParser, messageTracker, autoDeleteManager, clock,
+				messageParser, messageTracker, autoDeleteManager,
-				BlogSharingManager.CLIENT_ID, BlogSharingManager.MAJOR_VERSION,
+				conversationManager, clock, BlogSharingManager.CLIENT_ID,
-				BlogManager.CLIENT_ID, BlogManager.MAJOR_VERSION);
+				BlogSharingManager.MAJOR_VERSION, BlogManager.CLIENT_ID,
+				BlogManager.MAJOR_VERSION);
 		this.blogManager = blogManager;
 		this.invitationFactory = invitationFactory;
 	}

briar-core/src/main/java/org/briarproject/briar/sharing/ForumProtocolEngineImpl.java

@@ -13,6 +13,7 @@ import org.briarproject.bramble.api.system.Clock;
 import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.conversation.ConversationRequest;
 import org.briarproject.briar.api.forum.Forum;
 import org.briarproject.briar.api.forum.ForumInvitationResponse;
@@ -41,14 +42,15 @@ class ForumProtocolEngineImpl extends ProtocolEngineImpl<Forum> {
 			MessageParser<Forum> messageParser,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock,
 			ForumManager forumManager,
 			InvitationFactory<Forum, ForumInvitationResponse> invitationFactory) {
 		super(db, clientHelper, clientVersioningManager, messageEncoder,
-				messageParser, messageTracker, autoDeleteManager, clock,
+				messageParser, messageTracker, autoDeleteManager,
-				ForumSharingManager.CLIENT_ID,
+				conversationManager, clock, ForumSharingManager.CLIENT_ID,
-				ForumSharingManager.MAJOR_VERSION,
+				ForumSharingManager.MAJOR_VERSION, ForumManager.CLIENT_ID,
-				ForumManager.CLIENT_ID, ForumManager.MAJOR_VERSION);
+				ForumManager.MAJOR_VERSION);
 		this.forumManager = forumManager;
 		this.invitationFactory = invitationFactory;
 	}

briar-core/src/main/java/org/briarproject/briar/sharing/ProtocolEngine.java

@@ -12,7 +12,7 @@ import javax.annotation.Nullable;
 interface ProtocolEngine<S extends Shareable> {
 
 	Session onInviteAction(Transaction txn, Session session,
-			@Nullable String text, long timestamp) throws DbException;
+			@Nullable String text) throws DbException;
 
 	Session onAcceptAction(Transaction txn, Session session) throws DbException;
 

briar-core/src/main/java/org/briarproject/briar/sharing/ProtocolEngineImpl.java

@@ -21,6 +21,7 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
 import org.briarproject.briar.api.client.ProtocolStateException;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.sharing.Shareable;
 import org.briarproject.briar.api.sharing.event.ContactLeftShareableEvent;
 
@@ -29,6 +30,7 @@ import java.util.Map;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.Immutable;
 
+import static java.lang.Math.max;
 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;
@@ -58,6 +60,7 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 	private final MessageEncoder messageEncoder;
 	private final MessageTracker messageTracker;
 	private final AutoDeleteManager autoDeleteManager;
+	private final ConversationManager conversationManager;
 	private final Clock clock;
 	private final ClientId sharingClientId, shareableClientId;
 	private final int sharingClientMajorVersion, shareableClientMajorVersion;
@@ -70,6 +73,7 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 			MessageParser<S> messageParser,
 			MessageTracker messageTracker,
 			AutoDeleteManager autoDeleteManager,
+			ConversationManager conversationManager,
 			Clock clock,
 			ClientId sharingClientId,
 			int sharingClientMajorVersion,
@@ -82,6 +86,7 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 		this.messageParser = messageParser;
 		this.messageTracker = messageTracker;
 		this.autoDeleteManager = autoDeleteManager;
+		this.conversationManager = conversationManager;
 		this.clock = clock;
 		this.sharingClientId = sharingClientId;
 		this.sharingClientMajorVersion = sharingClientMajorVersion;
@@ -91,10 +96,10 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 
 	@Override
 	public Session onInviteAction(Transaction txn, Session s,
-			@Nullable String text, long timestamp) throws DbException {
+			@Nullable String text) throws DbException {
 		switch (s.getState()) {
 			case START:
-				return onLocalInvite(txn, s, text, timestamp);
+				return onLocalInvite(txn, s, text);
 			case LOCAL_INVITED:
 			case REMOTE_INVITED:
 			case SHARING:
@@ -107,9 +112,9 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 	}
 
 	private Session onLocalInvite(Transaction txn, Session s,
-			@Nullable String text, long timestamp) throws DbException {
+			@Nullable String text) throws DbException {
 		// Send an INVITE message
-		Message sent = sendInviteMessage(txn, s, text, timestamp);
+		Message sent = sendInviteMessage(txn, s, text);
 		// Track the message
 		messageTracker.trackOutgoingMessage(txn, sent);
 		// Make the shareable visible to the contact
@@ -125,7 +130,7 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 	}
 
 	private Message sendInviteMessage(Transaction txn, Session s,
-			@Nullable String text, long timestamp) throws DbException {
+			@Nullable String text) throws DbException {
 		Group g = db.getGroup(txn, s.getShareableId());
 		BdfList descriptor;
 		try {
@@ -133,8 +138,8 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 		} catch (FormatException e) {
 			throw new DbException(e); // Invalid group descriptor
 		}
-		long localTimestamp = Math.max(timestamp, getLocalTimestamp(s));
 		Message m;
+		long localTimestamp = getTimestampForVisibleMessage(txn, s);
 		ContactId c = getContactId(txn, s.getContactGroupId());
 		if (contactSupportsAutoDeletion(txn, c)) {
 			long timer = autoDeleteManager.getAutoDeleteTimer(txn, c);
@@ -201,16 +206,17 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 	private Message sendAcceptMessage(Transaction txn, Session s)
 			throws DbException {
 		Message m;
+		long localTimestamp = getTimestampForVisibleMessage(txn, s);
 		ContactId c = getContactId(txn, s.getContactGroupId());
 		if (contactSupportsAutoDeletion(txn, c)) {
 			long timer = autoDeleteManager.getAutoDeleteTimer(txn, c);
 			m = messageEncoder.encodeAcceptMessage(s.getContactGroupId(),
-					s.getShareableId(), getLocalTimestamp(s),
+					s.getShareableId(), localTimestamp,
 					s.getLastLocalMessageId(), timer);
 			sendMessage(txn, m, ACCEPT, s.getShareableId(), true, timer);
 		} else {
 			m = messageEncoder.encodeAcceptMessage(s.getContactGroupId(),
-					s.getShareableId(), getLocalTimestamp(s),
+					s.getShareableId(), localTimestamp,
 					s.getLastLocalMessageId());
 			sendMessage(txn, m, ACCEPT, s.getShareableId(), true,
 					NO_AUTO_DELETE_TIMER);
@@ -254,16 +260,17 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 	private Message sendDeclineMessage(Transaction txn, Session s)
 			throws DbException {
 		Message m;
+		long localTimestamp = getTimestampForVisibleMessage(txn, s);
 		ContactId c = getContactId(txn, s.getContactGroupId());
 		if (contactSupportsAutoDeletion(txn, c)) {
 			long timer = autoDeleteManager.getAutoDeleteTimer(txn, c);
 			m = messageEncoder.encodeDeclineMessage(s.getContactGroupId(),
-					s.getShareableId(), getLocalTimestamp(s),
+					s.getShareableId(), localTimestamp,
 					s.getLastLocalMessageId(), timer);
 			sendMessage(txn, m, DECLINE, s.getShareableId(), true, timer);
 		} else {
 			m = messageEncoder.encodeDeclineMessage(s.getContactGroupId(),
-					s.getShareableId(), getLocalTimestamp(s),
+					s.getShareableId(), localTimestamp,
 					s.getLastLocalMessageId());
 			sendMessage(txn, m, DECLINE, s.getShareableId(), true,
 					NO_AUTO_DELETE_TIMER);
@@ -307,9 +314,10 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 
 	private Message sendLeaveMessage(Transaction txn, Session session)
 			throws DbException {
+		long localTimestamp = getTimestampForInvisibleMessage(session);
 		Message m = messageEncoder.encodeLeaveMessage(
 				session.getContactGroupId(), session.getShareableId(),
-				getLocalTimestamp(session), session.getLastLocalMessageId());
+				localTimestamp, session.getLastLocalMessageId());
 		sendMessage(txn, m, LEAVE, session.getShareableId(), false,
 				NO_AUTO_DELETE_TIMER);
 		return m;
@@ -605,9 +613,10 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 
 	private Message sendAbortMessage(Transaction txn, Session session)
 			throws DbException {
+		long localTimestamp = getTimestampForInvisibleMessage(session);
 		Message m = messageEncoder.encodeAbortMessage(
 				session.getContactGroupId(), session.getShareableId(),
-				getLocalTimestamp(session), session.getLastLocalMessageId());
+				localTimestamp, session.getLastLocalMessageId());
 		sendMessage(txn, m, ABORT, session.getShareableId(), false,
 				NO_AUTO_DELETE_TIMER);
 		return m;
@@ -677,10 +686,34 @@ abstract class ProtocolEngineImpl<S extends Shareable>
 		return !dependency.equals(expected);
 	}
 
-	private long getLocalTimestamp(Session session) {
+	/**
-		return Math.max(clock.currentTimeMillis(),
+	 * Returns a timestamp for a visible outgoing message. The timestamp is
-				Math.max(session.getLocalTimestamp(),
+	 * later than the timestamp of any message sent or received so far in the
-						session.getInviteTimestamp()) + 1);
+	 * conversation, and later than the {@link #getSessionTimestamp(Session)
+	 * session timestamp}.
+	 */
+	private long getTimestampForVisibleMessage(Transaction txn, Session s)
+			throws DbException {
+		ContactId c = getContactId(txn, s.getContactGroupId());
+		long conversationTimestamp =
+				conversationManager.getTimestampForOutgoingMessage(txn, c);
+		return max(conversationTimestamp, getSessionTimestamp(s) + 1);
+	}
+
+	/**
+	 * Returns a timestamp for an invisible outgoing message. The timestamp is
+	 * later than the {@link #getSessionTimestamp(Session) session timestamp}.
+	 */
+	private long getTimestampForInvisibleMessage(Session s) {
+		return max(clock.currentTimeMillis(), getSessionTimestamp(s) + 1);
+	}
+
+	/**
+	 * Returns the latest timestamp of any message sent so far in the session,
+	 * and any invite message sent or received so far in the session.
+	 */
+	private long getSessionTimestamp(Session s) {
+		return max(s.getLocalTimestamp(), s.getInviteTimestamp());
 	}
 
 	private ContactId getContactId(Transaction txn, GroupId contactGroupId)

briar-core/src/main/java/org/briarproject/briar/sharing/SharingManagerImpl.java

@@ -248,7 +248,7 @@ abstract class SharingManagerImpl<S extends Shareable>
 
 	@Override
 	public void sendInvitation(GroupId shareableId, ContactId contactId,
-			@Nullable String text, long timestamp) throws DbException {
+			@Nullable String text) throws DbException {
 		SessionId sessionId = getSessionId(shareableId);
 		Transaction txn = db.startTransaction(false);
 		try {
@@ -273,7 +273,7 @@ abstract class SharingManagerImpl<S extends Shareable>
 				storageId = ss.storageId;
 			}
 			// Handle the invite action
-			session = engine.onInviteAction(txn, session, text, timestamp);
+			session = engine.onInviteAction(txn, session, text);
 			// Store the updated session
 			storeSession(txn, storageId, session);
 			db.commitTransaction(txn);

briar-core/src/test/java/org/briarproject/briar/forum/ForumManagerTest.java

@@ -45,8 +45,7 @@ public class ForumManagerTest
 		forum0 = forumManager0.addForum("Test Forum");
 		groupId0 = forum0.getId();
 		// share forum
-		forumSharingManager0.sendInvitation(groupId0, contactId1From0, null,
+		forumSharingManager0.sendInvitation(groupId0, contactId1From0, null);
-				clock.currentTimeMillis());
 		sync0To1(1, true);
 		forumSharingManager1.respondToInvitation(forum0, contact0From1, true);
 		sync1To0(1, true);
@@ -194,8 +193,7 @@ public class ForumManagerTest
 		// share a second forum
 		Forum forum1 = forumManager0.addForum("Test Forum1");
 		GroupId g1 = forum1.getId();
-		forumSharingManager0.sendInvitation(g1, contactId1From0, null,
+		forumSharingManager0.sendInvitation(g1, contactId1From0, null);
-				clock.currentTimeMillis());
 		sync0To1(1, true);
 		forumSharingManager1.respondToInvitation(forum1, contact0From1, true);
 		sync1To0(1, true);

briar-core/src/test/java/org/briarproject/briar/introduction/IntroductionIntegrationTest.java

@@ -140,11 +140,9 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		Contact introducee1 = contact1From0;
 		Contact introducee2 = contact2From0;
-		introductionManager0
+		introductionManager0.makeIntroduction(introducee1, introducee2, "Hi!");
-				.makeIntroduction(introducee1, introducee2, "Hi!", time);
 
 		// check that messages are tracked properly
 		Group g1 = introductionManager0.getContactGroup(introducee1);
@@ -264,11 +262,9 @@ public class IntroductionIntegrationTest
 		addListeners(false, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		Contact introducee1 = contact1From0;
 		Contact introducee2 = contact2From0;
-		introductionManager0
+		introductionManager0.makeIntroduction(introducee1, introducee2, null);
-				.makeIntroduction(introducee1, introducee2, null, time);
 
 		// sync request messages
 		sync0To1(1, true);
@@ -356,9 +352,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, false);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync request messages
 		sync0To1(1, true);
@@ -412,9 +407,8 @@ public class IntroductionIntegrationTest
 		addListeners(false, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync request messages
 		sync0To1(1, true);
@@ -438,9 +432,8 @@ public class IntroductionIntegrationTest
 		assertFalse(listener1.aborted);
 		assertFalse(listener2.aborted);
 
-		time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync request messages
 		sync0To1(1, true);
@@ -457,9 +450,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync first request message
 		sync0To1(1, true);
@@ -482,7 +474,7 @@ public class IntroductionIntegrationTest
 
 		// answer request manually
 		introductionManager2.respondToIntroduction(contactId0From2,
-				listener2.sessionId, time, true);
+				listener2.sessionId, true);
 
 		// sync second response and AUTH
 		sync2To0(2, true);
@@ -518,11 +510,10 @@ public class IntroductionIntegrationTest
 		listener2.answerRequests = false;
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		Contact introducee1 = contact1From0;
 		Contact introducee2 = contact2From0;
 		introductionManager0
-				.makeIntroduction(introducee1, introducee2, null, time);
+				.makeIntroduction(introducee1, introducee2, null);
 
 		// sync request messages
 		sync0To1(1, true);
@@ -564,7 +555,7 @@ public class IntroductionIntegrationTest
 
 		// answer request manually
 		introductionManager2.respondToIntroduction(contactId0From2,
-				listener2.sessionId, time, false);
+				listener2.sessionId, false);
 
 		// now introducee2 should have returned to the START state
 		introduceeSession = getIntroduceeSession(c2);
@@ -611,9 +602,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, false);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact1From0, null, time);
+				.makeIntroduction(contact1From0, contact1From0, null);
 
 		// sync request messages
 		sync0To1(1, false);
@@ -637,9 +627,8 @@ public class IntroductionIntegrationTest
 				.canIntroduce(contact1From0, contact2From0));
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// no more introduction allowed while the existing one is in progress
 		assertFalse(introductionManager0
@@ -647,7 +636,7 @@ public class IntroductionIntegrationTest
 
 		// try it anyway and fail
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 	}
 
 	@Test
@@ -661,9 +650,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync REQUEST messages
 		sync0To1(1, true);
@@ -719,9 +707,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync REQUEST messages
 		sync0To1(1, true);
@@ -766,9 +753,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync REQUEST to introducee1
 		sync0To1(1, true);
@@ -803,9 +789,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync REQUEST to introducee1
 		sync0To1(1, true);
@@ -838,9 +823,8 @@ public class IntroductionIntegrationTest
 		addListeners(false, true);
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync REQUEST to introducee1
 		sync0To1(1, true);
@@ -873,9 +857,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make the introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// sync REQUEST messages
 		sync0To1(1, true);
@@ -914,9 +897,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync first request message
 		sync0To1(1, true);
@@ -943,9 +925,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync first request message
 		sync0To1(1, true);
@@ -987,9 +968,8 @@ public class IntroductionIntegrationTest
 	@Test
 	public void testIntroductionAfterReAddingContacts() throws Exception {
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// 0 and 1 remove and re-add each other
 		contactManager0.removeContact(contactId1From0);
@@ -1016,9 +996,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make new introduction
-		time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, null, time);
+				.makeIntroduction(contact1From0, contact2From0, null);
 
 		// introduction should sync and not be INVALID or PENDING
 		sync0To1(1, true);
@@ -1032,9 +1011,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync request messages
 		sync0To1(1, true);
@@ -1147,9 +1125,8 @@ public class IntroductionIntegrationTest
 		addListeners(true, true);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync first REQUEST message
 		sync0To1(1, true);
@@ -1292,7 +1269,7 @@ public class IntroductionIntegrationTest
 		assertTrue(introductionManager0
 				.canIntroduce(contact1From0, contact2From0));
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Ho!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Ho!");
 		sync0To1(1, true);
 		sync0To2(1, true);
 
@@ -1332,9 +1309,8 @@ public class IntroductionIntegrationTest
 		addListeners(false, false);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync REQUEST messages
 		sync0To1(1, true);
@@ -1399,9 +1375,8 @@ public class IntroductionIntegrationTest
 		// a new introduction is still possible
 		assertTrue(introductionManager0
 				.canIntroduce(contact1From0, contact2From0));
-		time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Ho!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Ho!");
 		sync0To1(1, true);
 		sync0To2(1, true);
 
@@ -1428,9 +1403,8 @@ public class IntroductionIntegrationTest
 		addListeners(false, false);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Hi!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
 
 		// sync REQUEST messages
 		sync0To1(1, true);
@@ -1458,9 +1432,8 @@ public class IntroductionIntegrationTest
 		// a new introduction is still possible
 		assertTrue(introductionManager0
 				.canIntroduce(contact1From0, contact2From0));
-		time = clock.currentTimeMillis();
 		introductionManager0
-				.makeIntroduction(contact1From0, contact2From0, "Ho!", time);
+				.makeIntroduction(contact1From0, contact2From0, "Ho!");
 		sync0To1(1, true);
 		sync0To2(1, true);
 
@@ -1496,9 +1469,8 @@ public class IntroductionIntegrationTest
 		addListeners(false, false);
 
 		// make introduction
-		long time = clock.currentTimeMillis();
+		introductionManager0
-		introductionManager0.makeIntroduction(contact1From0, contact2From0,
+				.makeIntroduction(contact1From0, contact2From0, "Hi!");
-				"Hi!", time);
 
 		// deleting the introduction for introducee1 will fail
 		Collection<ConversationMessageHeader> m1From0 = getMessages1From0();
@@ -1795,16 +1767,13 @@ public class IntroductionIntegrationTest
 				IntroductionRequest ir = introEvent.getMessageHeader();
 				ContactId contactId = introEvent.getContactId();
 				sessionId = ir.getSessionId();
-				long time = clock.currentTimeMillis();
 				try {
 					if (introducee == 1 && answerRequests) {
-						introductionManager1
+						introductionManager1.respondToIntroduction(contactId,
-								.respondToIntroduction(contactId, sessionId,
+								sessionId, accept);
-										time, accept);
 					} else if (introducee == 2 && answerRequests) {
-						introductionManager2
+						introductionManager2.respondToIntroduction(contactId,
-								.respondToIntroduction(contactId, sessionId,
+								sessionId, accept);
-										time, accept);
 					}
 				} catch (DbException exception) {
 					eventWaiter.rethrow(exception);

briar-core/src/test/java/org/briarproject/briar/privategroup/PrivateGroupIntegrationTest.java

@@ -25,6 +25,7 @@ import java.util.Collection;
 import javax.annotation.Nullable;
 
 import static org.briarproject.bramble.api.identity.AuthorInfo.Status.OURSELVES;
+import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
 import static org.briarproject.briar.api.privategroup.Visibility.INVISIBLE;
 import static org.briarproject.briar.api.privategroup.Visibility.REVEALED_BY_CONTACT;
 import static org.briarproject.briar.api.privategroup.Visibility.REVEALED_BY_US;
@@ -220,8 +221,8 @@ public class PrivateGroupIntegrationTest
 		byte[] signature = groupInvitationFactory
 				.signInvitation(contact, groupId0, timestamp,
 						author0.getPrivateKey());
-		groupInvitationManager0
+		groupInvitationManager0.sendInvitation(groupId0, c, text, timestamp,
-				.sendInvitation(groupId0, c, text, timestamp, signature);
+				signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	private GroupMember getGroupMember(PrivateGroupManager groupManager,

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/AbstractProtocolEngineTest.java

@@ -19,6 +19,7 @@ import org.briarproject.bramble.api.versioning.ClientVersioningManager;
 import org.briarproject.bramble.test.BrambleMockTestCase;
 import org.briarproject.briar.api.autodelete.AutoDeleteManager;
 import org.briarproject.briar.api.client.MessageTracker;
+import org.briarproject.briar.api.conversation.ConversationManager;
 import org.briarproject.briar.api.privategroup.GroupMessageFactory;
 import org.briarproject.briar.api.privategroup.PrivateGroup;
 import org.briarproject.briar.api.privategroup.PrivateGroupFactory;
@@ -62,6 +63,8 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 	final MessageTracker messageTracker = context.mock(MessageTracker.class);
 	final AutoDeleteManager autoDeleteManager =
 			context.mock(AutoDeleteManager.class);
+	final ConversationManager conversationManager =
+			context.mock(ConversationManager.class);
 	final Clock clock = context.mock(Clock.class);
 
 	final Transaction txn = new Transaction(null, false);
@@ -115,16 +118,26 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 		assertEquals(inviteTimestamp, s.getInviteTimestamp());
 	}
 
-	void expectGetLocalTimestamp(long time) {
+	void expectGetTimestampForInvisibleMessage(long time) {
 		context.checking(new Expectations() {{
 			oneOf(clock).currentTimeMillis();
 			will(returnValue(time));
 		}});
 	}
 
+	void expectGetTimestampForVisibleMessage(long time) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getContactId(txn, contactGroupId);
+			will(returnValue(contactId));
+			oneOf(conversationManager)
+					.getTimestampForOutgoingMessage(txn, contactId);
+			will(returnValue(time));
+		}});
+	}
+
 	void expectSendInviteMessage(String text) throws Exception {
-		expectCheckWhetherContactSupportsAutoDeletion(true);
+		expectGetTimestampForVisibleMessage(messageTimestamp);
-		expectGetLocalTimestamp(messageTimestamp);
+		expectCheckWhetherContactSupportsAutoDeletion();
 		context.checking(new Expectations() {{
 			oneOf(messageEncoder).encodeInviteMessage(contactGroupId,
 					privateGroupId, inviteTimestamp, privateGroup.getName(),
@@ -137,8 +150,10 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 
 	void expectSendJoinMessage(JoinMessage m, boolean visible)
 			throws Exception {
-		expectCheckWhetherContactSupportsAutoDeletion(visible);
+		if (visible) expectGetTimestampForVisibleMessage(messageTimestamp);
-		expectGetLocalTimestamp(messageTimestamp);
+		else expectGetTimestampForInvisibleMessage(messageTimestamp);
+		expectCheckWhetherContactSupportsAutoDeletion();
+		if (visible) expectGetAutoDeleteTimer();
 		context.checking(new Expectations() {{
 			oneOf(messageEncoder).encodeJoinMessage(m.getContactGroupId(),
 					m.getPrivateGroupId(), m.getTimestamp(),
@@ -149,8 +164,10 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 	}
 
 	void expectSendLeaveMessage(boolean visible) throws Exception {
-		expectCheckWhetherContactSupportsAutoDeletion(visible);
+		if (visible) expectGetTimestampForVisibleMessage(messageTimestamp);
-		expectGetLocalTimestamp(messageTimestamp);
+		else expectGetTimestampForInvisibleMessage(messageTimestamp);
+		expectCheckWhetherContactSupportsAutoDeletion();
+		if (visible) expectGetAutoDeleteTimer();
 		context.checking(new Expectations() {{
 			oneOf(messageEncoder).encodeLeaveMessage(contactGroupId,
 					privateGroupId, messageTimestamp, lastLocalMessageId,
@@ -161,7 +178,7 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 	}
 
 	void expectSendAbortMessage() throws Exception {
-		expectGetLocalTimestamp(messageTimestamp);
+		expectGetTimestampForInvisibleMessage(messageTimestamp);
 		context.checking(new Expectations() {{
 			oneOf(messageEncoder)
 					.encodeAbortMessage(contactGroupId, privateGroupId,
@@ -226,8 +243,7 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 		}});
 	}
 
-	void expectCheckWhetherContactSupportsAutoDeletion(boolean visible)
+	void expectCheckWhetherContactSupportsAutoDeletion() throws Exception {
-			throws Exception {
 		context.checking(new Expectations() {{
 			oneOf(clientHelper).getContactId(txn, contactGroupId);
 			will(returnValue(contactId));
@@ -235,10 +251,13 @@ abstract class AbstractProtocolEngineTest extends BrambleMockTestCase {
 					GroupInvitationManager.CLIENT_ID,
 					GroupInvitationManager.MAJOR_VERSION);
 			will(returnValue(GroupInvitationManager.MINOR_VERSION));
-			if (visible) {
+		}});
-				oneOf(autoDeleteManager).getAutoDeleteTimer(txn, contactId);
+	}
-				will(returnValue(NO_AUTO_DELETE_TIMER));
+
-			}
+	void expectGetAutoDeleteTimer() throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(autoDeleteManager).getAutoDeleteTimer(txn, contactId);
+			will(returnValue(NO_AUTO_DELETE_TIMER));
 		}});
 	}
 }

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/CreatorProtocolEngineTest.java

@@ -24,7 +24,8 @@ public class CreatorProtocolEngineTest extends AbstractProtocolEngineTest {
 			new CreatorProtocolEngine(db, clientHelper, clientVersioningManager,
 					privateGroupManager, privateGroupFactory,
 					groupMessageFactory, identityManager, messageParser,
-					messageEncoder, messageTracker, autoDeleteManager, clock);
+					messageEncoder, messageTracker, autoDeleteManager,
+					conversationManager, clock);
 
 	private CreatorSession getDefaultSession(CreatorState state) {
 		return new CreatorSession(contactGroupId, privateGroupId,
@@ -43,7 +44,7 @@ public class CreatorProtocolEngineTest extends AbstractProtocolEngineTest {
 		expectOnLocalInvite(text);
 		CreatorSession newSession =
 				engine.onInviteAction(txn, session, text, inviteTimestamp,
-						signature);
+						signature, NO_AUTO_DELETE_TIMER);
 		assertEquals(INVITED, newSession.getState());
 		assertEquals(messageId, newSession.getLastLocalMessageId());
 		assertNull(newSession.getLastRemoteMessageId());
@@ -60,7 +61,7 @@ public class CreatorProtocolEngineTest extends AbstractProtocolEngineTest {
 		expectOnLocalInvite(null);
 		CreatorSession newSession =
 				engine.onInviteAction(txn, session, null, inviteTimestamp,
-						signature);
+						signature, NO_AUTO_DELETE_TIMER);
 		assertEquals(INVITED, newSession.getState());
 		assertEquals(messageId, newSession.getLastLocalMessageId());
 		assertNull(newSession.getLastRemoteMessageId());
@@ -83,31 +84,31 @@ public class CreatorProtocolEngineTest extends AbstractProtocolEngineTest {
 	@Test(expected = ProtocolStateException.class)
 	public void testOnInviteActionFromInvited() throws Exception {
 		engine.onInviteAction(txn, getDefaultSession(INVITED), null,
-				inviteTimestamp, signature);
+				inviteTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = ProtocolStateException.class)
 	public void testOnInviteActionFromJoined() throws Exception {
 		engine.onInviteAction(txn, getDefaultSession(JOINED), null,
-				inviteTimestamp, signature);
+				inviteTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = ProtocolStateException.class)
 	public void testOnInviteActionFromLeft() throws Exception {
 		engine.onInviteAction(txn, getDefaultSession(LEFT), null,
-				inviteTimestamp, signature);
+				inviteTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = ProtocolStateException.class)
 	public void testOnInviteActionFromDissolved() throws Exception {
 		engine.onInviteAction(txn, getDefaultSession(DISSOLVED), null,
-				inviteTimestamp, signature);
+				inviteTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = ProtocolStateException.class)
 	public void testOnInviteActionFromError() throws Exception {
 		engine.onInviteAction(txn, getDefaultSession(ERROR), null,
-				inviteTimestamp, signature);
+				inviteTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	// onJoinAction

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/GroupInvitationIntegrationTest.java

@@ -27,6 +27,7 @@ import java.util.Set;
 import javax.annotation.Nullable;
 
 import static java.util.Collections.emptySet;
+import static org.briarproject.briar.api.autodelete.AutoDeleteConstants.NO_AUTO_DELETE_TIMER;
 import static org.briarproject.briar.test.BriarTestUtils.assertGroupCount;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -687,7 +688,8 @@ public class GroupInvitationIntegrationTest
 		byte[] signature = groupInvitationFactory.signInvitation(contact1From0,
 				privateGroup.getId(), timestamp, author0.getPrivateKey());
 		groupInvitationManager0.sendInvitation(privateGroup.getId(),
-				contactId1From0, text, timestamp, signature);
+				contactId1From0, text, timestamp, signature,
+				NO_AUTO_DELETE_TIMER);
 	}
 
 }

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/GroupInvitationManagerImplTest.java

@@ -482,7 +482,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 		context.checking(new Expectations() {{
 			oneOf(creatorEngine).onInviteAction(with(txn),
 					with(any(CreatorSession.class)), with(text), with(time),
-					with(signature));
+					with(signature), with(NO_AUTO_DELETE_TIMER));
 			will(returnValue(creatorSession));
 		}});
 		expectStoreSession(creatorSession, storageMessage.getId());
@@ -491,7 +491,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).endTransaction(txn);
 		}});
 		groupInvitationManager.sendInvitation(privateGroup.getId(), contactId,
-				text, time, signature);
+				text, time, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test
@@ -514,7 +514,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 			will(returnValue(creatorSession));
 			oneOf(creatorEngine).onInviteAction(with(txn),
 					with(any(CreatorSession.class)), with(text), with(time),
-					with(signature));
+					with(signature), with(NO_AUTO_DELETE_TIMER));
 			will(returnValue(creatorSession));
 		}});
 		expectStoreSession(creatorSession, storageMessage.getId());
@@ -523,7 +523,7 @@ public class GroupInvitationManagerImplTest extends BrambleMockTestCase {
 			oneOf(db).endTransaction(txn);
 		}});
 		groupInvitationManager.sendInvitation(privateGroup.getId(), contactId,
-				text, time, signature);
+				text, time, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = IllegalArgumentException.class)

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/InviteeProtocolEngineTest.java

@@ -43,7 +43,8 @@ public class InviteeProtocolEngineTest extends AbstractProtocolEngineTest {
 			new InviteeProtocolEngine(db, clientHelper, clientVersioningManager,
 					privateGroupManager, privateGroupFactory,
 					groupMessageFactory, identityManager, messageParser,
-					messageEncoder, messageTracker, autoDeleteManager, clock);
+					messageEncoder, messageTracker, autoDeleteManager,
+					conversationManager, clock);
 	private final LocalAuthor localAuthor = getLocalAuthor();
 
 	private InviteeSession getDefaultSession(InviteeState state) {
@@ -57,43 +58,43 @@ public class InviteeProtocolEngineTest extends AbstractProtocolEngineTest {
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromStart() {
 		engine.onInviteAction(txn, getDefaultSession(START), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromLeft() {
 		engine.onInviteAction(txn, getDefaultSession(ACCEPTED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromInvited() {
 		engine.onInviteAction(txn, getDefaultSession(INVITED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromDissolved() {
 		engine.onInviteAction(txn, getDefaultSession(DISSOLVED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromAccepted() {
 		engine.onInviteAction(txn, getDefaultSession(ACCEPTED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromJoined() {
 		engine.onInviteAction(txn, getDefaultSession(JOINED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromError() {
 		engine.onInviteAction(txn, getDefaultSession(ERROR), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	// onJoinAction

briar-core/src/test/java/org/briarproject/briar/privategroup/invitation/PeerProtocolEngineTest.java

@@ -27,7 +27,8 @@ public class PeerProtocolEngineTest extends AbstractProtocolEngineTest {
 			new PeerProtocolEngine(db, clientHelper, clientVersioningManager,
 					privateGroupManager, privateGroupFactory,
 					groupMessageFactory, identityManager, messageParser,
-					messageEncoder, messageTracker, autoDeleteManager, clock);
+					messageEncoder, messageTracker, autoDeleteManager,
+					conversationManager, clock);
 
 	private PeerSession getDefaultSession(PeerState state) {
 		return new PeerSession(contactGroupId, privateGroupId,
@@ -39,43 +40,43 @@ public class PeerProtocolEngineTest extends AbstractProtocolEngineTest {
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromStart() {
 		engine.onInviteAction(txn, getDefaultSession(START), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromAwaitMember() {
 		engine.onInviteAction(txn, getDefaultSession(AWAIT_MEMBER), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromNeitherJoined() {
 		engine.onInviteAction(txn, getDefaultSession(NEITHER_JOINED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromLocalJoined() {
 		engine.onInviteAction(txn, getDefaultSession(LOCAL_JOINED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromBothJoined() {
 		engine.onInviteAction(txn, getDefaultSession(BOTH_JOINED), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromLocalLeft() {
 		engine.onInviteAction(txn, getDefaultSession(LOCAL_LEFT), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testOnInviteActionFromError() {
 		engine.onInviteAction(txn, getDefaultSession(ERROR), null,
-				messageTimestamp, signature);
+				messageTimestamp, signature, NO_AUTO_DELETE_TIMER);
 	}
 
 	// onJoinAction

briar-core/src/test/java/org/briarproject/briar/sharing/BlogSharingIntegrationTest.java

@@ -122,8 +122,7 @@ public class BlogSharingIntegrationTest
 
 		// send invitation
 		blogSharingManager0
-				.sendInvitation(blog2.getId(), contactId1From0, "Hi!",
+				.sendInvitation(blog2.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// invitee has own blog and that of the sharer
 		assertEquals(2, blogManager1.getBlogs().size());
@@ -213,8 +212,8 @@ public class BlogSharingIntegrationTest
 		blogManager0.addBlog(rssBlog);
 
 		// send invitation
-		blogSharingManager0.sendInvitation(rssBlog.getId(), contactId1From0,
+		blogSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(rssBlog.getId(), contactId1From0, "Hi!");
 
 		// invitee has own blog and that of the sharer
 		assertEquals(2, blogManager1.getBlogs().size());
@@ -285,8 +284,7 @@ public class BlogSharingIntegrationTest
 
 		// send invitation
 		blogSharingManager0
-				.sendInvitation(blog2.getId(), contactId1From0, null,
+				.sendInvitation(blog2.getId(), contactId1From0, null);
-						clock.currentTimeMillis());
 
 		// sync first request message
 		sync0To1(1, true);
@@ -341,8 +339,7 @@ public class BlogSharingIntegrationTest
 
 		// send invitation
 		blogSharingManager0
-				.sendInvitation(blog2.getId(), contactId1From0, "Hi!",
+				.sendInvitation(blog2.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync first request message
 		sync0To1(1, true);
@@ -398,8 +395,7 @@ public class BlogSharingIntegrationTest
 
 		// sharer sends invitation for 2's blog to 1
 		blogSharingManager0
-				.sendInvitation(blog2.getId(), contactId1From0, "Hi!",
+				.sendInvitation(blog2.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync first request message
 		sync0To1(1, true);
@@ -436,8 +432,7 @@ public class BlogSharingIntegrationTest
 
 		// send invitation
 		blogSharingManager0
-				.sendInvitation(blog2.getId(), contactId1From0, "Hi!",
+				.sendInvitation(blog2.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync first request message
 		sync0To1(1, true);
@@ -515,8 +510,7 @@ public class BlogSharingIntegrationTest
 
 		// sharer sends invitation for 2's blog to 1
 		blogSharingManager0
-				.sendInvitation(blog2.getId(), contactId1From0, "Hi!",
+				.sendInvitation(blog2.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync first request message
 		sync0To1(1, true);

briar-core/src/test/java/org/briarproject/briar/sharing/ForumSharingIntegrationTest.java

@@ -126,8 +126,7 @@ public class ForumSharingIntegrationTest
 	public void testSuccessfulSharing() throws Exception {
 		// send invitation
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, "Hi!",
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// check that request message state is correct
 		Collection<ConversationMessageHeader> messages = getMessages1From0();
@@ -191,8 +190,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testDeclinedSharing() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 
 		// sync request message
 		sync0To1(1, true);
@@ -243,8 +242,8 @@ public class ForumSharingIntegrationTest
 
 		// send a new invitation again after re-adding the forum
 		db0.transaction(false, txn -> forumManager0.addForum(txn, forum));
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 
 		// reset listener state for new request
 		listener1.requestReceived = false;
@@ -259,8 +258,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testInviteeLeavesAfterFinished() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
 
 		// sync request message
 		sync0To1(1, true);
@@ -322,8 +321,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testSharerLeavesAfterFinished() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 
 		// sync request message
 		sync0To1(1, true);
@@ -383,8 +382,8 @@ public class ForumSharingIntegrationTest
 
 		// send a new invitation again after re-adding the forum
 		db0.transaction(false, txn -> forumManager0.addForum(txn, forum));
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 
 		// reset listener state for new request
 		listener1.requestReceived = false;
@@ -399,8 +398,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testSharerLeavesBeforeResponse() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 
 		// sharer un-subscribes from forum
 		forumManager0.removeForum(forum);
@@ -420,8 +419,7 @@ public class ForumSharingIntegrationTest
 
 		// send invitation
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, null,
+				.sendInvitation(forum.getId(), contactId1From0, null);
-						clock.currentTimeMillis());
 
 		// sync request message
 		sync0To1(1, true);
@@ -445,8 +443,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testSharingSameForumWithEachOther() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
 
 		// sync request message
 		sync0To1(1, true);
@@ -471,10 +469,9 @@ public class ForumSharingIntegrationTest
 		assertEquals(1, forumManager1.getForums().size());
 
 		// invitee now shares same forum back
-		forumSharingManager1.sendInvitation(forum.getId(),
+		forumSharingManager1
-				contactId0From1,
+				.sendInvitation(forum.getId(), contactId0From1,
-				"I am re-sharing this forum with you.",
+						"I am re-sharing this forum with you.");
-				clock.currentTimeMillis());
 
 		// assert that the last invitation wasn't send
 		assertEquals(2, c1.getMessageTracker().getGroupCount(group.getId())
@@ -485,8 +482,8 @@ public class ForumSharingIntegrationTest
 	public void testSharingSameForumWithEachOtherBeforeAccept()
 			throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
 		sync0To1(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 		assertRequestReceived(listener1, contactId0From1);
@@ -501,10 +498,9 @@ public class ForumSharingIntegrationTest
 				.getMsgCount());
 
 		// invitee now shares same forum back
-		forumSharingManager1.sendInvitation(forum.getId(),
+		forumSharingManager1
-				contactId0From1,
+				.sendInvitation(forum.getId(), contactId0From1,
-				"I am re-sharing this forum with you.",
+						"I am re-sharing this forum with you.");
-				clock.currentTimeMillis());
 
 		// assert that the last invitation wasn't send
 		assertEquals(1, c1.getMessageTracker().getGroupCount(group.getId())
@@ -518,13 +514,12 @@ public class ForumSharingIntegrationTest
 
 		// send invitation
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, "Hi!",
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// invitee now shares same forum back
-		forumSharingManager1.sendInvitation(forum.getId(),
+		forumSharingManager1
-				contactId0From1, "I am re-sharing this forum with you.",
+				.sendInvitation(forum.getId(), contactId0From1,
-				clock.currentTimeMillis());
+						"I am re-sharing this forum with you.");
 
 		// only now sync request message
 		sync0To1(1, true);
@@ -554,8 +549,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testContactRemoved() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
 
 		// sync request message
 		sync0To1(1, true);
@@ -597,8 +592,7 @@ public class ForumSharingIntegrationTest
 
 		// send invitation
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, "Hi!",
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync request message
 		sync0To1(1, true);
@@ -626,8 +620,7 @@ public class ForumSharingIntegrationTest
 
 		// send invitation
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, "Hi!",
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync request message
 		sync0To1(1, true);
@@ -637,8 +630,7 @@ public class ForumSharingIntegrationTest
 		// second sharer sends invitation for same forum
 		assertNotNull(contactId1From2);
 		forumSharingManager2
-				.sendInvitation(forum.getId(), contactId1From2, null,
+				.sendInvitation(forum.getId(), contactId1From2, null);
-						clock.currentTimeMillis());
 
 		// sync second request message
 		sync2To1(1, true);
@@ -680,8 +672,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testSyncAfterReSharing() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
 
 		// sync request message
 		sync0To1(1, true);
@@ -745,8 +737,7 @@ public class ForumSharingIntegrationTest
 
 		// send invitation again
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, "Hi!",
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
-						clock.currentTimeMillis());
 
 		// sync request message
 		sync0To1(1, true);
@@ -787,8 +778,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testSessionResetAfterAbort() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				"Hi!", clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, "Hi!");
 
 		// sync request message
 		sync0To1(1, true);
@@ -836,8 +827,7 @@ public class ForumSharingIntegrationTest
 
 		// new invitation is possible now
 		forumSharingManager0
-				.sendInvitation(forum.getId(), contactId1From0, null,
+				.sendInvitation(forum.getId(), contactId1From0, null);
-						clock.currentTimeMillis());
 		sync0To1(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 		assertRequestReceived(listener1, contactId0From1);
@@ -859,8 +849,8 @@ public class ForumSharingIntegrationTest
 	public void testDeletingAllMessagesWhenCompletingSession()
 			throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 		sync0To1(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 
@@ -909,8 +899,8 @@ public class ForumSharingIntegrationTest
 		sync1To0(1, true);
 
 		// sending invitation is possible again
-		forumSharingManager1.sendInvitation(forum.getId(), contactId0From1,
+		forumSharingManager1
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId0From1, null);
 		sync1To0(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 
@@ -944,8 +934,8 @@ public class ForumSharingIntegrationTest
 	public void testDeletingAllMessagesAfterDecline()
 			throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 		sync0To1(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 
@@ -969,8 +959,8 @@ public class ForumSharingIntegrationTest
 		assertEquals(0, getMessages0From1().size());
 
 		// re-sending invitation is possible
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 		sync0To1(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 
@@ -984,8 +974,8 @@ public class ForumSharingIntegrationTest
 	@Test
 	public void testDeletingSomeMessages() throws Exception {
 		// send invitation
-		forumSharingManager0.sendInvitation(forum.getId(), contactId1From0,
+		forumSharingManager0
-				null, clock.currentTimeMillis());
+				.sendInvitation(forum.getId(), contactId1From0, null);
 		sync0To1(1, true);
 		eventWaiter.await(TIMEOUT, 1);
 
@@ -996,7 +986,8 @@ public class ForumSharingIntegrationTest
 		Set<MessageId> toDelete = new HashSet<>();
 		toDelete.add(messageId);
 		assertFalse(deleteMessages1From0(toDelete).allDeleted());
-		assertTrue(deleteMessages1From0(toDelete).hasInvitationSessionInProgress());
+		assertTrue(deleteMessages1From0(toDelete)
+				.hasInvitationSessionInProgress());
 
 		// decline invitation
 		respondToRequest(contactId0From1, true);
@@ -1006,9 +997,11 @@ public class ForumSharingIntegrationTest
 		// both can still not delete the invitation,
 		// because the response was not selected for deletion as well
 		assertFalse(deleteMessages1From0(toDelete).allDeleted());
-		assertTrue(deleteMessages1From0(toDelete).hasNotAllInvitationSelected());
+		assertTrue(
+				deleteMessages1From0(toDelete).hasNotAllInvitationSelected());
 		assertFalse(deleteMessages0From1(toDelete).allDeleted());
-		assertTrue(deleteMessages0From1(toDelete).hasNotAllInvitationSelected());
+		assertTrue(
+				deleteMessages0From1(toDelete).hasNotAllInvitationSelected());
 
 		// after selecting response, both messages can be deleted
 		m0 = getMessages1From0();
@@ -1023,8 +1016,10 @@ public class ForumSharingIntegrationTest
 
 		// 1 can still not delete the messages, as last one has not been ACKed
 		assertFalse(deleteMessages0From1(toDelete).allDeleted());
-		assertFalse(deleteMessages0From1(toDelete).hasNotAllInvitationSelected());
+		assertFalse(
-		assertTrue(deleteMessages0From1(toDelete).hasInvitationSessionInProgress());
+				deleteMessages0From1(toDelete).hasNotAllInvitationSelected());
+		assertTrue(deleteMessages0From1(toDelete)
+				.hasInvitationSessionInProgress());
 
 		// 0 sends an ACK to their last message
 		sendAcks(c0, c1, contactId1From0, 1);