diff --git a/briar-api/src/net/sf/briar/api/db/DatabaseComponent.java b/briar-api/src/net/sf/briar/api/db/DatabaseComponent.java
index c908d3e47..6399ad328 100644
--- a/briar-api/src/net/sf/briar/api/db/DatabaseComponent.java
+++ b/briar-api/src/net/sf/briar/api/db/DatabaseComponent.java
@@ -11,6 +11,8 @@ import net.sf.briar.api.TransportProperties;
 import net.sf.briar.api.db.event.DatabaseListener;
 import net.sf.briar.api.protocol.Ack;
 import net.sf.briar.api.protocol.AuthorId;
+import net.sf.briar.api.protocol.ExpiryAck;
+import net.sf.briar.api.protocol.ExpiryUpdate;
 import net.sf.briar.api.protocol.Group;
 import net.sf.briar.api.protocol.GroupId;
 import net.sf.briar.api.protocol.Message;
@@ -96,6 +98,18 @@ public interface DatabaseComponent {
 	Collection<byte[]> generateBatch(ContactId c, int maxLength,
 			Collection<MessageId> requested) throws DbException;
 
+	/**
+	 * Generates an expiry ack for the given contact. Returns null if no ack
+	 * is due.
+	 */
+	ExpiryAck generateExpiryAck(ContactId c) throws DbException;
+
+	/**
+	 * Generates an expiry update for the given contact. Returns null if no
+	 * update is due.
+	 */
+	ExpiryUpdate generateExpiryUpdate(ContactId c) throws DbException;
+
 	/**
 	 * Generates an offer for the given contact. Returns null if there are no
 	 * messages to offer.
@@ -186,6 +200,12 @@ public interface DatabaseComponent {
 	/** Processes an ack from the given contact. */
 	void receiveAck(ContactId c, Ack a) throws DbException;
 
+	/** Processes an expiry ack from the given contact. */
+	void receiveExpiryAck(ContactId c, ExpiryAck a) throws DbException;
+
+	/** Processes an expiry update from the given contact. */
+	void receiveExpiryUpdate(ContactId c, ExpiryUpdate u) throws DbException;
+
 	/** Processes a message from the given contact. */
 	void receiveMessage(ContactId c, Message m) throws DbException;
 
@@ -204,14 +224,14 @@ public interface DatabaseComponent {
 			throws DbException;
 
 	/** Processes a subscription update from the given contact. */
-	void receiveSubscriptionUpdate(ContactId c, SubscriptionUpdate s)
+	void receiveSubscriptionUpdate(ContactId c, SubscriptionUpdate u)
 			throws DbException;
 
 	/** Processes a transport ack from the given contact. */
 	void receiveTransportAck(ContactId c, TransportAck a) throws DbException;
 
 	/** Processes a transport update from the given contact. */
-	void receiveTransportUpdate(ContactId c, TransportUpdate t)
+	void receiveTransportUpdate(ContactId c, TransportUpdate u)
 			throws DbException;
 
 	/** Removes a contact (and all associated state) from the database. */
diff --git a/briar-api/src/net/sf/briar/api/protocol/ProtocolWriter.java b/briar-api/src/net/sf/briar/api/protocol/ProtocolWriter.java
index 58785a290..718e8be37 100644
--- a/briar-api/src/net/sf/briar/api/protocol/ProtocolWriter.java
+++ b/briar-api/src/net/sf/briar/api/protocol/ProtocolWriter.java
@@ -22,11 +22,11 @@ public interface ProtocolWriter {
 
 	void writeSubscriptionAck(SubscriptionAck a) throws IOException;
 
-	void writeSubscriptionUpdate(SubscriptionUpdate s) throws IOException;
+	void writeSubscriptionUpdate(SubscriptionUpdate u) throws IOException;
 
 	void writeTransportAck(TransportAck a) throws IOException;
 
-	void writeTransportUpdate(TransportUpdate t) throws IOException;
+	void writeTransportUpdate(TransportUpdate u) throws IOException;
 
 	void flush() throws IOException;
 
diff --git a/briar-core/src/net/sf/briar/db/Database.java b/briar-core/src/net/sf/briar/db/Database.java
index 98f4b0adb..3e1e06ec2 100644
--- a/briar-core/src/net/sf/briar/db/Database.java
+++ b/briar-core/src/net/sf/briar/db/Database.java
@@ -11,6 +11,8 @@ import net.sf.briar.api.TransportProperties;
 import net.sf.briar.api.db.DbException;
 import net.sf.briar.api.db.MessageHeader;
 import net.sf.briar.api.protocol.AuthorId;
+import net.sf.briar.api.protocol.ExpiryAck;
+import net.sf.briar.api.protocol.ExpiryUpdate;
 import net.sf.briar.api.protocol.Group;
 import net.sf.briar.api.protocol.GroupId;
 import net.sf.briar.api.protocol.Message;
@@ -34,6 +36,7 @@ import net.sf.briar.api.transport.TemporarySecret;
  * deadlock, locks must be acquired in the following (alphabetical) order:
  * <ul>
  * <li> contact
+ * <li> expiry
  * <li> message
  * <li> rating
  * <li> subscription
@@ -206,11 +209,19 @@ interface Database<T> {
 	Collection<ContactTransport> getContactTransports(T txn) throws DbException;
 
 	/**
-	 * Returns the approximate expiry time of the database.
+	 * Returns an expiry ack for the given contact, or null if no ack is due.
 	 * <p>
-	 * Locking: message read.
+	 * Locking: contact read, expiry write.
 	 */
-	long getExpiryTime(T txn) throws DbException;
+	ExpiryAck getExpiryAck(T txn, ContactId c) throws DbException;
+
+	/**
+	 * Returns an expiry update for the given contact, or null if no update is
+	 * due.
+	 * <p>
+	 * Locking: contact read, expiry write.
+	 */
+	ExpiryUpdate getExpiryUpdate(T txn, ContactId c) throws DbException;
 
 	/**
 	 * Returns the amount of free storage space available to the database, in
@@ -447,6 +458,14 @@ interface Database<T> {
 	long incrementConnectionCounter(T txn, ContactId c, TransportId t,
 			long period) throws DbException;
 
+	/**
+	 * Increments the expiry versions for all contacts to indicate that the
+	 * database's expiry time has changed and expiry updates should be sent.
+	 * <p>
+	 * Locking: contact read, expiry write.
+	 */
+	void incrementExpiryVersions(T txn) throws DbException;
+
 	/**
 	 * Merges the given configuration with the existing configuration for the
 	 * given transport.
@@ -531,11 +550,14 @@ interface Database<T> {
 			long centre, byte[] bitmap) throws DbException;
 
 	/**
-	 * Sets the given contact's database expiry time.
+	 * Sets the expiry time of the given contact's database, unless an update
+	 * with an equal or higher version number has already been received from
+	 * the contact.
 	 * <p>
-	 * Locking: contact write.
+	 * Locking: contact read, expiry write.
 	 */
-	void setExpiryTime(T txn, ContactId c, long expiry) throws DbException;
+	void setExpiryTime(T txn, ContactId c, long expiry, long version)
+			throws DbException;
 
 	/**
 	 * Sets the user's rating for the given author.
@@ -560,7 +582,7 @@ interface Database<T> {
 	 * <p>
 	 * Locking: contact read, transport write.
 	 */
-	void setRemoteProperties(T txn, ContactId c, TransportUpdate t)
+	void setRemoteProperties(T txn, ContactId c, TransportUpdate u)
 			throws DbException;
 
 	/**
@@ -604,7 +626,16 @@ interface Database<T> {
 	 * <p>
 	 * Locking: contact read, subscription write.
 	 */
-	void setSubscriptions(T txn, ContactId c, SubscriptionUpdate s)
+	void setSubscriptions(T txn, ContactId c, SubscriptionUpdate u)
+			throws DbException;
+
+	/**
+	 * Records an expiry ack from the given contact for the given version
+	 * unless the contact has already acked an equal or higher version.
+	 * <p>
+	 * Locking: contact read, expiry write.
+	 */
+	void setExpiryUpdateAcked(T txn, ContactId c, long version)
 			throws DbException;
 
 	/**
diff --git a/briar-core/src/net/sf/briar/db/DatabaseComponentImpl.java b/briar-core/src/net/sf/briar/db/DatabaseComponentImpl.java
index 0ab4bfc60..6517e1817 100644
--- a/briar-core/src/net/sf/briar/db/DatabaseComponentImpl.java
+++ b/briar-core/src/net/sf/briar/db/DatabaseComponentImpl.java
@@ -46,6 +46,8 @@ import net.sf.briar.api.db.event.TransportRemovedEvent;
 import net.sf.briar.api.lifecycle.ShutdownManager;
 import net.sf.briar.api.protocol.Ack;
 import net.sf.briar.api.protocol.AuthorId;
+import net.sf.briar.api.protocol.ExpiryAck;
+import net.sf.briar.api.protocol.ExpiryUpdate;
 import net.sf.briar.api.protocol.Group;
 import net.sf.briar.api.protocol.GroupId;
 import net.sf.briar.api.protocol.Message;
@@ -81,6 +83,8 @@ DatabaseCleaner.Callback {
 
 	private final ReentrantReadWriteLock contactLock =
 			new ReentrantReadWriteLock(true);
+	private final ReentrantReadWriteLock expiryLock =
+			new ReentrantReadWriteLock(true);
 	private final ReentrantReadWriteLock messageLock =
 			new ReentrantReadWriteLock(true);
 	private final ReentrantReadWriteLock ratingLock =
@@ -590,6 +594,54 @@ DatabaseCleaner.Callback {
 		return Collections.unmodifiableList(messages);
 	}
 
+	public ExpiryAck generateExpiryAck(ContactId c) throws DbException {
+		contactLock.readLock().lock();
+		try {
+			expiryLock.writeLock().lock();
+			try {
+				T txn = db.startTransaction();
+				try {
+					if(!db.containsContact(txn, c))
+						throw new NoSuchContactException();
+					ExpiryAck a = db.getExpiryAck(txn, c);
+					db.commitTransaction(txn);
+					return a;
+				} catch(DbException e) {
+					db.abortTransaction(txn);
+					throw e;
+				}
+			} finally {
+				expiryLock.writeLock().unlock();
+			}
+		} finally {
+			contactLock.readLock().unlock();
+		}
+	}
+
+	public ExpiryUpdate generateExpiryUpdate(ContactId c) throws DbException {
+		contactLock.readLock().lock();
+		try {
+			expiryLock.writeLock().lock();
+			try {
+				T txn = db.startTransaction();
+				try {
+					if(!db.containsContact(txn, c))
+						throw new NoSuchContactException();
+					ExpiryUpdate e = db.getExpiryUpdate(txn, c);
+					db.commitTransaction(txn);
+					return e;
+				} catch(DbException e) {
+					db.abortTransaction(txn);
+					throw e;
+				}
+			} finally {
+				expiryLock.writeLock().unlock();
+			}
+		} finally {
+			contactLock.readLock().unlock();
+		}
+	}
+
 	public Offer generateOffer(ContactId c, int maxMessages)
 			throws DbException {
 		Collection<MessageId> offered;
@@ -651,9 +703,9 @@ DatabaseCleaner.Callback {
 				try {
 					if(!db.containsContact(txn, c))
 						throw new NoSuchContactException();
-					SubscriptionUpdate s = db.getSubscriptionUpdate(txn, c);
+					SubscriptionUpdate u = db.getSubscriptionUpdate(txn, c);
 					db.commitTransaction(txn);
-					return s;
+					return u;
 				} catch(DbException e) {
 					db.abortTransaction(txn);
 					throw e;
@@ -1038,6 +1090,54 @@ DatabaseCleaner.Callback {
 		}
 	}
 
+	public void receiveExpiryAck(ContactId c, ExpiryAck a) throws DbException {
+		contactLock.readLock().lock();
+		try {
+			expiryLock.writeLock().lock();
+			try {
+				T txn = db.startTransaction();
+				try {
+					if(!db.containsContact(txn, c))
+						throw new NoSuchContactException();
+					db.setExpiryUpdateAcked(txn, c, a.getVersionNumber());
+					db.commitTransaction(txn);
+				} catch(DbException e) {
+					db.abortTransaction(txn);
+					throw e;
+				}
+			} finally {
+				expiryLock.writeLock().unlock();
+			}
+		} finally {
+			contactLock.readLock().unlock();
+		}
+	}
+
+	public void receiveExpiryUpdate(ContactId c, ExpiryUpdate u)
+			throws DbException {
+		contactLock.readLock().lock();
+		try {
+			expiryLock.writeLock().lock();
+			try {
+				T txn = db.startTransaction();
+				try {
+					if(!db.containsContact(txn, c))
+						throw new NoSuchContactException();
+					db.setExpiryTime(txn, c, u.getExpiryTime(),
+							u.getVersionNumber());
+					db.commitTransaction(txn);
+				} catch(DbException e) {
+					db.abortTransaction(txn);
+					throw e;
+				}
+			} finally {
+				expiryLock.writeLock().unlock();
+			}
+		} finally {
+			contactLock.readLock().unlock();
+		}
+	}
+
 	public void receiveMessage(ContactId c, Message m) throws DbException {
 		boolean added = false;
 		contactLock.readLock().lock();
@@ -1149,7 +1249,7 @@ DatabaseCleaner.Callback {
 		}
 	}
 
-	public void receiveSubscriptionUpdate(ContactId c, SubscriptionUpdate s)
+	public void receiveSubscriptionUpdate(ContactId c, SubscriptionUpdate u)
 			throws DbException {
 		contactLock.readLock().lock();
 		try {
@@ -1159,7 +1259,7 @@ DatabaseCleaner.Callback {
 				try {
 					if(!db.containsContact(txn, c))
 						throw new NoSuchContactException();
-					db.setSubscriptions(txn, c, s);
+					db.setSubscriptions(txn, c, u);
 					db.commitTransaction(txn);
 				} catch(DbException e) {
 					db.abortTransaction(txn);
@@ -1200,7 +1300,7 @@ DatabaseCleaner.Callback {
 		}
 	}
 
-	public void receiveTransportUpdate(ContactId c, TransportUpdate t)
+	public void receiveTransportUpdate(ContactId c, TransportUpdate u)
 			throws DbException {
 		contactLock.readLock().lock();
 		try {
@@ -1210,7 +1310,7 @@ DatabaseCleaner.Callback {
 				try {
 					if(!db.containsContact(txn, c))
 						throw new NoSuchContactException();
-					db.setRemoteProperties(txn, c, t);
+					db.setRemoteProperties(txn, c, u);
 					db.commitTransaction(txn);
 				} catch(DbException e) {
 					db.abortTransaction(txn);
@@ -1223,7 +1323,7 @@ DatabaseCleaner.Callback {
 			contactLock.readLock().unlock();
 		}
 		// Call the listeners outside the lock
-		callListeners(new RemoteTransportsUpdatedEvent(c, t.getId()));
+		callListeners(new RemoteTransportsUpdatedEvent(c, u.getId()));
 	}
 
 	public void removeContact(ContactId c) throws DbException {
@@ -1502,27 +1602,37 @@ DatabaseCleaner.Callback {
 	 * removed.
 	 */
 	private boolean expireMessages(int size) throws DbException {
-		Collection<MessageId> old;
+		boolean removed = false;
 		contactLock.readLock().lock();
 		try {
-			messageLock.writeLock().lock();
+			expiryLock.writeLock().lock();
 			try {
-				T txn = db.startTransaction();
+				messageLock.writeLock().lock();
 				try {
-					old = db.getOldMessages(txn, size);
-					for(MessageId m : old) removeMessage(txn, m);
-					db.commitTransaction(txn);
-				} catch(DbException e) {
-					db.abortTransaction(txn);
-					throw e;
+					T txn = db.startTransaction();
+					try {
+						Collection<MessageId> old =
+								db.getOldMessages(txn, size);
+						if(!old.isEmpty()) {
+							for(MessageId m : old) removeMessage(txn, m);
+							db.incrementExpiryVersions(txn);
+							removed = true;
+						}
+						db.commitTransaction(txn);
+					} catch(DbException e) {
+						db.abortTransaction(txn);
+						throw e;
+					}
+				} finally {
+					messageLock.writeLock().unlock();
 				}
 			} finally {
-				messageLock.writeLock().unlock();
+				expiryLock.writeLock().unlock();
 			}
 		} finally {
 			contactLock.readLock().unlock();
 		}
-		return old.isEmpty();
+		return removed;
 	}
 
 	/**
diff --git a/briar-core/src/net/sf/briar/db/JdbcDatabase.java b/briar-core/src/net/sf/briar/db/JdbcDatabase.java
index a4263a62a..96db7bd82 100644
--- a/briar-core/src/net/sf/briar/db/JdbcDatabase.java
+++ b/briar-core/src/net/sf/briar/db/JdbcDatabase.java
@@ -31,6 +31,8 @@ import net.sf.briar.api.db.DbClosedException;
 import net.sf.briar.api.db.DbException;
 import net.sf.briar.api.db.MessageHeader;
 import net.sf.briar.api.protocol.AuthorId;
+import net.sf.briar.api.protocol.ExpiryAck;
+import net.sf.briar.api.protocol.ExpiryUpdate;
 import net.sf.briar.api.protocol.Group;
 import net.sf.briar.api.protocol.GroupId;
 import net.sf.briar.api.protocol.Message;
@@ -54,9 +56,22 @@ abstract class JdbcDatabase implements Database<Connection> {
 	private static final String CREATE_CONTACTS =
 			"CREATE TABLE contacts"
 					+ " (contactId COUNTER,"
-					+ " expiry BIGINT NOT NULL DEFAULT 0," // FIXME: Move this
 					+ " PRIMARY KEY (contactId))";
 
+	// Locking: expiry
+	private static final String CREATE_EXPIRY_VERSIONS =
+			"CREATE TABLE expiryVersions"
+					+ " (contactId INT NOT NULL,"
+					+ " expiry BIGINT NOT NULL,"
+					+ " localVersion BIGINT NOT NULL,"
+					+ " localAcked BIGINT NOT NULL,"
+					+ " remoteVersion BIGINT NOT NULL,"
+					+ " remoteAcked BOOLEAN NOT NULL,"
+					+ " PRIMARY KEY (contactId),"
+					+ " FOREIGN KEY (contactId)"
+					+ " REFERENCES contacts (contactId)"
+					+ " ON DELETE CASCADE)";
+
 	// Locking: message
 	private static final String CREATE_MESSAGES =
 			"CREATE TABLE messages"
@@ -340,6 +355,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			s = txn.createStatement();
 			s.executeUpdate(insertTypeNames(CREATE_CONTACTS));
+			s.executeUpdate(insertTypeNames(CREATE_EXPIRY_VERSIONS));
 			s.executeUpdate(insertTypeNames(CREATE_MESSAGES));
 			s.executeUpdate(INDEX_MESSAGES_BY_PARENT);
 			s.executeUpdate(INDEX_MESSAGES_BY_AUTHOR);
@@ -497,6 +513,16 @@ abstract class JdbcDatabase implements Database<Connection> {
 			if(rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
+			// Create an expiry version row
+			sql = "INSERT INTO expiryVersions (contactId, expiry,"
+					+ " localVersion, localAcked, remoteVersion, remoteAcked)"
+					+ " VALUES (?, ZERO(), ?, ZERO(), ZERO(), TRUE)";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, 1);
+			affected = ps.executeUpdate();
+			if(affected != 1) throw new DbStateException();
+			ps.close();
 			// Create a group version row
 			sql = "INSERT INTO groupVersions (contactId, localVersion,"
 					+ " localAcked, remoteVersion, remoteAcked)"
@@ -1016,27 +1042,68 @@ abstract class JdbcDatabase implements Database<Connection> {
 		} else return f.length();
 	}
 
-	public long getExpiryTime(Connection txn) throws DbException {
+	public ExpiryAck getExpiryAck(Connection txn, ContactId c)
+			throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
-			long timestamp = 0L;
-			String sql = "SELECT timestamp FROM messages"
-					+ " ORDER BY timestamp LIMIT ?";
+			String sql = "SELECT remoteVersion FROM expiryVersions"
+					+ " WHERE contactId = ? AND remoteAcked = FALSE";
 			ps = txn.prepareStatement(sql);
-			ps.setInt(1, 1);
+			ps.setInt(1, c.getInt());
 			rs = ps.executeQuery();
-			if(rs.next()) {
-				timestamp = rs.getLong(1);
-				timestamp -= timestamp % EXPIRY_MODULUS;
+			if(!rs.next()) {
+				rs.close();
+				ps.close();
+				return null;
 			}
+			long version = rs.getLong(1);
 			if(rs.next()) throw new DbStateException();
 			rs.close();
 			ps.close();
-			return timestamp;
+			sql = "UPDATE expiryVersions SET remoteAcked = TRUE"
+					+ " WHERE contactId = ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			int affected = ps.executeUpdate();
+			if(affected != 1) throw new DbStateException();
+			ps.close();
+			return new ExpiryAck(version);
 		} catch(SQLException e) {
-			tryToClose(rs);
 			tryToClose(ps);
+			tryToClose(rs);
+			throw new DbException(e);
+		}
+	}
+
+	public ExpiryUpdate getExpiryUpdate(Connection txn, ContactId c)
+			throws DbException {
+		PreparedStatement ps = null;
+		ResultSet rs = null;
+		try {
+			String sql = "SELECT timestamp, localVersion"
+					+ " FROM messages JOIN expiryVersions"
+					+ " WHERE contactId = ? AND localVersion > localAcked"
+					+ " ORDER BY timestamp LIMIT ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, c.getInt());
+			ps.setInt(2, 1);
+			rs = ps.executeQuery();
+			if(!rs.next()) {
+				rs.close();
+				ps.close();
+				return null;
+			}
+			long expiry = rs.getLong(1);
+			expiry -= expiry % EXPIRY_MODULUS;
+			long version = rs.getLong(2);
+			if(rs.next()) throw new DbStateException();
+			rs.close();
+			ps.close();
+			return new ExpiryUpdate(expiry, version);
+		} catch(SQLException e) {
+			tryToClose(ps);
+			tryToClose(rs);
 			throw new DbException(e);
 		}
 	}
@@ -1210,8 +1277,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " JOIN groupVisibilities AS gv"
 					+ " ON m.groupId = gv.groupId"
 					+ " AND cg.contactId = gv.contactId"
-					+ " JOIN contacts AS c"
-					+ " ON cg.contactId = c.contactId"
+					+ " JOIN expiryVersions AS ev"
+					+ " ON cg.contactId = ev.contactId"
 					+ " JOIN statuses AS s"
 					+ " ON m.messageId = s.messageId"
 					+ " AND cg.contactId = s.contactId"
@@ -1316,8 +1383,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " JOIN groupVisibilities AS gv"
 					+ " ON m.groupId = gv.groupId"
 					+ " AND cg.contactId = gv.contactId"
-					+ " JOIN contacts AS c"
-					+ " ON cg.contactId = c.contactId"
+					+ " JOIN expiryVersions AS ev"
+					+ " ON cg.contactId = ev.contactId"
 					+ " JOIN statuses AS s"
 					+ " ON m.messageId = s.messageId"
 					+ " AND cg.contactId = s.contactId"
@@ -1577,8 +1644,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " JOIN groupVisibilities AS gv"
 					+ " ON m.groupId = gv.groupId"
 					+ " AND cg.contactId = gv.contactId"
-					+ " JOIN contacts AS c"
-					+ " ON cg.contactId = c.contactId"
+					+ " JOIN expiryVersions AS ev"
+					+ " ON cg.contactId = ev.contactId"
 					+ " JOIN statuses AS s"
 					+ " ON m.messageId = s.messageId"
 					+ " AND cg.contactId = s.contactId"
@@ -1721,7 +1788,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			String sql = "SELECT g.groupId, name, key, localVersion"
 					+ " FROM groups AS g"
-					+ " JOIN groupVisibilities as gv"
+					+ " JOIN groupVisibilities AS gv"
 					+ " ON g.groupId = gv.groupId"
 					+ " JOIN groupVersions AS v"
 					+ " ON gv.contactId = v.contactId"
@@ -1800,7 +1867,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			String sql = "SELECT transportId, key, value, localVersion"
 					+ " FROM transportProperties AS tp"
-					+ " JOIN transportVersions as tv"
+					+ " JOIN transportVersions AS tv"
 					+ " ON tp.transportId = tv.transportId"
 					+ " WHERE tv.contactId = ?"
 					+ " AND localVersion > localAcked";
@@ -1909,8 +1976,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " JOIN groupVisibilities AS gv"
 					+ " ON m.groupId = gv.groupId"
 					+ " AND cg.contactId = gv.contactId"
-					+ " JOIN contacts AS c"
-					+ " ON cg.contactId = c.contactId"
+					+ " JOIN expiryVersions AS ev"
+					+ " ON cg.contactId = ev.contactId"
 					+ " JOIN statuses AS s"
 					+ " ON m.messageId = s.messageId"
 					+ " AND cg.contactId = s.contactId"
@@ -1977,6 +2044,20 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
+	public void incrementExpiryVersions(Connection txn) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE expiryVersions"
+					+ " SET localVersion = localVersion + ?";
+			ps = txn.prepareStatement(sql);
+			ps.setInt(1, 1);
+			ps.executeUpdate();
+		} catch(SQLException e) {
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
 	public void removeOutstandingMessages(Connection txn, ContactId c,
 			Collection<MessageId> acked) throws DbException {
 		PreparedStatement ps = null;
@@ -2244,15 +2325,39 @@ abstract class JdbcDatabase implements Database<Connection> {
 		}
 	}
 
-	public void setExpiryTime(Connection txn, ContactId c, long expiry)
+	public void setExpiryTime(Connection txn, ContactId c, long expiry,
+			long version) throws DbException {
+		PreparedStatement ps = null;
+		try {
+			String sql = "UPDATE expiryVersions"
+					+ " SET expiry = ?, remoteVersion = ?, remoteAcked = FALSE"
+					+ " WHERE contactId = ? AND remoteVersion < ?";
+			ps = txn.prepareStatement(sql);
+			ps.setLong(1, expiry);
+			ps.setLong(2, version);
+			ps.setInt(3, c.getInt());
+			ps.setLong(4, version);
+			int affected = ps.executeUpdate();
+			if(affected > 1) throw new DbStateException();
+			ps.close();
+		} catch(SQLException e) {
+			tryToClose(ps);
+			throw new DbException(e);
+		}
+	}
+
+	public void setExpiryUpdateAcked(Connection txn, ContactId c, long version)
 			throws DbException {
 		PreparedStatement ps = null;
 		try {
-			String sql = "UPDATE contacts SET expiry = ?"
-					+ " WHERE contactId = ?";
+			String sql = "UPDATE expiryVersions SET localAcked = ?"
+					+ " WHERE contactId = ?"
+					+ " AND localAcked < ? AND localVersion >= ?";
 			ps = txn.prepareStatement(sql);
-			ps.setLong(1, expiry);
+			ps.setLong(1, version);
 			ps.setInt(2, c.getInt());
+			ps.setLong(3, version);
+			ps.setLong(4, version);
 			int affected = ps.executeUpdate();
 			if(affected > 1) throw new DbStateException();
 			ps.close();
@@ -2362,16 +2467,17 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	public void setRemoteProperties(Connection txn, ContactId c,
-			TransportUpdate t) throws DbException {
+			TransportUpdate u) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
+			TransportId t = u.getId();
 			// Find the existing version, if any
 			String sql = "SELECT remoteVersion FROM contactTransportVersions"
 					+ " WHERE contactId = ? AND transportId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
-			ps.setBytes(2, t.getId().getBytes());
+			ps.setBytes(2, t.getBytes());
 			rs = ps.executeQuery();
 			long version = rs.next() ? rs.getLong(1) : -1L;
 			if(rs.next()) throw new DbStateException();
@@ -2385,8 +2491,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 						+ " VALUES (?, ?, ?, FALSE)";
 				ps = txn.prepareStatement(sql);
 				ps.setInt(1, c.getInt());
-				ps.setBytes(2, t.getId().getBytes());
-				ps.setLong(3, t.getVersionNumber());
+				ps.setBytes(2, t.getBytes());
+				ps.setLong(3, u.getVersionNumber());
 				int affected = ps.executeUpdate();
 				if(affected != 1) throw new DbStateException();
 				ps.close();
@@ -2396,32 +2502,32 @@ abstract class JdbcDatabase implements Database<Connection> {
 						+ " SET remoteVersion = ?, remoteAcked = FALSE"
 						+ " WHERE contactId = ? AND transportId = ?";
 				ps = txn.prepareStatement(sql);
-				ps.setLong(1, Math.max(version, t.getVersionNumber()));
+				ps.setLong(1, Math.max(version, u.getVersionNumber()));
 				ps.setInt(1, c.getInt());
-				ps.setBytes(2, t.getId().getBytes());
+				ps.setBytes(2, t.getBytes());
 				int affected = ps.executeUpdate();
 				if(affected > 1) throw new DbStateException();
 				ps.close();
 				// Return if the update is obsolete
-				if(t.getVersionNumber() <= version) return;
+				if(u.getVersionNumber() <= version) return;
 			}
 			// Delete the existing properties, if any
 			sql = "DELETE FROM contactTransportProperties"
 					+ " WHERE contactId = ? AND transportId = ?";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
-			ps.setBytes(2, t.getId().getBytes());
+			ps.setBytes(2, t.getBytes());
 			ps.executeUpdate();
 			ps.close();
 			// Store the new properties, if any
-			TransportProperties p = t.getProperties();
+			TransportProperties p = u.getProperties();
 			if(p.isEmpty()) return;
 			sql = "INSERT INTO contactTransportProperties"
 					+ " (contactId, transportId, key, value)"
 					+ " VALUES (?, ?, ?, ?)";
 			ps = txn.prepareStatement(sql);
 			ps.setInt(1, c.getInt());
-			ps.setBytes(2, t.getId().getBytes());
+			ps.setBytes(2, t.getBytes());
 			for(Entry<String, String> e : p.entrySet()) {
 				ps.setString(1, e.getKey());
 				ps.setString(2, e.getValue());
@@ -2568,8 +2674,8 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " JOIN groupVisibilities AS gv"
 					+ " ON m.groupId = gv.groupId"
 					+ " AND cg.contactId = gv.contactId"
-					+ " JOIN contacts AS c"
-					+ " ON cg.contactId = c.contactId"
+					+ " JOIN expiryVersions AS ev"
+					+ " ON cg.contactId = ev.contactId"
 					+ " WHERE messageId = ?"
 					+ " AND cg.contactId = ?"
 					+ " AND timestamp >= expiry";
@@ -2600,7 +2706,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 	}
 
 	public void setSubscriptions(Connection txn, ContactId c,
-			SubscriptionUpdate s) throws DbException {
+			SubscriptionUpdate u) throws DbException {
 		PreparedStatement ps = null;
 		ResultSet rs = null;
 		try {
@@ -2620,7 +2726,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 					+ " SET remoteVersion = ?, remoteAcked = FALSE"
 					+ " WHERE contactId = ?";
 			ps = txn.prepareStatement(sql);
-			ps.setLong(1, Math.max(version, s.getVersionNumber()));
+			ps.setLong(1, Math.max(version, u.getVersionNumber()));
 			ps.setInt(2, c.getInt());
 			int affected = ps.executeUpdate();
 			if(affected > 1) throw new DbStateException();
@@ -2631,7 +2737,7 @@ abstract class JdbcDatabase implements Database<Connection> {
 			ps.setInt(1, c.getInt());
 			ps.executeUpdate();
 			// Store the new subscriptions, if any
-			Collection<Group> subs = s.getGroups();
+			Collection<Group> subs = u.getGroups();
 			if(subs.isEmpty()) return;
 			sql = "INSERT INTO contactGroups (contactId, groupId, name, key)"
 					+ " VALUES (?, ?, ?, ?)";
@@ -2664,11 +2770,13 @@ abstract class JdbcDatabase implements Database<Connection> {
 		PreparedStatement ps = null;
 		try {
 			String sql = "UPDATE groupVersions SET localAcked = ?"
-					+ " WHERE contactId = ? AND localAcked < ?";
+					+ " WHERE contactId = ?"
+					+ " AND localAcked < ? AND localVersion >= ?";
 			ps = txn.prepareStatement(sql);
 			ps.setLong(1, version);
 			ps.setInt(2, c.getInt());
 			ps.setLong(3, version);
+			ps.setLong(4, version);
 			int affected = ps.executeUpdate();
 			if(affected > 1) throw new DbStateException();
 			ps.close();
@@ -2684,12 +2792,13 @@ abstract class JdbcDatabase implements Database<Connection> {
 		try {
 			String sql = "UPDATE transportVersions SET localAcked = ?"
 					+ " WHERE contactId = ? AND transportId = ?"
-					+ " AND localAcked < ?";
+					+ " AND localAcked < ? AND localVersion >= ?";
 			ps = txn.prepareStatement(sql);
 			ps.setLong(1, version);
 			ps.setInt(2, c.getInt());
 			ps.setBytes(3, t.getBytes());
 			ps.setLong(4, version);
+			ps.setLong(5, version);
 			int affected = ps.executeUpdate();
 			if(affected > 1) throw new DbStateException();
 			ps.close();
diff --git a/briar-core/src/net/sf/briar/protocol/ProtocolWriterImpl.java b/briar-core/src/net/sf/briar/protocol/ProtocolWriterImpl.java
index d5ed0e1f3..e345aa478 100644
--- a/briar-core/src/net/sf/briar/protocol/ProtocolWriterImpl.java
+++ b/briar-core/src/net/sf/briar/protocol/ProtocolWriterImpl.java
@@ -126,11 +126,11 @@ class ProtocolWriterImpl implements ProtocolWriter {
 		if(flush) out.flush();
 	}
 
-	public void writeSubscriptionUpdate(SubscriptionUpdate s)
+	public void writeSubscriptionUpdate(SubscriptionUpdate u)
 			throws IOException {
 		w.writeStructId(SUBSCRIPTION_UPDATE);
 		w.writeListStart();
-		for(Group g : s.getGroups()) {
+		for(Group g : u.getGroups()) {
 			w.writeStructId(GROUP);
 			w.writeString(g.getName());
 			byte[] publicKey = g.getPublicKey();
@@ -138,7 +138,7 @@ class ProtocolWriterImpl implements ProtocolWriter {
 			else w.writeBytes(publicKey);
 		}
 		w.writeListEnd();
-		w.writeInt64(s.getVersionNumber());
+		w.writeInt64(u.getVersionNumber());
 		if(flush) out.flush();
 	}
 
@@ -149,11 +149,11 @@ class ProtocolWriterImpl implements ProtocolWriter {
 		if(flush) out.flush();
 	}
 
-	public void writeTransportUpdate(TransportUpdate t) throws IOException {
+	public void writeTransportUpdate(TransportUpdate u) throws IOException {
 		w.writeStructId(TRANSPORT_UPDATE);
-		w.writeBytes(t.getId().getBytes());
-		w.writeMap(t.getProperties());
-		w.writeInt64(t.getVersionNumber());
+		w.writeBytes(u.getId().getBytes());
+		w.writeMap(u.getProperties());
+		w.writeInt64(u.getVersionNumber());
 		if(flush) out.flush();
 	}
 
diff --git a/briar-core/src/net/sf/briar/protocol/duplex/DuplexConnection.java b/briar-core/src/net/sf/briar/protocol/duplex/DuplexConnection.java
index 9321750e4..ab31510cf 100644
--- a/briar-core/src/net/sf/briar/protocol/duplex/DuplexConnection.java
+++ b/briar-core/src/net/sf/briar/protocol/duplex/DuplexConnection.java
@@ -173,11 +173,11 @@ abstract class DuplexConnection implements DatabaseListener {
 					// Start sending the requested messages
 					dbExecutor.execute(new GenerateBatches(requested));
 				} else if(reader.hasSubscriptionUpdate()) {
-					SubscriptionUpdate s = reader.readSubscriptionUpdate();
-					dbExecutor.execute(new ReceiveSubscriptionUpdate(s));
+					SubscriptionUpdate u = reader.readSubscriptionUpdate();
+					dbExecutor.execute(new ReceiveSubscriptionUpdate(u));
 				} else if(reader.hasTransportUpdate()) {
-					TransportUpdate t = reader.readTransportUpdate();
-					dbExecutor.execute(new ReceiveTransportUpdate(t));
+					TransportUpdate u = reader.readTransportUpdate();
+					dbExecutor.execute(new ReceiveTransportUpdate(u));
 				} else {
 					throw new FormatException();
 				}
@@ -524,8 +524,8 @@ abstract class DuplexConnection implements DatabaseListener {
 
 		public void run() {
 			try {
-				SubscriptionUpdate s = db.generateSubscriptionUpdate(contactId);
-				if(s != null) writerTasks.add(new WriteSubscriptionUpdate(s));
+				SubscriptionUpdate u = db.generateSubscriptionUpdate(contactId);
+				if(u != null) writerTasks.add(new WriteSubscriptionUpdate(u));
 			} catch(DbException e) {
 				if(LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 			}
@@ -578,7 +578,7 @@ abstract class DuplexConnection implements DatabaseListener {
 		public void run() {
 			assert writer != null;
 			try {
-				for(TransportUpdate t : updates) writer.writeTransportUpdate(t);
+				for(TransportUpdate u : updates) writer.writeTransportUpdate(u);
 			} catch(IOException e) {
 				if(LOG.isLoggable(WARNING)) LOG.log(WARNING, e.toString(), e);
 				dispose(true, true);
diff --git a/briar-core/src/net/sf/briar/protocol/simplex/IncomingSimplexConnection.java b/briar-core/src/net/sf/briar/protocol/simplex/IncomingSimplexConnection.java
index e9abf0c16..b876c578c 100644
--- a/briar-core/src/net/sf/briar/protocol/simplex/IncomingSimplexConnection.java
+++ b/briar-core/src/net/sf/briar/protocol/simplex/IncomingSimplexConnection.java
@@ -83,11 +83,11 @@ class IncomingSimplexConnection {
 					UnverifiedMessage m = reader.readMessage();
 					verificationExecutor.execute(new VerifyMessage(m));
 				} else if(reader.hasSubscriptionUpdate()) {
-					SubscriptionUpdate s = reader.readSubscriptionUpdate();
-					dbExecutor.execute(new ReceiveSubscriptionUpdate(s));
+					SubscriptionUpdate u = reader.readSubscriptionUpdate();
+					dbExecutor.execute(new ReceiveSubscriptionUpdate(u));
 				} else if(reader.hasTransportUpdate()) {
-					TransportUpdate t = reader.readTransportUpdate();
-					dbExecutor.execute(new ReceiveTransportUpdate(t));
+					TransportUpdate u = reader.readTransportUpdate();
+					dbExecutor.execute(new ReceiveTransportUpdate(u));
 				} else {
 					throw new FormatException();
 				}
diff --git a/briar-core/src/net/sf/briar/protocol/simplex/OutgoingSimplexConnection.java b/briar-core/src/net/sf/briar/protocol/simplex/OutgoingSimplexConnection.java
index ef9c7c932..cccfa22dd 100644
--- a/briar-core/src/net/sf/briar/protocol/simplex/OutgoingSimplexConnection.java
+++ b/briar-core/src/net/sf/briar/protocol/simplex/OutgoingSimplexConnection.java
@@ -71,11 +71,11 @@ class OutgoingSimplexConnection {
 			Collection<TransportUpdate> updates =
 					db.generateTransportUpdates(contactId);
 			if(updates != null) {
-				for(TransportUpdate t : updates) writer.writeTransportUpdate(t);
+				for(TransportUpdate u : updates) writer.writeTransportUpdate(u);
 			}
 			// Write a subscription update. FIXME: Check for space
-			SubscriptionUpdate s = db.generateSubscriptionUpdate(contactId);
-			if(s != null) writer.writeSubscriptionUpdate(s);
+			SubscriptionUpdate u = db.generateSubscriptionUpdate(contactId);
+			if(u != null) writer.writeSubscriptionUpdate(u);
 			// Write acks until you can't write acks no more
 			capacity = conn.getRemainingCapacity();
 			int maxMessages = writer.getMaxMessagesForAck(capacity);