Merge branch '118-contact-introductions' into 'master'

Contact Introduction Backend

This MR allows you to introduce two of your contacts to each other. They both will receive an introduction with an optional message and then can accept or refuse the introduction which is presented as a notification.

When reviewing, I propose to review the individual commits separately as I took great care to split functional independent parts into separate commits. You might also want to have a look at the [Introduction Client Wiki page](https://code.briarproject.org/akwizgran/briar/wikis/IntroductionClient) to better understand what is going on before looking into the actual code.

Protocol sessions and states are not yet deleted and the UI is still missing (#253). In order to practically test this feature, the UI from !122 is needed.

See merge request !116

briar-api/src/org/briarproject/api/ProtocolEngine.java

@@ -0,0 +1,31 @@
+package org.briarproject.api;
+
+import org.briarproject.api.event.Event;
+
+import java.util.List;
+
+public interface ProtocolEngine<A, S, M> {
+	StateUpdate<S, M> onLocalAction(S localState, A action);
+
+	StateUpdate<S, M> onMessageReceived(S localState, M received);
+
+	StateUpdate<S, M> onMessageDelivered(S localState, M delivered);
+
+	class StateUpdate<S, M> {
+		public final boolean deleteMessages;
+		public final boolean deleteState;
+		public final S localState;
+		public final List<M> toSend;
+		public final List<Event> toBroadcast;
+
+		public StateUpdate(boolean deleteMessages, boolean deleteState,
+				S localState, List<M> toSend, List<Event> toBroadcast) {
+
+			this.deleteMessages = deleteMessages;
+			this.deleteState = deleteState;
+			this.localState = localState;
+			this.toSend = toSend;
+			this.toBroadcast = toBroadcast;
+		}
+	}
+}

briar-api/src/org/briarproject/api/contact/ContactManager.java

@@ -16,12 +16,21 @@ public interface ContactManager {
 	/** Registers a hook to be called whenever a contact is removed. */
 	void registerRemoveContactHook(RemoveContactHook hook);
 
+	/**
+	 * Stores a contact within the given transaction associated with the given
+	 * local and remote pseudonyms, and returns an ID for the contact.
+	 */
+	ContactId addContact(Transaction txn, Author remote, AuthorId local,
+			SecretKey master, long timestamp, boolean alice, boolean active)
+			throws DbException;
+
 	/**
 	 * Stores a contact associated with the given local and remote pseudonyms,
 	 * and returns an ID for the contact.
 	 */
-	ContactId addContact(Author remote, AuthorId local, SecretKey master,
-			long timestamp, boolean alice, boolean active) throws DbException;
+	ContactId addContact(Author remote, AuthorId local,
+			SecretKey master, long timestamp, boolean alice, boolean active)
+			throws DbException;
 
 	/** Returns the contact with the given ID. */
 	Contact getContact(ContactId c) throws DbException;
@@ -35,6 +44,14 @@ public interface ContactManager {
 	/** Marks a contact as active or inactive. */
 	void setContactActive(ContactId c, boolean active) throws DbException;
 
+	/** Return true if a contact with this name and public key already exists */
+	boolean contactExists(Transaction txn, AuthorId remoteAuthorID,
+			AuthorId localAuthorId) throws DbException;
+
+	/** Return true if a contact with this name and public key already exists */
+	boolean contactExists(AuthorId remoteAuthorID, AuthorId localAuthorId)
+			throws DbException;
+
 	interface AddContactHook {
 		void addingContact(Transaction txn, Contact c) throws DbException;
 	}

briar-api/src/org/briarproject/api/db/DatabaseComponent.java

@@ -162,6 +162,13 @@ public interface DatabaseComponent {
 	Collection<ContactId> getContacts(Transaction txn, AuthorId a)
 			throws DbException;
 
+	/**
+	 * Returns true if the database contains the given contact for the given
+	 * local pseudonym.
+	 */
+	boolean containsContact(Transaction txn, AuthorId remote, AuthorId local)
+			throws DbException;
+
 	/**
 	 * Returns the unique ID for this device.
 	 * <p/>

briar-api/src/org/briarproject/api/event/ContactAddedEvent.java

@@ -6,12 +6,18 @@ import org.briarproject.api.contact.ContactId;
 public class ContactAddedEvent extends Event {
 
 	private final ContactId contactId;
+	private final boolean active;
 
-	public ContactAddedEvent(ContactId contactId) {
+	public ContactAddedEvent(ContactId contactId, boolean active) {
 		this.contactId = contactId;
+		this.active = active;
 	}
 
 	public ContactId getContactId() {
 		return contactId;
 	}
+
+	public boolean isActive() {
+		return active;
+	}
 }

briar-api/src/org/briarproject/api/event/IntroductionRequestReceivedEvent.java

@@ -0,0 +1,26 @@
+package org.briarproject.api.event;
+
+import org.briarproject.api.contact.ContactId;
+import org.briarproject.api.introduction.IntroductionRequest;
+
+public class IntroductionRequestReceivedEvent extends Event {
+
+	private final ContactId contactId;
+	private final IntroductionRequest introductionRequest;
+
+	public IntroductionRequestReceivedEvent(ContactId contactId,
+			IntroductionRequest introductionRequest) {
+
+		this.contactId = contactId;
+		this.introductionRequest = introductionRequest;
+	}
+
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	public IntroductionRequest getIntroductionRequest() {
+		return introductionRequest;
+	}
+
+}

briar-api/src/org/briarproject/api/event/IntroductionResponseReceivedEvent.java

@@ -0,0 +1,25 @@
+package org.briarproject.api.event;
+
+import org.briarproject.api.contact.ContactId;
+import org.briarproject.api.introduction.IntroductionResponse;
+
+public class IntroductionResponseReceivedEvent extends Event {
+
+	private final ContactId contactId;
+	private final IntroductionResponse introductionResponse;
+
+	public IntroductionResponseReceivedEvent(ContactId contactId,
+			IntroductionResponse introductionResponse) {
+
+		this.contactId = contactId;
+		this.introductionResponse = introductionResponse;
+	}
+
+	public ContactId getContactId() {
+		return contactId;
+	}
+
+	public IntroductionResponse getIntroductionResponse() {
+		return introductionResponse;
+	}
+}

briar-api/src/org/briarproject/api/event/IntroductionSucceededEvent.java

@@ -0,0 +1,16 @@
+package org.briarproject.api.event;
+
+import org.briarproject.api.contact.Contact;
+
+public class IntroductionSucceededEvent extends Event {
+
+	private final Contact contact;
+
+	public IntroductionSucceededEvent(Contact contact) {
+		this.contact = contact;
+	}
+
+	public Contact getContact() {
+		return contact;
+	}
+}

briar-api/src/org/briarproject/api/event/MessageValidatedEvent.java

@@ -1,5 +1,6 @@
 package org.briarproject.api.event;
 
+import org.briarproject.api.db.Metadata;
 import org.briarproject.api.sync.ClientId;
 import org.briarproject.api.sync.Message;
 

briar-api/src/org/briarproject/api/introduction/IntroduceeAction.java

@@ -0,0 +1,43 @@
+package org.briarproject.api.introduction;
+
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_ABORT;
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_ACK;
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_REQUEST;
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_RESPONSE;
+
+public enum IntroduceeAction {
+
+	LOCAL_ACCEPT,
+	LOCAL_DECLINE,
+	LOCAL_ABORT,
+	REMOTE_REQUEST,
+	REMOTE_ACCEPT,
+	REMOTE_DECLINE,
+	REMOTE_ABORT,
+	ACK;
+
+	public static IntroduceeAction getRemote(int type, boolean accept) {
+		if (type == TYPE_REQUEST) return REMOTE_REQUEST;
+		if (type == TYPE_RESPONSE && accept) return REMOTE_ACCEPT;
+		if (type == TYPE_RESPONSE) return REMOTE_DECLINE;
+		if (type == TYPE_ACK) return ACK;
+		if (type == TYPE_ABORT) return REMOTE_ABORT;
+		return null;
+	}
+
+	public static IntroduceeAction getRemote(int type) {
+		return getRemote(type, true);
+	}
+
+	public static IntroduceeAction getLocal(int type, boolean accept) {
+		if (type == TYPE_RESPONSE && accept) return LOCAL_ACCEPT;
+		if (type == TYPE_RESPONSE) return LOCAL_DECLINE;
+		if (type == TYPE_ABORT) return LOCAL_ABORT;
+		return null;
+	}
+
+	public static IntroduceeAction getLocal(int type) {
+		return getLocal(type, true);
+	}
+
+}

briar-api/src/org/briarproject/api/introduction/IntroduceeProtocolState.java

@@ -0,0 +1,76 @@
+package org.briarproject.api.introduction;
+
+import static org.briarproject.api.introduction.IntroduceeAction.ACK;
+import static org.briarproject.api.introduction.IntroduceeAction.LOCAL_ACCEPT;
+import static org.briarproject.api.introduction.IntroduceeAction.LOCAL_DECLINE;
+import static org.briarproject.api.introduction.IntroduceeAction.REMOTE_ACCEPT;
+import static org.briarproject.api.introduction.IntroduceeAction.REMOTE_DECLINE;
+import static org.briarproject.api.introduction.IntroduceeAction.REMOTE_REQUEST;
+
+public enum IntroduceeProtocolState {
+
+	ERROR(0),
+	AWAIT_REQUEST(1) {
+		@Override
+		public IntroduceeProtocolState next(IntroduceeAction a) {
+			if (a == REMOTE_REQUEST) return AWAIT_RESPONSES;
+			return ERROR;
+		}
+	},
+	AWAIT_RESPONSES(2) {
+		@Override
+		public IntroduceeProtocolState next(IntroduceeAction a) {
+			if (a == REMOTE_ACCEPT) return AWAIT_LOCAL_RESPONSE;
+			if (a == REMOTE_DECLINE) return FINISHED;
+			if (a == LOCAL_ACCEPT) return AWAIT_REMOTE_RESPONSE;
+			if (a == LOCAL_DECLINE) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_REMOTE_RESPONSE(3) {
+		@Override
+		public IntroduceeProtocolState next(IntroduceeAction a) {
+			if (a == REMOTE_ACCEPT) return AWAIT_ACK;
+			if (a == REMOTE_DECLINE) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_LOCAL_RESPONSE(4) {
+		@Override
+		public IntroduceeProtocolState next(IntroduceeAction a) {
+			if (a == LOCAL_ACCEPT) return AWAIT_ACK;
+			if (a == LOCAL_DECLINE) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_ACK(5) {
+		@Override
+		public IntroduceeProtocolState next(IntroduceeAction a) {
+			if (a == ACK) return FINISHED;
+			return ERROR;
+		}
+	},
+	FINISHED(6);
+
+	private final int value;
+
+	IntroduceeProtocolState(int value) {
+		this.value = value;
+	}
+
+	public int getValue() {
+		return value;
+	}
+
+	public static IntroduceeProtocolState fromValue(int value) {
+		for (IntroduceeProtocolState s : values()) {
+			if (s.value == value) return s;
+		}
+		throw new IllegalArgumentException();
+	}
+
+	public IntroduceeProtocolState next(IntroduceeAction a) {
+		return this;
+	}
+
+}

briar-api/src/org/briarproject/api/introduction/IntroducerAction.java

@@ -0,0 +1,46 @@
+package org.briarproject.api.introduction;
+
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_ABORT;
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_ACK;
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_REQUEST;
+import static org.briarproject.api.introduction.IntroductionConstants.TYPE_RESPONSE;
+
+public enum IntroducerAction {
+
+	LOCAL_REQUEST,
+	LOCAL_ABORT,
+	REMOTE_ACCEPT_1,
+	REMOTE_ACCEPT_2,
+	REMOTE_DECLINE_1,
+	REMOTE_DECLINE_2,
+	REMOTE_ABORT,
+	ACK_1,
+	ACK_2;
+
+	public static IntroducerAction getLocal(int type) {
+		if (type == TYPE_REQUEST) return LOCAL_REQUEST;
+		if (type == TYPE_ABORT) return LOCAL_ABORT;
+		return null;
+	}
+
+	public static IntroducerAction getRemote(int type, boolean one,
+			boolean accept) {
+
+		if (one) {
+			if (type == TYPE_RESPONSE && accept) return REMOTE_ACCEPT_1;
+			if (type == TYPE_RESPONSE) return REMOTE_DECLINE_1;
+			if (type == TYPE_ACK) return ACK_1;
+		} else {
+			if (type == TYPE_RESPONSE && accept) return REMOTE_ACCEPT_2;
+			if (type == TYPE_RESPONSE) return REMOTE_DECLINE_2;
+			if (type == TYPE_ACK) return ACK_2;
+		}
+		if (type == TYPE_ABORT) return REMOTE_ABORT;
+		return null;
+	}
+
+	public static IntroducerAction getRemote(int type, boolean one) {
+		return getRemote(type, one, true);
+	}
+
+}

briar-api/src/org/briarproject/api/introduction/IntroducerProtocolState.java

@@ -0,0 +1,94 @@
+package org.briarproject.api.introduction;
+
+import static org.briarproject.api.introduction.IntroducerAction.ACK_1;
+import static org.briarproject.api.introduction.IntroducerAction.ACK_2;
+import static org.briarproject.api.introduction.IntroducerAction.LOCAL_REQUEST;
+import static org.briarproject.api.introduction.IntroducerAction.REMOTE_ACCEPT_1;
+import static org.briarproject.api.introduction.IntroducerAction.REMOTE_ACCEPT_2;
+import static org.briarproject.api.introduction.IntroducerAction.REMOTE_DECLINE_1;
+import static org.briarproject.api.introduction.IntroducerAction.REMOTE_DECLINE_2;
+
+public enum IntroducerProtocolState {
+
+	ERROR(0),
+	PREPARE_REQUESTS(1) {
+		@Override
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == LOCAL_REQUEST) return AWAIT_RESPONSES;
+			return ERROR;
+		}
+	},
+	AWAIT_RESPONSES(2) {
+		@Override
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == REMOTE_ACCEPT_1) return AWAIT_RESPONSE_2;
+			if (a == REMOTE_ACCEPT_2) return AWAIT_RESPONSE_1;
+			if (a == REMOTE_DECLINE_1) return FINISHED;
+			if (a == REMOTE_DECLINE_2) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_RESPONSE_1(3) {
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == REMOTE_ACCEPT_1) return AWAIT_ACKS;
+			if (a == REMOTE_DECLINE_1) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_RESPONSE_2(4) {
+		@Override
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == REMOTE_ACCEPT_2) return AWAIT_ACKS;
+			if (a == REMOTE_DECLINE_2) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_ACKS(5) {
+		@Override
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == ACK_1) return AWAIT_ACK_2;
+			if (a == ACK_2) return AWAIT_ACK_1;
+			return ERROR;
+		}
+	},
+	AWAIT_ACK_1(6) {
+		@Override
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == ACK_1) return FINISHED;
+			return ERROR;
+		}
+	},
+	AWAIT_ACK_2(7) {
+		@Override
+		public IntroducerProtocolState next(IntroducerAction a) {
+			if (a == ACK_2) return FINISHED;
+			return ERROR;
+		}
+	},
+	FINISHED(8);
+
+	private final int value;
+
+	IntroducerProtocolState(int value) {
+		this.value = value;
+	}
+
+	public int getValue() {
+		return value;
+	}
+
+	public static IntroducerProtocolState fromValue(int value) {
+		for (IntroducerProtocolState s : values()) {
+			if (s.value == value) return s;
+		}
+		throw new IllegalArgumentException();
+	}
+
+	public static boolean isOngoing(IntroducerProtocolState state) {
+		return state != FINISHED && state != ERROR;
+	}
+
+	public IntroducerProtocolState next(IntroducerAction a) {
+		return this;
+	}
+}

briar-api/src/org/briarproject/api/introduction/IntroductionConstants.java

@@ -0,0 +1,68 @@
+package org.briarproject.api.introduction;
+
+public interface IntroductionConstants {
+
+	/* Protocol roles */
+	int ROLE_INTRODUCER = 0;
+	int ROLE_INTRODUCEE = 1;
+
+	/* Message types */
+	int TYPE_REQUEST = 1;
+	int TYPE_RESPONSE = 2;
+	int TYPE_ACK = 3;
+	int TYPE_ABORT = 4;
+
+	/* Message Constants */
+	String TYPE = "type";
+	String GROUP_ID = "groupId";
+	String SESSION_ID = "sessionId";
+	String CONTACT = "contactId";
+	String NAME = "name";
+	String PUBLIC_KEY = "publicKey";
+	String E_PUBLIC_KEY = "ephemeralPublicKey";
+	String MSG = "msg";
+	String ACCEPT = "accept";
+	String TIME = "time";
+	String DEVICE_ID = "deviceId";
+	String TRANSPORT = "transport";
+	String MESSAGE_ID = "messageId";
+	String MESSAGE_TIME = "timestamp";
+
+	/* Introducer Local State Metadata */
+	String STATE = "state";
+	String ROLE = "role";
+	String GROUP_ID_1 = "groupId1";
+	String GROUP_ID_2 = "groupId2";
+	String CONTACT_1 = "contact1";
+	String CONTACT_2 = "contact2";
+	String AUTHOR_ID_1 = "authorId1";
+	String AUTHOR_ID_2 = "authorId2";
+	String CONTACT_ID_1 = "contactId1";
+	String CONTACT_ID_2 = "contactId2";
+	String RESPONSE_1 = "response1";
+	String RESPONSE_2 = "response2";
+	String READ = "read";
+
+	/* Introduction Request Action */
+	String PUBLIC_KEY1 = "publicKey1";
+	String PUBLIC_KEY2 = "publicKey2";
+
+	/* Introducee Local State Metadata (without those already defined) */
+	String STORAGE_ID = "storageId";
+	String INTRODUCER = "introducer";
+	String LOCAL_AUTHOR_ID = "localAuthorId";
+	String REMOTE_AUTHOR_ID = "remoteAuthorId";
+	String OUR_PUBLIC_KEY = "ourEphemeralPublicKey";
+	String OUR_PRIVATE_KEY = "ourEphemeralPrivateKey";
+	String OUR_TIME = "ourTime";
+	String ADDED_CONTACT_ID = "addedContactId";
+	String NOT_OUR_RESPONSE = "notOurResponse";
+	String EXISTS = "contactExists";
+	String ANSWERED = "answered";
+
+	String TASK = "task";
+	int TASK_ADD_CONTACT = 0;
+	int TASK_ACTIVATE_CONTACT = 1;
+	int TASK_ABORT = 2;
+
+}

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

@@ -0,0 +1,62 @@
+package org.briarproject.api.introduction;
+
+import org.briarproject.api.FormatException;
+import org.briarproject.api.contact.Contact;
+import org.briarproject.api.contact.ContactId;
+import org.briarproject.api.data.BdfDictionary;
+import org.briarproject.api.db.DbException;
+import org.briarproject.api.db.Transaction;
+import org.briarproject.api.sync.ClientId;
+import org.briarproject.api.sync.Group;
+import org.briarproject.api.sync.MessageId;
+
+import java.util.Collection;
+
+public interface IntroductionManager {
+
+	/** Returns the unique ID of the introduction client. */
+	ClientId getClientId();
+
+	/**
+	 * sends two initial introduction messages
+	 */
+	void makeIntroduction(Contact c1, Contact c2, String msg)
+			throws DbException, FormatException;
+
+	/**
+	 * Accept an introduction that had been made
+	 */
+	void acceptIntroduction(final SessionId sessionId)
+			throws DbException, FormatException;
+
+	/**
+	 * Decline an introduction that had been made
+	 */
+	void declineIntroduction(final SessionId sessionId)
+			throws DbException, FormatException;
+
+	/**
+	 * Get all introduction messages for the contact with this contactId
+	 */
+	Collection<IntroductionMessage> getIntroductionMessages(ContactId contactId)
+			throws DbException;
+
+	/** Marks an introduction message as read or unread. */
+	void setReadFlag(MessageId m, boolean read) throws DbException;
+
+
+	/** Get the session state for the given session ID */
+	BdfDictionary getSessionState(Transaction txn, byte[] sessionId)
+			throws DbException, FormatException;
+
+	/** Gets the group used for introductions with Contact c */
+	Group getIntroductionGroup(Contact c);
+
+	/** Get the local group used to store session states */
+	Group getLocalGroup();
+
+	/** Send an introduction message */
+	void sendMessage(Transaction txn, BdfDictionary message)
+			throws DbException, FormatException;
+
+}

briar-api/src/org/briarproject/api/introduction/IntroductionMessage.java

@@ -0,0 +1,54 @@
+package org.briarproject.api.introduction;
+
+import org.briarproject.api.sync.MessageId;
+
+abstract public class IntroductionMessage {
+
+	private final SessionId sessionId;
+	private final MessageId messageId;
+	private final long time;
+	private final boolean local, sent, seen, read;
+
+	public IntroductionMessage(SessionId sessionId, MessageId messageId,
+			long time, boolean local, boolean sent, boolean seen,
+			boolean read) {
+
+		this.sessionId = sessionId;
+		this.messageId = messageId;
+		this.time = time;
+		this.local = local;
+		this.sent = sent;
+		this.seen = seen;
+		this.read = read;
+	}
+
+	public SessionId getSessionId() {
+		return sessionId;
+	}
+
+	public long getTime() {
+		return time;
+	}
+
+	public MessageId getMessageId() {
+		return messageId;
+	}
+
+	public boolean isLocal() {
+		return local;
+	}
+
+	public boolean isSent() {
+		return sent;
+	}
+
+	public boolean isSeen() {
+		return seen;
+	}
+
+	public boolean isRead() {
+		return read;
+	}
+
+}
+

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

@@ -0,0 +1,36 @@
+package org.briarproject.api.introduction;
+
+import org.briarproject.api.identity.AuthorId;
+import org.briarproject.api.sync.MessageId;
+
+public class IntroductionRequest extends IntroductionResponse {
+
+	private final String message;
+	private final boolean answered, exists;
+
+	public IntroductionRequest(SessionId sessionId, MessageId messageId,
+			long time, boolean local, boolean sent, boolean seen, boolean read,
+			AuthorId authorId, String name, boolean accepted, String message,
+			boolean answered, boolean exists) {
+
+		super(sessionId, messageId, time, local, sent, seen, read, authorId,
+				name, accepted);
+
+		this.message = message;
+		this.answered = answered;
+		this.exists = exists;
+	}
+
+	public String getMessage() {
+		return message;
+	}
+
+	public boolean wasAnswered() {
+		return answered;
+	}
+
+	public boolean doesExist() {
+		return exists;
+	}
+
+}

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

@@ -0,0 +1,31 @@
+package org.briarproject.api.introduction;
+
+import org.briarproject.api.identity.AuthorId;
+import org.briarproject.api.sync.MessageId;
+
+public class IntroductionResponse extends IntroductionMessage {
+
+	private final AuthorId remoteAuthorId;
+	private final String name;
+	private final boolean accepted;
+
+	public IntroductionResponse(SessionId sessionId, MessageId messageId,
+			long time, boolean local, boolean sent, boolean seen, boolean read,
+			AuthorId remoteAuthorId, String name, boolean accepted) {
+
+		super(sessionId, messageId, time, local, sent, seen, read);
+
+		this.remoteAuthorId = remoteAuthorId;
+		this.name = name;
+		this.accepted = accepted;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public boolean wasAccepted() {
+		return accepted;
+	}
+
+}

briar-api/src/org/briarproject/api/introduction/SessionId.java

@@ -0,0 +1,19 @@
+package org.briarproject.api.introduction;
+
+import org.briarproject.api.sync.MessageId;
+
+/**
+ * Type-safe wrapper for a byte array that uniquely identifies an
+ * introduction session.
+ */
+public class SessionId extends MessageId {
+
+	public SessionId(byte[] id) {
+		super(id);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof SessionId && super.equals(o);
+	}
+}

briar-api/src/org/briarproject/api/properties/TransportPropertyManager.java

@@ -4,6 +4,7 @@ import org.briarproject.api.DeviceId;
 import org.briarproject.api.TransportId;
 import org.briarproject.api.contact.ContactId;
 import org.briarproject.api.db.DbException;
+import org.briarproject.api.db.Transaction;
 
 import java.util.Map;
 
@@ -13,7 +14,7 @@ public interface TransportPropertyManager {
 	 * Stores the given properties received while adding a contact - they will
 	 * be superseded by any properties synced from the contact.
 	 */
-	void addRemoteProperties(ContactId c, DeviceId dev,
+	void addRemoteProperties(Transaction txn, ContactId c, DeviceId dev,
 			Map<TransportId, TransportProperties> props) throws DbException;
 
 	/** Returns the local transport properties for all transports. */