--- a/src/net/java/otr4j/OtrEngine.java	Mon Dec 06 01:06:44 2010 +0100
+++ b/src/net/java/otr4j/OtrEngine.java	Tue Dec 07 22:57:56 2010 +0100
@@ -19,9 +19,10 @@
 	 * @param content
 	 *            The message content to be transformed.
 	 * @return The transformed message content.
+	 * @throws OtrException 
 	 */
 	public abstract String transformReceiving(SessionID sessionID,
-			String content);
+			String content) throws OtrException;
 
 	/**
 	 * 
@@ -30,32 +31,36 @@
 	 * @param content
 	 *            The message content to be transformed.
 	 * @return The transformed message content.
+	 * @throws OtrException 
 	 */
-	public abstract String transformSending(SessionID sessionID, String content);
+	public abstract String transformSending(SessionID sessionID, String content) throws OtrException;
 
 	/**
 	 * Starts an Off-the-Record session, if there is no active one.
 	 * 
 	 * @param sessionID
 	 *            The session identifier.
+	 * @throws OtrException 
 	 */
-	public abstract void startSession(SessionID sessionID);
+	public abstract void startSession(SessionID sessionID) throws OtrException;
 
 	/**
 	 * Ends the Off-the-Record session, if exists.
 	 * 
 	 * @param sessionID
 	 *            The session identifier.
+	 * @throws OtrException 
 	 */
-	public abstract void endSession(SessionID sessionID);
+	public abstract void endSession(SessionID sessionID) throws OtrException;
 
 	/**
 	 * Stops/Starts the Off-the-Record session.
 	 * 
 	 * @param sessionID
 	 *            The session identifier.
+	 * @throws OtrException 
 	 */
-	public abstract void refreshSession(SessionID sessionID);
+	public abstract void refreshSession(SessionID sessionID) throws OtrException;
 
 	/**
 	 *