Added a (learning) test to verify that every signature is different. This indicates that randomness is used.
Created an initial draft of the authentication handshake logic. It has still to be tested against attacks.
Cleanup.
Added custom .equals(..)/.hashCode() methods to the Participant.
Added a more convenient method to get content.
Added an easy to use getContent() method to the Message class in order to simplify its usage.
Removed a few empty lines and added a little javadoc.