Nikita Borisov and Ian Goldberg have released Off-the-Record Messaging
("http://www.xelerance.com/mirror/otr/";),
an IM plugin for private communication providing not only
the usual encryption and authentication, but also deniability and
perfect forward secrecy. Deniability avoids digital signatures on
messages (while preserving authenticity and integrity), so there is no
hard-to-deny proof you wrote anything in particular; in fact, there is a
toolkit to help people forge messages, making it extra-hard to pin
things on you. Perfect forward secrecy means that your past messages
and conversations remain protected even if your keys are compromised.
