Off-the-Record (OTR) Messaging allows you to have private conversations over instant messaging by providing:
- Encryption – No one else can read your instant messages.
- Authentication – You are assured the correspondent is who you think it is.
- Deniability – The messages you send do not have digital signatures that are checkable by a third party. Anyone can forge messages after a conversation to make them look like they came from you. However, during a conversation, your correspondent is assured the messages he sees are authentic and unmodified.
- Perfect forward secrecy – If you lose control of your private keys, no previous conversation is compromised
More info: http://www.cypherpunks.ca/otr/Tags: crypto, cypher, jabber, messaging, otr, pidgin