OTR allows you to have private conversations over instant messaging by providing: (1) Encryption: No one else can read your instant messages. (2) Authentication: You are assured the correspondent is who you think it is. (3) 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. (4) Perfect forward secrecy: If you lose control of your private keys, no previous conversation is compromised.