Off-the-Record Messaging, commonly referred to as OTR, is a cryptographic protocol that provides strong encryption for instant messaging conversations. OTR uses a combination of the AES symmetric-key algorithm, the Diffie–Hellman key exchange, and the SHA hash function. In addition to authentication and encryption, OTR provides perfect forward secrecy and malleable encryption.
OTR allows you to have private conversations over instant messaging by providing:
- No one else can read your instant messages.
- 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.
- Perfect forward secrecy,if you lose control of your private keys, no previous conversation is compromised.