OTR

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-1 hash function. In addition to authentication and encryption, OTR provides perfect forward secrecy and malleable encryption.

Strengths

OTR 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.

Client support

Native

• Adium (Mac OS X)
• BitlBee (Cross-platform)
• CenterIM (Unix-like)
• climm (Unix-like)
• Gibberbot (Android)
• Jitsi (Cross-platform)
• MCabber (Unix-like)
• Phoenix Viewer, a Second Life client (Cross-platform)
• Vacuum IM (Cross-platform)

Plugin

• Pidgin (Cross-platform) with OTR plugin for Pidgin
• Kopete (Unix-like) with Kopete Off-the-Record plugin
• Miranda IM (Microsoft Windows) with MirOTR - OTR for Miranda IM!
• Psi+ (Cross-platform) with OTR Plugin for Psi+
• Trillian (Microsoft Windows) with Trillian OTR
• irssi (Cross-platform) with irssi-otr
• XChat (Cross-platform) with xchat-otr
• WeeChat (Cross-platform) with weechat-otr

External links

• Homepage
• Off-the-Record Messaging Protocol version 2