Off-the-Record Messaging library

 Off-the-Record (OTR) Messaging Library and Toolkit
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 OTR allows you to have private conversations over IM 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.