NAME

       otr_parse,  otr_sesskeys,  otr_mackey, otr_readforge, otr_modify, otr_remac - Process Off-
       the-Record Messaging transcripts

SYNOPSIS

       otr_parse
       otr_sesskeys our_privkey their_pubkey
       otr_mackey aes_enc_key
       otr_readforge aes_enc_key [newmsg]
       otr_modify mackey old_text new_text offset
       otr_remac  mackey  sender_instance  receiver_instance  flags  snd_keyid  rcv_keyid  pubkey
       counter encdata revealed_mackeys

DESCRIPTION

       Off-the-Record  (OTR)  Messaging  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.

       The OTR Toolkit is useful for analyzing and/or forging OTR  messages.   Why  do  we  offer
       this?  Primarily, to make absolutely sure that transcripts of OTR conversations are really
       easy to forge after the fact.  [Note that during an OTR conversation,  messages  can't  be
       forged  without real-time access to the secret keys on the participants' computers, and in
       that case, all security has already been  lost.]   Easily-forgeable  transcripts  help  us
       provide the "Deniability" property: if someone claims you said something over OTR, they'll
       have no proof, as anyone at all can modify a transcript to make it say whatever they like,
       and still have all the verification come out correctly.

       Here are the six programs in the toolkit:

        - otr_parse
          - Parse OTR messages given on stdin, showing the values of all the
            fields in OTR protocol messages.

        - otr_sesskeys our_privkey their_pubkey
          - Shows our public key, the session id, two AES and two MAC keys
            derived from the given Diffie-Hellman keys (one private, one public).

        - otr_mackey aes_enc_key
          - Shows the MAC key derived from the given AES key.

        - otr_readforge aes_enc_key [newmsg]
          - Decrypts an OTR Data message using the given AES key, and displays
            the message.
          - If newmsg is given, replace the message with that one, encrypt
            and MAC it properly, and output the resulting OTR Data Message.
            This works even if the given key was not correct for the original
            message, so as to enable complete forgeries.

        - otr_modify mackey old_text new_text offset
          - Even if you can't read the data because you don't know either
            the AES key or the Diffie-Hellman private key, but you can make a
            good guess that the substring "old_text" appears at the given
            offset in the message, replace the old_text with the new_text
            (which must be of the same length), recalculate the MAC with the
            given mackey, and output the resulting Data message.
          - Note that, even if you don't know any text in an existing message,
            you can still forge messages of your choice using the
            otr_readforge command, above.

        -  otr_remac  mackey  sender_instance  receiver_instance flags snd_keyid rcv_keyid pubkey
       counter encdata revealed_mackeys
          - Make a new OTR protocol version 3 Data Message, with the given
            pieces (note that the data part is already encrypted).  MAC it
            with the given mackey.

SEE ALSO

       Off-the-Record           Messaging,           at           https://www.cypherpunks.ca/otr/
       ⟨https://www.cypherpunks.ca/otr/⟩

AUTHOR

       otr_toolkit was written by the OTR Dev Team <otr@cypherpunks.ca>.

                                          March 14, 2012                             OTR_PARSE(1)