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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  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 flags snd_keyid rcv_keyid  pubkey  counter  encdata
       revealed_mackeys
          - Make a new OTR 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 http://www.cypherpunks.ca/otr/

AUTHOR

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

                               October 27, 2005                   OTR_PARSE(1)