Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
OTR_PARSE(1)		    General Commands Manual		  OTR_PARSE(1)

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

       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  re-

       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 tran-
       scripts 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 pub-

	- 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
	  - Make a new OTR Data	Message, with the given	pieces (note that the
	    data part is already encrypted).  MAC it with the given mackey.

       Off-the-Record	  Messaging,	 at

       otr_toolkit was written by the OTR Dev Team <>.

			       October 27, 2005			  OTR_PARSE(1)


Want to link to this manual page? Use this URL:

home | help