[OTR-dev] OTR encryption state

Ian Goldberg ian at cypherpunks.ca
Thu Jan 27 17:22:16 EST 2005


On Thu, Jan 27, 2005 at 03:20:23PM -0600, Evan Schoenberg wrote:
> >    OPPORTUNISTIC: (the current mode) probe the other side with the
> >                   whitespace tag, and reply to any indication that he
> >		   speaks OTR with a Key Exchange Message (if we're not
> >		   already private)
> >
> How does the "whitespace tag" work?  Do all contacts I speak with which 
> don't have OTR receive an IM from me every time I start a chat?  This 
> doesn't seem to be the case.. but it's the current mode.

It's the clever thing suggested by Gregory Maxwell.  The first time you
send a message to someone, append a magic pattern of whitespace.  OTR
clients recognize the whitespace at the end of the message, and
opportunistically start OTR.  It's just meant as a more invisible
(and automatic) version of the OTR Query message.

So in OPPORTUNISTIC mode, if you send any old message to someone who
speaks OTR (and is also in OPPORTUNISTIC mode), OTR will start.

> >    MANUAL: Don't send the whitespace tag, and don't reply to one you
> >            receive.  Respond to explicit OTR Query Messages and Key 
> >Exchange
> >	    Messages, but not other indications of OTR.  This mode is
> >	    useful if you for some reason want to communicate in the
> >	    clear, even though you know the other guy speaks OTR, and
> >	    also allow either side to start a private conversation
> >	    at any time.  [If you don't want to allow that last
> >	    condition, use NEVER instead.]
> This seems more like the current mode to me.  How would it differ from 
> current behavior?

MANUAL only starts OTR in response to explicit requests to do so.
OPPORTUNISTIC (the current mode) starts OTR in response to any
indication the other side speaks OTR, including the whitespace tag and
OTR Error messages.

   - Ian



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