[OTR-dev] Thinking about mpOTR and secure multiparty chat protocols in general

[Ileana]

On Thu, 21 Feb 2013 13:10:37 -0600
Ileana <ileana at fairieunderground.info> wrote:

> On Thu, 21 Feb 2013 20:30:53 +0200
> George Kadianakis <desnacked at riseup.net> wrote:
> 
> > Greetings,
> > 
> > this is a post about mpOTR and secure multiparty chat protocols in
> > general. I'm very interested in the secure multiparty chat problem,
> > and I _really_ want to see it moving forward.
> [snip]
> > * Based on the previous question, how much do we want the protocol
> > to scale? Do we want 5 people to be able to talk to each other, what
> >   about 40? What about 200 people or even 1000?
> 
> As an aside question, 
> 
> About DH for multiple party, doesn't that require g^x g^y... g^xy
> 
> calculation of g^[n factors] where n is the number of chat
> participants...so isn't the complexity exponential in the number of
> chatters?  So the number of chatters is dependent on the amount of
> processing power of the computations?  And still trying to retain
> sufficient crypto strength of the parameters.  In other words, it
> seems the cap is computationally capped at some point.
> 
> Correct me if I am wrong.

Sorry...its seems I am always correcting myself on this list

It appears possible with divide and conquer approach to do the
exponentiation in log2(N)+1 exponentiations.

This is achieved by different parties doing only the required
exponentiations and sending midterm results to each other.

(for 8 participants, only 4 exponentiations are necessary).


> 
> Ileana
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