From: "Mark M." <markm@voicenet.com>
Date: Fri, 15 Nov 1996 11:48:54 -0800 (PST)
To: cypherpunks@toad.com
Subject: Re: Playing Cards
In-Reply-To: <v02140b03aeb239f7c4bb@[192.0.2.1]>
Message-ID: <Pine.LNX.3.95.961115143422.813B-100000@gak.voicenet.com>
MIME-Version: 1.0
Content-Type: text/plain


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On Fri, 15 Nov 1996, Peter Hendrickson wrote:

> (My apologies to those who are seeing this twice.  I sent it
> yesterday but it does not seem to have made it through.)
> 
> A number of us have been concerned about how PGP generates entropy.
> Striking the keyboard beats using time as a source of random numbers,
> but the degree of entropy is not well understood.  Are there machines
> where - for some reason - the keyboard strikes fall into some sort
> of pattern?
> 
> And that's just when you are generating your public/private key pair.
> What happens when you are just generating 128-bit keys for individual
> messages?  Where is the entropy coming from?  I don't understand
> completely, but somehow PGP collects entropy from the system and then
> runs it into IDEA and then uses the numbers from the output.  When the
> program is not running, a pool of this data is kept in randseed.bin.

PGP uses the hash of the message to preprocess the randseed.bin file and
postprocesses it with the session key.  It uses the randseed.bin file as
a PRNG to generate the session key.

> We already know it's a problem because it is hard to understand what
> it is even doing, much less determine if it is consistent with sound
> engineering practice.

PGP uses a variation of ANSI X9.17 for key generation.  This is considered to
be a secure method.

Mark
- -- 
finger -l for PGP key
PGP encrypted mail prefered.





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