From: George A. Gleason <gg@well.sf.ca.us>
Date: Sun, 11 Oct 92 00:50:52 PDT
To: hughes@soda.berkeley.edu
Subject: Re:  +-=*^
Message-ID: <199210110757.AA22987@well.sf.ca.us>
MIME-Version: 1.0
Content-Type: text/plain



Eric, good point about public keys and trust by association.  

More on OTPs.
You say the key distribution problem for OTPs is "much worse" than for PKS
and even other conventional ciphers.  "Much worse" in what ways?  The need
for F2F meetings with all possible correspondents is something which exists
with conventional ciphers.  The cost of key storage is trivial: a fraction
of the cost of the yearly (or less frequent) travel to meet each
correspondent in person.  Consider replaceable hard drive cartridges (30 meg
for about a buck a meg), digital cassette formats including applications
involving videocassettes, and so on.  Yes, as you say, you have to exchange
keys each time you run out of key; but you can keep ten years' with of key
(error: "worth" not "with") on hand if you like, taking up less physical
space than a box of cookies.  

"Bandwidth required is much higher..."  In what way?  Certainly not in terms
of transmission; a stream cipher is a stream cipher.  Perhaps in that each
plaintext character requires one key character?  This is just another
formulation of the "storage" issue: and again, if you have a stack of 30MB
cartridges, who cares?  Not like we're talking about punched paper tape.

I do agree that PKS offer convenience and features not available with
conventional ciphers.  However, RSA is just one mathematical breakthrough
away from being obsolete, and we have no way of knowing when that
breakthrough occurs.  It may also be that massively parallel processors can
be built through VLSI technology, allowing the cost of brute force solutions
to come down to a reasonable level.  

All of this is not by way of getting down on PKS.  I would suggest that we
need a number of different systems, and need to keep them all in fairly
constant use.  I think we're already all in agreement that one of those
systems should be RSA-based.  Now I'm just suggesting that a One-Time system
should be another one among the many.

BTW, sorry I couldn't make today's meeting; various local tasks demanding
attention; plus physical travel distance.   Be back next time...

-gg