From: Jerry Whiting <jwhiting@igc.apc.org>
Date: Sat, 9 Dec 95 00:22:55 PST
To: cypherpunks@toad.com
Subject: More elveator problem
Message-ID: <199512090823.AAA15124@igc2.igc.apc.org>
MIME-Version: 1.0
Content-Type: text/plain


More on The Elevator Problem:

I'll confess that we're working on a new private key encryption product. Free 
and clear of existing claims on intellectual property, I'd like a protocol 
that answers the elevator problem: how can Alice and Bob agree on a private 
key via a compromised channel? I don't want them to meet under a street lamp 
and whisper in each other's ears _before_ trying to establish a secret on a 
crowded elevator.

I'm willing to accept that the basic question is undoable without stepping on 
DH et al., I just don't want to give up until all parties are convinced it 
can't be done.

As I stated in my original post, we're willing to consider less-than-perfect 
implimentations if we can quantify mathematically the risk involved. In some 
scenarios, Alice and Bob might not expect any Eve's in the crowded elevator 
or value the content at such a price that they're willing to live with less 
than 100%. As long as we can document the risk, the end user can make the 
decision as to whether the risk is worth it.

Something that I neglected to mention before is that Alice and Bob do have a 
unique ID within this system, not that they necessarily know each others. If 
one assumes that they do, they then share a secret: the knowledge of each 
other's unique ID.

Another segment of our attention is being spent daydreaming about the 
potential applications of a secondary channel in the cleartext portion of a 
crypto "package" or "bundle".  The comment about secondary channels that I 
believe Tim made regarding the inmates and the warden is something we discuss 
in our spare time.

Then again the wheels of justice doth turn and patents ain't forever...


Jerry Whiting
jwhiting@azalea.com