The Elevator Problem

[Jerry Whiting]

A group of us have been wrestling with a problem and I'd like to ask for some 
outside help.  We've come to call it the Elevator Problem.

Alice and Bob want to establish a secret in from of Eve.  In other words, 
they want to agree on a secret key in an elevator full of Eve's.

We don't want the protocol to step on any existing patents (DH, HM, etc.).  
If the protocol takes numerous steps, that's OK because ultimately we'd like 
Alice's machine to contact Bob's, who could respond, and back and forth as 
often as needed.

We have also talked about a less than perfect solution IF we can establish 
mathmatically what the confidence level and risk factor are.  Alice and Bob 
might agree that the value of the secret is such that they can live with a 
1 in n probability that Eve too has the secret.

Shamir's 3 step seems close but I'm afraid we've been doing the blackboard 
talks so long that we're missing the solution.  IF THERE EVEN IS ONE.

thanks in advance,


Jerry Whiting
jwhiting at azalea.com