Robert Cain writes:

We shall see. I contend that with this I can establish a spoof-proof point to point with a total stranger to any desired probability that a spoof could not be there without disclosing him/her.

Page 44 of "Applied Cryptography" discusses a point to point *public* key exchange protocol called the "Interlock Protocol" (invented by Ron Rivest and Adi Shamir). This protocol is an attempt to foil the man-in-the-middle attack. The protocol does not provide a %100 guarantee against man-in-middle, but it does make it much harder (or so says the book). Perhaps Robert's device really uses a variation of the Interlock Protocol, and not Diffie-Hellman (mentioned only as a red herring?). <shrug> Jim_Miller@suite.com