Bill Frantz <frantz@netcom.com> writes:
At 6:25 PM -0700 10/5/97, Adam Back wrote:
On the other hand, using persistent key public key crypto, Tim has been signing his posts recently, and I have an ancient public key of his stashed away which his new key is signed with. If we were able to construct a protocol to bolt on top of the reading of hashes, we could have much greater protection against MITM.
Of course if you can use PGP as well as the secure phone, you can use PGP to exchange a pad of one-time passwords.
The passwords alone don't do you any good: if you read them out over the phone, Eve can just repeat them.
There's no reason you couldn't use the passwords in a bidirectional challenge/response scenario. The units can pass (optionally encrypted) control messages back and forth while in secure voice mode. Eric