From: "Mike Rosing" <eresrch@eskimo.com>
Is there a defense against MITM for Diffie-Hellman? Is there another protocol with equivalent properties, with such a defense? (Secure communications between two parties, with no shared secret and no out-of-band abilities, on an insecure network.)
What do you mean by no shared secret? The point of DH is that you get a shared secret.
I guess I should have said "no *previously* shared secret".
Check out MQV protocol for MITM defense and forward secrecy. It uses permenent public keys and ephemeral public keys for each session. In any protocol, the out-of-band check of the public keys is still a "good thing".
Well... I assume an active MITM (like my ISP). He's able to intercept my public key request and change it. Plus, I now realize I should have put an even harder condition - no previously shared *information*, even if it's public. I need to know if two complete strangers can communicate securely over an insecure network, even if they communicate through an untrusted party. Wasn't there a protocol for two prisoners communicating through an untrusted guard? Thanks, Mark