Generic Compilers for Authenticated Key Exchange

Abstract

So far, all solutions proposed for authenticated key agreement combine key agreement and authentication into a single cryptographic protocol. However, in many important application scenarios, key agreement and entity authentication are clearly separated protocols. This fact enables efficient attacks on the naïve combination of these protocols. In this paper, we propose new compilers for two-party key agreement and authentication, which are provably secure in the standard Bellare-Rogaway model. The constructions are generic: key agreement is executed first and results (without intervention of the adversary) in a secret session key on both sides. This key (or a derived key) is handed over, together with a transcript of all key exchange messages, to the authentication protocol, where it is combined with the random challenge(s) exchanged during authentication.