Towards computationally sound symbolic analysis of key exchange protocols ( extended abstract )

We present a cryptographically sound formal method for proving correctness of key exchange protocols. Our main tool is a fragment of a symbolic protocol logic. We demonstrate that proofs of key agreement and key secrecy in this logic imply simulatability in Shoup’s secure multi-party framework for key exchange. As part of the logic, we present cryptographically sound abstractions of CMA-secure digital signatures and a restricted form of Diffie-Hellman exponentiation, which is a technical result of independent interest. We illustrate our method by constructing a proof of security for a simple authenticated Diffie-Hellman protocol.