Authenticated key exchange protocol with enhanced freshness properties

This paper investigates the security model for authenticated key exchange protocols. We further enhance the enhanced Canetti-Krawczyk (eCK) model by introducing a notion called strong key compromise impersonation (SKCI) resilience which is first identified in this paper. SKCI resilience guarantees that the adversary cannot masquerade as another party B to communicate with party A even if the static private key and the ephemeral private key of party A are compromised. We point out that the three-pass authenticated key exchange protocol generically transformed from the two-pass one secure in the eCK model cannot resist the SKCI attack. Finally, we introduce a new authenticated key exchange protocol SIG-DH⁺ and prove that it satisfies our new definition.