AbstractThis 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. Copyright © 2010 John Wiley & Sons, Ltd.