Security of an efficient ID-based authenticated key agreement protocol from pairings

Authenticated key agreement protocols are essential for secure communications in open and distributed environments. In 2004, Ryu et al. proposed an efficient two-party identity-based authenticated key agreement protocol based on pairings, However, in this paper, we demonstrate that their protocol is vulnerable to a key-compromise impersonation attack. The attacking scenario is described in details. Furthermore,we point out that their protocol provides the property of deniability and at the same time it is the mechanism used to achieve deniability that allows the key-compromise impersonation attack.