Security Weakness in a Three-Party Password-Based Key Exchange Protocol Using Weil Pairing

Recently, Wen, Lee, and Hwang proposed a three-party password-authenticated key exchange protocol making use of the Weil pairing. The protocol was claimed to be provably secure. But despite the claim of provable security, the protocol is in fact insecure in the presence of an active adversary. We demonstrate this by presenting an attack that completely compromises the authentication mechanism of the protocol. Consequently, the proof of security for the protocol is invalidated.