Cryptanalysis of a three-party password- based authenticated key exchange protocol using Weil pairing

Recently, Zeng et al. proposed a three-party password-based authenticated key exchange protocol, in which two users could generate a common secret key with the help of the server. Although Zeng et al. claimed that their protocol could withstand various attacks, we point out that their protocol cannot resist impersonation attacks and undetectable online dictionary attacks. The analysis shows Zeng et al.' s protocol is insecure for practical applications.