A New Anonymous Password-Based Authenticated Key Exchange Protocol

In Indocrypt 2005 Viet et al. first proposed an anonymous password-based key exchange protocol: APAKE and its extension: k-out-of-n APAKE. Then Shin et al. presented an improved protocol TAP. In this paper, we first show that the TAP protocol is vulnerable to two attacks. One is an impersonating attack and the other is an off-line dictionary attack, which is also applied to k-out-of-n APAKE. Furthermore, we propose a novel anonymous password-based key exchange protocol, and prove its security in the random oracle model under the square computational Diffie-Hellman assumption and decision inverted-additive Diffie-Hellman assumption. We also extend our protocol to the distributed setting, which is secure against the proposed attacks.