Smart card-based authenticated key exchange protocol with CAPTCHA for wireless mobile network

In this paper, we propose a novel smart card-based authenticated key exchange (AKE) protocol for wireless mobile networks which is combined with CAPTCHAs to effectively prevent legitimate users' abuse. Compared with the other related protocols, our protocol provides perfect forward secrecy and resists several kinds of attacks. Because adversaries may utilize the instances of CAPTCHAs to program bots by analytical attacks, the protocol also protects the CAPTCHAs' instances from being gained freely. And our protocol needs no password or validation tables storing on the server.