Cryptanalysis of a Three-Party Password Authenticated Key Exchange Protocol Resistant to Stolen Smart Card Attacks

Authenticate Key Agreement Protocol is a crucial and yet imperative Cryptographic parameter to establish a secure transaction over a public channel. To land such secured transaction a Three Party Authenticate Key Agreement Protocol is the procedure where a Secured server verifies the authenticity of a genuine user. There is an ample number of scholars working on Three Party Authenticate Key Agreement Protocols. In recent past, Chen-et al designed a new Three Party Password based Authenticate Key Exchange Protocol which is secured against the Stolen-Smart-Card Attack and User Impersonation Attack. It means even though a smart card of a genuine user gets lost and an adversary finds it, he is unable to launch any kind of Attack. Unfortunately Chen et. al. \pmbs protocol remains unforeseeable to achieve User Anonymity. This User Anonymity problem makes their protocol vulnerable towards the DOS-Attack and it becomes more prone to it. In this paper we explain how Chen et. al.'s protocol is endangered to DOS-ATTACK as it lacks to reach out for User Anonymity.