Cryptanalysis and security enhancement of a 'more efficient & secure dynamic ID-based remote user authentication scheme'

Remote user authentication is a method, in which remote server verifies the legitimacy of a user over an insecure communication channel. Currently, smart card-based remote user authentication schemes have been widely adopted due to their low computational cost and convenient portability for the authentication purpose. Recently, Wang et al. proposed a dynamic ID-based remote user authentication scheme using smart cards. They claimed that their scheme preserves anonymity of user, has the features of strong password chosen by the server, and protected from several attacks. However, in this paper, we point out that Wang et al.'s scheme has practical pitfalls and is not feasible for real-life implementation. We identify that their scheme: does not provide anonymity of a user during authentication, user has no choice in choosing his password, vulnerable to insider attack, no provision for revocation of lost or stolen smart card, and does provide session key agreement. To remedy these security flaws, we propose an enhanced authentication scheme, which covers all the identified weaknesses of Wang et al.'s scheme and is more secure and efficient for practical application environment.