Secure and efficient authentication schemes over insecure networks have been a very important issue with the rapid development of networking technologies. Wang et al. proposed a remote user authentication scheme using smart cards. However, recently, C...
Secure and efficient authentication schemes over insecure networks have been a very important issue with the rapid development of networking technologies. Wang et al. proposed a remote user authentication scheme using smart cards. However, recently, Chen et al. pointed out that their scheme is vulnerable to the impersonation attack and the parallel session attack, and they proposed an enhanced authentication scheme. Chen et al. claimed that their scheme is secure against the various attacks. However, we have found that their scheme cannot resist the parallel attack and the stolen smart card attack. Therefore, in this paper, we show the security flaws in Chen et al."s scheme and propose an improved remote user authentication scheme using tamper-resistant smart cards to solve the problem of Chen et al."s scheme. We also analyze our scheme in terms of security and performance.