An enhanced remote user authentication scheme using smart cards

In 2000, Hwang and Li proposed a new remote user authentication scheme using smart cards. Chan and Chang showed that the masquerade attack is successful on this scheme. Recently Shen, Lin and Hwang pointed out a different type of attack on this scheme and presented a modified scheme to remove these defects. Further in 2003, Leung et al. showed that this modified scheme is still vulnerable to the attack proposed by Chan and Cheng. In addition they showed that the extended attack proposed by Chang and Hwang also works well. In this paper we enhanced Shen, Lin and Hwang´s scheme to overcome these attacks.