Cryptanalysis of "An Improved Remote Password Authentication Scheme with Smartcard"

Recently, an improved remote user authentication scheme using smartcard was proposed. The authentication scheme by J. Chao claimed that it could provide user anonymity and withstand various attacks. In this paper, we analyze the security of Chao´s scheme and point out that his scheme cannot provide user anonymity. Moreover, we demonstrate that his scheme cannot withstand the user masquerade attack and the server masquerade attack.