Comments on Five Smart Card Based Password Authentication Protocols

In this paper, we use the ten security requirements proposed by Liao et al. for a smart card based authentication protocol to examine five recent work in this area. After analyses, we found that the protocols of Juang et al.'s , Hsiang et al.'s, Kim et al.'s, and Li et al.'s all suffer from offline password guessing attack if the smart card is lost, and the protocol of Xu et al.'s is subjected to an insider impersonation attack.