Attacks on the Shen et al.'s Timestamp-Based Password Authentication Scheme Using Smart Cards

In 2003, Shen et al. proposed an improvement on YangShieh’s timestamp-based password authentication scheme using smart cards. Then they claimed that their scheme cannot withstand a forged login attack, but also eliminate a problem of Yang-Shieh’s. However, their scheme is still susceptible to forged login attack. In this letter, we show how the forged login attack can be worked out on Shen et al.’s scheme. key words: cryptography, password, authentication, security, smart card