Cryptanalysis of Yeh et al.'s timestamp based scheme using smart card

In 2010, Yeh et al. proposed a timestamp based scheme using smart cards. They claims that their schemes defended against ID-theft attacks, reply attacks, undetectable on-line password guessing attacks, off-line password guessing attacks, user impersonation attack, server counterfeit attack, and man-in-the-middle attack. In this paper, we show that Yeh et al.'s scheme is still vulnerable to ID-theft attack, off-line password guessing attacks and undetectable on-line password guessing attacks.