The Weakness of Moon et al.'s Password Authentication Scheme

Using smart cards make remote transactions easier for users in Internet. It's important to identity the legal users to have the access right to obtain the resources. In 2017, Liu et al. proposed an efficient and secure smart card based password authentication scheme. Recently, Moon et al. pointed some weaknesses of Liu et al.'s scheme. They also proposed a password authentication scheme to overcome Liu et al.'s weaknesses. They claim that their scheme is more secure and practical as a remote user authentication scheme. However, we find that some weaknesses of Moon et al.'s scheme. In this article, we will show that Moon et al.'s scheme is vulnerable to the guessing identity and impersonation attacks.