Cryptanalysis of Two Dynamic ID-Based Remote User Authentication Schemes for Preserving User Privacy
Remote user authentication is an essential part in electronic commerce to identify legitimate users over the Internet. However, how to protect user privacy in the authentication has become an important issue recently. Therefore, many secure authentication schemes with smart cards have been proposed. In this paper, the authors will analyze the security weaknesses of two recently proposed authentication schemes for preserving user privacy. First, Chang et al. proposed a robust and efficient remote user authentication scheme to provide user anonymity.