An Improvement of the Remote Authentication Scheme for Anonymous Users Using an Elliptic Curve Cryptosystem

It is convenient to obtain the information resources via intelligent devices over cloud systems. The user authentication mechanism is a fundamental tool for ensuring the validity of communicating parties and securing communications among the communicating party. Recently, Zhang et al. proposed a new remote authentication scheme for anonymous users using an elliptic curve cryptosystem. Their scheme could achieve the mutual authentication and forward security. They claimed that their scheme could withstand various attacks by employing BAN-logic formal methods. They claimed that their scheme could withstand the preserving anonymity and non-traceability, perfect forward secrecy, offline password guessing attacks, forgery attacks, server impersonating attacks, known key attacks, and reply attacks. However, we will show that their scheme is vulnerable to forgery attacks, server impersonating attacks, and man-in-the-middle attacks. In this article, we also propose an improved anonymous user authentication scheme proposed by Zhang et al. to withstand the vulnerability in their scheme.