Cryptanalysis and improvement of an efficient password authentication scheme based on smart card

User authentication is an important technology to guarantee that only the legal users can access resources from the remote server. In 2013, based on chaotic maps, Guo and Chang proposed an efficient mutual authentication protocol with user anonymity for the smart card. Unfortunately, this study will demonstrate their scheme could not achieve the user anonymity property, and do not allow changing password freely for the user. Then, we proposed a new method to remedy the weaknesses. The proposed method is secure even if the secret information stored in the smart card is compromised. Only one-way hash function and simple polynomial computations are involved in our protocol. It is more suitable for practice implementation.