Cryptanalysis and improvement of chen-hsiang-shih's remote user authentication scheme using smart cards

Recently, Chen-Hsiang-Shih proposed a new dynamic ID-based remote user authentication scheme. The authors claimed that their scheme was more secure than previous works. However, this paper demonstrates that theirscheme is still unsecured against different kinds of attacks. In order to enhance the security of the scheme proposed by Chen-Hsiang-Shih, a new scheme is proposed. The scheme achieves the following security goals: without verification table, each user chooses and changes the password freely, each user keeps the password secret, mutual authentication, the scheme establishes a session key after successful authentication, and the scheme maintains the user's anonymity. Security analysis and comparison demonstrate that the proposed scheme is more secure than Das-Saxena-Gulati's scheme, Wang et al.'s scheme and Chen-Hsiang-Shih.Peer ReviewedPostprint (published version

Cryptanalysis and Improvement of a Two-Factor User Authentication Scheme

Recently, Wang-Wang have discussed a two birds with one stone: two-factor authentication with security beyond conventional bound. We find that this scheme is vulnerable to the password exposure attack and also does not offer user anonymity, which is an important feature for some of the applications like e-healthcare services, e-banking, etc. In this paper, we provide the solution to these problems