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Cryptanalysis of a Secure Dynamic Identity Based Authentication Protocol for Multi-server Architecture

The dynamic identity based authentication was a worth researching issue in the mutual authentication. In 2011, Sood et al. proposed a secure dynamic identity based authentication protocol for multi-server architecture to improve Hsiang and Shih's protocol. However, we find that Sood et al.'s scheme lacks of the authentication between server and user. In this paper, we propose an improved scheme to achieve the mutual authentication. It not only solves the security problem but also hold the merits of Sood et al.'s protocol. Our scheme is more secure and robust for authentication of multi-server.