Date Added: Apr 2012
Recently, Lee et al. proposed a secure dynamic ID based remote user authentication scheme for multi-server environment. They claimed their scheme can remedy the weaknesses of prior schemes and is thus more effective. However, the authors find Lee et al.'s scheme still fails to achieve the anonymity and has the security weakness of a smart card clone. In this paper, they shall propose a new scheme to improve Lee et al.'s scheme. Their scheme not only overcomes the weaknesses of Lee et al.'s scheme, but also maintains a high efficiency standard.