On the anonymity of some authentication schemes for wireless communications

In 2004, Zhu and Ma proposed a new and efficient authentication scheme claiming to provide anonymity for wireless environments. Two years later, Lee et al. revealed several previously unpublished flaws in Zhu-Ma´s authentication scheme and proposed a fix. More recently in 2008, Wu et al. pointed out that Lee et al.´s proposed fix fails to preserve anonymity as claimed and then proposed yet another fix to address the problem. In this paper, we use Wu et al.´s scheme as a case study and demonstrate that due to an inherent design flaw in Zhu-Ma´s scheme, the latter and its successors are unlikely to provide anonymity. We hope that by identifying this design flaw, similar structural mistakes can be avoided in future designs.