Security Flaws in Authentication Protocols with Anonymity for Wireless Environments

The emerging wireless networks require the design of new authentication protocols due to their dynamic nature and vulnerable-to-attack structure. Recently, Wu and others proposed a wireless authentication protocol which is claimed to be an improvement of the authentication protocol proposed by Lee and others which provides user anonymity. In this letter we show that these protocols have a common flaw and that these protocols fail to provide user anonymity. We also propose a modification method to solve this problem.