Improved Remote User Authentication Scheme Preserving User Anonymity

In 2004, Das et. al proposed a Dynamic ID based remote authentication scheme to authenticate the users while preserving the user's anonymity .Chein et. al. pointed out that Das et. al scheme fails to protect the user's anonymity and proposed a new scheme to conquer the weakness in 2005. This paper shows that Chein et al scheme is insecure against Insider attack and Man-in-middle attack. An improved scheme is proposed that overcomes the security risk.