Cryptanalysis of remote user authentication scheme with key agreement

Password authentication with smart card is one of the most convenient and effective two-factor authentication mechanisms for remote systems to assure one communicating party of the legitimacy of the corresponding party by acquisition of corroborative evidence. This technique has been widely deployed for various kinds of authentication applications, such as remote host login, online banking, e-commerce and e-health. Recently, Kumari et al. presented a dynamic-identity-based user authentication scheme with session key agreement. In this research, we illustrate that Kumari et al.´s scheme violates the purpose of dynamic-identity contrary to author´s claim. We show that once the smart card of an arbitrary user is lost, messages of all registered users are at risk. Using information from an arbitrary smart card, an adversary can impersonate any user of the system.