Improving the security of ‘a flexible biometrics remote user authentication scheme’

Recently, Lin–Lai proposed ‘a flexible biometrics remote user authentication scheme,’ which is based on El Gamal's cryptosystem and fingerprint verification, and does not need to maintain verification tables on the server. They claimed that their scheme is secured from attacks and suitable for high security applications; however, we point out that their scheme is vulnerable and can easily be cryptanalyzed. We demonstrate that their scheme performs only unilateral authentication (only client authentication) and there is no mutual authentication between user and remote system, thus their scheme is susceptible to the server spoofing attack. To fill this security gap, we present an improvement which overcomes the weakness of Lin–Lai's scheme. As a result, our improved security patch establishes trust between client and remote system in the form of mutual authentication. Moreover, some standards for biometric-based authentication are also discussed, which should be followed during the development of biometric systems.