THE PROBLEM of information security entails the protection of information elements (e.g., multimedia data) thereby ensuring that only authorized users are able to access the contents available in digital media. Content owners, such as authors and authorized distributors, are losing billions of dollars annually in revenue due to the illegal copying and sharing of digital media. In order to address this growing problem, digital rights management (DRM) systems are being deployed to regulate the duplication and dissemination of digital content . The critical component of a DRM system is user authentication which determines whether a certain individual is indeed authorized to access the content available in a particular digital medium. In a generic cryptographic system, the user authentication method is possession based. That is, the possession of the decrypting key is sufficient to establish the authenticity.