A forward secure remote authentication based on factoring

Due to its growing importance in various fields, such as computer networks, wireless networks, operation systems, and database management systems, password authentication has been accepted as a common practice to protect resources from illegal access. Many remote password authentication schemes have been proposed to minimize the time and storage requirements, as well as to maximize their robustness in face of various attacks. However, none of the existing schemes properly addresses key exposure problem, which always leads to a disastrous consequence. In most of recently proposed schemes, a remoter server does not need to maintain a whole list of identities and passwords of registered users, but a single system secret key instead, which is used to grant access rights to a user and validate a login request. Once the secret key is leaked, an attacker could impersonate anyone, and what is even worse is that all the registered users become unauthenticated. Our paper addresses such problem by presenting a forward secure authentication scheme to minimize the damage caused by server key exposure. In our scheme, an attacker could not impersonate a previously registered user, even if he has obtained server's current secret key. We also prove that the security of our scheme is based on the hardness of factoring. Moreover, we discuss many other properties of the scheme and analyze its efficiency.