A CRYPTOGRAPHIC IMPLEMENTATION FOR DYNAMIC ACCESS-CONTROL IN A USER HIERARCHY

In this paper, we propose a cryptographic key assignment scheme based on the Rabin public key system and the concepts of the Chinese remainder theorem and Newton's interpolating method to solve the access control problem in an arbitrary partially ordered user hierarchy. Compared to the existing assignment schemes, our scheme ensures that the security class in the higher level can derive any of its successor's secret keys efficiently and shows that no issued keys should be changed when a new security class is added into the hierarchy. Moreover, any user in the hierarchy can freely change his own key for some security reason without altering the other existing keys in the system.