Cryptographic key assignment scheme for dynamic access control in a user hierarchy

The authors present a cryptographic key assignment scheme based on both the Rabin public key system and the Chinese remainder theorem, in order to solve dynamic access control problems in user hierarchies. Compared to earlier assignment schemes, the new scheme ensures that a security class can efficiently derive secret keys of its successors. Dynamic access control problems, such as adding/deleting classes, adding/deleting relationships, and changing secret keys, are considered. Moreover, without altering other keys present in the system, each user in the hierarchy can freely change his own key