Key distribution scheme based on two cryptosystems for hierarchical access control

To combine the merits of symmetric key cryptosystem and public-key cryptosystem, the authors present a key distribution scheme based on both the Rabin public-key system and the Chinese remainder theorem (CRT) for conditional access system (CAS) in digital TV broadcast, in order to solve dynamic access control problems in user hierarchies. Due to the simplicity of key generation and derivation, the proposed scheme can greatly reduce the encrypting computation and transportation load in the meantime acquire high security. Dynamic access control problems, such as adding/deleting group, adding/deleting relationships and changing secret keys, are easily solved. The proposed scheme is also very suitable for the pay-per-view method