Authorization refreshment management using ARL in DTV broadcasting

Conditional access system (CAS) performs entitlement management to make only legitimate subscribers watch pay-services. Generally, CAS uses passive entitlement management to fulfil that entitlement control, and various schemes are existed for that. Among them, Tu introduced two schemes in F.K. Tu et al., (1999), which are the simple scheme and complete scheme of four levels hierarchy. The advantage of the simple scheme of four levels hierarchy is a small key generation and encryption load for a CAS, but it is not good for the dynamic entitlement management. On the other hand, the complete scheme of four levels hierarchy is good for the dynamic entitlement management, but key generation and encryption load for CAS is considerable when it is compared to the simple scheme. In this circumstance, we proposed a novel scheme, which is an active entitlement key management. The proposed scheme not only performs the dynamic entitlement management very efficiently, but also generates and encrypts keys with a small load for CAS, which is just the same as the load of the simple scheme