CONDITIONAL ACCESS SYSTEM FOR CONTROLLING THE ACCESS TO A DATA CONTENT

摘要

A conditional access system for controlling the access of receivers of end-users to data content transmitted from a data content source in an uplink system. The uplink system comprises a scrambler for scrambling the content supplied from the content source, an entitlement control message generator for generating entitlement control messages containing a control word and an entitlement identification and a transmitter for transmitting the scrambled content and the entitlement control messages. A descrambler, an entitlement control message decoder and means for recording entitlement identifications are associated to the receiver. The entitlement control message decoder supplies a control word to the descrambler for descrambling a part of the received scrambled content for which the receiver is entitled, if a match between the entitlement identification in the entitlement control message and the recorded entitlement identification exists. The content is subdivided into scenes having their own scene identification. The uplink system is provided with a scene identification generator connected to the entitlement control message generator for incorporating the scene identifications in the entitlement control messages. Means are provided for registering the accessed scenes at the receiver.