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 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 storing entitlements 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 entitlement of the end-user exists. The receiver side is provided with means for receiving and storing a meta-entitlement of the end-user, said meta-entitlement including an event number range, and means for extracting from the meta-entitlement an actual entitlement identification including the event selected by the end-user. A control word from the entitlement control message is supplied to the descrambler if the entitlement identification in the entitlement control message matches the actual entitlement.