Abstract: Conditional access system for controlling the access of receivers of end-users to a data content source in an uplink system. Said uplink system comprises a scrambler for scrambling data content supplied from the data 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 data content and the entitlement control messages. A descrambler and an entitlement control message decoder are associated to the receiver. If a match between the entitlement in the entitlement control message and the entitlement of the end-user exists, 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.