System mit bedingtem Zugang und dazugehöriger Karte

摘要

The invention relates to a conditional access system allowing a service provider to supply services only to those users who have acquired entitlements to these services. The services supplied by a service provider consist of an item scrambled by control words. In order to keep the control words secret, they are supplied after having been encrypted with an algorithm with key K. The entitlements of each user are forwarded in messages commonly denoted EMM (the abbreviation EMM standing for "Entitlement Management Messages"). According to the invention, the key K of the control words encryption algorithm is contained in the EMMs.