System and methods for transmitting encrypted data with encryption key

摘要

A method for transmitting information between a transmitter station and a plurality of receiving stations in which encrypted information is transmitted from the transmitter station to the receiver station with a first key and at least a control message bearing a second key. The first key used for decryption is restored in each receiving station from the second key and from at least one datum selected from a set of data available in the receiving stations, according to a selection command periodically transmitted between the transmitting station and the receiving station. Such a system may find particular application to pay television.