METHODS FOR BROADCASTING AND RECEIVING i^ SCRAMBLED MULTIMEDIA PROGRAMME, NETWORK HEAD, TERMINAL, RECEIVER AND SECURITY PROCESSOR FOR THESE METHODS The present invention relates to methods for broadcasting and receiving a scrambled multimedia programme and to a network head, a terminal, a receiver and a security processor for these methods. Methods for broadcasting multimedia programmes by way of broadband networks exist in which: - information can be routed to a multicast address so that only one group of several terminals corresponding to this multicast address receives the information while other terminals connected to the same network do not receive this information, and - information can be routed to a unicast address so that only the terminal corresponding to this unicast address receives the information while the other terminals cor\r\eo\&6 to the same network do not receive 'it For example, such a network is a network based on the IP protocol {Internet Protocol) such as the Internet network, which is also known as the world wide web. In the existing methods, a network head: - scrambles the multimedia programme with a control word, - encrypts the control word in order to obtain a first cryptogram, - encrypts the first cryptogram in order to obtain a second cryptogram, the first and second encryptions being effected by means of different encryption keys selected from the group composed of a processing key and a licence key, - multiplexes the second cryptogram with the scrambled multimedia programme to obtain multiplexed contents, - broadcasts the multiplexed contents to a multicast broadcast address in order to establish a point-to-multipoint connection between the network head and several receivers of the multiplexed contents, and - on a point-to-point link established with a terminal using the unicast address of this terminal, transmits the licence key individually to this terminal by way of this point-to-point link. A; the same time, terminals connected to the same network execute a method for receiving the scrambled multimedia programmes broadcast. In existing receiving methods, the terminal: - monitors the multtcast broadcast address and receives the multiplexed contents, - demultiplexes the multiplexed contents received in order to obtain the second cryptogram and the scrambled multimedia programme, - decrypts the second cryptogram in order to obtain the first cryptogram. - decrypts the first cryptogram in order to obtain the control word, the first and second decryptions being effected by means of different encryption l