An access control method is described for an encrypted program transmitted by an operator to a plurality of groups of subscribers, where each group of subscribers has a group key KG, and each subscriber is able to receive from the operator an operating key KT, enciphered by the group key KG for decryption of the transmitted program. The method further involves linking the enciphered operating key KT to a random value R to generate a secret code, transmitting the secret code to subscribers prior to transmission of the encrypted program, and transmitting the random value R to subscribers for calculation of the operating key KT.