We can distinguish three elements in Viaccess access control: a protocol for remotely delivering, on the equipment installed at the subscriber's premises, the encryption keys opening access to the programs corresponding to the subscription subscribed; a conditional access module, installed at the subscriber (either integrated in the satellite receiver, or available separately in the form of a card containing the physical format of the PCMCIA standard), and equipped with a smart card reader; this module dialogue on the one hand with the smart card according to the set of instructions provided by the Viaccess protocol, and when the smart card provides him back the necessary keys, descrambles on the other hand the received channels; an ISO 7816 chip card, implementing the Viaccess protocol, and providing the conditional access module the short-lived means of descrambling the strings (control words), while keeping the means of duration secret long life (exploitation and management keys). Viaccess does not have the function of encrypting either the image or the sound of the television transmission. This scrambling work is performed by another method, called Common Scrambling Algorithm (common, because used by all televisions broadcast in DVB, whatever the conditional access system they use elsewhere). A conditional access system such as Viaccess is limited to providing or not the means of descrambling programs with the CSA algorithm, depending on the secret keys and access rights held by the subscriber smart card, and update these keys and rights on this map.

 List channels with crypting