Viaccess

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Viaccess is an encrypting system for digital television developed by France Télécom. There are four versions in use today, Viaccess PC2.3, Viaccess PC2.4, Viaccess PC2.5 and Viaccess PC2.6.

Viaccess was developed as the digital version of the EuroCrypt system used with the hybrid MAC system.

The first version is sometimes referred to as Viaccess 1, and the latter three, although different, as Viaccess 2. PC2.3 and PC2.4 are known to be ineffective, and many set-top boxes can be 'patched' to decrypt Viaccess signals without payment, however PC2.5 and PC2.6 are secure, with PC2.5 remaining secure two years after its first commercial deployment. PC2.6 was introduced at the end of 2005.

There are two modifications of Viaccess PC2.3 in use. The first, known as TPS Crypt, is used by TPS. Despite being compromised also, the TPS Crypt system has been further modified to utilise Advanced Encryption System (AES) keys. These AES keys were originally updated once daily, however after this inconvenienced unauthorised viewers little, a second TPS crypt system was introduced, by which keys are changed every 15-20 minutes, with keys being sent over TPS's internal Open TV system. This therefore meant that only TPS receivers could receive the new AES key, and not the insecure TPS subscription cards. Monitoring and analysing of the keys by hacking groups, however, has brought about key lists, where the AES keys have been successfully predicted. Implimentation of this procedure of automatically updating keys has proved difficult, if not impossible, to impliment on many satellite receivers, rendering the TPS Crypt AES system a general success.

The second Viaccess modification, called ThalesCrypt, is used by Canal Satellite France to protect its contents on the transport network to the head-ends of the cable networks; it is an over-encryption mechanism of the original protocol encryption keys.

Viaccess is currently used by a large number of providers. These include;