Just wanted to add that the different encryption are needed so that different providers who have adapted a certain encryption would enable their subscribers to open the specific channel, if it is included in their subscription.
For example Mezzo channel on Hot Bird 13E has:
Viaccess
Irdeto
Nagravision
Viaccess was used by TPS (wonder why it is still on, although TPS has left)
Irdeto is used by Nova (Greece)
Nagravision is used by Cyfra Plus (Poland) |