| 摘要 |
Delivery of conditional access (CA) data to a receiver (410) that is able to connect to a plurality of scrambled programs. Conditional access for a current channel is handled (310) using standard ECMs delivered with the channel. In parallel, the receiver (410) retrieves (320) an ECM for a separate stream comprising control words for every channel. The control word of this ECM is used to descramble (330) the separate stream to access the control words for every channel. In a preferred embodiment, these control words are super-encrypted using channel keys and the receiver is only able to obtain channel keys for channels for which it has access rights. In case the control words are super-encrypted, they are decrypted (340). Upon channel change, the relevant retrieved control word is used to descramble (350) the new channel. Also provided is a receiver device (410) and a transmitter device (420). According to a variant, the control words received in the separate stream is treated only upon a change of channel. The invention enables a reduction or removal of the CA delay when switching between channels. |
