APPARATUS AND METHOD FOR PROCESSING STREAMS

摘要

For conditional access purposes a stream is used in which at least two different decryption algorithms are needed for decryption of packets that encode different interspersed parts of the same signal for (quasi-)continuous rendering (such as an audio or video signal). Information is included in the stream to indicate dynamically which decryption algorithm should be used for which packets. In this way, it is possible for example to use a more robust algorithm with a less frequently changing key and a less robust algorithm with a more frequently changing key, interspersed with one another for the same signal. Also, different algorithms may be used for transcrypted and not transcrypted-packets of the same signal for example when an alternative is needed for the original encryption algorithm that was used for the non-transcrypted packets.