| 摘要 |
The present invention concerns a method and a device for encrypting an encoded scalable enhancement frame (3.2) sent by an emitter (5.1) to a receiver (5.2), the enhancement frame comprising a plurality of complementary streams ordered in term of quality level, each complementary stream corresponding to a combination of more than one scalability type, where a complementary stream of a lower quality level corresponds to a lower quality on each scalability type, comprising at the level of the emitter the steps of generating a key (S1) per complementary stream for encrypting said complementary stream in such a way that all scalability types can be either simultaneously or individually used, said keys being generated in such a way that only the keys of the complementary streams of quality levels lower than the quality level of a complementary stream can be obtained from the key of said complementary stream, and sending (S3) the key of a complementary stream corresponding to a required quality level to the receiver, the key permitting a receiver to generate the keys of the complementary streams of the lower quality levels only. The present invention also concerns a method and a device for decrypting a received encoded scalable enhancement frame.
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