ABSTRACT
The decryption operation and compression operation should fit each other. In the player, the decryption operation and decompression operation can be ordered in different mode, which depends on the encryption method. For example, if the media data is first compressed then encrypted on the sender side, then in the player, the decryption operation is followed by the decompression operation, as shown in Figure 13.1. If the encryption operation is combined with the compression operation, then, in the player, the decryption operation should be combined with the decompression operation. The third case is that media data is first encrypted then compressed. However, this case seldom happens, and thus, it is not considered here. The decryption operation should be efficient enough for real-time operations. Considering that, during playing, media data is first decompressed
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and then rendered, the inserted decryption operation may cause delays to the decompression operation. Generally, a symmetric cipher is more widely used, and thus, the encryption operation is symmetric to the decryption operation. Therefore, for the secure player, a media encryption method with high encryption efficiency is preferred.
