ABSTRACT
First, according to the relation between encryption and compression, they can be classified into two types, raw data encryption and compressed data encryption. In raw data encryption, the media data is encrypted before it is compressed. Since the encryption operation changes the performance of the multimedia data, for example, the adjacent relation of image pixels, the compression ratio may be changed greatly. In compressed data encryption, the media data is first compressed and then encrypted. Because the compression operation reduces the data volume of original
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media data, the followed encryption operation saves much computational cost. They will be presented in detail in Section 4.3.
