Compressing Encrypted Images With Auxiliary Information

This paper proposes a novel scheme of compressing encrypted images with auxiliary information. The content owner encrypts the original uncompressed images and also generates some auxiliary information, which will be used for data compression and image reconstruction. Then, the channel provider who cannot access the original content may compress the encrypted data by a quantization method with optimal parameters that are derived from a part of auxiliary information and a compression ratio-distortion criteria, and transmit the compressed data, which include an encrypted sub-image, the quantized data, the quantization parameters and another part of auxiliary information. At receiver side, the principal image content can be reconstructed using the compressed encrypted data and the secret key. Experimental result shows the ratio-distortion performance of the proposed scheme is better than that of previous techniques.