Performing scalable lossy compression on pixel encrypted images
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Performing scalable lossy compression on pixel encrypted images Xiangui Kang1,3*, Anjie Peng1, Xianyu Xu2 and Xiaochun Cao3
Abstract Compression of encrypted data draws much attention in recent years due to the security concerns in a service-oriented environment such as cloud computing. We propose a scalable lossy compression scheme for images having their pixel value encrypted with a standard stream cipher. The encrypted data are simply compressed by transmitting a uniformly subsampled portion of the encrypted data and some bitplanes of another uniformly subsampled portion of the encrypted data. At the receiver side, a decoder performs content-adaptive interpolation based on the decrypted partial information, where the received bit plane information serves as the side information that reflects the image edge information, making the image reconstruction more precise. When more bit planes are transmitted, higher quality of the decompressed image can be achieved. The experimental results show that our proposed scheme achieves much better performance than the existing lossy compression scheme for pixel-value encrypted images and also similar performance as the state-of-the-art lossy compression for pixel permutation-based encrypted images. In addition, our proposed scheme has the following advantages: at the decoder side, no computationally intensive iteration and no additional public orthogonal matrix are needed. It works well for both smooth and texture-rich images. Keywords: Image compression; Image encryption; Lossy compression; Image reconstruction; Scalable coding
1. Introduction Compression of encrypted data draws much attention in recent years due to the security concerns in a service-oriented environment such as cloud computing [1,2]. The traditional way of securely and efficiently transmitting redundant data is to first compress the data to reduce the redundancy then encrypt the compressed data. At the receiver side, decryption is performed prior to decompression. However, in some application scenarios (e.g., sensor networking), a sender may first perform encryption with a simple cipher and then send it to a network provider. The network provider always has the interest to reduce the rate. It is desirable to be able to compress the encrypted data without the key to reduce the security concerns. At the receiver side, joint decryption and
* Correspondence: [email protected] 1 School of Information Science and Technology, Sun Yat-Sen University, Guangzhou, Guangdong 510006, China 3 State Key Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, Beijing 100093, China Full list of author information is available at the end of the article
decompression will be used to reconstruct the original data. It has been proved in [1] that the overall system performance of such approach can be as good as the conventional approach, that is, neither the security nor the compression efficiency will be sacrificed by performing compression in the en
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