A secure image compression-encryption algorithm using DCT and hyperchaotic system

Nowadays, thanks to the rapid development of communication network technology, the multimedia data with image and video as the carrier increases exponentially. Therefore, how to transmit data efficiently and securely has become an important research topic. In order to reduce the amount of data during image transmission and ensure the security of images, we propose a joint image compression and encryption method based on discrete cosine transform (DCT) and hyperchaotic system (HCS) in this paper. This scheme consists of two stages, i.e., compression and encryption. In the compression stage, plain-image is transformed by cosine transform in blocks, and then only a small number of DCT coefficients in the upper left corner of each block are retained to achieve the purpose of compression. In the encryption stage, the compressed image is first divided into blocks, and then each block is permutated by Arnold transformation to achieve a local scrambling effect. Next, the scrambled matrix generated by HCS is used to scramble the image after Arnold transformation. By local and global scrambling, the correlation between adjacent pixels can be destroyed effectively. Finally, the chaotic sequence generated by HCS is used to diffuse the scrambled image, and the cipher image is obtained. Moreover, our algorithm exhibits excellent compression performance compared with existing related algorithms. The result of experiment test indicate that our approach possesses excellent image compression ability and cryptographic properties.