High-quality color image compression-encryption using chaos and block permutation

Abstract

This paper proposes a high-quality color image compression-encryption scheme based on chaos and block permutation. In this scheme, the color digital image is first converted and sampled in the YCbCr gamut, and then the coefficients in the sub-blocks are extracted for compression coding after 8×8 post-blocking discrete cosine transformation (DCT) to the frequency domain. Then, an image encryption algorithm using chaos-based block permutation and two-round row-column diffusion is designed for the compressed frequency domain information. In terms of security, a chaos-based block permutation module is designed, which includes the encryption operations of block scrambling, block rotation and inversion, pixel value complement and color component interchange to enhance security. In addition, a mechanism for associating plaintext and intermediate ciphertext is introduced to generate dynamic chaotic sequences to effectively resist various cryptographic attacks. Moreover, the joint compression-encryption reduces the computational complexity of the encrypted object significantly and improves the efficiency. The simulation results show that the joint compression-encryption scheme has the advantages of high compression ratio and high image recovery quality, and has a fairly high security level to resist common cryptographic attacks. Therefore, the compression-encryption scheme proposed in this paper is a preferred and promising method for protecting the privacy of digital images.