Study on an efficient hyper-chaos-based image encryption scheme using global bit permutation

BACKGROUND: The chaotic system with low dimensions has a low security compared to the high-dimensional chaotic system. Furthermore, major pixel-level permutations merely transform the pixel position and cannot change the intensity distribution of the original image. Bit-level permutation could change the intensity distribution, as it devotes more time to conduct bit-level computation. OBJECTIVE: In this study, we present a more efficient image encryption approach based on hyper-chaos and a global bit cycle shift (HC-GBCS). METHODS: According to the input image we adopted the SHA-256 secure hash algorithm to obtain the initial key, which served as the premier parameter of the chaotic system. Then we employed a 4D hyper-chaotic system for generating the chaotic series, on which we utilized global bit permutation to enhance the security of the encryption system. Finally, the diffusion process was conducted by using the generated chaotic series extended with a logistic map. RESULTS: Experimental results and analysis reveal that the presented approach encrypts plain images effectively and achieves high security and stability. CONCLUSION: The proposed method can deal with the problems inherently existing in encryption methods utilizing lowdimensional chaotic map. Furthermore, global bit permutation can transform the pixel distribution of plain images and enhance the cryptosystem security.