Research On High Real-time Digital Image Encryption Technology For Broadband Open Networks

Chaos-based image cipher has been extensively investigated over the last two decades or so to meet the increasing demand for secure image transmission over open networks. In this paper, a new chaos-based image cipher will be carried out to meet the demand of the network: A Chaotic Image Cipher Using Hash Mechanisms Based on Parallel method.Because the proposed scheme is used to deal with the color image and the color image has three components:R, G, B, the proposed scheme can use parallel method to encrypt the image. In parallel method, each thread deals with one component of the color image. Compared with traditional non-parallel method, although parallel method cannot raise the efficiency of subtask, it can raise the efficiency of the system constituted by subtasks.On the modules of the proposed scheme, as the main restricts the chaotic image encryption system’s efficiency is the high computational load of the diffusion process of "permutation" and "diffusion" of traditional scheme, the new method change the scheme to "pseudo diffusion-permutation". Chebyshev chaotic map and hyper chaotic system are used in the pseudo-diffusion and permutation stage respectively as corresponding key stream generator. The algorithm applies the SHA-256 value of the image as the initial state of hyper chaotic system (i.e. permutation key). Based on the characteristics of the Hash function and chaotic systems are extremely sensitive to initial conditions. For two plaintext images with minimal differences, hyper chaotic system will generate completely different permutation key streams, thus introducing a significant diffusion effect in permutation stage. This permutation which is associated with the plaintext can replace the original diffusion module which has high computational complexity, thereby greatly improved the speed of image encryption. Furthermore, the hyper chaotic has a large key space in a great unpredictability and the advantage of security property. Therefore, the security of the encryption system is enhanced.Finally, cryptanalysis is carried out and the experimental results demonstrate that the two cryptosystems can withstand all kinds of known attacks, which includes brute-force attack, differential attack, known/chosen plain-text attack as well as various statistical attacks.