Research On Joint Image Compression And Encryption Method

With the development of information era, the rapid increase of information storage makes network transmission face a big challenge. At the same time, more and more information security problems, such as information stealing and network attack, force people to actively explore the relevant technology of the information security. Digital image compression and digital image encryption are essential in the field of information processing, since they focus on how to transmit images safely and efficiently. Traditional methods carry out these two steps independently before transmission. It is time-consuming and laborious. There may also exists interference between multiple algorithms, which affects the system’s performance. With the combination of the encryption and compression, one can ensure the unity of the whole algorithm, so as to enhance the security of the algorithm. This paper focuses on the joint image compression and encryption method. We try to establish a unified model and realize the combination of these two techniques.In this paper, we firstly review the research status of this subject, expounding and evaluating the existing joint models. A particular analysis of how the sparse decomposition is used to realize image compression and how the hash function along with chaos mapping are used to realize image encryption is carry out. Among them the measure of sparsity, the optimal solution of sparsity, the greedy pursuit algorithm, the convex relaxation method, the dictionary training method, hash function, and chaotic mapping have been studied in detail. Then a novel joint image compression and encryption method using sparse representation, Secure Hash Algorithm-1(SHA-1) and chaotic mapping is proposed. Patches of image are sparsely represented by a pursuit algorithm and a pre-trained dictionary. The locations and values of the representation coefficients are detached and encrypted separately, and then those two encrypted bit streams are multiplexed as the cipher image. Finally, as an alternative, another algorithm on the basis of sparse representation and mixed chaotic system is proposed. The single chaotic map is replaced with mixed chaotic system in the encryption step. Through the interaction of mixed chaotic maps it can make up for the loss that in finite precision calculations chaotic algorithm may lose some useful properties.Experimental results show that the proposed algorithm is able to achieve high compression ratio and security. At the same time, the joint algorithm based on mixed chaotic system can enhance security without deteriorating the reconstructed images’ quality and the compression ratio can match with the desired requirements in many application areas.