| globalization has caused the human society to enter new information time. At the same time, information security has exposed more and more serious problems, and its importance is increasingly obvious. Some features of chaotic systems, such as sensitive dependence on initial conditions, inherent randomness and topological transitivity, are closely related to the principle of encryption systems (diffusion, confusion) in cryptography. So the cryptography based on chaos theory has become an important topic in the research of the digital image security technology.Based on the characteristics of digital image and Chaotic Coupled Map Network (CCMN), the image encryption algorithm is studied in this dissertation. The main contents include:(1) The features of CCMN are analyzed. This model differs from the common chaotic systems in that it introduces a local dynamic effect function and coupling elements, so it has good properties of spatiotemporal chaos.(2) An image encryption algorithm based on CCMN is then proposed. Through the analysis of the encryption process, the algorithm based on CCMN has low efficiency, and generates a lot of redundant output. To overcome the defects in this algorithm, the model and process of the algorithm are revised. In order to enable the new model of CCMN to build higher security BLOB in image encryption, the new model improves the calculation with matrix transformation, and uses a new coupling policy. In this dissertation, some simulations and analysis are given to verify the improved algorithm has good anti-attack ability and feasibility.(3) The performance of the improved algorithm is analyzed. Then, an optimization algorithm is proposed, having higher encryption rate. |
