Researches Of Several Digital Image Encryption Algorithm Based On Chaos Theory

In now-days world, with the rapid development and wide application of internet technology and muti-media technology, more and more information has been transmitted quickly and conveniently through the networks. At the same time, a lot of potential problems of information security also has arisen. Therefore, how to protect the information security, especially the image information security, is getting more and more important. Chaos was discovered by an American meteorologist Lorenz in 1963. Based on chaotic systems with good properties such as pseudorandom behavior and sensitive characteristics to the initial condition and system parameter, chaotic theory and encryption technology are combined so that it can design the better algorithm with high security quality, more stronger information encryption systems as well.In this paper, digital image encryption algorithm based on chaotic theory has been deeply researched. The fundamental chaos principles are intrduced, including the concept of chaos, the formation and development of chaos, especially the method of judging the chaos system thought Lyapounov index. Then some typical image encryption algorithms are analyzed systematically, including Arnold transformation, magic cube encryption and CKBA encryption. After that, this paper make some improvement on the exsting encryption algorithm as well as doing analyzation and comparation with some method of accessing the effect of encryption.Based on the wok done above, this paper summarizes the improvement scheme of image encryption security and mainly proposed several improved digital image encryption methods based on chaotic theory , such as applying hyperchaotic sequence, encrytption on frequency domain of image, image compound encryption and so on.Simulation results indicate that the improved method has good efficiency and security characteristic and it can defend known-plaintext attack. At last, some other image encryption algorithms are also given.This paper is supported by Natural Science Fundation of Shaanxi Province, 2004(No.2004A15); Special Science Research Plan Project of the Education Department of Shaanxi Province(No.06JK193).