Study On Chaos Theory And Its Application On Image Encryption

Digital Image Information is an important part of Network Information, with the rapid development of modern communication and computer network techniques; image security comes to be an increasing important problem. Because there are many characteristics of image which are different from text and voice information, such as large data, high redundancy and self-similarity and so on, traditional encryption methods are not suitable to image information. In recent years a variety of special schemes for image encryption have been proposed in accordance with the characteristics of digital image by many researchers. The image algorithms based on chaos show good encryption performance in practice. But there are also problems that the limited accuracy of chaotic sequences in the computer simulation and complex chaotic sequences' chaotic characteristic needs to be further studied.This paper briefly introduces the history of chaos development and the basic concepts of chaos and its related knowledge, and then an algorithm of Lyapunov exponent is designed. Through the simulation of that algorithm, the characteristic of a complex chaotic sequence has been tested. And then the basic knowledge of cryptography and several digital image encryption methods and the relationship between chaos and cryptography have been introduced. Several encrypted criterions of image encryption system have been given in accordance with the cryptanalysis. At last, several image encryption algorithms based on chaotic are introduced and a new method of image encryption algorithm based on new complex chaotic sequences is proposed. A series of new complex chaotic sequences are generated by chaotic systems including Lorenz system, Chen system, Lu system and Logistic chaotic mapping. With these new sequences, a new image encryption system that shuffles the positions and changes the grey values of the image pixels is designed. The results of simulation experiments and security analyses indicate that this encryption system has a large key space and a quite good sensitivity to the secret key and the original image. And it also possesses perfect diffusion and confusion properties. At the same time it can resist noise disturbances strongly.