Chaotic System Of Image Encryption Algorithm Research

With the development of the Internet communication technology and the multimedia technology, the digital image has been played a very important role in multimedia information. Because digital image contains more information than the voice and character. The requirement of transporting the digital information by internet safely has been more and more urgent.The characteristics of the chaotic system such as the sensitive depen-dence on initial conditions and system parameters, pseudorandom pro-perty, nonperiodicity and topological transitivity, make it be applied in the code field. In first part of the paper I introduce the chaos theory and the basic knowledge of cryptography, In the second part the theory of digital image encryption and some chaotic systems related to this paper are proposed.The drawbacks of small key space and weak security in one-dimensional chaotic cryptosystems are obvious. So based on a non-linear chaotic algorithm an image encryption algorithm in a one-time-one-password system is designed in part Ⅲ. It shows advantages of large key space and high-level security. Then another new image encryption algorithm is designed based on hyper-chaos, First, a sort transformation based on nonlinear chaotic algorithm is used to shuffle the positions of image pixels. Then the states of hyper-chaos are used to change the grey values of the shuffled image according to the changed chaotic values of the same position between the above nonlinear chaotic sequence and the sorted chaotic sequence. Compared with some general encryption algorithms such as DES, the new encryption algorithm is more secure.