The Research Of Digital Image Encryption Algorithm Based On Chaotic Theory

In information times, with the rapid development and wide applications of network technology and computer technology, more and more information has been quickly and conveniently transmitted through the network, at the same time that has the potential problems of the security of information. Therefore, the security of information is getting more and more important. The cryptography, which aims at the security of information, has become one of the important research fields in information science and technology. Up to now, data encryption technology is the best method to obtain information security undoubtedly; it is greatly practical and urgent to develop key technology. In this paper, significance of image encryption is represented, present state and perspectives of image encryption are generalized, and applied limitations are pointed out. Based on chaotic systems with good properties such as ease of generation, noise like statistic characteristics and sensitive dependence on their initial condition and system parameter, chaotic theory and digital image encryption are combined, which can design the better system of image encryption. Digital image encryption algorithms based on the chaotic theory have been researched in this paper.The main contributions of the paper are:(1) Based on understanding permuted algorithms of the digital image and their properties, the specialties of Logistic map and truncated baker transform are combining. Because the image encryption algorithms based on matrix transform are not enough secret, the encryption algorithm combining truncated baker transform with Logistic map is presented, experiment of algorithm is done using computer and the results of simulation are analyzed.(2) Based on analyzing the specialty of Kent map, the method that pseudo-magic transform matrix is created by the chaotic sequences is given. Because the effect of permuted algorithm in space domain is not good, a new algorithm using the pseudo-magic matrix to encryption different parts of wavelet coefficients are presented in wavelet domain; the algorithm is verified and analyzed by simulations. (3) Based on analyzing the characters of discrete Hopfield neural network and the specialties of piecewise linear chaotic map, a new image encryption algorithm combining piecewise linear chaotic map with Hopfield neural network is presented, the realized method of the algorithm is given, the experiment is done in computer, whose simulation results show advantages of the algorithm.