Research On Digital Image Encryption Method Based On Chaos

With the rapid development of the Internet and multimedia technology, image information has become a main way for information communication. Image transmission is very convenient for people, but its security problem is brought before us. Up to now, information encryption technology is the best method to obtain information security undoubtedly and a lot of achievements have been obtained by the researchers in this field. Information encryption technologies are not perfect, besides, with the lucubrating of encryption theory, many of encryption technologies have been attacked efficiently, so new information security theory and advanced encryption technologies are required urgently.Traditional encryption methods are adapted to text encryption and appear not to be good candidates for image applications. For adapting to the inherence character of image and increasing the efficiency and security of image encryption, new image encryption methods are required. Chaotic dynamical system is a kind of deterministic nonlinear system and has random-like behavior. Since it is very sensitive to the initial conditions and control parameters, a large number of uncorrelated, random-like, yet deterministic and reproducible signals can be generated easily. These properties have natural affiliations with the information security technology. Based on chaotic systems with good properties such as pseudo-random, unpredictability of evolution of its orbits 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.In this paper, significance of image encryption is represented, present state of image encryption are generalized; Basic knowledge of encryption theory, summarizing of encryption means. Then we introduce the theory about chaos system. Based on the analysis of chaos encryption the main contributions of the paper are:Based on understanding permuted algorithms of the digital image and their properties, a typical image encryption method is introduced. The encryption process is disturbing color values of each image point and the array of original image based on two kinds of chaotic mapping. Because the chaotic sequence is drawn out after the beginning segment, it can enhance the security of encryption system. The experiment of algorithm is done using computer and the results of simulation are analyzed. Simulation testing and theory analysis show that encryption method has large key room, is very sensitive to key and this method has some resistivity for noise and damage attack.But this method is not sensitive to the change of plaintext. Aim at the lack of this method, this paper improved the producing fashion of position scrambling matrix from two aspects, Simulation testing shows that encryption speed has been improved and this method is sensitive to the change of plaintext in some degree. The ability of resisting plaintext attack is improved.In this paper, a image encryption method using chaotic and wavelet theory is also gived. In this method a part of wavelet coefficients are encrypted by high security, the rest of wavelet coefficients are encrypted by common security. The experiment of algorithm is done using computer and the results of simulation are analyzed. This method encrypts the image's key information and improves capability of the encryption system.