Research And Implementation Of Image Encryption Algorithm Based On Chaotic Technique

In this information age, the network's rising and prevalence makes the information communion more and more convenient and quick meanwhile the traditional encrypting method is not effectively used to encrypt multimedia information which has a mount of data and requires real-time transmission. In order to protecting information safety, it becomes an important study in the world that encrypting multimedia information.Chaotic dynamical systems have the following properties: stochastic characteristics, be deterministic, be sensitive to initial conditions and system parameter, so it provides a new simple way for digital image encryption. Thereby, a deep research on how to protect digital information safety and proposes some digital image encrypting algorithms based on the chaotic theory, is made in this paper.At first, the basic knowledge of chaotic systems: development, definition and characteristic is briefly introduced in this paper then the basic theory of key technology and the principle, algorithms of digital image encryption is introduced. Based on analyzing image encrypting algorithms presently, this paper proposes two image, encrypting algorithms: a true color image encryption algorithm and a green color image encryption algorithm both based chaotic systems.The first one includes image scrambling algorithm and image substitution algorithm. It uses three dimensions Lorenz sequence, of which on the base, the algorithm obtains three address codes of the images transposition by the sort transformation of three dimensions Lorenz sequence. The true color image matrix is composed of red image matrix, green image matrix, blue image matrix, which is scrambled by three address codes respectively. It generates an assistant key K in the image scrambling algorithm which is useful in the decryption. After that, tricolor matrix is diffused by Logistic chaotic sequence.The second one adopts four types of chaotic maps. Firstly, The image is substituted pixel by pixel, before every pixel diffusing it will automatically choose a chaotic sequence between two sequences according to the true or false for the condition. Secondly, when the image is scrambled there are also two different elective chaotic sequences corresponding with different scrambling algorithms.The simulation results shows that these two image encrypting algorithms have good properties of scrambling and diffusion and a large key space to resist the brute-force attack .The algorithms possess high security.