The Research Of Colour Image Encryption Algorithm Based On Chaotic Theory

With the rapid development of network technology, a large number of digital image information is transmitted on the network by the different form.It brings us not only the convenient way of obtain information, but also the danger of information security: sensitive information may be easily stolen, tampered or illegal duplicated and spreading, etc. How to protect information security has become a widespread concernd guestion by public. Due to the chaotic dynamical system has the characteristic of pseudo-random, determinism and extremely sensitive to the initial conditions and parameters of the system, taking it combinat with the technologies of digital image encryption can make up a very extremely image encryption system. This article has more extensive and in-depth study on the application of chaotic theory in digital image encryption.Firstly, through the description of chaos rudimental theory, cryptology elements and image encryption on chaostic theory, we analyzed the advantage of chaos using on cryptology. It reveals the purpose and significance of the subject.Secondly, On the basis of analysis in the existing chaotic encryption method, for most of the existing encryption algorithm are encrypted to gray image, propossing an enoryption algorithm of colour image based on generalized Arnold transformation. This algorithm promotes Arnold transformation, and using the sequence generated by the Lorenz chaotic system to control parameters of generalized Arnold transformation. It greatly enhances the safety of algorithm. The algorithm has a large key space, good key sensitivity and good image restoration.Finally, in view of low-dimensional chaotic system have a small key space, and the encryption algorithm using single chaotic system is not a high security encryption algorithm, propossing an enoryption algorithm of colour image based on complex chaotic systems.The algorithm using pre-treatmented image as the initial conditions of Lorenz systems to product disturbed matrix. Adopting the chaotic seguence of Lorenz system to changed the pixel values of the color images. It ensures sensitivity of encryption algorithm, and enhances the resistibility for attack. The algorithm has good security, it is the same with the image encryption which has large data and high real-time requirement.