Research On Chaotic Encryption Based On Dual Scrambling Of Image Pixel Positions And Values

Digital image has already become one of the most important expression forms of information due to the advantages such as visual, intuitive performances and dramatic. However, digital image has many security issues at the process of transmission. Consequently, the security of image information is becoming the focus on the public and to study image encryption is of great significance. Digital image has huge amount of information and high redundancy, as a result, the traditional encryption methods have difficulties to encrypt digital image. In recent years, enormous image encryption algorithms based on image's characteristics have been proposed, whereas the efficiency and security should be improved further.As a type of nonlinear dynamic systems, chaotic system is a cryptosystem naturally result from the extremely sensitive to the parameters and initial condition, unpredictability and pseudorandom. The image encryption algorithm will be of high security and effectively if chaotic system is used in image encryption.Based on chaotic characteristics, the image encryption has been researched further in this dissertation. The contributions of this dissertation can be summarized as follows:1,A digital image encryption algorithm, dual scrambling based on chaos of pixel positions and pixel values, is presented. The dissertation improves the traditional image encryption algorithm based on chaos, and then presents an image encryption algorithm via combining the image encryption technique based on chaos with the image scrambling encryption method.The algorithm uses Logistic chaotic sequences to scramble digital image's pixel positions and then scramble digital image's pixel values by using Logistic chaotic sequences again. Consequently, dual scrambling of pixel position and value based on chaos is completed.2,A type of chaotic system with variable parameter is proposed..The basic characteristics are researched deeply and the objective requirements which the image encryption demands from the chaotic system are discussed. For advancing the complexity and pseudo-randomness of chaotic system, a type of variable parameter chaotic system, whose fractal parameter is variable, is presented, via analyzing and improving the ordinary classical chaotic systems. 3,A class of dual scrambling image encryption algorithm based on variable parameter chaotic system is proposed.The dissertation researches the dual scrambling image encryption algorithm further, and then proposes a class of dual scrambling image encryption algorithm based on variable parameter chaotic system. Instead of traditional chaotic system, the encryption algorithm uses the variable parameter chaotic system to scramble pixel positions and pixel values.Experimental results show that the effect of the proposed encryption algorithm, dual scrambling based on chaos of pixel position and pixel value, is perfect and it outperforms the traditional image encryption algorithm based on Logistic chaotic sequences in digital image pixel dots. Moreover, the variable parameter chaotic system has better chaotic characters than several classical chaotic systems. Besides, the algorithm, which is based on the dual scrambling and the variable parameter chaotic system, has stronger resistance against attacks such as exhaustion attack, count attack, cropping attack, noise attack, which is consequently of higher security and efficiency.