Image Encryption Algorithms Based On Chaos And Circular Shift

More and more people use the pictures to record details in daily life and work. Therefore, its security has become increasingly important. Because the image has the characteristic of large amount of information and the strong correlation between adjacent pixels. Some traditional encryption algorithms can’t suit for image encryption. Chaos system is sensitive to initial conditions and has the pseudo random, So the Chaos system is widely used in image encryption algorithms. All the image encryption algorithms in this paper which combined with the plain text used one-time pad algorithms in order to resist the known plaintext attacks and chosen plaintext attacks. Some work has been made as follows:(1) An image alternative encryption algorithm based on Logistic map is proposed. The algorithm proposed a new image scrambling based on 0,1 sequence. The 0,1 sequence which is formed by the plain text and a Logistic sequence. The image scrambling method is used in the process of the image alternative encryption by itself. So the image scrambling and diffusion are conducted simultaneously.(2) An image encryption algorithm based on many Logistic chaotic maps is proposed. The 0,1 sequence which is generated by the first Logistic map is used for image scrambling. The second Logistic map is used for the image diffusion. Every pixel point in the cipher image combines with its own the positional information and information of the last pixel point in the cipher image is generated in the stage of image diffusion. A matrix is generated by the third Logistic map in order to enlarge the key space.(3) An image encryption algorithm based on nonlinear equation and circular shift is proposed. A group of nonlinear equations is used for the image scrambling. The technology of circular shift and Chaos system is used for the image diffusion. In the process of image diffusion, the pixel points in the odd lines and their corresponding odd columns are encrypted simultaneously. The pixel points in the even lines and their corresponding even columns are encrypted simultaneously. The encryption order has not been seen in other papers before.(4) An image encryption algorithm based on circular shift is proposed. In the process of image scrambling, a chaotic sequence is used for scanning the image by line and another chaotic sequence is used for scanning the image by column. The technology of circular shift and Chaos system is used for the image diffusion. The algorithm in the second chapter uses the strategy of the block encryption. So it has the fast speed and is fit for gray image which has the even columns.The algorithm in the third chapter is fit for any gray image and color image. It has the biggest key space in order for the best security. The algorithm in the fourth chapter which has the novel encryption order is fit for a square image. The algorithm in the fifth chapter is fit for the small gray images which has the tricky steps and high security. Matlab software is taken as the platform, with Lena, Pepper and Bird figure for material on the computer. According to the simulated and analyzed, The experimental results show that the proposed algorithms in this paper have the good encryption effect.