Analysis And Design Of The Security Of Image Encryption Algorithm

With the development of multimedia technology and network, information security was paid to widely attention. Image encryption technology is the important part of information security, and is also an effective means of image protection. According to the characteristics of image, various image encryption algorithms were proposed. Generally, it is divided into two categories, that is spatial domain and transform domain.In this paper a class of spatial domain image encryption algorithms and a class of transform domain image encryption algorithms are studied. The main work and contribution of this paper includes the following two aspects:1. A class of fractional Fourier transform image encryption algorithm was analyzed.Based on the nature of the fractional Fourier transform, theoretical and experimental analyses are conducted on a class of fractional Fourier transform image encryption algorithm. Through the intermediate results it is found that the algorithm is not sensitive to the algorithm, and also the decrypted image has great distortion. Then the fractional Fourier transform is theoretically analyzed and discussed. Additionally, to achieve the displaying and transmission of cipher text, the RGB image is introduced, however, we found it would result in the distortion of the pixel values in the decrypted image.2. Based on the affine transformation, a chaotic three-dimensional block scrambling image encryption algorithm is proposed.In order to improve the image encryption effect and safety effectively, we propose an improved image encryption algorithm based on the three-dimensional affine transformation. The pixels in image are diffused nonlinearly one by one from top to bottom and from left to right, then the image was divided into several blocks, next the block is randomly selected to encrypt according to the chaotic sequence. Theoretical analysis and simulation results show that the algorithm has a very large key space, faster computing speed, better safety performance.Finally, the full text of the work and research are concluded, and the main advantages and disadvantages of the spatial domain and transform domain image encryption algorithm based image encryption algorithm are noted, also the future research directions of image encryption are pointed.