Research On Image Encryption Algorithms Based On Invertible Maps

Image encryption techniques are widely applied in the fields of social life, economy, medical treatment, weather and military affairs. Invertible maps, one of image encryption algorithm, using the chaotic idea of stretch-and-fold, permute the positions of pixels or pixel values, encrypt the images.This paper studies the invertible map called Line-map, which can permute the image information with high efficiency. Compared with the traditional encryption algotithm of DES, Line-map has higher speed of encryption, and com pared with SCAN language and Baker map, this algorithm has higher efficiency of permutation, larger key space and higher sensitivity of key. And it can encrypt image of arbitrary size.This paper derivates a class of two-dimensional chaotic map algorithm based on the deeply study of the stretch-and-fold process, found the set of two-dimensional invertible map, based on which the algorithm of image encryption is designed. After analysising the process of stretch-and-fold, the optimized program of image encryption is advanced, which enhanced the speed of encryption.This paper advances a class of three-dimensional invertible maps which can be used in image encryption. Representing pixel values with 8 binary digits, the original image can be considered as 8 binary images. Compose the 8 binary images into 1 large binary image and use two-dimensional invertible map to permute the pixel positions of that binary image, then the original image is encrypted. The algorithm has achieved tow goals, which are the permutation of the pixel positions and the confusion of the pixel values.The simulation results show that the proposed encryption approach is valid.