Image Encryption Algorithms Based On Random Blocking And Chaotic Techniques

Image is one of the most important multimedia elements in the Internet andhas been widely used in the political, economic, defense, and military. Duringthe transmission process, there are urgent needsof reliable technology to protect image security in defense and military applications. Motivated by these needs, researchers have designedmany useful techniques, where image encryption is one of effective solutions. Image encryption, also known as image scrambling, convertsa meaningful image into a chaotic picture.Asattackers cannot get meaningful information from the chaotic image, image content is thus protected.This thesis inverstigates image encryption algorithm with random block strategy and chaos technology, and proposes three effective encryption algorithms. This thesis has meaningful results. In the thesis, recent development of image encryption is firstly reviewed. Then, three algorithms are introduced, i.e., image encryption using pixel swap and random division, image encryption algorithm with block shuffling and chaotic map, multiple image encryption based on chaotic map. Detailed results are as follows.1. I proposed animage encryption algorithm using pixel swap and random divisionIt firstly divides an input image into four overlapping blocks by choosing a random rectangle, and then randomly selects an encryption order of these blocks. Finally, it scrambles each block by pixel swap and writes the corresponding encrypted block to the image. Theoretical analysis and experiments are conducted to show the effectiveness, security, and robustness of the proposed algorithm. It is faster and more secure than Arnold transformation. It has no size limitation and can be applied to any size images.2.1proposed an efficient image encryption algorithm with block shuffling and chaotic mapThe proposed algorithm divides an input image into overlapping blocks, shuffles image blocks to make initial encryption, exploits a chaotic map and Arnold transform to generate secret matrices, and achieves final encryption by conducting exclusive OR operations between corresponding elements of each block and a random secret matrix. Experimental results show that the proposed algorithm has a fast speed and good security, and outperforms three existing algorithms.3.1proposed anencryption algorithm for multiple images based on chaotic mapFor multi-image encryption, I developed an algorithm for encrypting three images each time. The proposed algorithm views three gray imageswith the same size as the three components of acolor image. Firstly, itgenerates a sequence of secure data through chaotic map. Then, it makesinitial encryption by XOR operations between each gray image and the sequence data. Next,the three encryptedimages are used to form a large size image, which is further scrambled by pixel swappingtechnology. The scambling operation can make encrypted image pixels randomly distributed inthe three components of the color image. Finally, the three encryptedimages are combined into a color image. Experimental results show that the proposed algorithm can convertthree gray images into a color secret image,the file size of the encrypted image is smaller than the total size of the original three gray images, and performance of the proposed algorithm is superior to the traditional Arnold transform.