Image Encryption Algorithms Based On Bit-plane Decomposition And Chaotic Theory

With the rapid development of multimedia technology, a growing number of images and videos are generated, transmitted and shared on the Internet. The increasing use of images and videos makes our lives wonderful, but also brings some problems. For example, more and more people would like to save their images in cyberspace, e.g. cloud storage. If these images are stored without technical protection, private and confidential information will be leaked. Therefore, it is necessary to take some measures to protect the images. In view of the needs of this area, researchers have also proposed many methods, in which image encryption is a very effective method. Image encryption can be converted original images into a meaningless encrypted images, which makes it impossible to obtain useful information from the encrypted images, so it can protect the security of the images.In this thesis, two new image encryption algorithms are designed, which enrich the theory and technology of image content security, and have important theoretical significance and good application value. At first, the paper introduces the background and development of image encryption. On the basis, we design two kinds of high performance encryption algorithms based on bit-plane decomposition and Chen’s Hyper-chaos Map Theorem, and the experimental results prove the effectiveness of the algorithm. The specific research contents are as follows:1.I proposed multiple-image encryption with bit-plane decomposition and chaotic mapsThe algorithm can encrypt four gray images at the same time, and get an output image of PNG format, specific steps are as follows. First, the four gray images do bit-plane decomposition and do overlap blocks in each bit-plane respectively, then randomly swap bit-blocks among different bit-planes in the process of scrambling under the control of Henon map, and conducts XOR operation between the scrambled images and secret matrix generated by Logistic map after. Finally the four components are considered as the PNG image of red component, green component, blue component and transparent component, and then get a final result of encryption. Theoretical analysis and experimental results show that the algorithm has good security and robustness.2.I proposed a color image encryption algorithm based on Arnold transform and hyper chaos.In order to make the encryption algorithm sensitive to the changes of the several pixels of the input image, I proposed a color image encryption algorithm based on the combination of SHA- 256 hash function, Arnold transform and hyper chaotic theory. Specifically, the input image is input into SHA-256 first, and the key is constructed with the hash value of the output to control the Chen’s hyper chaotic system. Then, the red component, green component and blue component of color image do vertical splice, and do overlap partition in the stitching matrix. The Arnold transform is made to scramble and encrypt of each block. Next, four secret sequences are generated by using Chen’s hyper chaotic system, do diffusion between the other three sequences of hyper chaotic and three color components of red, green and blue of scrambling image, control the operation sequence of the three color components of red, green and blue with another sequence, the encryption results are finally obtained. Experimental results show that the proposed algorithm is sensitive to the key and the change of the input image, the key space is large enough, and it has better encryption performance.