Research On Chaos Scrambling Algorithm Of Image

In the past decades, protection of confidential messages has gained wide attention in the field of information security. Digital image, which developed with the highly computer technology, calls for efficient encryption method. Different from texts, images are characterized by large data volume and strong correlation among pixels, and some conventional encryption methods are not suit for them. Due to chaos'intrinsic properties, such as sensitivity to initial conditions and system parameters, pseudo randomness, broadband spectrum and so on, it has been introduced to image encryption in recent years. Many chaotic image ciphers were proposed.Most of image encryption methods employ two measures: pixel position shuffle and pixel value confusion. But unfortunately, some of them have been proved insecure. There are several reasons for it. Firstly, the cryptosystem is lake of connection among plaintext, which makes it vulnerable to chosen-plaintext attack. Secondly, the solely dependence of pseudo random sequences on the keys, which leads to the adversary to get the information by known-plaintext attack .Thirdly, there exists a number of invalid keys and weak keys. To over these potential drawbacks, a novel image encryption is suggested in this paper.In the first, this paper introduces the current status of image scrambling and the basic knowledge of chaos encryption. Secondly, several image scrambling methods are analyzed and assessed, based on which, a novel method for chaotic image scrambling is presented in this thesis. Two chaotic maps are combined to generate the complex random sequences, and some of the keys generated by plaintext in this scheme. Pixel position shuffling is achieved by combination with layer rotation and circle shifting, and then this process is applied to image encryption. Scrambling assessment and security analysis show the image encryption has good scrambling effect and high security.