Research On Chaotic Digital Image Encryption Algorithm Based On Scrambling, Substitution And Diffusion Operation

The 21 st century declares the arrival of the era of information network, the rapid development of smart cellphone and other various storage devices and Internet technology, bring rich and colorful life on the Internet, but at the same time, it also brings the potential threat to the people. Among them, the security issues of picture which contains largest amount of information has become the focus of the problem.Therefore, the image encryption technology, as one of the important ways to protect the security of image, has also attracted attention widely. Chaos theory, because it has similar features of cryptography such as sensitive to initial state, unstable orbits,ergodic, and so on, it is used in the image encryption widely. After dozens of years of sedimentation, the image encryption based on chaos has been developed greatly.However, the image information security problems still exist in the current rapid development of science and technology. Therefore, to deal with the need of reality, it is very important to further research on the image encryption technology based on chaos. Therefore, in order to cater for the need of reality, it has a very important significance for further research on the image encryption technology based on chaos.At present, there are so many image encryption algorithms which based on airspace.Most of them look very complicated, however, there is little common design for comprehensive utilization of scrambling, substitution and diffusion structure in these algorithms. Therefore, it is necessary to combine image scrambling, substitution,diffusion structure based on chaos in the design of encryption algorithm.First, This paper outlines the research background and significance, and then summarizes the existing problems of image encryption at the basis of chaotic. Next, it introduces the relevant knowledge of cryptography and digital image. It also stated the basic theory of chaos, such as the definition of chaos, judging criteria,characteristics, etc.. Then on the basis of these theories, this paper gives a simple analysis of the chaotic cryptography and image encryption algorithm. It also summarizes the important step of chaotic encryption algorithm and introduces the basic encryption effect analysis method. After that, the structure of the chaotic image encryption algorithm is summarized and a large number of experiments are carried out.Finally, on the basis of all above, an improved image encryption algorithm based on chaotic scrambling and diffusion is proposed, tested, and analyzed.The simulation experimental results show that the proposed algorithm extended the key spaceeffectively, and have a strong dependence on the initial key values. It improves the ability of the image encryption algorithm resistance ability to exhaustive attack,statistical attack and differential attack effectively.