The Codingalgorithm For Image Encryption And Compression Based On Chaos And Fractal

With the development of modern information science, technology and Internet applications, a large number of digital information in various forms has been transmitted quickly and conveniently through the network moment by moment. As a reault, the requirements of information security and data transmission are also increasing. In this paper, based on the knowledge of chaotic dynamics and fractal theory, several application methods about image encryption and image compression are proposed.Chaotic system has servial excellent cryptographic properties, such as randomness, the sensitivity of the initial value and the noise-like broadband frequency spectrum. Using the chaos theory to implement secret communication has been one of the most active researching areas. In this paper a new chaotic cryptosystem based on discrete skew tent map was proposed by making use of a mixed chaotic sequences, which are produced by combining the dynamic encryption parameter and a simple single - dimensional chaotic map .Using Matlab simulation to achieve, the results compare with the traditional skew tent map sequence encryption algorithm, it greatly enhances the security of image encryption in the image without distortion.Fractal image compression is a new image coding method which developed in recent years. It has a high theoretical and application value because of its desirable properties such as fast decoding, resolution independence of decoded image and high compression ratio.For its shortage of coding speed, this paper proposes a fast fractal image compression coding algorithm on DCT. By sorting the eigenvalues of sub-block and father block, it makes the sub-block search only those parent blocks that satisfies the certain conditions, thereby reducing the complexity of the search and speed up the search speed. In order to improve the quality of reconstructed images, this algorithm implements the fractal image coding and then carries on DCT on all of the grey error blocks. Combining the avantage of the two aglorighms, we can get a good coding result.