The Design Of The Feedback Shift Register Based On Chaos And It's Application On Image Encryption

With the rapid development and application of modern communication and computer network techniques, digital image information of network information has became more and more important, image security comes to be an increasing important problem. Because there are many characteristics of image which are different from text and voice information, such as large data, high redundancy and self-similarity and so on, traditional encryption methods are not suitable to image information. In recent years a variety of special schemes for image encryption have been proposed in accordance with the characteristics of digital image by many researchers. The image algorithms based on chaos show good encryption performance in practice. But there are also problems that the short period of chaotic sequences in the restricted computer precision and complex chaotic sequences' chaotic characteristic needs to be further studied. In fact, the image is inevitably translated into binary sequence in transmission, so, encrypted by binary secret key can improve efficiency, but the traditional generator of binary secret key, called line feedback shift register, is incapable of meeting the need of image encryption.First of all, this paper summarizes the basic knowledge of chaos from several aspects, and briefly introduces the cryptography and encrpytion tachniques of digital image, especially the structure of line feedback shift register. Next, this paper mainly dose the following tasks, firstly , integrating the excellent cryptographical character of chaos with the structure of traditional line feedback shift register, a new design of the generator for binary secret key-feedback shift register based on chaos(CFSR) is presented; secondly, the characters of the binary secret key which include key space, randomicity, sensitivity, relativity, complexity are analysed; thirdly, image encryption algorithm based on the binary sequences generated by this design is proposed, which shuffles the positions and changes the grey values of the image pixels; fourthly, we finish the emulational experiments and security analyses, which indicate that this encryption system has a favorable cryptological characters, such as large key space, a quite good sensitivity to the secret key and the original image, resistibility of statistical and difference attack.