Analysis And Design Of Image Encryption Algorithms Based On Digitalized Chaos

With the development of computing and network technologies, multimedia information is used in many fields more widely. As a result, the security of multimedia information becomes increasingly important and cryptography is considered as the primary method to resolve it. Contrast to common texts, multimedia contents usually contain huge volume of data, which makes their encryption become very slow and power-consuming with the traditional cryptosystem. Furthermore, the digital image information is the main content of multimedia information and the applications of it can spread to other multimedia formats effectively. Therefore, the main research of this dissertation is based on digital image encryption. During these years, as the merits of chaos are suitable for image encryption, the image encryption based on chaos which comes from nonlinear science is studied widely. This paper focuses on analyzing and designing the novel image encryption schemes based on chaos, under the condition that those approaches satisfy the security requirements. The main contents of this paper are listed as follows.①Chaos theory and chaotic image encryption algorithms are introduced. The chaos theory is described from multiple fields in details. At the same time, the concept of the art in modern cryptography is stated. Then, the relationship between them is compared. Finally, same chaotic image encryption methods and algorithms are recommended, respectively.②The image cryptosystem proposed by Sun Fu-Yan et al. is improved effectively. First, a generalized description of Sun Fu-Yan's cryptosystem is given. Then, three inherent weaknesses of their algorithm are presented. Based on these analyses, an improved image encryption scheme is proposed, and some tests about security and effect are carried out.③A multi-dimensional matrix map named Z-matrix map is proposed. Compared with some maps which are used for image encryption, it is found that the proposed Z-matrix map has some favorable characters including long period and different period with different dimension. Therefore, this matrix map is more suitable for image encryption.④Based on the proposed Z-matrix map, two different image encryption schemes including confidentiality encryption and degradation encryption are presented. For the confidentiality encryption, a new image encryption algorithm based on Z-matrix map and PDP model is introduced. Some merits of this scheme is also analyzed and tested; For the degradation encryption, two different templates (random selective template and entropy dividing) are used in degradation scheme. The theory analysis and experimental tests demonstrate the prospects for practical application.Finally, the dissertation is concluded. Some problems as well as further work are also given.