Research On Image Security Of Regions Of Interest Based On Chaos

The 21 st century is an era witnessing rapid development of technology, the digital images, as the most intuitive and vivid carrier, are widely spread in people's life. Therefore, it is urgent to protect the security of the image data. Because image data has its own unique features, so the traditional encryption algorithm cannot meet its security requirement. It is necessary to design some new image encryption algorithms. Because of the excellent characteristics of chaos theory, it brings new opportunity for image encryption. However, in some special commercial areas, only the interest regions(ROI) of users need to be encrypted. Although some ROI encryption algorithms have been proposed, their interest regions are regular, while the actual regions are usually irregular. And almost no one pays attention to it. Since so much resources are needed in the image transmission or storage, it is necessary to compress image. Besides, a message authentication code(MAC) is needed to protect the image integrity.Our main work is listed as below:(1) By researching the mainstream image encryption algorithm, systematic knowledge about image cryptography is obtained. Then the existing image encryption algorithms of ROI are deeply studied to master their merits and demerits. And we carry out a systematic study of the basic theory of the existing construction algorithm of message authentication code. All above work lays solid foundation for further improvement and innovation.(2)The basic theories are thoroughly studied including the chaos theory, image encryption and the chaotic image cryptography. And then we study the image compression code and the basic of MAC.(3)We propose a non-chaining message authentication code algorithm which is based on chaos. The algorithm adopts the parallel realization which avoids the disadvantage existing in the chaining mode. By means of the mechanism of both changeable-parameter and self-synchronization, the keystream establishes a close relation with the algorithm key, the content and the order of each message block. Theoretical analysis and computer simulation indicate that the proposed algorithm can satisfy the performance requirements of MAC. It is a good choice for MAC on parallel computing platform.(4)We propose an image encryption of ROI based on chaos. And the ROI are irregular. Firstly, we encrypt the ROI based on Logistic-Tent system and combine with three S-boxes. Secondly, taking the essential characteristics of the image data into consideration, the partial encrypted image is compressed by Huffman code in order to improve the efficiency of transmission or storage. At last, to ensure the integrity of the message, a MAC is used. The simulation experiment results show that the encryption algorithm has a good security level and can resist various attacks. And the compression method improves the storage and transmission efficiency to some extent. The MAC ensures the integrity of the transmission data.In the end of this thesis, the future direction is also discussed and the conclusions and drawbacks of this thesis are given.