Research On Compressed Digital Image Encryption Technology Based On TD-ERCS Chaotic System

With the rapid development of the multimedia and information processing technology, multimedia communications become an important means of information exchange increasingly. Because of its features that rich in the information and intuitive, Digital Image has become an indispensable medium for information storage and dissemination. With the increasing popularity of computer network technology, more and more digital images have been transmitted on the Internet. Then the image data of the security issues are increasingly highlighted. Since some image informations may be related to national security, military secrets, commercial secrets or personal privacy, it will be very serious that malicious attackers browse, copy and spread the images in the dissemination process of the network illegally. Therefore, ensuring the security of the image infomation becomes a hot issue of the international academic research.Studing image encryption is of profound theoretical and practical significance. This article focuses on the research of compressed domain image encryption technology based on chaotic system, including digital image compression coding, chaotic sequence generation, and chaotic encryption applied to the compressed image.Firstly, the basic theory of cryptography is briefly introduced in this paper, then the basic knowledge of chaos theory such as definition and characteristic is systematically introduced, several common chaotic maps are also discussed. Secondly, the overview of basic knowledge about the digital image coding and image encryption technology is given. Then, a compressed domain digital image encryption algorithm based on TD-ERCS (Tangent-Delay Ellipse Reflecting Cavity-map System) is put forward. In this algorithm, method based on discrete cosine transform (DCT) encoding of JPEG image compression standard is adapted to compress the digital image. In the chaotic encryption process the TD-ERCS chaotic system is used to generate pseudo-random number sequence which is applied to spatial scrambling and frequency transformation of the compressed image.Finally, simulation experiment for the proposed encryption algorithm is made, and the proposed scheme's key space, key sensitivity, plain-text image sensitivity, plain histogram, cipher histogram and so on are analyzed. Experimental results show that the proposed algorithm can achieve image processing for efficiency and safety requirements, and is a practical digital image encryption scheme. The end of the article is is a summary of research, and future research directions are suggested.