Study Of Digital Forensics Based On Image Content

Digital Forensics,as a part of information security, which identifies the authenticity,integrity and origin of the digital images without embedding watermarks beforehand. In this paper, the present research progress and the prospective development are analyzed and summarized systematically. This dissertaion conveyed research on Digital image forensics in the five aspects: the theoretical model of the digital image forensics,the authenticity forensics against tempering means,the theory model of digital image forensic steganalysis,the integrity forensics aimed at stegnographic methods and the origin identification by means of the natural characteristics of digital images. The main contributions of this dissertation are recapitulated as follows.About the theory model of digital forensicsFirstly, the theoretical model and the system frame are studied. Based on the summarization of the present research, the future system frame of the blind digital image forensics is proposed. According to the natural characteristics of digital image, the principles of constructing the standard testing database of sample images are also put forward. Moreover, the extensible topology structure is set up and the size of the database needed theoretically is calculated statistically.About the authenticity forensics against tempering meansAiming at detecting the common tempering measure, the new forensic methods for the detection of the copy-move forgery in one image,JPEG re-compressing,re-sampling caused by extending,rotating,resizing etc., and blurring process are proposed to study the authenticity of the digital image.About the theory model of digital image forensic steganalysisBased on the introduction of the concept and the theory structure of digital image forensic steganalysis, the present research progress is summarized and the prospective developing direction is also put forward briefly.About the integrity forensics aimed at stegnographic methodsThe integrity forensics of digital images corresponding to variable stegnographic methods is investigated fourthly. The specific steganalytic means to detecting the SES,adaptive stegnography and MB1 used in BMP,GIF and JPEG images are proposed by the way of integrity forensics. Through these technologies, the universal steganalysis used for detecting the existence of the covert communication and the specific steganalysis used for estimating the length of the secret message under the situation that the embedding method is known are achieved.About the origin identification by means of the natural characteristics of digital imagesBased on the summarization of the present research progress on natural features of the images from variable origins such as digital camera,scanner,electrograph etc., a new digital image feature by means of the digital image run-length statistical rules are put forward. Moreover, using this method, the contrastive run-length statistical rules between different images,text and image data,pseudo sequence and image data are analyzed qualitatively.Finally, the paper is summarized and the prospective developing direction of the digital forensics is also put forward.