A Study Of Authentication Algorithm For Digital Images

With the rapid development of modern science technology and the great abundance of the information resource, humanity's ability in information processing is extended and our human has entered the Digital Era. Daily life is becoming more and more colorful with the exchange of multimedia information. However, it's inevitable that problems such as illegal spread, malicious manipulation or piracy of multimedia are presented. Multimedia information security problem is one of the focuses in recent year.Multimedia authentication techniques are the important ways to look after the security of the multimedia information. They are usually designed based on two kinds of tools: digital signature or digital watermarking. The purpose of this dissertation is to find a way to authenticate images and to recover the tampered images by using digital watermarking.In this thesis, we first introduce the general theories to digital watermarking and multimedia authentication technology. It contains the characteristics, classifications, applications and system framework of digital watermarking techniques, and analyzes several classical image authentication algorithm. It also states the manner, method, requirement and system framework of multimedia authentication techniques. On the basis of these conclusions, we present a novel image authentication algorithm based on digital watermarking. The novelty of this algorithm is that we embed two kinds of digital watermarks into the image to detect and recover it: location watermarking and restoration watermarking. By detecting the watermarks, it can not only detect the location of any minute changes in images but also restore the tampered image data. Experimental results show that it is an effective algorithm. In this paper, we also design and develop a digital image authentication and recovery prototype system based on the algorithm that we present. The system can show the whole process how to authenticate an image use the method perfectly.