Research On Fragile Digital Watermarking Algorithms For Image Authentication

In a networked environment, digital media has the characteristic of being filched, modified, copied and transmitted easily, so preventing digital products being pirated and tampered randomly is an increasing important issue. In order to solve the security problems of multimedia information, the digital watermarking technology has gained extensive concern since it's arisen, and it has already become a research hotspot of international academia at present. Digital watermarking technology is the process that embeds data called watermarking information into a multimedia object, such as images, audio or video, for some purpose. According to the robust degree of watermarking information, digital watermark is divided into fragile watermark and robust watermark.Fragile watermark is a watermarking technology highly sensitive to modification. A fragile watermarking scheme is able to detect any change in the signal, identify where it has been tampered and even possibly renew what the signal was before being modified. Because of its traits, fragile watermark works effectively for multimedia authentication by embedding a watermark into multimedia data without influencing the vision or hearing effect of multimedia. When the content of multimedia is suspected, the extraction of fragile watermark can be used to detect and localize tampers, even present the category of the tamper. According to the ability of identifying tampers, fragile watermark can be divided into two classes: complete fragile watermark and semi-fragile watermark. There are still few people study on fragile watermarking algorithms in China, especially semi-fragile watermarking schemes, this paper is about the research on fragile watermarking algorithms for image content authentication and integrity verification.This paper gives a brief overview of fragile watermark into the context of image authentication at first, then comes to the discussion of current algorithms, including complete fragile watermark and semi-fragile watermark. At last, two effective fragile watermarking algorithms are proposed. One is based on spatial domain and combines with the advantages of fragile watermark and Hash function, which has high concealment, security and ability of authentication, and the other is based on transform domain, which can differentiate common image processing and intentional tampering. Both of them will not effect quantity of the original image obviously and have the ability of detecting tampers and accurately locating where the watermarked image has been tampered.