The Research For Watermarking Technique

Digital watermarking is the technology that embeds secret information into digital multimedia data such as sound, image or video by using signal processing technology. With the information hiden in multimedia data the author, purchaser or confirmation of the multimedia content can be verified. It is an effective way for protecting the security of digital media data. The research for digital watermarking began in the 1990s, and with the development of Internet and multimedia technology, digital watermarking attracts more and more attention. But there still exist many problems about digital watermarking technology recently. In the paper, we have a discussion about basic theory, application basis and application study of digital watermarking technology. The main content as follows:(1) As to basic theory, summarizes existing research results with our own and expatiates some important basic theory of digital watermarking system design. From the point of mathematics, watermark system can be reviewed from the relation of hi-dimension space and other space, state action and switch. With existing research results, present a new theory model of robust watermark system, and describes the state switch of watermark system using the model. To begin with the model, present a conclusion that the information load of watermark system should consist of data information entropy of perceptible system generated by detector and the amount of information of characteristic space.(2) General form of watermarking signal is discussed in the paper, which gives the generation of pseudo-random sequences, uniformly distributed sequences and random binary sequences of zero bit watermarks in the meaningless watermark and in which the coding principle of multiple symbols and direct information coding of multiple bit watermark are presented.(3) It is important for watermark algorithms to select a characteristic space, and many embedding algorithms are due to the statistics hypothesis that host signals switch to the characteristic space. Therefore, it is necessary that we should pay attention to, designing the characteristic space, the relationship between it and the original carrier, and thus have a basic understanding of the distribution property in possible characteristic watermark space. The generation and distribution property of formal characteristic space, more often used, such as spatial domain, Fourier domain, DCT domain, DWT domain, generalized 2-D discrete transform domain are detailed, and several measuring model designs and property of characteristic space are described.(4)The use of digital watermark technology is the need of development of multimedia and internet technology. The robustness against attack is a main requirement of watermarking design. Not only watermark will confront the normal processing, but many attackers will do research on methods of damaging or false watermark in order to gain guilty benefit. It is meaningful to research on watermarking attack method .In this paper,we classify attacks that watermarking system may suffer and analysis its basic principle,and present strategies according to all attacks.(5) Now, many watermarking algorithms have been presented, but the value methods, attack ways and images are different when they are tested, so it is difficult to have a comparison, which hampers the development of watermarking technology. Besides designing watermarking algorithms, establishing a watermarking value criterion is another important problem .In the paper, that the principle requirement and properties should be considered is discussed when it comes to a watermarking system design. After researching the value ways of watermarking system, we recommend ways to value a watermarking system from two sides. First, recognizing the properties and requirement of watermark and valuing the watermarking system; second, aiming at application and valuing the difference of watermarking systems. Namely, distinguishing condition of watermarking applications, choosing different value guidelin...