Research Of The Application Of Cryptography In WaterMark

With the popularization of network communications, many traditional media shift their styles into that of digitalization, which shares a big part in the market, such as the online-selling of MP3 players,Digital Cinemas,pictures,E-books and the like. In the wireless area, with the change of mobile network from the second to the third generation, customers of Mobile Communications will promptly visit the Digital Media websites online, and the Digital Media based on wire or wireless network will be the new custom of information era, but the security of the digital media has now become a bottleneck which restricts the development of informationization.Digital Watermaking is that to insert some digital signal (watermark)—which can be recovered partly or whole from mixed data—into multimedia data(such as pictures,sounds,video signals) and not to make any effect on the source data(we are here just discussing the invisible watermark that is widely concerned),thus the copyrights can be well protected.In general, Digital Watermarking features those as below:Security(the watermark embedded in host data cannot be deleted and can offer a complete copyright proof ),robustness(watermark have resistance to indeliberate or deliberate distortion or process of image ),non-perceptibility (watermark is nonperceptible or transparent for people's sense organ)and fidelity(the content of watermarked media will not depreciate).However, when put in practice, watermark is facing various kinds of problems such as capability, security, authentication and so on, which seriously restrict the process of watermark technology application. Aiming at these problems, this thesis suggested a reliable solution that is also a new outlook on the progress of Digital Watermarking, which is expected to press ahead with the development of Digital Watermarking. Now the structure of thesis is outlined as follow:Chapter 1 is the foreword part, which introduces the background and dynamic of the research, and the job this paper has done included.In Chapter 2, we introduce some basic conceptions about Digital Watermarking, situations for study,application, analysis on some problems existing in Digital Watermarking—which are now severely restricting the application of Digital Watermarking technology and it is necessary to promote new solutions.In Chapter 3, we put forward a new solution depending on cryptography,efficient watermarking algorithm,the theory of error-correcting codes ,and the solution realizes the features of the embedded watermark such as reliability,authentification and considerable capacity. We will explain it in the following chapters in detail.In Chapter 4, we introduce the Cryptography ( including Symmetric Cryptography and Public Key Cryptography ), Message-Digest Algorithm and the theory of error-correcting codes, which play a important role in the security and reliability of Digital Watermarking, and will be illustrated while discussing the watermark system.In Chapter 5, we analyze the limitation of watermark detection system with assistant information, and new viewpoint is put forth called Attack Estimation Model. To realize this model, this thesis listed estimation methods resisting attacks such as signal processing (including compression,filter and so on)and geometrical attack (including zoom,rotation,cropping and so on),which gained a well persuasion when detecting watermark from the watermark system with assistant information.In chapter 6, we implement a watermarking algorithm based on gray image in dwt domain through the Attack Estimation Model mentioned above, which can effectively resist many attacks as it will give concrete data.In the last chapter, we summarize all the above and realizing a high reliable Digital Watermarking system based on gray image, which features secrecy,signature,error-correcting,capability,fidelity,low bit error rate and so on, offers a preferable reference for the watermark detection system with assistant information.