Safe Official Documents System Based On Digital Watermark

The digital watermark technology is one kind of effective digital product copyright protection and the data security maintenance technology which appears in the recent ten years. It has overcome the problem that content encrypted in the traditional cryptology technology is no longer safe after it has been deciphered and breaked through,thus as the intellectual property rights protection and the digital multimedia anti-counterfeit effective method,digital watermark technology is obtaining extensive research and the application.This thesis mainly discussed digital image watermark technology about safe official documents system,put forth a robust watermark algorithm based on seal image,realized the corresponding hardware reader,on this basis,proposed a safety reliability official documents system solution combining PKI technology,and discussed certain issues in the realize process.This thesis describes relevant theories of digital watermark and cryptography at first, emphasizely analyses on robust digital image watermark technology,indroduces main stream robust digital image watermark algorithm at present,and analyses and estimates the algorithms that have been researched by author among them,on this basis, proposes a robust blind watermark algorithm in spatial domian based on seal image. This paper uses a large number of experiments to test feasibility and accuracy of this algorithm, the experimental result indicates the watermark obtains better robustness against print/scan process,rotates, noise ,JPEG compresses and some other common image process (such as low-pass Gassian filter,translation,sharppening tc.),also it has good invisiblenes,detecets without origin image, can commonly apply to copyright protection and data forgery prevention in official documents system.Image watermark technology is compactly associated with image process technology. With regard to our system,the effection of image pre-process has directly impact to accuracy and speed of watermark detection,so this text has detailedly designed the image process with a large number of experiments,and gained good result.The hardware reader is key link in the whole system,also it is important and difficult point in system development.Therefore Author has done much work on scheme design, material selection,hardware relization and Improvement.This thesis will discuss it by modules and summarize the work process of hardware system.At last,combining the technology above,we present a safety official documents system solution that has fully guaranteed the confidentiality,integrity and non-repudiation in E-commerce trade-off.