Design And Implement Of Document Watermarking Algorithm Based On Space Encoding

In recent years, with the fast development of communication technology in computer network, both the new chances and challenges have been created for protecting the digital information. With the superiority in the field of the copyright protection in multimedia and the authentication of media, the technology of digital watermarking is becoming one of the hot-spots. Achievements of digital watermarking have been concentrated on images, audio and video because they have been paid attention to. In fact, the paper document is more valuable than other digital medias. To some extent, the study of the document watermarking can preserve the intellectual property effectively.Now, the research on watermarking focuses on images and video, people pay little attention to document watermarking. What's more, there are many problems such as vulnerability, low capacity, and weak invisibility in the document watermarking. The main causes are listed in the following: watermarking is attached to text content, so the change of document may destroy the watermarking;changing text code may lead to the change of text content and the decrease of redundancies of text. Basing on the theory of digital watermarking, including the algorithm of digital watermarking, the vision model of human eyes, cryptology, digital signature, we can improve the invisibility and the security of the document watermarking through combining these all together for authentication. This paper puts forward new model of watermarking layer and corresponding method designed from bottom to top. We design a new layout strategy, and an algorithm of document watermarking that based on the space encoding. The author finds a new model of inserting watermarking by analyzing the document structure of the Microsoft Word. The new model improves all the performances of the document watermarking effectively, especially in the capacity.Specially aiming at the three indexes: invisibility, robustness, and capacity, the author has carried out a great number of experiments, including embedding, extracting, and attacking the watermark, which use the watermarking software that based on Delphi. The new digital watermarking algorithm was verified that it has excellent invisibility, strong robustness, and large capacity.The document watermarking algorithm in this paper is a useful way to solve the problems of the existing watermarking mechanism. It is a beneficial attempt to solve the problem of the document's security in the Internet. It is useful in researchingalgorithm of digital watermarking, and it's helpful for developments of document watermarking.