With the popularity of network communication, many traditional media contents are changing to digital, and will soon occupy a huge market share in e-commerce, such as online sales of mp3, vigorous promotion of digital cinemas, online sales of pictures and e-books. In the wireless field, with the evolution of mobile networks from the second generation to the third generation, mobile users will be able to access digital media content on the Internet conveniently and quickly, and the application of digital media content based on wired or wireless networks will soon become a new tradition in the information age. However, the security of digital media content has become a bottleneck problem that restricts the informatization process.

Although mature cryptography can solve the problem of secure transmission and access control, once the digital media content is decrypted, it can be copied and spread at will, which is the problem of over-distribution of digital media content, which has caused great losses to media content manufacturers and restricted the realization of digital multimedia applications. As a potential solution, digital watermarking has become a hot topic in business and academic circles in recent years. Some international organizations have set up specialized institutions, such as CPT WG (Copyright Protection Technology Working Group) which has been working on the research of video copyright protection based on DVD since 1995, and SDMI (Secure Digital Music Initiative) which has been working on audio copyright protection since 1999, in which digital watermarking is the core technology.

Digital watermarking is adding some digital information (watermark) to multimedia data (such as images, sounds, video signals, etc.). ) without affecting the audio-visual effect of the original data (only the invisible watermark, which people are generally concerned about, is discussed here). These digital information can be partially or completely recovered from the mixed data to realize copyright protection and other functions. Generally speaking, digital watermarking should have the following characteristics: security (the watermark embedded in the host data can not be deleted and can provide complete copyright evidence), robustness (the watermark has certain resistance to intentional or unintentional image manipulation and distortion), invisibility (the watermark should be invisible or transparent to human sensory organs) and fidelity (the original media content value will not be destroyed after adding the watermark).

Watermarking algorithm can identify the owner information embedded in the protected object (such as registered user number, product identification or meaningful words) and extract it when necessary to judge whether the object is protected, and can monitor the propagation, authenticity identification and illegal copy control of protected data, which is actually the basic driving force for the development of watermarking technology. Although copyright protection is the most important driving force for the development of digital watermarking technology, in fact, people also find that digital watermarking has other important applications, such as authenticity identification, secret communication, symbol suggestion and so on. Digital watermarking technology is closely related to ancient information hiding and data encryption technologies, and the development and integration of these technologies provide an essential security means for the future development of information technology.

At present, a series of digital rights management products have appeared at home and abroad, but there are many problems due to the lack of core digital watermarking technology. In 2002, the United States passed a law to provide legal protection for solving the problem of digital copyright. The rise of e-government and e-commerce in China needs to solve the fundamental problems of copyright protection and information security, and digital watermarking is a potential technical solution.

Research Status of Digital Watermarking and Multimedia Information Security

Since 1994, international academic circles have published articles on digital watermarking, and the number of articles has shown a rapid growth trend. Several influential international conferences (such as IEEE ICIP, IEEE ICASSP, ACM Multimedia, etc. ) and some international authoritative magazines (such as IEEE Proceedings of IEEE, Signal Processing, IEEE Journal of Selected Areas on Communications, ACM Communication s, etc. ) have published digital watermarking albums. Up to now, digital watermarking mainly involves image watermarking, video watermarking, audio watermarking, text watermarking and three-dimensional grid data watermarking. Most of the watermarking research and papers focus on image research, because images are the most basic multimedia data, and the development of the Internet provides a large number of direct application requirements for the application of image watermarking. In addition, video watermarking has attracted some researchers. Because video can be regarded as a continuous image sequence in time and space, in a sense, it is very similar to the principle of image watermarking, and many research results of image watermarking can be directly applied to video watermarking. However, there are important differences between them in the order of magnitude of signal processing, especially the real-time problem that video watermarking needs to consider.