A brief introduction to digital watermarking technology

Digital watermarking business card printing | technology is the latest information hiding technology in the world. The so-called digital watermarking technology is to embed copyright information such as number, serial number, text, image mark, etc. into multimedia data to play the role of copyright tracking and copyright protection. In addition, digital watermarking has important application value in authenticity identification, covert communication, sign concealment, electronic identity authentication, etc. The research of digital watermarking technology involves the research fields of informatics, cryptography, mathematics, computer science, pattern recognition and other disciplines, which makes the hidden information more covert and secure, and also has symmetry and error correction. The research indicates that digital watermarking has a huge and broad application prospect, and has attracted widespread attention from academia, industry and the military.
In order to identify the authenticity of paper money in daily life, people usually point the paper money at the light source and find that there is clear image information displayed in the real paper money, which is our familiar "watermark". The watermark technology is adopted because it has its unique characteristics: first, the watermark is an almost invisible mark, which must be placed in a specific environment to be seen, without affecting the use of items; Second, the production and reproduction of the watermark is relatively complex, requiring special processes and materials, and the watermark on the printed matter is difficult to be removed. Therefore, watermarks are often used in important prints, such as checks, certificates, passports, invoices, and so on. For a long time, an important means to determine the authenticity of a print is to check whether it contains watermarks.
With the advent of the digital era, the multimedia digital world is rich and colorful, and digital products affect almost everyone's daily life. How to protect these digital products that are closely related to us, such as copyright protection, information security, data authentication and access control, has become increasingly important and urgent. Drawing on the meaning and function of common watermarking, people use similar concepts to protect multimedia data such as digital images and digital music, thus generating the concept of "digital watermarking". The so-called "digital watermark" is some digital information added to the multimedia data, such as the information of the photographer will be added to the digital photo, the information of the film company will be added to the digital video disc, and so on. Similar to the characteristics of ordinary watermarks, digital watermarks are almost invisible in multimedia data (such as digital photos) and difficult to be destroyed. Therefore, digital watermarking has great potential in today's computer and Internet era.
What can digital watermarking do
The concept and method of digital business card printing | watermark was first proposed to protect the copyright of multimedia jf1dgjk body data. With the development of computers and the Internet, more and more artistic works, inventions or ideas have begun to be expressed in the form of multimedia data, such as photography with digital cameras, watching movies with digital cinemas, listening to music with MP3 players, and drawing with computers. The multimedia data involved in all activities contain a lot of valuable information. Compared with the hard work of the author to create these multimedia data, tampering, forgery, copying and illegal release of original works has become an easy task in the information age. Anyone can easily create a copy of multimedia data. Compared with the original data, the copied multimedia data will not have any quality loss, that is, it can completely "clone" the multimedia data. Therefore, how to protect the "intellectual property" attached to these data is an urgent problem to be solved. Then digital watermarking is just an effective way to solve this kind of "copyright problem". For example, an artist used a seal or signature to identify the author of a work. Today, he can add his name to the work through digital watermarking to complete the identification of copyright. Similarly, audio and video companies can also add the company's name, logo and other information to the published tapes and CDs. In this way, the copyright of multimedia data is protected by tracking the digital watermark information in the multimedia data.
In addition to its application in copyright protection, digital watermarking technology also has great use in the authenticity authentication of documents (printed matter, electronic documents, etc.). For example, for red-headed documents issued by government departments, the traditional method of document authentication is to identify whether the paper, seal or steel seal of the document conforms to the specifications and standards. The disadvantage is that both the paper, seal or steel seal are easy to be forged. In particular, although the government departments have strict regulations on the management and production of seals, there is still a saying in society that "one carrot carves one seal". This shows that the traditional method is extremely imperfect. Using digital watermarking technology can effectively solve this problem. Using digital watermark as the information carrier, adding some information to the red-headed document will make the document not only have a seal or steel seal, but also have imperceptible digital watermark information, which greatly increases the difficulty of document forgery. Adding digital watermark information to the document also means that some information can be written twice in the document. For example, the name of the passport holder is clearly printed in the passport, and can also be hidden as a digital watermark in the avatar. If someone wants to forge a passport by changing the avatar, it is possible to detect that the watermark information hidden in the avatar does not match the name printed on the passport by scanning the passport, so as to find the forged passport.
In addition, digital watermarking is also used for access control and replication control of multimedia data. For example, the secret digital watermark information in the CD data disk can conditionally control who can access the contents of the CD disk. At present, DVD has become popular in the domestic electronic market, and many large companies have begun to study how to apply digital watermarking system to improve the access and copy control of DVD. For example, the DVD player in the hands of consumers is expected to allow unlimited copying of home videos or expired TV programs. The digital watermarks added in home videos do not contain any control marks. The digital watermarks in TV programs are marked as "copy once" or "copy multiple times", while the commercial video programs are marked as "not allowed to copy". The relevant playback devices will identify and play a corresponding role in these digital watermarks. This not only ensures the freedom of private reproduction and exchange of programs for consumers who print business cards, but also effectively controls commercial infringement. At present, all solutions have been formed, but the problem is that the security, effectiveness and simplicity of the solution need to be further tested, and cannot be provided to DVD manufacturers and users for the time being.
Digital watermarking technology can also be applied to secure communication of information. Because it is difficult for people to detect the existence of digital watermarking information in multimedia data, some important information can be hidden in ordinary multimedia data during transmission, thus avoiding the eavesdropping and monitoring of third parties. Foreign newspapers reported that terrorist leader Osama bin Laden used the publicly released digital watermarking technology to hide the instructions to al-Qaida in ordinary digital photos through digital watermarking, and then published them on BBS of some websites. Al-Qaida members extracted the digital watermarking information from digital photos according to agreed rules. Compared with ordinary telephone communication, e-mail communication and encrypted communication, this method is highly covert, difficult to monitor, and difficult to detect.