Analyze digital watermarking technology (2)
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The tampering hint watermark is a fragile watermark that aims to identify the integrity and authenticity of the host signal. The purpose of the concealed identification watermark is to hide important annotations of confidential data and limit the use of illegal users.
According to the hidden position of the digital watermark, it can be divided into time (empty) domain, frequency domain, time/frequency domain and time/scale domain digital watermark. The time (empty) domain digital watermark is to superimpose the watermark information directly in the signal space. The frequency domain, time/frequency domain and time/scale domain digital watermark are hidden watermarks in the DCT transform domain, the time/frequency transform domain and the wavelet transform domain, respectively. .
According to the media attached to the watermark, it can be divided into image, audio, video, text and grid watermark for 3D mesh model. With the development of digital technology, more kinds of digital media will appear, and corresponding watermarking technology will also be produced.
The application prospect of digital watermark
In recent years, digital watermarking technology has continued to expand into new application areas. The application in printing anti-counterfeiting is a new topic at present. According to relevant information, about 500,000 people in the United States suffer from fake documents or fake documents each year, directly or indirectly losing about 750 million US dollars. The traditional anti-counterfeiting watermarks make the lawless elements available due to the imperfect technology. Digital watermarking technology takes a different approach and uses digital signal processing related techniques to embed trace data in media data works. After the watermarking technology is embedded, the original media data has not changed, nor does it affect the normal use of the original data. People can't perceive watermarks from the surface, only dedicated detectors or software can detect them. It has a wide range of uses in printing and packaging of various products, trademarks, invoices, checks, security of securities, and copyright protection of digital media.
At present, the digital watermarking technology for copyright protection has entered the preliminary practical stage. IBM provides digital watermarking in its "Digital Library" software, and Adobe has integrated Digimarc's digital watermarking plug-in into its famous Photoshop software. However, digital watermark products on the market are still immature in technology and can be easily destroyed or cracked. There is still a long way to go before real use.
According to official US reports, only $40 million of counterfeit banknotes intercepted in 1997 were made up of 19% of water counterfeit banknotes made with high-precision color printers, which is 9.05 times that of 1995. At present, the United States, Japan and the Netherlands have begun to study digital watermarking technology for ticket anti-counterfeiting. The MIT Media Lab, commissioned by the US Treasury Department, has begun to study the inclusion of unique, invisible digital watermarks in each image output from color printers and copiers. The presence or absence of watermarks can be determined from scanned tickets when needed. , quickly know the truth.
Digimarc of the United States pioneered the world's first commercial digital watermarking software, and then integrated the software into Adobe Photoshop and Corel as a plug-in. Draw image processing software. Subsequently, a series of digital watermark products were launched, and its "Mediabridge" technology opened up a new way to access the Internet by hiding invisible digital watermarks in magazine advertisements, product packaging, catalogs and even various types of notes. Users only need to put these traditional media on the webcam (Web) Before the camera, media bridge technology can directly take the user to the network site associated with the printed image content, eliminating the need for the user to tap the keyboard and click the mouse. For example, if the magazine with advertisements is placed in front of the network camera, the media bridge technology will display the information of the advertisement company's homepage and the products in the advertisement on the computer, and avoid the process of searching on the Internet by using the browser. By adding confidential features to product packaging design, Brand Protection technology can identify products at any point in the product distribution chain, identify original and duplicated versions, prevent product counterfeiting, and track products through the supply chain. Circulation. The "Secure Document" technology adds Digimarc's watermark features to important documents to confirm the authenticity of the document, prevent unauthorized copying of the document and confirm the authorized application of the original document.
In the process of traditional business-e-commerce conversion, there will be a large number of excessive electronic documents, such as scanned images of various paper bills. Even after the network security technology is mature, various electronic bills also need some non-password authentication. the way. Digital watermarking technology can provide invisible certification marks for various tickets, which greatly increases the difficulty of forgery.
Domestic research on digital watermarking
In China, researchers in relevant departments are stepping up research on digital watermark printing anti-counterfeiting technology. For example, Dalian University of Technology has achieved fruitful research results in digital watermark printing anti-counterfeiting technology. The technology can realize digital watermarking in printed images, and can automatically detect digital watermarks in printed images through scanners and special software. This technology is suitable for various models of printers and scanners.
The development of digital technology and the Internet is changing the carrier and means of cultural communication. It is not enough to complete data encryption, authentication and protection by traditional cryptography. Digital watermarking has an irreplaceable role in copyright identification, network security, hidden security, tampering tips, data security, etc. It will bring huge commercial profits for commercial, financial, military and personal consumption.
It is believed that digital watermarking will play a huge role in social and economic development and can generate considerable economic benefits. It is imperative to develop independent core software and products as soon as possible so that China can face relevant technologies in the opportunities and challenges of joining the WTO. The research, application and industrialization process are in an invincible position.