The value, significance and advantages of digital watermark ~ Who can help

Ignacio

December 2, 2022 at 4:09 am

The last line of defense of digital copyright — digital watermark

■ Zhu Xingshan

------------------------------------------------------------------------------------ ------------------------------------------------ ---------------

D digital watermark is regarded as the "last line of defense" that resist multimedia piracy. Therefore, from the watermark technology itself, it has extensive application prospects and huge economic value.

The development in today's society has presented two obvious characteristics: digital and networked. Digitalization refers to the form of information storage, which is characterized by large information storage, easy to edit and copy; network refers to the form of information transmission, which has the advantages of fast speed and wide distribution. Over the past 10 years, the use and distribution of digital media information have been explosive. People can quickly and conveniently obtain digital information and online services through the Internet. But at the same time, piracy has become easier, and the management and protection of digital content has become an urgent need to solve the industry.

D digital information is essentially different from analog information. The traditional solution for protecting the simulation information no longer works for digital information. Coupled with some general -purpose processors, such as PCs, it makes them easy to break through hardware -based media protection solutions. In fact, the encryption technology that is usually used can only protect the content of the media during the transmission process of information from the sender to the recipient's transmission. After the information is received, all data in the process of reuse is transparent to users and no longer be protected. In this situation, digital watermarks, as a potential solution, have been favored by many scholars.

The basic idea of digital watermark is in the original media data, such as audio, video, images, etc., hidden add information with certain significance as a mark. Transmitted. At the receiving end, the computer watermark signal is extracted for various purposes. Possible applications include digital signatures, digital fingerprints, broadcast surveillance, content certification, copy control, and secret communication. Digital watermarks are regarded as the "last line of defense" to resist multimedia piracy. Therefore, from the watermark technology itself, it has extensive application prospects and huge economic value.
The general framework of digital watermark

The basic framework of digital watermark

A typical watermark system consists of an embedded and detector, as shown in the figure. The embedded (formula (1)) generates a real watermark signal based on the information m to be transmitted, and hides it to the media data X to obtain the signal Y of the aqueous marks. For safety reasons, the generation of watermark signals usually depends on key K.

y may have certain information loss after the transmission network, and the end of the detector becomes Y ′. This passage is uncontrollable and unknown for the embedded and detector. It can be called It is an attack channel. The detector is responsible for extracting information from Y ′, such as formula (2). For the detection of the host signal, we are called a blind watermark, and on the contrary, the non-blind watermark (Non-Blind). Due to the needs of application, blind watermarks have always been the mainstream of research.

The characteristics of digital watermark

Although the idea of digital watermark is simple, to achieve the purpose of application, it is necessary to meet certain performance indicators. The relatively important characteristics include:

● Fidelity: It is often called invisible, which refers to the degree of changes in the quality of the host signal signal in the watermark embedding. Given that the host signal is mostly multimedia data for people to watch, the watermark should have high preservation, and at the same time increase the safety of the watermark itself.

● Robbing (): refers to the survivability of watermarks in the media data editing and processing process. Various operations of media data will cause the host signal information loss, thereby destroying watermark integrity, such as compression, filtering, noise, shear, zooming, and rotation, including some malicious attacks.

● Data Payload: refers to the amount of information that can be passed by the watermark signal under a certain preservation. The actual application requires that watermarks can send multiple digits of information.

● Safety: In the application, there are always people who must embed, detect or remove watermarks, and must limit others to do the same operation. This is the safety of watermarks. To achieve safety, important information must be kept confidential, such as usually using a key to generate watermarks.

● Error alarm: refers to the probability of error detection in the host signal without watermark. Obviously, the system can be used safely and reliably if the wrong alarm rate is low enough.

The design of watermarks must be selected around the above performance indicators. Some characteristics are incompatible, such as invisibleness, robustness, and information capacity, weighing considerations.

This from the preservation of watermarks divided it into visible watermarks and invisible watermarks. As the name suggests, watermarks can be detected by human eye. The robbles of the watermark can be divided into Robust and fragile watermarks. Raising watermarks can resist a certain degree of signal processing; and the fragile watermark is characterized by any change in media information to destroy the integrity of the watermark and make the watermark detection. Therefore, robust watermarks are trying to ensure the integrity of watermark information, and fragile watermarks are trying to ensure the integrity of media information, and they have their own use. There is also a kind of watermark agency between the two, called semi -fragile watermark, which is fragile for some operational robust operations, but the modification operation of important data features is fragile.

The progress of digital watermark technology

In the early days, watermark designers paid attention to how to hide information in digital media and not discovered. To this end, the watermark information is placed in the lowest bit of binary data, and such schemes are collectively referred to as the lowest effective bit modulation. Obviously, the at least effective information is easy to lose in the commonly used signal processing, and the robustness of the watermark is poor.

St afterwards, a large number of watermark algorithms in the space domain appeared. Watermark embedding is no longer a single point to modify the spatial area, but the characteristics of a point set or a region, such as mean, variance, and amazing. Patchwork is a typical representative of this method. It randomly selects N -pairing pixels (AI, BI) in the image space, and adds D of the pixel AI to D, BI's brightness is reduced. As a result, the average value difference between the two groups of pixels is modified to 2D. This average and statistical hypothetical test theory can determine whether the watermark is. However, Patchwork can embed the amount of information and is sensitive to geometric transformation. The common problem of the waterprint algorithm in the space domain is the poor robustness of the image processing.

Compared with the space domain, spectrum is a good signal description method. Low -frequency components represent the smooth part of the signal, which is the main information; the high -frequency component represents the jitter of the signal, which is the edge information. The analysis and processing of the signal are very intuitive and convenient. The expansion watermark introduces the theory of spreading communication, which is a very popular watermark design idea in the frequency domain. It regards digital media as a channel. It usually has a wider bandwidth. The watermark signal to be embedded as the transmitting signal, which is narrow. You can first expand the watermark to multiple frequency points, and then superimposed with the media signal. In this way, each frequency component contains only watermarks with tiny energy, which not only guarantees the invisibleness. At the same time, the watermark must be destroyed, and the noise with a high amplitude value at each frequency must be superimposed at each frequency. This idea was first applied to the DCT domain, and then it was promoted to the Fourier transformation domain and wavelet domain. In addition, in order to take into account the preservation of watermarks, the human perception model is used to control the energy of the watermark on each frequency to point the watermark, so that it will not destroy the signal quality, thereby forming a type of adaptive frequencies.

. Another important watermark model is to see the watermark as a communication with the known edge information. The edge information refers to the information known by the embedded side, including media data. The embedder should make full use of the edge information to increase the probability of the correct detection of watermark as much as possible. This has important guiding significance for the design of the watermark. It shows that the host signal containing the watermark should choose to detect the area where the watermark is detected, while ensuring a certain preservation.

At present, the hotspot of watermark research is to explore the maximum amount of information that can be embedded and reliably detected in media signals. It applies the knowledge of the communication model and information theory of known edge information. The study of watermark algorithms focuses on compression standards for compression domains, that is, compression standards such as JPEG and MPEG, because compression is technology that must be used in information transmission.

The attack technology of digital watermark

The editors and modifications of media data often lead to information loss. Because of the close combination of watermarks and media data, it will also affect watermarks. The detection and extraction, we call these operations as an attack. The attack technology of watermarks can be used to test the performance of watermarks. It is an important aspect of the development of watermark technology. How to improve the robustness of watermarks and resist attacks is the most concerned issue for watermark designers.

The first generation of watermark performance evaluation system Stirmark includes a large number of signal and image processing operations. They can be divided into:

A/D, D/A conversion, noise, filtering, square diagram modification, quantification and loss compression, etc. These operations cause information loss of media data, especially compression, and can remove the redundancy as much as possible under the premise of ensuring a certain information quality, so that the watermark is removed.

● Geometry attack (ATTACK): It mainly includes various geometric transformations, such as rotation, translation, scale transformation, shearing, deleting row or column, random geometric transformation, etc. These operations make the spatial or time sequence of media data changes, causing the watermarks to be unlimited, so it is also called asynchronous attack.

● Together attack: The attacker uses multiple watermark copies of the same media information to construct media data without watermarks using statistical methods.

● Repeated embedded attack: The attacker embeds its own copyright information in the media data that has been embedded in other people's watermarks, causing copyright disputes.

The second -generation watermark attack system is proposed that its core idea is to use reasonable media data statistical models and maximum post -test probability to estimate watermark or original media signals, thereby excluding watermarks.

The analysis and research on attack technology has promoted the innovation of watermark technology, but it also put forward one after another for the watermark itself. At present, there is no algorithm that can resist all attacks, especially geometric attacks. It is the most difficult issue recognized by the academic community. There is no mature plan yet.

D digital watermark products

The late 1990s began to appear in international watermark products. Digimarc in the United States took the lead in launching the first digital watermark software to protect the copyright protection of still image, and then integrated the software into ADOBE's Photoshop and Corel DRAW image processing software in the form of plugins. The LaVELIT software launched by Alpvision is able to hide several characters in any scanned picture for the protection and tracking of documents. MediaSec's Syscop uses watermark technology to protect multimedia content, and to prevent illegal copying, dissemination and editing.

The US Copyright Protection Technology Organization (CPTWG) set up a special data hidden group (DHSG) to formulate technical standards for copyright protection watermarks. They proposed a 5C system for DVD copyright protection. IBM uses digital watermarks in the copyright protection system of the digital library. Many internationally renowned commercial groups, such as South Korea's Samsung and Japan's NEC, have also established DRM technology development projects. In addition, there are currently some potential application requirements, such as the statistics of the number of software search and download, web security early warning, the protection of digital TV programs, and the loss of defense of confidential documents.

The international standards have combined digital watermarks or reserved space for it. The goal of SDMI is to provide an open framework for the playback, storage and release of music. The SDMI specification specifies a variety of audio file formats, and combined with encryption and digital watermark technology to achieve copyright protection. Among the promulgated international standards of JPEG2000, there has been reserved space for digital watermarks. The upcoming digital video compression standard MPEG-4 (ISO/IEC 14496) provides an interface for intellectual property management and protection, allowing copyright protection technology including watermarks.

In China, the government attaches great importance to the development of the information security industry. The study of digital watermark has been funded by the National Natural Science Foundation of China and the "863" plan. The domestic information hidden academic seminar (CIHW) has been successfully held for five sessions since 1999, which has strongly promoted the research and development of watermark technology. Last year, the government also promulgated the Electronic Signature Law of the People's Republic of China, which provided the necessary legal basis for the application of watermark technology.

Although digital watermarks develop rapidly, there is still a distance to go away from the actual application. Many projects and research are still in the start and experimental stage, and the watermark products that have appeared cannot fully meet the needs of use. Nowadays, the watermark technology is developing in depth, and some basic technologies and legal issues are being solved one by one. I believe that in the near future, the combination of watermarking and other DRM technology will completely solve the management and protection of digital content.

M small information 2

Immed cases of multimedia digital copyright protection

D digital property rights launched by SafNet, which has a history of 20 years in the security field, The protection solution DMD is a DRM product that uses encrypted technology. Chen Hong, vice president of SafNet, introduced several successful application cases at the request of reporters from the Asia -Pacific region.

dmd is mainly used in music and ringtones, VOD, multimedia content release services, and recent mobile TV. Basically, customers choose the following points: based on telecommunications -level performance, can handle thousands of users at the same time; can simultaneously support multiple DRM technologies, and have high support capabilities for future DRM technologies; high interoperability to ensure the server to ensure the server of the server The end and the client can communicate safely and stable; advanced authorization capabilities, such as effectively controlling the amount of authorization; high integration, ensuring that the DRM platform is not independent, and can be easily integrated to the server platform, and the charging system with the toll system Wait.

It in terms of music download, NPO is the customer of SafNet in France. They are mainly responsible for the release of CD music and put the published music on FN@C's network for people to pay to download. After NPO processing the music content, the content will be published by Fn@C (this is an open portal website) and provides a payment to download. When the terminal user pays the money, Fn@C will encrypt and submit a part of the proof data to NPO, and the NPO will be authorized to the user.

At the application level of VOD, German Arcor is an ISP supplier. Through the DRM solution, ARCOR encrypts the content of the audio and video, and gives customers the service for users to pay for users through the Internet and Cable. The customer paid the money, and Arcor was formally authorized by the SafNet's DRM solution, allowing customers to enjoy audiovisual services.

In terms of 3G applications, BT Lifttime also uses the SafNet DMD solution. BT Lifetime purchases the content of Cable TV from the content supplier (such as sports programs or music programs, etc.), and converts this content into DAB format. After DMD encryption and put it on its platform, it is resold to wireless operators, providing mobile devices Users pay directly to download content. Provide authorization to customers who have paid through SafNet DMD.

(Computer World Newspaper, November 14, 2005, No. 44 B6, B7)

mpeg-4 video digital watermark technology
Wuhan University signal signal With information processing laboratory (430079) Qiu Fengjing Li Fuping
With the rapid development of information technology and computer networks, people can not only easily and quickly obtain multimedia information through the Internet and CD-ROM, but also get completely with original data with the original data The same replica, the result of piracy and copyright disputes caused by this have become increasingly serious social issues. Therefore, the watermark treatment technology of digital multimedia products has become one of the hot areas of research in recent years.
Although digital watermark technology has developed in recent years, the direction is mainly concentrated in static images. Because more accurate human eye visual models, including the characteristics of time domain cover effects, have not been fully established, the development of video watermark technology lags behind static image watermark technology. On the other hand, due to the emergence of special attack forms for video watermarks, some unique requirements for video watermarks are put forward from the unique requirements of static image watermarks.

This This article analyzes the characteristics of the characteristics of the video digital watermarking plan based on the expansion spectrum.

1 Video Digital Watermark Technology Introduction

1.1 Digital Watermark Technology Introduction

Digital watermarking technology directly embeds some iconic information through certain algorithms to In multimedia content, it does not affect the value and use of the original content, and cannot be perceived or noticed by human perception systems. Unlike traditional encrypted technology, digital watermark technology does not prevent pirated activities from occurring, but it can be determined whether the object is protected, monitoring the dissemination of the protected data, identifying authenticity, resolving copyright disputes, and providing certification evidence to court. In order to increase the difficulty of removing the watermark, most of the current water printing schemes use the encryption system in cryptography to enhance. When the watermark is embedded and extracted, a key, or even several keys are used. The general method of watermark embedding and extraction is shown in Figure 1.

1.2 Video digital watermark design should consider several aspects

· Watermark capacity: embedded watermark information must be sufficient to identify the buyers or owners of multimedia content.

· Unacceptable: The digital watermark embedded in the video data should be invisible or unacceptable.

· Robbing: Under the condition that the video quality is not significantly reduced, the watermark is difficult to remove.

· Blind detection: The original video does not require the watermark detection, because it is almost impossible to save all the original videos.

. Tarmented reminder: When the multimedia content changes, the extraction algorithm can be detected sensitively through the watermark extraction algorithm.

1.3 Video Digital Watermark Scheme Select

In analyzing the existing digital video codec and decoding system, you can divide the current MPEG-4 video watermarking schemes into the following Several categories, as shown in Figure 2.

(1) Video watermark embedding scheme 1: Watermark is directly embedded in the original video stream. The advantages of such schemes are: there are many methods of watermark embedding, in principle, the digital image watermark solution can be applied here. The disadvantage is:

· The data bit rate of the video code flow will be increased;

· The watermark will be lost after lossing and compression of MPEG-4;

· reduce video quality;

· For compressed videos, you need to decode first, then embedded in watermarks, and then re -coded.

(2) Video watermark embedding scheme 2: The watermark is embedded in the DC coefficient (DC) of discrete string transformation (DCT) in the coding stage (after quantification, before prediction). The advantages of such schemes are:

. Watermarks are only embedded in the DCT coefficient, and the data bit rate of the video stream will not be increased;

Watermarks;

· The adaptive mechanism can be modulated according to the visual characteristics of the person, and the better anti -attack capability can be obtained while obtaining good subjective visual quality.

The disadvantage is that for compressed videos, there is a process of decoding, embedding, and coding.

(3) Video watermark embedded scheme 3: The watermark is directly embedded in the MPEG-4 compression ratio. The advantage is that there is no need to fully decoding and coding, which has a small impact on the overall video signal. The disadvantage is:

· The restraint of the video compression code rate of the video system will limit the amount of watermark;

. The embedding of the watermark may cause the motion compensation ring in the video decoding system The adverse effects of the road;

· The design of this type of algorithm has a certain complexity.

2 MPEG-4 Video watermark implementation

Based on the above-mentioned various schemes, this article proposes a expansion of the MPEG-4 video coding system on the basis of the second solution. The spectrum digital watermark technology improvement scheme embeds the watermark information after the spreading to the lowest bit of the DCT DCT coefficient of the medium -chromaticity DCT DCT DCT DCT (INTRA Video Object Plane). This solution does not need to be fully decoded, which greatly reduces the
of the operation, and improves real -time. At the same time, because the watermark is embedded in the DC coefficient, the watermark has a strong robustness under the premise that the video effect is not unsatisfactory.

2.1 MPEG-4 video features MPEG-4 video codec is based on VOP (Video Object Plane).

From time to time, VOP is divided into internal VOP (1VOP), forward causal prediction VOP (PVOP), two -way non -causal prediction VOP (BVOP), panoramic Lingying VOP (SVOP). IVOP only uses its own information; PVOP uses the previous reference VOP to perform sports compensation prediction; BVOP uses the prediction coding of two -way sports compensation for two -way sports compensation; SVOP's static background in a series of sports images. Therefore, IVOP's image information is more independent, and it is most suitable for embedding watermark information.

In space, it consists of several macro blocks with a size of 16 × 16. Each macro block includes 6 sub -blocks with 8 × 8. Four of them Y, 1 color different child block U, and 1 color different child block V. The basic process of IVOP encoding is shown in Figure 3.

In order not to be affected by the process of quantification, this plan embeds the watermark into the quantified DCT coefficient, thereby improving the stability of the watermark survival. In the MPEG-4 compression algorithm, the quantization of the DCT coefficient is the key, and it directly affects the quality and code current control algorithm of the video. To this end, the MPEG-4 provides a standard quantification table for reference. The table is established based on human visual models (HVS). Considering that the sensitivity of human eyes to high -frequency information loss is much less than the low frequency loss, watermarks are usually embedded in low -frequency information, which improves the stentability of watermark information. In addition, according to the characteristics of the human eye's change of brightness information than the sensitive color information, in order to maintain the video quality to the maximum, the watermark is embedded in the color (U sub -block) DCT coefficient. Because DCT is currently widely used in multimedia video compression, DCT -based video watermark solutions have significant advantages. The watermark information is embedded in the DCT DC coefficient after IVOP color quantitative, not only does it not need to introduce additional transformations to obtain the spectrum distribution of video, and the watermark information is not affected by the number of DCT coefficients.

2.2 Video digital water print algorithm and implementation

In the MPEG-4 video, because the DCT DC coefficient of the IVOP mid-color block is And a very robust parameter, this scheme is used to modulate the watermark information through the M sequence (the longest linear feedback migrant sequence) and embedded in the DCT coefficient of the color child block DCT of the IVOP. In this way, the watermark information is difficult to remove without affecting the effect of the video, so the robustness is strong enough. This scheme adopts the method of frequency expansion to facilitate and effectively detect watermarks, resist various attacks and interference, and good confidentiality. The key problem is that the DCT DCT DC system is a parameter that is very sensitive to the visual system. In this solution, adding a watermark on the DCT coefficient of the color DCT is equivalent to adding trace interference to it. Value makes the visual system of human eyes feel that the small changes in the video in the video cannot feel. The minimum bits of the DCT of the IVOP color DCT after experiment can meet the requirements of the DCT of the IVOP.

2.2.1 Video Digital Watermark embedded

The length of pseudo-random expansion sequence is 255 (28-1). The modulation is embedded in the lowest bit of the DCT DC coefficient (quantization, before prediction) corresponding to the corresponding IVOP chroma, so that the watermark information is generally difficult to remove without affecting the video effect. At the same time, the minimum bit of the DC coefficient is very small. rnrn伪随机的扩展序列产生代码如下：rnrn#define M_LEN 255rn#define M_SERIES 8rnfor(I=0；i for(i = M_series; i {
m [i] = m [i-1] m [i-5] m [i-6] m [i-7]
m [i] = m [ i] % 2;
}
The watermark information bit expansion modulation method is:

· Watermark information bit 0, pseudo -random expansion sequences remain unchanged;
n n n n n n n n n n n n n n n n n n R n · Watermark information bit is 1, pseudo -random extension sequence is reversed.

The process can be implemented with different or operations. The code is as follows:
nWmij = wi^m [J];

/*Each watermark information bit is expanded to 255 -bit extended modulation position* /
Wi here wi indicates watermark information code flow, wmij represents watermark information expansion modulation code flow flow . Set UDCIJ to represent the DC coefficient of the video IVOP chroma DCT (quantified, before the DC prediction calculation) sequence. For the sake of convenience, use a byte to represent a binary code flow information. :

if (wmij) udcij 1 = 1;

/*The code flow after the expansion is embedded into the watermark information* /

else udcij

2 thoughts on “The value, significance and advantages of digital watermark ~ Who can help”

Ignacio
December 2, 2022 at 4:09 am

The last line of defense of digital copyright — digital watermark

■ Zhu Xingshan

------------------------------------------------------------------------------------ ------------------------------------------------ ---------------

D digital watermark is regarded as the "last line of defense" that resist multimedia piracy. Therefore, from the watermark technology itself, it has extensive application prospects and huge economic value.

The development in today's society has presented two obvious characteristics: digital and networked. Digitalization refers to the form of information storage, which is characterized by large information storage, easy to edit and copy; network refers to the form of information transmission, which has the advantages of fast speed and wide distribution. Over the past 10 years, the use and distribution of digital media information have been explosive. People can quickly and conveniently obtain digital information and online services through the Internet. But at the same time, piracy has become easier, and the management and protection of digital content has become an urgent need to solve the industry.

D digital information is essentially different from analog information. The traditional solution for protecting the simulation information no longer works for digital information. Coupled with some general -purpose processors, such as PCs, it makes them easy to break through hardware -based media protection solutions. In fact, the encryption technology that is usually used can only protect the content of the media during the transmission process of information from the sender to the recipient's transmission. After the information is received, all data in the process of reuse is transparent to users and no longer be protected. In this situation, digital watermarks, as a potential solution, have been favored by many scholars.

The basic idea of digital watermark is in the original media data, such as audio, video, images, etc., hidden add information with certain significance as a mark. Transmitted. At the receiving end, the computer watermark signal is extracted for various purposes. Possible applications include digital signatures, digital fingerprints, broadcast surveillance, content certification, copy control, and secret communication. Digital watermarks are regarded as the "last line of defense" to resist multimedia piracy. Therefore, from the watermark technology itself, it has extensive application prospects and huge economic value.
The general framework of digital watermark

The basic framework of digital watermark

A typical watermark system consists of an embedded and detector, as shown in the figure. The embedded (formula (1)) generates a real watermark signal based on the information m to be transmitted, and hides it to the media data X to obtain the signal Y of the aqueous marks. For safety reasons, the generation of watermark signals usually depends on key K.

y may have certain information loss after the transmission network, and the end of the detector becomes Y ′. This passage is uncontrollable and unknown for the embedded and detector. It can be called It is an attack channel. The detector is responsible for extracting information from Y ′, such as formula (2). For the detection of the host signal, we are called a blind watermark, and on the contrary, the non-blind watermark (Non-Blind). Due to the needs of application, blind watermarks have always been the mainstream of research.

The characteristics of digital watermark

Although the idea of digital watermark is simple, to achieve the purpose of application, it is necessary to meet certain performance indicators. The relatively important characteristics include:

● Fidelity: It is often called invisible, which refers to the degree of changes in the quality of the host signal signal in the watermark embedding. Given that the host signal is mostly multimedia data for people to watch, the watermark should have high preservation, and at the same time increase the safety of the watermark itself.

● Robbing (): refers to the survivability of watermarks in the media data editing and processing process. Various operations of media data will cause the host signal information loss, thereby destroying watermark integrity, such as compression, filtering, noise, shear, zooming, and rotation, including some malicious attacks.

● Data Payload: refers to the amount of information that can be passed by the watermark signal under a certain preservation. The actual application requires that watermarks can send multiple digits of information.

● Safety: In the application, there are always people who must embed, detect or remove watermarks, and must limit others to do the same operation. This is the safety of watermarks. To achieve safety, important information must be kept confidential, such as usually using a key to generate watermarks.

● Error alarm: refers to the probability of error detection in the host signal without watermark. Obviously, the system can be used safely and reliably if the wrong alarm rate is low enough.

The design of watermarks must be selected around the above performance indicators. Some characteristics are incompatible, such as invisibleness, robustness, and information capacity, weighing considerations.

This from the preservation of watermarks divided it into visible watermarks and invisible watermarks. As the name suggests, watermarks can be detected by human eye. The robbles of the watermark can be divided into Robust and fragile watermarks. Raising watermarks can resist a certain degree of signal processing; and the fragile watermark is characterized by any change in media information to destroy the integrity of the watermark and make the watermark detection. Therefore, robust watermarks are trying to ensure the integrity of watermark information, and fragile watermarks are trying to ensure the integrity of media information, and they have their own use. There is also a kind of watermark agency between the two, called semi -fragile watermark, which is fragile for some operational robust operations, but the modification operation of important data features is fragile.

The progress of digital watermark technology

In the early days, watermark designers paid attention to how to hide information in digital media and not discovered. To this end, the watermark information is placed in the lowest bit of binary data, and such schemes are collectively referred to as the lowest effective bit modulation. Obviously, the at least effective information is easy to lose in the commonly used signal processing, and the robustness of the watermark is poor.

St afterwards, a large number of watermark algorithms in the space domain appeared. Watermark embedding is no longer a single point to modify the spatial area, but the characteristics of a point set or a region, such as mean, variance, and amazing. Patchwork is a typical representative of this method. It randomly selects N -pairing pixels (AI, BI) in the image space, and adds D of the pixel AI to D, BI's brightness is reduced. As a result, the average value difference between the two groups of pixels is modified to 2D. This average and statistical hypothetical test theory can determine whether the watermark is. However, Patchwork can embed the amount of information and is sensitive to geometric transformation. The common problem of the waterprint algorithm in the space domain is the poor robustness of the image processing.

Compared with the space domain, spectrum is a good signal description method. Low -frequency components represent the smooth part of the signal, which is the main information; the high -frequency component represents the jitter of the signal, which is the edge information. The analysis and processing of the signal are very intuitive and convenient. The expansion watermark introduces the theory of spreading communication, which is a very popular watermark design idea in the frequency domain. It regards digital media as a channel. It usually has a wider bandwidth. The watermark signal to be embedded as the transmitting signal, which is narrow. You can first expand the watermark to multiple frequency points, and then superimposed with the media signal. In this way, each frequency component contains only watermarks with tiny energy, which not only guarantees the invisibleness. At the same time, the watermark must be destroyed, and the noise with a high amplitude value at each frequency must be superimposed at each frequency. This idea was first applied to the DCT domain, and then it was promoted to the Fourier transformation domain and wavelet domain. In addition, in order to take into account the preservation of watermarks, the human perception model is used to control the energy of the watermark on each frequency to point the watermark, so that it will not destroy the signal quality, thereby forming a type of adaptive frequencies.

. Another important watermark model is to see the watermark as a communication with the known edge information. The edge information refers to the information known by the embedded side, including media data. The embedder should make full use of the edge information to increase the probability of the correct detection of watermark as much as possible. This has important guiding significance for the design of the watermark. It shows that the host signal containing the watermark should choose to detect the area where the watermark is detected, while ensuring a certain preservation.

At present, the hotspot of watermark research is to explore the maximum amount of information that can be embedded and reliably detected in media signals. It applies the knowledge of the communication model and information theory of known edge information. The study of watermark algorithms focuses on compression standards for compression domains, that is, compression standards such as JPEG and MPEG, because compression is technology that must be used in information transmission.

The attack technology of digital watermark

The editors and modifications of media data often lead to information loss. Because of the close combination of watermarks and media data, it will also affect watermarks. The detection and extraction, we call these operations as an attack. The attack technology of watermarks can be used to test the performance of watermarks. It is an important aspect of the development of watermark technology. How to improve the robustness of watermarks and resist attacks is the most concerned issue for watermark designers.

The first generation of watermark performance evaluation system Stirmark includes a large number of signal and image processing operations. They can be divided into:

A/D, D/A conversion, noise, filtering, square diagram modification, quantification and loss compression, etc. These operations cause information loss of media data, especially compression, and can remove the redundancy as much as possible under the premise of ensuring a certain information quality, so that the watermark is removed.

● Geometry attack (ATTACK): It mainly includes various geometric transformations, such as rotation, translation, scale transformation, shearing, deleting row or column, random geometric transformation, etc. These operations make the spatial or time sequence of media data changes, causing the watermarks to be unlimited, so it is also called asynchronous attack.

● Together attack: The attacker uses multiple watermark copies of the same media information to construct media data without watermarks using statistical methods.

● Repeated embedded attack: The attacker embeds its own copyright information in the media data that has been embedded in other people's watermarks, causing copyright disputes.

The second -generation watermark attack system is proposed that its core idea is to use reasonable media data statistical models and maximum post -test probability to estimate watermark or original media signals, thereby excluding watermarks.

The analysis and research on attack technology has promoted the innovation of watermark technology, but it also put forward one after another for the watermark itself. At present, there is no algorithm that can resist all attacks, especially geometric attacks. It is the most difficult issue recognized by the academic community. There is no mature plan yet.

D digital watermark products

The late 1990s began to appear in international watermark products. Digimarc in the United States took the lead in launching the first digital watermark software to protect the copyright protection of still image, and then integrated the software into ADOBE's Photoshop and Corel DRAW image processing software in the form of plugins. The LaVELIT software launched by Alpvision is able to hide several characters in any scanned picture for the protection and tracking of documents. MediaSec's Syscop uses watermark technology to protect multimedia content, and to prevent illegal copying, dissemination and editing.

The US Copyright Protection Technology Organization (CPTWG) set up a special data hidden group (DHSG) to formulate technical standards for copyright protection watermarks. They proposed a 5C system for DVD copyright protection. IBM uses digital watermarks in the copyright protection system of the digital library. Many internationally renowned commercial groups, such as South Korea's Samsung and Japan's NEC, have also established DRM technology development projects. In addition, there are currently some potential application requirements, such as the statistics of the number of software search and download, web security early warning, the protection of digital TV programs, and the loss of defense of confidential documents.

The international standards have combined digital watermarks or reserved space for it. The goal of SDMI is to provide an open framework for the playback, storage and release of music. The SDMI specification specifies a variety of audio file formats, and combined with encryption and digital watermark technology to achieve copyright protection. Among the promulgated international standards of JPEG2000, there has been reserved space for digital watermarks. The upcoming digital video compression standard MPEG-4 (ISO/IEC 14496) provides an interface for intellectual property management and protection, allowing copyright protection technology including watermarks.

In China, the government attaches great importance to the development of the information security industry. The study of digital watermark has been funded by the National Natural Science Foundation of China and the "863" plan. The domestic information hidden academic seminar (CIHW) has been successfully held for five sessions since 1999, which has strongly promoted the research and development of watermark technology. Last year, the government also promulgated the Electronic Signature Law of the People's Republic of China, which provided the necessary legal basis for the application of watermark technology.

Although digital watermarks develop rapidly, there is still a distance to go away from the actual application. Many projects and research are still in the start and experimental stage, and the watermark products that have appeared cannot fully meet the needs of use. Nowadays, the watermark technology is developing in depth, and some basic technologies and legal issues are being solved one by one. I believe that in the near future, the combination of watermarking and other DRM technology will completely solve the management and protection of digital content.

M small information 2

Immed cases of multimedia digital copyright protection

D digital property rights launched by SafNet, which has a history of 20 years in the security field, The protection solution DMD is a DRM product that uses encrypted technology. Chen Hong, vice president of SafNet, introduced several successful application cases at the request of reporters from the Asia -Pacific region.

dmd is mainly used in music and ringtones, VOD, multimedia content release services, and recent mobile TV. Basically, customers choose the following points: based on telecommunications -level performance, can handle thousands of users at the same time; can simultaneously support multiple DRM technologies, and have high support capabilities for future DRM technologies; high interoperability to ensure the server to ensure the server of the server The end and the client can communicate safely and stable; advanced authorization capabilities, such as effectively controlling the amount of authorization; high integration, ensuring that the DRM platform is not independent, and can be easily integrated to the server platform, and the charging system with the toll system Wait.

It in terms of music download, NPO is the customer of SafNet in France. They are mainly responsible for the release of CD music and put the published music on FN@C's network for people to pay to download. After NPO processing the music content, the content will be published by Fn@C (this is an open portal website) and provides a payment to download. When the terminal user pays the money, Fn@C will encrypt and submit a part of the proof data to NPO, and the NPO will be authorized to the user.

At the application level of VOD, German Arcor is an ISP supplier. Through the DRM solution, ARCOR encrypts the content of the audio and video, and gives customers the service for users to pay for users through the Internet and Cable. The customer paid the money, and Arcor was formally authorized by the SafNet's DRM solution, allowing customers to enjoy audiovisual services.

In terms of 3G applications, BT Lifttime also uses the SafNet DMD solution. BT Lifetime purchases the content of Cable TV from the content supplier (such as sports programs or music programs, etc.), and converts this content into DAB format. After DMD encryption and put it on its platform, it is resold to wireless operators, providing mobile devices Users pay directly to download content. Provide authorization to customers who have paid through SafNet DMD.

(Computer World Newspaper, November 14, 2005, No. 44 B6, B7)

mpeg-4 video digital watermark technology
Wuhan University signal signal With information processing laboratory (430079) Qiu Fengjing Li Fuping
With the rapid development of information technology and computer networks, people can not only easily and quickly obtain multimedia information through the Internet and CD-ROM, but also get completely with original data with the original data The same replica, the result of piracy and copyright disputes caused by this have become increasingly serious social issues. Therefore, the watermark treatment technology of digital multimedia products has become one of the hot areas of research in recent years.
Although digital watermark technology has developed in recent years, the direction is mainly concentrated in static images. Because more accurate human eye visual models, including the characteristics of time domain cover effects, have not been fully established, the development of video watermark technology lags behind static image watermark technology. On the other hand, due to the emergence of special attack forms for video watermarks, some unique requirements for video watermarks are put forward from the unique requirements of static image watermarks.

This This article analyzes the characteristics of the characteristics of the video digital watermarking plan based on the expansion spectrum.

1 Video Digital Watermark Technology Introduction

1.1 Digital Watermark Technology Introduction

Digital watermarking technology directly embeds some iconic information through certain algorithms to In multimedia content, it does not affect the value and use of the original content, and cannot be perceived or noticed by human perception systems. Unlike traditional encrypted technology, digital watermark technology does not prevent pirated activities from occurring, but it can be determined whether the object is protected, monitoring the dissemination of the protected data, identifying authenticity, resolving copyright disputes, and providing certification evidence to court. In order to increase the difficulty of removing the watermark, most of the current water printing schemes use the encryption system in cryptography to enhance. When the watermark is embedded and extracted, a key, or even several keys are used. The general method of watermark embedding and extraction is shown in Figure 1.

1.2 Video digital watermark design should consider several aspects

· Watermark capacity: embedded watermark information must be sufficient to identify the buyers or owners of multimedia content.

· Unacceptable: The digital watermark embedded in the video data should be invisible or unacceptable.

· Robbing: Under the condition that the video quality is not significantly reduced, the watermark is difficult to remove.

· Blind detection: The original video does not require the watermark detection, because it is almost impossible to save all the original videos.

. Tarmented reminder: When the multimedia content changes, the extraction algorithm can be detected sensitively through the watermark extraction algorithm.

1.3 Video Digital Watermark Scheme Select

In analyzing the existing digital video codec and decoding system, you can divide the current MPEG-4 video watermarking schemes into the following Several categories, as shown in Figure 2.

(1) Video watermark embedding scheme 1: Watermark is directly embedded in the original video stream. The advantages of such schemes are: there are many methods of watermark embedding, in principle, the digital image watermark solution can be applied here. The disadvantage is:

· The data bit rate of the video code flow will be increased;

· The watermark will be lost after lossing and compression of MPEG-4;

· reduce video quality;

· For compressed videos, you need to decode first, then embedded in watermarks, and then re -coded.

(2) Video watermark embedding scheme 2: The watermark is embedded in the DC coefficient (DC) of discrete string transformation (DCT) in the coding stage (after quantification, before prediction). The advantages of such schemes are:

. Watermarks are only embedded in the DCT coefficient, and the data bit rate of the video stream will not be increased;

Watermarks;

· The adaptive mechanism can be modulated according to the visual characteristics of the person, and the better anti -attack capability can be obtained while obtaining good subjective visual quality.

The disadvantage is that for compressed videos, there is a process of decoding, embedding, and coding.

(3) Video watermark embedded scheme 3: The watermark is directly embedded in the MPEG-4 compression ratio. The advantage is that there is no need to fully decoding and coding, which has a small impact on the overall video signal. The disadvantage is:

· The restraint of the video compression code rate of the video system will limit the amount of watermark;

. The embedding of the watermark may cause the motion compensation ring in the video decoding system The adverse effects of the road;

· The design of this type of algorithm has a certain complexity.

2 MPEG-4 Video watermark implementation

Based on the above-mentioned various schemes, this article proposes a expansion of the MPEG-4 video coding system on the basis of the second solution. The spectrum digital watermark technology improvement scheme embeds the watermark information after the spreading to the lowest bit of the DCT DCT coefficient of the medium -chromaticity DCT DCT DCT DCT (INTRA Video Object Plane). This solution does not need to be fully decoded, which greatly reduces the
of the operation, and improves real -time. At the same time, because the watermark is embedded in the DC coefficient, the watermark has a strong robustness under the premise that the video effect is not unsatisfactory.

2.1 MPEG-4 video features MPEG-4 video codec is based on VOP (Video Object Plane).

From time to time, VOP is divided into internal VOP (1VOP), forward causal prediction VOP (PVOP), two -way non -causal prediction VOP (BVOP), panoramic Lingying VOP (SVOP). IVOP only uses its own information; PVOP uses the previous reference VOP to perform sports compensation prediction; BVOP uses the prediction coding of two -way sports compensation for two -way sports compensation; SVOP's static background in a series of sports images. Therefore, IVOP's image information is more independent, and it is most suitable for embedding watermark information.

In space, it consists of several macro blocks with a size of 16 × 16. Each macro block includes 6 sub -blocks with 8 × 8. Four of them Y, 1 color different child block U, and 1 color different child block V. The basic process of IVOP encoding is shown in Figure 3.

In order not to be affected by the process of quantification, this plan embeds the watermark into the quantified DCT coefficient, thereby improving the stability of the watermark survival. In the MPEG-4 compression algorithm, the quantization of the DCT coefficient is the key, and it directly affects the quality and code current control algorithm of the video. To this end, the MPEG-4 provides a standard quantification table for reference. The table is established based on human visual models (HVS). Considering that the sensitivity of human eyes to high -frequency information loss is much less than the low frequency loss, watermarks are usually embedded in low -frequency information, which improves the stentability of watermark information. In addition, according to the characteristics of the human eye's change of brightness information than the sensitive color information, in order to maintain the video quality to the maximum, the watermark is embedded in the color (U sub -block) DCT coefficient. Because DCT is currently widely used in multimedia video compression, DCT -based video watermark solutions have significant advantages. The watermark information is embedded in the DCT DC coefficient after IVOP color quantitative, not only does it not need to introduce additional transformations to obtain the spectrum distribution of video, and the watermark information is not affected by the number of DCT coefficients.

2.2 Video digital water print algorithm and implementation

In the MPEG-4 video, because the DCT DC coefficient of the IVOP mid-color block is And a very robust parameter, this scheme is used to modulate the watermark information through the M sequence (the longest linear feedback migrant sequence) and embedded in the DCT coefficient of the color child block DCT of the IVOP. In this way, the watermark information is difficult to remove without affecting the effect of the video, so the robustness is strong enough. This scheme adopts the method of frequency expansion to facilitate and effectively detect watermarks, resist various attacks and interference, and good confidentiality. The key problem is that the DCT DCT DC system is a parameter that is very sensitive to the visual system. In this solution, adding a watermark on the DCT coefficient of the color DCT is equivalent to adding trace interference to it. Value makes the visual system of human eyes feel that the small changes in the video in the video cannot feel. The minimum bits of the DCT of the IVOP color DCT after experiment can meet the requirements of the DCT of the IVOP.

2.2.1 Video Digital Watermark embedded

The length of pseudo-random expansion sequence is 255 (28-1). The modulation is embedded in the lowest bit of the DCT DC coefficient (quantization, before prediction) corresponding to the corresponding IVOP chroma, so that the watermark information is generally difficult to remove without affecting the video effect. At the same time, the minimum bit of the DC coefficient is very small. rnrn伪随机的扩展序列产生代码如下：rnrn#define M_LEN 255rn#define M_SERIES 8rnfor(I=0；i for(i = M_series; i {
m [i] = m [i-1] m [i-5] m [i-6] m [i-7]
m [i] = m [ i] % 2;
}
The watermark information bit expansion modulation method is:

· Watermark information bit 0, pseudo -random expansion sequences remain unchanged;
n n n n n n n n n n n n n n n n n n R n · Watermark information bit is 1, pseudo -random extension sequence is reversed.

The process can be implemented with different or operations. The code is as follows:
nWmij = wi^m [J];

/*Each watermark information bit is expanded to 255 -bit extended modulation position* /
Wi here wi indicates watermark information code flow, wmij represents watermark information expansion modulation code flow flow . Set UDCIJ to represent the DC coefficient of the video IVOP chroma DCT (quantified, before the DC prediction calculation) sequence. For the sake of convenience, use a byte to represent a binary code flow information. :

if (wmij) udcij 1 = 1;

/*The code flow after the expansion is embedded into the watermark information* /

else udcij

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Brandi
December 2, 2022 at 4:09 am

It's not a professional, but I just have some personal opinions

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The value, significance and advantages of digital watermark ~ Who can help

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