CN101021941A - Multi-channel filter group-based multifunction digital watermark method - Google Patents

Abstract

This invention puts forward a digital watermark method for protecting copyright information of digital multimedia products and content integrality at the same time, which embeds a Rodust watermark and a weak watermark in a multimedia product simultaneously to pick up the copyright information of the multimedia by testing the Rodust watermark and judge if the multimedia is trusted or juggled viciously by testing the weak watermark, which can protect the copyright to Jpeg image compression and image juggle operation and provides juggle prompt.

Description

A kind of multifunction digital watermark method based on the multi-channel filter group

Affiliated technical field

The present invention relates to information security field, particularly digital watermark technology is applicable to the copyright protection and the content integrity authentication of multimedia messages.

Background technology

What the digitizing of multimedia messages and network times made digital medium information obtains, transmits, handles more convenient, how effectively to carry out copyright protection and becomes very urgent problem.An information security technology---the digital watermarking that developed recently gets up for this problem provides a kind of solution route, causes the extensive concern of domestic and international academia and business circles.

Digital watermarking mainly is divided into robust watermarking and fragile watermark two classes according to its function, and robust watermarking generally is used to protect the copyright of digital product, it can still can steadily and surely be existed by copyright information (watermark) after standing various processing and attack, thereby all rights reserved for proof; Fragile watermark is used for the true and integrality authentication of digital product contents, and it can make prompting and evaluation to the various very sensitivities of distorting to position, type that digital product is tampered by detecting watermark information.The research of digital watermarking algorithm is mostly at simple robust watermarking or to simple fragile watermark at present, and digital watermarking is when being applied to actual copyright authentication, whether we wish can not only realize copyright authentication by the Detection and Extraction to watermark, can also learn to distort and what kind of has been subjected in the stolen process of digital product and distort.Realize protection simultaneously, become the strong day by day demand in digital medium information content safety field the copyright information and the content integrity of digital product.Fred Mintzer in 1999 and Gordon W.Braudaway have inquired into feasibility that embeds a plurality of watermark informations in media product simultaneously and the problem that may exist first, also there is the researcher to analyze and use afterwards, but mainly still is simple function with regard to the problem of multi-watermarking coexistence; Chun-Shien Lu etc. has proposed a kind of digital watermarking algorithm of realizing image copyright information protection and content integrity authentication simultaneously first, this algorithm adopts based on cocktail algorithm embed watermark in wavelet field, this cocktail algorithm not only needs the participation (non-blind algorithm) of original image when detecting, but also need the maping mapping matrix, limited application; Number of patent application is 03132640.4 invention, has proposed a kind of method that embeds visible and invisible dual watermark in digital picture, plays copyright protection and copyright notice/effect simultaneously, but does not have the function of fragile watermark.After this, there are a lot of scholars to carry out the research of related fields again, be mainly in wavelet field and embed robust and fragile watermark simultaneously, though it can obtain good effect, but need use the fragile watermark copy of original embedding when realizing distorting prompt facility, having increased needs the quantity of information of preserving, and wherein the algorithm that proposed in 2006 of people such as Shuhua Xiong only is to embed the different several watermarks of robustness, and its fragile watermark is not distorted the process of authentication.

The multiple sampling rate digital signal processing theory is early than proposing the seventies in 20th century and causing extensive concern, especially multi-channel filter group theory, in the numerous areas such as numerical solution of communication system, voice, compression of images, digital audio system, statistics and Adaptive Signal Processing, difference equation, show up prominently, in multiloop loop system, use more outstanding.K.P.Chan utilized the multi-channel filter group to propose a kind of time frequency coding method of multiplex system in 1999, and be applied in the digital watermarking system, the method of employing time-domain analyses such as Mohsen Ashourian in 2000 is analyzed the single robust digital watermark system based on the multi-channel filter group, and Li Xuebins in 2003 etc. have proposed a kind of image watermark algorithm based on even hyperchannel sub-band transforms.Though these algorithms combine with digital watermark technology and have certain robustness the multi-channel filter group is theoretical; but function singleness; it only is the copyright protection of robust; and can not realize blind extraction; as seen the character of multi-channel filter group is still waiting in this field to excavate; should further bring into play its advantage, improve the algorithm function in this field.

Summary of the invention

In view of above-mentioned analysis, the present invention is based on the multi-channel filter group, a kind of digital watermark method that can realize multimedia messages copyright protection and content integrity authentication simultaneously and distort prompt facility has been proposed.

The present invention includes following steps:

Embed step

(1) utilize M passage analysis filterbank by row original image to be decomposed into M by row respectively ²Individual subband;

(2) copyright information to be embedded is carried out scramble, generate robust watermarking; From M ²Select low frequency sub-band among the individual subband, robust watermarking is embedded algorithm with suitable robust watermarking be embedded in this low frequency sub-band;

(3) generate fragile watermark according to image low frequency sub-band information, and fragile watermark is embedded in the medium and low frequency subband;

(4) utilize corresponding M passage synthesis filter group that each subband is comprehensive for containing watermarking images.

Extraction step

(1) utilize with above-mentioned embedding step in identical M passage analysis filterbank original image is decomposed by being listed as by row respectively, be decomposed into M ²Individual subband;

(2) corresponding extraction algorithm extracts robust watermarking in utilization and the above-mentioned embedding step, and the copyright information by the random algorithm that is inverted obtains extracting carries out copyright authentication;

(3) extract the testing image characteristic information, regenerate fragile watermark, corresponding extraction algorithm extracts fragile watermark in utilization and the above-mentioned embedding step, and both are carried out XOR relatively, distorts authentication.

The present invention utilizes the multi-channel filter group to carry out the division of subband, and subband is selected flexibly, and can utilize the interference between the mutually orthogonal property minimizing watermark of multi-channel filter group.

Adopt frequency-domain analysis method that principle of the present invention is carried out the brief analysis explanation below.Simple for explaining, be example with the one-dimensional signal, accompanying drawing 1 is the digital watermarking embedding principle figure based on the multi-channel filter group.Step is as follows:

(1) original signal X (e ^{J ω}) by analysis filterbank H _i(e ^{J ω}) (i=0...M-1) after, carry out M point down-sampling respectively, be M subband signal V with signal decomposition _i(e ^{J ω}).

(2) embedding device is embedded into watermark signal respectively in each subband signal according to set algorithm.W among the figure ₀, W ₁W _M-1Represent M watermark signal, if certain subband not embed watermark, then watermark W _iBe zero.

(3) each subband signal of embed watermark is handled again by synthesis filter group G through M point up-sampling _i(e ^{J ω}) back addition promptly get moisture seal signal X ' (e ^{J ω}).

Utilize the ultimate principle of multi-channel filter group to analyze to such an extent that each subband signal is to accompanying drawing 1

$V_i\left(e^{\mathrm{j\ω}}\right)=\frac{1}{M}\underset{l=0}{\overset{M-1}{\mathrm{\Σ}}}{H}_i\left(e^{\mathrm{j\ω}/M-j\frac{2\mathrm{\π}l}{M}}\right)X\left(e^{\mathrm{j\ω}/M-j\frac{2\mathrm{\πl}}{M}}\right)---\left(1\right)$

If the embedding device in will last figure is simply regarded totalizer as, embedment strength is α, then

V′ _i(e ^jω)＝V _i(e ^jω)+αW _i(e ^jω) (2)

Obtaining moisture seal signal after comprehensive is

$X^{\′}\left(e^{\mathrm{j\ω}}\right)=\underset{k=0}{\overset{M-1}{\mathrm{\Σ}}}{G}_k\left(e^{\mathrm{j\ω}}\right)V_k^{\′}\left(e^{\mathrm{j\ωM}}\right)$

$=\underset{k=0}{\overset{M-1}{\mathrm{\Σ}}}{G}_k\left(e^{\mathrm{j\ω}}\right)[V_k\left(e^{\mathrm{j\ωM}}\right)+\mathrm{\α}{W}_i\left(e^{\mathrm{j\ωM}}\right)]---\left(3\right)$

$=\hat{X}\left(e^{\mathrm{j\ω}}\right)+\mathrm{\α}\underset{k=0}{\overset{M-1}{\mathrm{\Σ}}}{G}_i\left(e^{\mathrm{j\ω}}\right)W_i\left(e^{\mathrm{j\ωM}}\right)$

Wherein

Be reconstruction signal,

$\hat{X}\left(e^{\mathrm{j\ω}}\right)=\frac{1}{M}\underset{l=0}{\overset{M-1}{\mathrm{\Σ}}}X\left(e^{\mathrm{j\ω}-j\frac{2\mathrm{\πl}}{M}}\right)\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}{H}_i\left(e^{\mathrm{j\ω}-j\frac{2\mathrm{\πl}}{M}}\right)G_i\left(e^{\mathrm{j\ω}}\right)---\left(4\right)$

The bank of filters that is used for digital watermarking system should be complete reconfigurable filter group, promptly

$\hat{X}\left(e^{\mathrm{j\ω}}\right)=\mathrm{cX}\left(e^{j(\mathrm{\ω}-{\mathrm{\ω}}_0)}\right)---\left(5\right)$

In view of the consideration of watermark invisibility, should select the bank of filters of c=1, i.e. reconstruction signal

Be original signal X (e ^{J ω}) time-delay.Time delay factor ω ₀The length that depends on wave filter.

Because the existence of time-delay can reduce the invisibility of watermark, in order to eliminate the influence of the time delay that filtering brings, we can carry out following processing to original signal:

The length that makes single filter in the bank of filters is N, and it is individual zero that N is mended at the original signal two ends respectively, and then embed calculation process.2N-1 point and last point before giving up after the processing, the complete reconstruction signal that obtains.

$\hat{X}\left(e^{\mathrm{j\ω}}\right)=X\left(e^{\mathrm{j\ω}}\right)---\left(6\right)$

Can learn that by formula (3) and formula (6) moisture seal signal is:

$X^{\′}\left(e^{\mathrm{j\ω}}\right)=X\left(e^{\mathrm{j\ω}}\right)+\mathrm{\α}\underset{k=0}{\overset{M-1}{\mathrm{\Σ}}}{G}_i\left(e^{\mathrm{j\ω}}\right)W_i\left(e^{\mathrm{j\ωM}}\right)---\left(7\right)$

In the formula (7) $\mathrm{\α}\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}{G}_i\left(e^{\mathrm{j\ω}}\right)W_i\left(e^{\mathrm{j\ωM}}\right)$ Being the influence of the embedding of watermark to original signal, is a key factor of PSNR value between decision original signal and the moisture seal signal.The inverse process of the leaching process of watermark for embedding, concrete enforcement will illustrate in specific embodiment.

A kind of multifunction digital watermark method that the present invention proposes based on the multi-channel filter group, its usefulness is:

1. the present invention embeds a robust watermarking and a fragile watermark simultaneously in a width of cloth media work, protects its copyright information and content integrity simultaneously.

2. the present invention utilizes the multi-channel filter group that image is carried out the decomposition of subband, has following advantage:

(1) the less wavelength-division of the selection of subband is separated more flexible;

(2) can utilize phase mutual interference between the mutually orthogonal property minimizing watermark of bank of filters;

(3) the bank of filters parameter can be used as the key of this algorithm.

3. the present invention can realize blind extraction, can carry out tampering location to malicious attack.

Description of drawings

Fig. 1-based on the digital watermarking embedding principle synoptic diagram of multi-channel filter group

The sub-band division figure of Fig. 2-four-way

Fig. 3-embed block diagram based on the multifunction digital watermark of four-way bank of filters

Fig. 4-extract block diagram based on the multifunction digital watermark of four-way bank of filters

The original robust watermarking of Fig. 5-(a)

The robust watermarking behind the Arnold scramble of Fig. 5-(b)

The original lena image of Fig. 5-(c)

Fig. 5-(d) contains watermarking images, and the PSNR value between the original image is 32.2697

Fig. 6-(a) contain watermarking images, the robust watermarking that directly extracts without any attack

Fig. 6-(b) contain watermarking images, directly the fragile watermark difference figure of Ti Quing without any attack

Fig. 7-(a) the JEPG compression index is 50 attack graph

The robust watermarking of Fig. 7-(b) extract from Fig. 7 (a)

Fig. 7-the fragile watermark that (c) from Fig. 7 (a), extracts and the difference figure of regeneration fragile watermark

Malice after the shade that Fig. 8-(a) will contain watermark lena figure is distorted is distorted figure

The robust watermarking of Fig. 8-(b) extract from Fig. 8 (a)

Fig. 8-the fragile watermark that (c) from Fig. 8 (a), extracts and the difference figure of regeneration fragile watermark

Fig. 9-(a) has added the malice replacement figure of a flower on the cap of lena

The robust watermarking of Fig. 9-(b) extract from Fig. 9 (a)

Fig. 9-the fragile watermark that (c) from Fig. 9 (a), extracts and the difference figure of regeneration fragile watermark

Embodiment

The present invention will be further described below in conjunction with drawings and Examples.

Step of the present invention following (theory diagram is seen accompanying drawing 1):

Embed step

(1) utilize M passage analysis filterbank by row original image to be decomposed into M by row respectively ²Individual subband;

(2) copyright information to be embedded is carried out scramble, generate robust watermarking; From M ²Select low frequency sub-band among the individual subband, robust watermarking is embedded algorithm with suitable robust watermarking be embedded in this low frequency sub-band;

(3) generate fragile watermark according to image low frequency sub-band information, and fragile watermark is embedded in the medium and low frequency subband;

(4) utilize corresponding M passage synthesis filter group that each subband is comprehensive for containing watermarking images.

Extraction step

(1) utilize with above-mentioned embedding step in identical M passage analysis filterbank original image is decomposed by being listed as by row respectively, be decomposed into M ²Individual subband;

(2) corresponding extraction algorithm extracts robust watermarking in utilization and the above-mentioned embedding step, and the copyright information by the random algorithm that is inverted obtains extracting carries out copyright authentication;

(3) extract the testing image characteristic information, regenerate fragile watermark, corresponding extraction algorithm extracts fragile watermark in utilization and the above-mentioned embedding step, and both are carried out XOR relatively, distorts authentication.

Below in conjunction with example embodiment is described.

When utilizing the four-way bank of filters to realize the multifunction digital watermark method of the present invention's proposition, original image passes through bank of filters h by row by row respectively ₀, h ₁, h ₂, h ₃After through down-sampling, the picture element matrix of image can be divided into 16 subbands, as shown in accompanying drawing 2.V among the figure _Mn(m, n=0,1,2,3) expression is by the h that passes through _m, by being listed as through h _nThe subband of filtering gained.Wherein, subband V ₀₀Be low frequency sub-band, comprised most of approximate information of image, other subbands have comprised the detailed information of each frequency range of image.

Specifically, during based on 4 path filter groups, a kind of embodiment of the multifunctional watermark embedding grammar that the present invention proposes may further comprise the steps (as shown in Figure 3):

(1) utilizes 4 passage analysis filterbank original image to be decomposed by row by row respectively, image is divided into 16 subbands.

(2) utilize the copyright information (bianry image) of Arnold transfer pair image to carry out scramble, generate robust watermarking W ₁, (W ₁Be binary map, if original image size is m * n, then the watermark size for m/4 * n/4) with robust watermarking to be embedded in the low frequency sub-band V of image based on the method that quantizes ₀₀In.(scrambling algorithm and embedding algorithm are not unique, select for use the Arnold transform and quantization to embed in this example)

Used based on the robust watermarking embedding grammar that quantizes, specific practice is as follows:

$V_{00}^{\′}(i,j)=\left\{\begin{array}{cc}p*a& \mathrm{mod}(p,2)=W_1(i,j);\\ (p-1)*a& \mathrm{mod}(p,2)\≠W_1(i,j);\end{array}---\left(9\right)\right.$

Symbol   is a rounding operation in the formula (8), V ₀₀' carrying coefficient for behind the embed watermark, i, j are the position of this coefficient in subband, and α is a quantization step, represents the embedment strength of watermark, and the α value is big more, and the robustness of watermark is good more, and observability is poor more; Otherwise α is more little, and watermark robustness is poor more, and observability is good more.That is to say that α is a compromise of robustness and observability.

(3) extract low frequency sub-band V ₀₀Characteristic information generates fragile watermark, and fragile watermark is embedded in the medium and low frequency subband V of image with the method based on relation ₀₁, V ₁₀In.

According to low frequency sub-band V ₀₀The algorithm that generates fragile watermark is as follows:

C is characteristic coefficient (10)

In the formula (10), coefficient c is defined as characteristic coefficient, and the c value is more little, watermark is fragile more, wishes usually during practical application that fragile watermark can resist part and attack, as the JEPG compression etc., be that fragile watermark should be the fragility that satisfies under the certain robustness condition, therefore, the value of c is unsuitable too small.

Draw through emulation, before and after JEPG compressed, though sub-band coefficients changes, the magnitude relationship of sub-band coefficients remained unchanged substantially.Thereby the embedding of fragile watermark is selected to make V based on the embedding grammar that concerns (also can select other reasonably to embed algorithm) among the present invention ₀₁, V ₁₀Work song band coefficient is respectively V ₀₁(i, j), V ₁₀(i, j), fragile watermark W ₂With medium and low frequency subband V based on the method embedded images that concerns ₀₁, V ₁₀In method as follows:

As watermark pixel point value W ₂(i j)=0 o'clock, makes V ₀₁(i, j)-V ₁₀(i, j)＞the b establishment, if be false, then change

V ₀₁(i，j)＝(V ₀₁(i，j)+V ₁₀(i，j))/2+b/2

V ₁₀(i，j)＝(V ₀₁(i，j)+V ₁₀(i，j))/2-b/2 (12)

As watermark pixel point value W ₂(i j)=1 o'clock, makes V ₀₁(i, j)-V ₁₀(i, j)＜-the b establishment, if be false, then change

V ₀₁(i，j)＝(V ₀₁(i，j)+V ₁₀(i，j))/2-b/2

V ₁₀(i，j)＝(V ₀₁(i，j)+V ₁₀(i，j))/2+b/2 (13)

Wherein b is an embedment strength;

(4) utilization is comprehensive for containing watermarking images with each subband with the corresponding 4 passage synthesis filter groups of this routine step (1).

In this example, may further comprise the steps (as shown in Figure 4) based on the extracting method of the multifunctional watermark algorithm of four-way bank of filters:

(1) utilize with embed step in identical 4 passage analysis filterbank original image is decomposed by being listed as by row respectively, image is divided into 16 subbands.

(2) from low frequency sub-band V ₀₀' middle extraction robust watermarking W ₁, carry out the Arnold inverse transformation, calculate original watermark and the watermark that extracts between normalized crosscorrelation value (NC value) carry out copyright and prove.

The extracting method of above-mentioned robust watermarking, specific practice is as follows:

Calculate

Then

The computing formula of NC value is as follows: $\mathrm{NC}=\frac{\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\underset{j=0}{\overset{N}{\mathrm{\Σ}}}W(i,j)W^{\′}(i,j)}{\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\underset{j=0}{\overset{N}{\mathrm{\Σ}}}{\left[W(i,j)\right]}^2}---16$

(3) extract testing image V ₀₀The feature of subband regenerates fragile watermark, from V ₀₁, V ₁₀Extract fragile watermark in the subband, both are carried out XOR relatively, distort authentication.

Extract fragile watermark W ₂' and it is as follows to distort the algorithm of authentication:

$W_2^{\&prime;}(i,j)=\left\{\begin{array}{cc}0& V_{01}(i,j)>V_{10}(i,j)\\ 1& V_{01}(i,j)<V_{10}(i,j)\end{array}\right.$

When utilizing the fragile watermark that extracts to distort authentication in the extraction step, regenerate fragile watermark W by testing image ₂", with the watermark W that extracts ₂' with the fragile watermark W that generates ₂" carry out XOR relatively, can draw watermark and distort difference figure Y:

Y(i，j)＝W ₂′(i，j)W ₂″(i，j) (18)

Provide below and use the simulation result of MATLAB software above-mentioned instantiation.Standard lena gray level image with 256 * 256 is as original image, and copyright information is 64 * 64 the bianry image that has Beijing Institute of Technology's printed words (shown in Fig. 5 (a)), gets robust watermarking W behind the Arnold scramble ₁(shown in Fig. 5 (b)).Extract the low frequency sub-band feature and generate fragile watermark, embedment strength α=5 of robust watermarking, the embedment strength b=5 of fragile watermark, characteristic coefficient c=50 when fragile watermark generates, the PSNR value that contains between watermarking images and the original image is 32.2697, has good imperception, as shown in Figure 5.

If contain watermarking images without any attack, then we can extract robust watermarking and fragile watermark fully, and the NC value is 1 all, does not have the phase mutual interference between the watermark, as shown in Figure 6.

The test of JEPG compression attack as shown in Figure 7, Fig. 7 (a) contains watermarking images after 50 the compression, the robust watermarking Nc1=0.9837 of Fig. 7 (b) for extracting from Fig. 7 a, Fig. 7 (c) schemes Nc2=0.8947 for the fragile watermark and the poor of reconstruct fragile watermark of extracting.As seen it is superior that the present invention proposes the anti-JEPG compression performance of method.

Malice is distorted challenge trial as shown in Figure 8, Fig. 8 (a) is the image after the shade that contains watermark lena figure is distorted, and Fig. 8 (b) is the robust watermarking that extracts from Fig. 8 a, NC=0.9226, as seen under the situation that image suffers necessarily to distort, this algorithm can guarantee that still copyright information steadily and surely exists.Fig. 8 (c) is the fragile watermark difference figure that extracts from 8a, contains watermarking images the figure as can be seen from difference and has experienced which kind of malice and distort.

Malice is replaced challenge trial as shown in Figure 9, and Fig. 9 (a) has added a flower on the cap of lena, and Fig. 9 (b), Fig. 9 (c) are respectively robust watermarking, the fragile watermark difference figure that extracts from Fig. 9 (a).

As seen the multifunction digital watermark method copyright information after normal image Compression based on the multi-channel filter group of the present invention still steadily and surely exists; Malice such as is distorted at operation have sane copyright protection ability, and can provide and distort prompting.

Claims (3)

1. multifunctional water impression method based on the multi-channel filter group is characterized in that: may further comprise the steps:

Embed step

(1) utilize M passage analysis filterbank by row original image to be decomposed into M by row respectively ²Individual subband;

(2) copyright information to be embedded is carried out scramble, generate robust watermarking; From M ²Select low frequency sub-band among the individual subband, robust watermarking is embedded algorithm with suitable robust watermarking be embedded in this low frequency sub-band;

(3) generate fragile watermark according to image low frequency sub-band information, and fragile watermark is embedded in the medium and low frequency subband;

(4) utilize corresponding M passage synthesis filter group that each subband is comprehensive for containing watermarking images;

Extraction step

(1) utilize with above-mentioned embedding step in identical M passage analysis filterbank original image is decomposed by being listed as by row respectively, be decomposed into M ²Individual subband;

(2) corresponding extraction algorithm extracts robust watermarking in utilization and the above-mentioned embedding step, and the copyright information by the random algorithm that is inverted obtains extracting carries out copyright authentication;

(3) extract the testing image characteristic information, regenerate fragile watermark, corresponding extraction algorithm extracts fragile watermark in utilization and the above-mentioned embedding step, and both are carried out XOR relatively, distorts authentication.

2. according to the described a kind of multifunctional water impression method of claim 1, it is characterized in that based on the multi-channel filter group:

Embed in the step according to low frequency sub-band V ₀₀The algorithm that generates fragile watermark is as follows:

C is a characteristic coefficient;

3. according to the described a kind of multifunctional water impression method of claim 1, it is characterized in that based on the multi-channel filter group:

When utilizing the fragile watermark that extracts to distort authentication in the extraction step, regenerate fragile watermark W by testing image according to the described method of claim 2 ₂", with the watermark W that extracts ₂' with the fragile watermark W that generates ₂" carry out XOR relatively, can draw watermark and distort difference figure Y:

Y(i，j)＝W ₂′(i，j)W ₂″(i，j)。

Images