CN102938134A - Digital watermark embedding and detecting method based on phase-shifting interferometry and singular value decomposition - Google Patents

Abstract

The invention discloses a digital watermark embedding and detecting method based on phase-shifting interferometry and singular value decomposition. The method includes two processes of watermark embedding and watermark detection, the embedding process includes watermarking information encryption is achieved by double random phase encoding and the phase-shifting interferometry of a Fresnel domain, and after encryption, a watermark image is embedded into a singular value transform domain of a host image; and an extraction method includes extracting encrypted information from a watermark image contained singular value matrix to be detected, and deciphering through double random phase decoding and the phase-shifting interferometry of the Fresnel domain to obtain a gray-scale watermark image. Compared with prior digital watermarking methods, the digital watermark embedding and detecting method based on the phase-shifting interferometry and the singular value decomposition has the advantages that the invisibility and robustness are remarkably improved, the shear-resistant capability is greatly improved, a series of image processing modes can be resisted, and high robustness and excellent safety are achieved.

Description

Digital watermarking embedding and detection method based on phase shift interference art and svd

Technical field

The present invention relates to a kind of digital watermarking embedding and detection method based on phase shift interference art and svd, belong to field of information security technology.

Background technology

Along with the develop rapidly of information science and network technology, digital medium information exchanges and reaches unprecedented depth ﹠ wideth.Thing followed information security and intellectual property protection and authentication question also become increasingly conspicuous, and be extremely urgent to the copyright protection of digital product.Digital watermark technology is the technology that the copyright protection of digital product that occurs in recent years and data security are safeguarded, is the study hotspot of current international academic community.

At present, the embedding grammar research for image digital watermark can be divided into two classes: space watermark algorithm and transform domain watermarking algorithm.Wherein the space watermark algorithm is directly at the signal space watermark information that superposes, and the advantage of this class algorithm is that algorithm is simple, speed fast, easily realize, embedding capacity is large, and shortcoming is to lack the robustness of normal image being processed operation.The transform domain watermarking algorithm is first image to be carried out certain reversible mathematic(al) manipulation, then makes amendment by the coefficient to transform domain, reaches the purpose of embed watermark information.The existing general Digital Watermark Scheme based on conversion such as discrete cosine transform (DCT), discrete Fourier transformation (DFT) and wavelet transforms (DWT) all has preferably robustness for attacks such as compression of images, image filtering and noises, but still needs further to improve for the robustness of shearing attack and geometric attack.

In recent years, optical holography image itself relies on its characteristic that can not tear to pieces, has obtained extensive concern in Digital Watermark Scheme, and efficiently solve in the existing general digital watermark technology can not fine resisting cropping attack problem.

Svd (SVD) is a kind of numerical algorithm with diagonalization of matrix.The singular value of image array has characterized the intrinsic characteristic of image, has extraordinary stability, namely when image is applied in small disturbance (as add make an uproar, filtering, compression, convergent-divergent etc.), its singular value does not have larger variation, and singular value has transposition, rotation, displacement, mirror transformation unchangeability etc., these characteristics so that it aspect digital watermarking, be widely used.

Summary of the invention

The present invention is directed to the deficiency of existing digital watermarking embedding and detection technique, a kind of digital watermark method based on phase shift interference and svd is provided, the method not only has preferably not sentience and higher security, and can resist a series ofly as diminish the image processing method formulas such as compression, shearing, noise, filtering, geometric operation, have stronger robustness.

Digital watermarking embedding and detection method based on phase shift interference art and svd of the present invention comprise two processes of watermark embedding and watermark detection:

(1) telescopiny of watermark:

A. the plane with digital watermarking image O place is called input plane, is close to the back of input plane and places first random phase plate G ₁, with wavelength be the monochromatic plane wave vertical irradiation of λ to input plane, calculate digital watermarking image O and first random phase plate G ₁The product of complex amplitude transmitance, then this product being carried out distance parameter is d ₁Discrete fresnel diffraction conversion DFD, obtain complex amplitude field U ₂, this complex amplitude field U ₂The plane at place is called changing the plane;

B. be close to the changing the plane back and place second random phase plate G ₂, complex amplitude field U ₂Multiply by second random phase plate G ₂The complex amplitude transmitance obtain a product, doing once to this product, distance is d ₂Discrete fresnel diffraction conversion DFD, obtaining complex amplitude field U(is the object wave field), the plane at this U place, complex amplitude field is called the record plane, on this record plane, records the complex amplitude field U that carries digital watermark information by three step of follow-up standard phase shift interference art;

C. adopt standard three step phase shift interference art, by interfering with the reference light of introducing, obtain three width of cloth contain hide Info and the phase-plate modulation after interferogram I ₁, I ₂And I ₃When interfering for three times, the phase place of reference light is respectively 0, pi/2 and π;

D. three components of R, G, B of colored host image H are carried out svd SVD, three width of cloth interferogram I ₁, I ₂And I ₃In the singular value matrix of R, the G of the colored host image H of embedding, three components of B, obtain containing the image H ' of watermark, and pass to the take over party (can pass through network or alternate manner) of information after encrypting, simultaneously parameter G ₂, d ₁, d ₂Also together transmit as key with the new coloured image K that generates in λ and the svd process;

(2) testing process of watermark:

A. from the image H ' that contains watermark, extract I by svd ₁, I ₂And I ₃

B. recover the complex amplitude field U that records after encrypt on the plane by standard three step phase shift formula;

C. making distance is d ₂Contrary fresnel diffraction conversion;

D. the complex amplitude that draws multiply by second random phase plate G ₂The complex amplitude transmitance, make another distance for d ₁Contrary fresnel diffraction conversion;

E. extract the real amplitude part of diffraction complex amplitude field, can obtain watermarking images.

The invention has the advantages that: (1) combines the phase shift digital hologram with based on singularity value decomposition, constructs a kind of new Digital Watermarking System in Transform Domain method, compares with digital watermark method in the past, and its invisibility and robustness all increase significantly; (2) the phase shift Digital Holography is introduced in the digital watermark method, so that the ability of its opposing shearing attack improves greatly; (3) based on singularity value decomposition is introduced in the digital watermark method, so that it can be resisted a series of as diminish the image processing method formulas such as compression, shearing, noise, filtering, geometric operation, had stronger robustness; (4) because in the watermark encrypting process, with the geometrical structure parameter of virtual optical path and optical parametric as key, thereby designed multiple key, watermarking algorithm has good security.

Description of drawings

Fig. 1 is based on the information enciphering/deciphering principle schematic of double random phase coding and three step phase shift interference arts.

Fig. 2 is based on the digital watermarking embedding of phase shift interference art and svd and the process flow diagram that extracts.

Fig. 3 a is watermarking images, and Fig. 3 b is original image, and Fig. 3 c is the image behind the embed watermark (weight factor of embedding is 0.1).

Fig. 4 is the Robust Test chart in the lower the inventive method of rotation attack (being rotated counterclockwise).

Fig. 5 is the Robust Test curve map of the inventive method under three kinds of noises (salt-pepper noise, Gaussian noise, speckle noise) are attacked.

Fig. 6 is the Robust Test curve map of the inventive method under the JPEG lossy compression method.

Fig. 7 is the Robust Test chart of the inventive method under shearing attack.

Fig. 8 a is the watermarking images that contains behind medium filtering, and Fig. 8 b is the watermarking images of corresponding extraction, CC=0.7754.

Fig. 9 a is the watermarking images that contains behind gaussian filtering, and Fig. 9 b is the watermarking images of corresponding extraction, CC=0.9336.

Figure 10 a is the watermarking images that contains behind mean filter, and Figure 10 b is the watermarking images of corresponding extraction, CC=0.5489.

Figure 11 a is that Figure 11 b is the watermarking images of corresponding extraction, CC=0.8702 through the filtered watermarking images that contains of Laplce.

Figure 12 a is the watermarking images that contains after the sobel sharpening, and Figure 12 b is the watermarking images of corresponding extraction, CC=0.8371.

Figure 13 is the Robust Test chart of the inventive method under contrast and brightness adjustment.

Figure 14 a is the watermarking images that contains behind histogram equalization, and Figure 14 b is the watermarking images CC=0.8454 of corresponding extraction.

Among the figure: O is watermarking images, and I is input plane, and II is changing the plane, and III is the record plane, and the coordinate that three dimensions is chosen is respectively (x ₁, y ₁), (x ₂, y ₂) and (x, y).d ₁Be the distance between input plane and the changing the plane, d ₂Be the distance between changing the plane and the record plane.G ₁, G ₂Be two random phase plate, its complex amplitude transmitance can be expressed as respectively exp[i2 π P ₁(x ₁, y ₁)] and exp[i2 π P ₂(x ₂, y ₂)], P wherein ₁And P ₂Two white noises that are randomly dispersed between [0,1].PSNR is Y-PSNR, and CC is related coefficient.

Embodiment

Fig. 1 is based on the watermark enciphering/deciphering principle schematic of double random phase coding and phase shift interference art.O is watermarking images among the figure, and I is input plane, and II is changing the plane, and III is the record plane, and the coordinate that three dimensions is chosen is respectively (x ₁, y ₁), (x ₂, y ₂) and (x, y).d ₁Be the distance between input plane and the changing the plane, d ₂Be the distance between changing the plane and the record plane.G ₁, G ₂Be two random phase plate, its complex amplitude transmitance can be expressed as respectively exp[i2 π P ₁(x ₁, y ₁)] and exp[i2 π P ₂(x ₂, y ₂)], P wherein ₁And P ₂Two white noises that are randomly dispersed between [0,1].Suppose that diffraction related in the virtual optics system all satisfies the Fresnel approximation condition.In watermark embed process, can be with the wavelength X of virtual light wave, between input plane, changing the plane and the record plane apart from d ₁, d ₂, the complex amplitude transmitance of random phase plate is as watermark keys, thereby designs multiple key, improves the security of digital watermarking.

When a wavelength is the monochromatic plane wave illumination input plane of λ, under the condition of Fresnel approximation, the complex amplitude field U of changing the plane ₂Can be expressed as:

$U_2(x_2,y_2)=\frac{\exp \left({\mathrm{ikd}}_1\right)}{\mathrm{i\λ}{d}_1}\∫\∫O(x_1,y_1)\exp \left[i2\mathrm{\π}{P}_1(x_1,y_1)\right]\exp \left\{\frac{\mathrm{i\π}}{\mathrm{\λ}{d}_1}\right[{(x_1-x_2)}^2+{(y_1-y_2)}^2\left]\right\}{\mathrm{dx}}_1{\mathrm{dy}}_1---\left(1\right)$

K=2 π/λ wherein.For explaining for simplicity, following formula is write as:

$U_2(x_2,y_2)=\mathrm{Fr}{T}_{d_1}\left\{O(x_1,y_1)\exp \right[i2\mathrm{\π}{P}_1(x_1,y_1)\left]\right\}---\left(2\right)$

Wherein

Expression is to d ₁Fresnel transform.Therefore, the complex amplitude field U on record plane also can be expressed as

$U(x,y)=\mathrm{Fr}{T}_{d_2}\left\{U_2(x_2,y_2)\exp \right[i2\mathrm{\π}{P}_2(x_2,y_2)\left]\right\}---\left(3\right)$

By using beam splitter BS, introducing reference light wave one phase place is δ _nPlane wave.Reference light wave and thing light wave are at the CCD Surface Interference, and the light distribution that obtains is

$I_n(x,y)=A^2(x,y)+A_r^2+2A_{r}A(x,y)\cos (\mathrm{\ψ}-{\mathrm{\δ}}_n)---\left(4\right)$

Here define U (x, y)=A (x, y) exp[i Ψ (x, y)], A and Ψ represent respectively real amplitude and the phase place of thing light wave U, A _rBe the real amplitude of reference light, it is predeterminable to be a normal number; The phase place δ of reference light wave _nCan be by phase shifting devices such as wave plate or piezoelectric ceramic devices (PZT) control.Employing standard three step phase shift interference art, by interfering with the reference light of introducing when interfering (three times, the phase place of reference light is respectively 0, pi/2 and π), can obtain three width of cloth contain hide Info and the phase-plate modulation after interferogram I ₁, I ₂And I ₃, the geometric parameter of system and optical parametric G ₂, d ₁, d ₂, λ is as key.

Fig. 2 is based on the digital watermarking process flow diagram of phase shift interference and svd.Embedding in the original image process through the watermarking images after encrypting, at first R, G, the B component of original image H are carried out svd, obtain two orthogonal matrix U _m, V _mAnd diagonal matrix S _m

H _m=U _m* S _m* V _m ^T(m is respectively R, G, B) (5)

With the matrix S that is added to of the watermark after encrypting _mThe upper left corner, to new matrix S _m+ α I _mCarry out again svd, obtain U _m', S _m' and V _m'.

S _m+ α I _m=U _m' * S _m' * V _m' ^T(m is respectively R, G, B) (6)

Wherein α is that weight factor (α〉0) is to regulate the stack intensity of watermark.

HW _m=U _m*S _m'*V _m ^T (7)

K _m=U _m'*S _m*V _m′ ^T (8)

HW _mThe image that contains watermark that obtains, HW _m(m=R, G, B) forms the coloured image that comprises watermark, K as R, G, B component _mForm new coloured image K as R, G, B component, new coloured image K together transmits as retention parameter and key.

After the take over party obtains all keys, can rebuild original image on the object plane by following steps:

1) the RGB component of the image H ' that receives is done respectively svd

SVD(H _m')=UW _m*SW _m*VW _m ^T (m=R,G,B) (9)

2) to the RGB component K of key K _mCarry out respectively svd

SVD(K _m)=UK _m*SK _m*VK _m ^T (m=R,G,B)

(10)

3) extract by following formula

I _n=(UK _m* SW _m* VK _m ^T-SK _m)/α (n=1,2,3 respectively with m=R, G, B is corresponding)

(11)

4) recover the complex amplitude field U that records after encrypt on the plane by standard three step phase shift formula,

$U(x,y)=\frac{1}{4A_r}[I_1-I_3+i(2I_2-I_1-I_3)]---\left(12\right)$

5) recover complex amplitude field on the former input plane by twice contrary Fresnel transform

$O^{,}(x_1,y_1)=\mathrm{IFr}{T}_{d_1}\left\{\mathrm{IFr}{T}_{d_2}\right[U(x,y)\left]\exp \right[-i2\mathrm{\π}{P}_2(x_2,y_2)\left]\right\}---\left(13\right)$

6) the real amplitude of extraction O' can decrypt hiding watermarking images.

The present invention adopts the method based on phase shift interference art and svd to realize watermarking, and that its application program adopts is Matlab2009a.In order to verify the robustness of described algorithm under the common image processing is attacked, carried out a large amount of tests and provided the robustness test result containing watermarking images, totally 8 aspects: image rotation, interpolation noise (3 kinds), lossy compression method, image cropping, filtering (4 kinds), sharpening, contrast adjustment and histogram equalization.

In order to compare the robustness of watermark in the disturbance situation, adopt Y-PSNR (PSNR) and related coefficient (CC) as the evaluation criterion parameter, the below provides respectively its definition.

1) Y-PSNR (PSNR)

$\mathrm{PSNR}=20\×{\log }_{10}\left(\frac{255}{\sqrt{\mathrm{MSE}}}\right)---\left(14\right)$

Wherein, $\mathrm{MSE}=\frac{1}{\mathrm{MN}}\underset{y=1}{\overset{M}{\mathrm{\Σ}}}\underset{x=1}{\overset{N}{\mathrm{\Σ}}}{[I(x,y)-I^{\′}(x,y)]}^2---\left(15\right)$

MSE represents original host image and contains mean square deviation between the watermarking images, line number and the columns of the other presentation video of M, N.Estimate by Y-PSNR PSNR and to contain watermarking images with respect to host image quality decline degree.

2) related coefficient (CC)

$\mathrm{CC}=\frac{\mathrm{COV}(I,I^{\′})}{{\mathrm{\σ}}_I{\mathrm{\σ}}_{I^{\′}}}---\left(16\right)$

Wherein, σ is the standard deviation of respective image, and the associative operation of two width of cloth images is asked in COV (I, I ') representative, can be defined as

COV(I,I')=E{[I-E(I)]-[I'-E(I')]}， (17)

E[wherein] the expression mathematical expectation.

Fig. 3 a and Fig. 3 b represent respectively original watermarking images (256 * 256 pixels, gray level image) and host image (512 * 512 pixels, the RGB coloured image), the weight factor of choosing the watermark embedding is 0.1, the image that is embedded with watermark that employing the inventive method obtains is shown in Fig. 3 c, with the Y-PSNR (PSNR) of original image be 62.6666, the invisibility of watermark is fine.Fig. 4 is the Robust Test chart in the lower the inventive method of rotation attack (being rotated counterclockwise), can find out that by chart the inventive method can effectively resist rotation attack how much.Fig. 5 and Fig. 6 be respectively the inventive method to applying the robustness test curve of noise and JPEG lossy compression method, can find out that the inventive method is very good to the robustness effect of these two kinds of attacks.Fig. 7 is the Robust Test chart of the inventive method under shearing attack, and the watermarking images that recovers when falling 60% when image is cropped is still high-visible, and related coefficient reaches 0.6075.Fig. 8, Fig. 9, Figure 10 and Figure 11 carry out the watermarking images that medium filtering, gaussian filtering, mean filter and Laplce's filtering are processed (all adopting 3 * 3 spectral windows) and extracted to containing watermarking images respectively, as can be seen from the figure the inventive method has stronger immunity to Filtering Attacks, and is comparatively responsive to mean filter.Figure 12, Figure 13 and Figure 14 are that watermarking images carries out sobel sharpening, contrast and brightness adjustment, histogram equalization is processed and the watermarking images of extraction to containing respectively, and be also very high to its robustness by the visible this method of result.

Water mark method based on phase shift interference art and svd of the present invention is not limited only to the processing of image information, also is applicable to the multimedia messagess such as digital video, audio frequency simultaneously, has wide practical use in the copyright protection field of digital medium information.

Claims (1)

1. digital watermarking embedding and detection method based on phase shift interference art and a svd comprise two processes of watermark embedding and watermark detection, it is characterized in that:

(1) telescopiny of watermark:

A. the plane with digital watermarking image O place is called input plane, is close to the back of input plane and places first random phase plate G ₁, with wavelength be the monochromatic plane wave vertical irradiation of λ to input plane, calculate digital watermarking image O and first random phase plate G ₁The product of complex amplitude transmitance, then this product being carried out distance parameter is d ₁Discrete fresnel diffraction conversion DFD, obtain complex amplitude field U ₂, this complex amplitude field U ₂The plane at place is called changing the plane;

B. be close to the changing the plane back and place second random phase plate G ₂, complex amplitude field U ₂Multiply by second random phase plate G ₂The complex amplitude transmitance obtain a product, doing once to this product, distance is d ₂Discrete fresnel diffraction conversion DFD, obtain complex amplitude field U, the plane at this U place, complex amplitude field is called the record plane, on this record plane, records the complex amplitude field U that carries digital watermark information by follow-up standard three step phase shift interference art;

C. adopt standard three step phase shift interference art, by interfering with the reference light of introducing, obtain three width of cloth contain hide Info and the phase-plate modulation after interferogram I ₁, I ₂And I ₃When interfering for three times, the phase place of reference light is respectively 0, pi/2 and π;

D. three components of R, G, B of colored host image H are carried out svd SVD, three width of cloth interferogram I ₁, I ₂And I ₃In the singular value matrix of R, the G of the colored host image H of embedding, three components of B, obtain containing the image H ' of watermark, and pass to the take over party of information after encrypting, simultaneously parameter G ₂, d ₁, d ₂Also together transmit as key with the new coloured image K that generates in λ and the svd process;

(2) testing process of watermark:

A. from the image H ' that contains watermark, extract I by svd ₁, I ₂And I ₃

B. recover the complex amplitude field U that records after encrypt on the plane by standard three step phase shift formula;

C. making distance is d ₂Contrary fresnel diffraction conversion;

D. the complex amplitude that draws multiply by second random phase plate G ₂The complex amplitude transmitance, make another distance for d ₁Contrary fresnel diffraction conversion;

E. extract the real amplitude part of diffraction complex amplitude field, can obtain watermarking images.

Images