NSCT-UPEMD-PHT based robust zero-watermarking algorithm and system
A non-subsampled contourlet transform (NSCT)-uniform phase empirical mode decomposition (UPEMD)-polar harmonic transform (PHT) based robust zero-watermarking algorithm is provided, including the following steps: step 1: encryption on a watermark image through a Tent map; step 2: watermark embedding; step 3: watermark extraction; and step 4: decryption on the watermark image. Before embedded into a host image, the watermark image is encrypted based on the Tent map, ensuring the security of the watermark. The NSCT is performed on a host image, low-frequency information is extracted, and the UPEMD and the PHT are performed on the low-frequency information, thereby realizing the watermark embedding. This application organically combines the chaotic map algorithm and the novel watermarking technique, realizing the method of embedding a digital zero-watermark into a digital image.
1 . A computer-implemented copyright protection method, comprising:
obtaining a first image to be subjected to copyright verification;
extracting watermark from the first image, comprising:
step 1: performing full-scale non-subsampled contourlet transform (NSCT) on the first image I(i, j) to obtain one first low-frequency sub-band and four first high-frequency sub-bands, I representing the first image;
step 2: performing Hilbert-curve dimensionality reduction on the first low-frequency sub-band to obtain a first one dimensional (1D) low-frequency sub-band;
step 3: for the first 1D low-frequency sub-band, decomposing a signal S′(t) of the first 1D low-frequency sub-band into different bands with wavelet packet decomposition (WPD), each band carrying a signal component, and determining a last intrinsic mode of the first 1D low-frequency sub-band after WPD;
step 4: performing inverse Hilbert-curve dimensionality augmentation on the last intrinsic mode of the first 1D low-frequency sub-band after WPD, subjecting to a polar coordinate domain transformation and extracting values in a unit circle to obtain a modal matrix X;
step 5: performing a polar harmonic transform (PHT) on the modal matrix X′ to obtain a first PHT moment, and performing following calculation on the first PHT moment:
Y
j
′
=
∑
i
+
3
i
X
i
′
+
N
wherein Y′ j is a processed PHT value, and X′ i is an original value of an element of the first PHT moment; and
step 6: subjecting a first processed PHT moment Y′(i, j) to mean normalization, followed by XORing with a stored key W y (i, j) to obtain an encrypted watermark;
performing watermark decryption, comprising: XORing a stored decryption key W 0 and the encrypted watermark obtained in the step 6 to obtain a first watermark image;
comparing the first watermark image with a second watermark image stored and containing copyright information;
in response to a comparison result indicating that the first watermark image and the second watermark image are identical, determining that a copyright of the first image is legal.
2 . The computer-implemented copyright protection method according to claim 1 , wherein the decryption key W 0 is obtained by following steps:
generating a chaotic sequence from an initial value α, and followed by binarizing as X(j),X(j)|X(j)=1,0;
storing X(j),X(j)|X(j)=1,0 as a decryption key W 0 .
3 . The computer-implemented copyright protection method according to claim 2 , wherein the stored key W y (i, j) is obtained by following steps:
receiving the second watermark image containing the copyright information input by a user;
performing encryption on the second watermark image W(i, j) through a Tent map, comprising: XORing X(j),X(j)|X(j)=1,0 and the second watermark image to obtain an encrypted second watermark image W e (i, j);
performing watermark embedding, comprising
step 1: performing the full-scale NSCT on a second image I(i, j) input by the user to be subjected to copyright protection, to obtain one second low-frequency sub-band and four second high-frequency sub-bands, I representing the second image;
step 2: performing the Hilbert-curve dimensionality reduction on the second low-frequency sub-band to obtain a second one-dimensional (1D) low-frequency sub-band;
step 3: for the second 1D low-frequency sub-band, decomposing a signal S(t) of the second 1D low-frequency sub-band into different bands with the WPD, each band carrying a signal component, and determining a last intrinsic mode of the second 1D low-frequency sub-band after WPD;
step 4: performing the inverse Hilbert-curve dimensionality augmentation on the last intrinsic mode of the second 1D low-frequency sub-band after WPD, subjecting to a polar coordinate domain transformation and extracting values in a unit circle to obtain a modal matrix X;
step 5: performing the PHT on the modal matrix X to obtain a second PHT moment, and performing following calculation on the second PHT moment:
Y
j
=
∑
i
+
3
i
X
i
+
N
wherein Y i is a processed PHT value, X i is an original value of an element of the second PHT moment; and
step 6: subjecting a second processed PHT moment Y(i, j) to the mean normalization, followed by XORing with the encrypted second watermark image W e (i, j) to obtain the key W y (i, j).
4 . The computer-implemented copyright protection method according to claim 1 , wherein the decryption key W 0 , the key W y (i, j), and the second watermark image containing the copyright information are stored in a trustworthy third-party library.
5 . The computer-implemented copyright protection method according to claim 1 , wherein in the step 5, for
Y
j
′
=
∑
i
+
3
i
X
i
′
+
N
in a process of extracting watermark features and a method for processing the first PHT moment, N is initially 45.
6 . A copyright protection device, comprising a processor and a memory storing instructions that, when executed by the processor, cause the copyright protection device to perform the computer-implemented copyright protection method according to claim 1 .
7 . The copyright protection device according to claim 6 , wherein the decryption key W 0 is obtained by following steps:
generating a chaotic sequence from an initial value α, and followed by binarizing as X(j),X(j)|X(j)=1, 0;
storing X(j),X(j)|X(j)=1,0 as a decryption key W 0 .
8 . The copyright protection device according to claim 7 , wherein the stored key W y (i, j) is obtained by following steps:
receiving the second watermark image containing the copyright information input by a user;
performing encryption on the second watermark image W(i, j) through a Tent map, comprising: XORing X(j),X(j)|X(j)=1,0 and the second watermark image to obtain an encrypted second watermark image W e (i, j);
performing watermark embedding, comprising
step 1: performing the full-scale NSCT on a second image I(i, j) input by the user to be subjected to copyright protection, to obtain one second low-frequency sub-band and four second high-frequency sub-bands, I representing the second image;
step 2: performing the Hilbert-curve dimensionality reduction on the second low-frequency sub-band to obtain a second one-dimensional (1D) low-frequency sub-band;
step 3: for the second 1D low-frequency sub-band, decomposing a signal S(t) of the second 1D low-frequency sub-band into different bands with the WPD, each band carrying a signal component, and determining a last intrinsic mode of the second 1D low-frequency sub-band after WPD;
step 4: performing the inverse Hilbert-curve dimensionality augmentation on the last intrinsic mode of the second 1D low-frequency sub-band after WPD, subjecting to a polar coordinate domain transformation and extracting values in a unit circle to obtain a modal matrix X;
step 5: performing the PHT on the modal matrix X to obtain a second PHT moment, and performing following calculation on the second PHT moment:
Y
j
=
∑
i
+
3
i
X
i
+
N
wherein Y i is a processed PHT value, X i is an original value of an element of the second PHT moment; and
step 6: subjecting a second processed PHT moment Y(i, j) to the mean normalization, followed by XORing with the encrypted second watermark image W e (i, j) to obtain the key W y (i, j).
9 . The copyright protection device according to claim 6 , wherein the decryption key W 0 , the key W y (i, j), and the second watermark image containing the copyright information are stored in a trustworthy third-party library.
10 . The copyright protection device according to claim 6 , wherein in the step 5, for
Y
j
′
=
∑
i
+
3
i
X
i
′
+
N
in a process of extracting watermark features and a method for processing the first PHT moment, N is initially 45.
11 . A non-transitory computer readable storage medium, wherein the storage medium stores instructions which, when executed, cause a computer to perform the computer-implemented copyright protection method according to claim 1 .
12 . The non-transitory computer readable storage medium according to claim 11 , wherein the decryption key W 0 is obtained by following steps:
generating a chaotic sequence from an initial value α, and followed by binarizing as X(j),X(j)|X(j)=1, 0;
storing X(j),X(j)|X(j)=1,0 as a decryption key W 0 .
13 . The non-transitory computer readable storage medium according to claim 12 , wherein the stored key W y (i, j) is obtained by following steps:
receiving the second watermark image containing the copyright information input by a user;
performing encryption on the second watermark image W(i, j) through a Tent map, comprising: XORing X(j),X(j)|X(j)=1,0 and the second watermark image to obtain an encrypted second watermark image W e (i, j);
performing watermark embedding, comprising
step 1: performing the full-scale NSCT on a second image I(i, j) input by the user to be subjected to copyright protection, to obtain one second low-frequency sub-band and four second high-frequency sub-bands, I representing the second image;
step 2: performing the Hilbert-curve dimensionality reduction on the second low-frequency sub-band to obtain a second one-dimensional (1D) low-frequency sub-band;
step 3: for the second 1D low-frequency sub-band, decomposing a signal S(t) of the second 1D low-frequency sub-band into different bands with the WPD, each band carrying a signal component, and determining a last intrinsic mode of the second 1D low-frequency sub-band after WPD;
step 4: performing the inverse Hilbert-curve dimensionality augmentation on the last intrinsic mode of the second 1D low-frequency sub-band after WPD, subjecting to a polar coordinate domain transformation and extracting values in a unit circle to obtain a modal matrix X;
step 5: performing the PHT on the modal matrix X to obtain a second PHT moment, and performing following calculation on the second PHT moment:
Y
j
=
∑
i
+
3
i
X
i
+
N
wherein Y i is a processed PHT value, X i is an original value of an element of the second PHT moment; and
step 6: subjecting a second processed PHT moment Y(i, j) to the mean normalization, followed by XORing with the encrypted second watermark image W e (i, j) to obtain the key W y (i, j).
14 . The non-transitory computer readable storage medium according to claim 11 , wherein the decryption key W 0 , the key W y (i, j), and the second watermark image containing the copyright information are stored in a trustworthy third-party library.
15 . The non-transitory computer readable storage medium according to claim 11 , wherein in the step 5, for
Y
j
′
=
∑
i
+
3
i
X
i
′
+
N
in a process of extracting watermark features and a method for processing the first PHT moment, N is initially 45.