CN103985079A - Tampering detection method for digital image with invisible watermark - Google Patents

Abstract

The invention discloses a tampering detection method for a digital image with an invisible watermark. The tampering detection method comprises the steps that firstly, invisible watermark encryption is conducted on the digital image, wherein the host image and an encryption watermark image are respectively expressed in the form of a pixel matrix, and the pixel matrix of the encryption watermark image is embedded in the host image through a watermark encryption algorithm; then the digital image with the invisible watermark is decoded, wherein the pixel matrix of the watermark image is extracted and restored from the pixel matrix of the host image through a watermark decoding algorithm; finally, the encryption watermark image and the restored watermark image are compared, if the pixel matrix of the encryption watermark image is equal to the pixel matrix of the restored watermark image, it is indicated that the host image is not tampered, and if not, it is indicated that the host image is tampered. The tampering detection method is simple, easy and convenient to implement, capable of quickly judging whether an image is tampered, and beneficial to copyright protection.

Description

With the digital image tampering detection method of stealthy watermark

Technical field

The present invention relates to digital image watermarking technology, relate in particular to the digital image tampering detection method with stealthy watermark, belong to technical field of image processing.

Background technology

Along with the development of multimedia technology, people use and become further frequent with the digital product such as image, video, also more and more extensive to the utilization field of these digital products, so for the original identification of picture, distort to detect and become distinct issues.

Summary of the invention

The object of the present invention is to provide a kind of digital image tampering detection method with stealthy watermark, can effectively detect host image and whether distort.

The technical solution adopted in the present invention is: with the digital image tampering detection method of stealthy watermark, it is characterized in that, comprise the steps:

Step 1: digital picture is carried out to stealthy watermark encrypting: host image and encrypted watermark image are represented with picture element matrix form respectively, the picture element matrix of encrypted watermark image is embedded in host image through watermark encrypting algorithm;

Step 2: the digital picture with stealthy watermark is decoded: the picture element matrix that extracts reductive water watermark image from the picture element matrix of host image through watermark decode algorithm;

Step 3: relatively encrypted watermark image and reductive water watermark image: if the picture element matrix of encrypted watermark image equate with the picture element matrix of reductive water watermark image, illustrate that host image is not tampered, otherwise, illustrate that host image is tampered.

Described watermark encrypting algorithm comprises the steps:

1) host image and encrypted watermark image are represented with picture element matrix form respectively:

If the picture element matrix of host image by N capable × a M row arrangement of subpixels forms, and is designated as A _nM, A _nMin the sub-pixel of capable, the j of i row be designated as a _ij; Wherein, 1≤i≤N, 1≤j≤M, 0≤a _ij≤ 255;

If the picture element matrix of encrypted watermark image by n capable × a m row arrangement of subpixels forms, and is designated as B _nm, B _nmin the sub-pixel of capable, the t of s row be designated as b _st; Wherein, 1≤s≤n, 1≤t≤m, 0≤b _st≤ 255;

Wherein, N >=n, M >=3m;

2) extract B _nmhundred, ten, individual position of sub-pixel: establish sub-pixel b _sthundred, ten, individual position be designated as respectively x, y, z;

3) by A _nMin the position of sub-pixel to be encrypted make zero: selected A _nMthe middle value of being expert at is not more than n, and the sub-pixel that place train value is not more than 3m is sub-pixel to be encrypted, made zero in a position for sub-pixel to be encrypted, and the sub-pixel a'' after i is capable, j row make zero _ijrepresent;

4) encrypted watermark image is embedded to host image: by A _nMin the sub-pixel of capable, the j of i row after encrypting be designated as

By sub-pixel b _sthundred x and a'' _{s (3t-2)}be added,

By sub-pixel b _stten y and a'' _{s (3t-1)}be added,

By sub-pixel b _stposition z and a'' _{s (3t)}be added,

The rest may be inferred, until by B _nmin all sub-pixels be embedded into A _nMin, A _nMin the sub-pixel that is not encrypted remain unchanged, obtain thus the image pixel matrix C after encrypting _nM.

Described watermark decode algorithm comprises the steps:

1) selected C _nMthe middle value of being expert at is not more than n, and the region that place train value is not more than 3m is region to be decoded;

2) in region to be decoded, with behavior unit, from left to right successively at C _nMin get three sub-pixels, and extract the units of three sub-pixels: establish from C _nMin three capable got sub-pixels of p be respectively wherein, units be designated as x ', units be designated as y ', units be designated as z ';

3) units of three sub-pixels is multiplied by respectively to 100,10,1, and summation, reduction draws the picture element matrix of reductive water watermark image in sub-pixel: $b_{p\left(\frac{q+2}{3}\right)}^o={100x}^{,}+{10y}^{,}+{1z}^{,},$ represent in p capable, the sub-pixel of row.

Compared with prior art, the beneficial effect that the present invention reaches: a kind of digital image tampering detection method with stealthy watermark is provided, and its algorithm is simple, easy to operation, can judge that whether image distorts detection, is beneficial to copyright protection fast; By adjusting unessential data, less on the visual effect impact of original image; And the method calculated amount is little, requirement of real time.

Brief description of the drawings

Fig. 1 is operational flowchart of the present invention.

Embodiment

Following examples are only for technical scheme of the present invention is more clearly described, and can not limit the scope of the invention with this.

As shown in Figure 1, with the digital image tampering detection method of stealthy watermark, comprise the steps:

Step 1: digital picture is carried out to stealthy watermark encrypting: host image and encrypted watermark image are represented with picture element matrix form respectively, the picture element matrix of encrypted watermark image is embedded in host image through watermark encrypting algorithm.

Watermark encrypting algorithm comprises the steps:

1) host image and encrypted watermark image are represented with picture element matrix form respectively:

If the picture element matrix of host image by N capable × a M row arrangement of subpixels forms, and is designated as A _nM, A _nMin the sub-pixel of capable, the j of i row be designated as ai _j; Wherein, 1≤i≤N, 1≤j≤M, 0≤ai _j≤ 255;

If the picture element matrix of encrypted watermark image by n capable × a m row arrangement of subpixels forms, and is designated as B _nm, B _nmin the sub-pixel of capable, the t of s row be designated as b _st; Wherein, 1≤s≤n, 1≤t≤m, 0≤b _st≤ 255;

Wherein, N >=n, M >=3m;

2) extract B _nmhundred, ten, individual position of sub-pixel: establish sub-pixel b _sthundred, ten, individual position be designated as respectively x, y, z;

3) by A _nMin the position of sub-pixel to be encrypted make zero: selected A _nMthe middle value of being expert at is not more than n, and the sub-pixel that place train value is not more than 3m is sub-pixel to be encrypted, made zero in a position for sub-pixel to be encrypted, and the sub-pixel a'' after i is capable, j row make zero _ijrepresent;

4) encrypted watermark image is embedded to host image: by A _nMin the sub-pixel of capable, the j of i row after encrypting be designated as

By sub-pixel b _sthundred x and a'' _{s (3t-2)}be added,

By sub-pixel b _stten y and a'' _{s (3t-1)}be added,

By sub-pixel b _stposition z and a'' _{s (3t)}be added,

The rest may be inferred, until by B _nmin all sub-pixels be embedded into A _nMin, A _nMin the sub-pixel that is not encrypted remain unchanged, obtain thus the image pixel matrix C after encrypting _nM.

Now for example above-mentioned watermark encrypting algorithm is further explained to explanation: host image is represented with picture element matrix form, be assumed to be hypothesis A _nMbe 8 row 8 column matrix:

$A_{8\×8}\left[\begin{array}{cccc}{a}_{11}& a_{12}& ...& a_{81}\\ a_{21}& a_{22}& ...& a_{82}\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ a_{81}& a_{82}& ...& a_{88}\end{array}\right]$

Equally, encrypted watermark image is represented with picture element matrix form, suppose B _nmbe 2 row 2 column matrix:

$B_{2\×2}=\left[\begin{array}{cc}{b}_{11}& b_{12}\\ b_{21}& b_{22}\end{array}\right]$

Suppose a ₁₁=207, a ₁₂=143, a ₁₃=89, b ₁₁=120, extract b ₁₁hundred, ten, individual position be designated as respectively x, _y, z, x=1, _y=2, z=0, with b ₁₁corresponding sub-pixel to be encrypted is a ₁₁, a ₁₂, a ₁₃, by a ₁₁, a ₁₂, a ₁₃position make zero, obtain a'' ₁₁, a'' ₁₂, a'' ₁₃, a'' ₁₁=200, a'' ₁₂=140, a'' ₁₃=80, then by x and a'' ₁₁be added, obtain by y and a'' ₁₂be added, obtain by z and a'' ₁₃be added, obtain identical, if a ₁₄=137, a ₁₅=123, a ₁₆=29, b ₁₂=13, $a_{14}^o=130+0=130,a_{15}^o=120+1=121,a_{16}^o=20+3=23;$ If a ₂₁=47, a ₂₂=142, a ₂₃=189, b ₂₁=246, $a_{21}^o=40+2=42,a_{22}^o=140+4=144,a_{23}^o=180+6=186;$ If a ₂₄=242, a ₂₅=172, a ₂₆=191, b ₂₂=135, $a_{24}^o=240+1=241,a_{25}^o=170+3=173,a_{26}^o=190+5=195.$ A _{8 × 8}in the sub-pixel that is not encrypted remain unchanged, obtain thus the image pixel matrix C after encrypting _{8 × 8}:

$C_{8\×8}\left[\begin{array}{cccccccc}201& 142& 80& 130& 121& 23& a_{17}& a_{18}\\ 42& 144& 186& 241& 173& 195& a_{27}& a_{28}\\ a_{13}& a_{32}& a_{33}& a_{34}& a_{35}& a_{36}& a_{37}& a_{38}\\ .& .& .& .& .& .& .& .\\ .& .& .& .& .& .& .& .\\ .& .& .& .& .& .& .& .\\ a_{81}& a_{82}& a_{83}& a_{84}& a_{85}& a_{86}& a_{87}& a_{88}\end{array}\right]$

Step 2: the digital picture with stealthy watermark is decoded: the picture element matrix that extracts reductive water watermark image from the picture element matrix of host image through watermark decode algorithm;

Watermark decode algorithm comprises the steps:

1) selected C _nMthe middle value of being expert at is not more than n, and the region that place train value is not more than 3m is region to be decoded;

2) in region to be decoded, with behavior unit, from left to right successively at C _nMin get three sub-pixels, and extract the units of three sub-pixels: establish from C _nMin three capable got sub-pixels of p be respectively wherein, units be designated as x ', units be designated as y ', units be designated as z ';

3) units of three sub-pixels is multiplied by respectively to 100,10,1, and summation, reduction draws the picture element matrix of reductive water watermark image in sub-pixel: $b_{p\left(\frac{q+2}{3}\right)}^o={100x}^{,}+{10y}^{,}+{1z}^{,},$ represent in p capable, the sub-pixel of row.

Now with the image pixel matrix C after encrypting _{8 × 8}for example:

$C_{8\×8}\left[\begin{array}{cccccccc}201& 142& 80& 130& 121& 23& a_{17}& a_{18}\\ 42& 144& 186& 241& 173& 195& a_{27}& a_{28}\\ a_{13}& a_{32}& a_{33}& a_{34}& a_{35}& a_{36}& a_{37}& a_{38}\\ .& .& .& .& .& .& .& .\\ .& .& .& .& .& .& .& .\\ .& .& .& .& .& .& .& .\\ a_{81}& a_{82}& a_{83}& a_{84}& a_{85}& a_{86}& a_{87}& a_{88}\end{array}\right]$

To C _{8 × 8}the computing of decoding, the picture element matrix B of known encryption watermarking images _nmbe 2 row 2 column matrix, i.e. n=m=2, C _{8 × 8}middle row value is not more than 2, and it is region to be decoded that train value is not more than 6 region, from C _{8 × 8}the first row starts, and 3 are one group and get sub-pixel from left to right, and first group is: units be designated as x '=1, units be designated as y '=2, units be designated as z '=0; $b_{1\left(\frac{1+2}{3}\right)}^o=b_{11}^o=1\×100+2\×10+0\×1=120,$ Second group is: $a_{14}^o=130,a_{15}^o=121,a_{16}^o=23,$ units be designated as x '=0, units be designated as y '=1, units be designated as z '=3; after the first row has been decoded, continue the second row decoding, draw $b_{2\left(\frac{1+2}{3}\right)}^o=b_{21}^o=2\×100+4\×10+6\×1=246,$ $b_{2\left(\frac{4+2}{3}\right)}^o=b_{22}^o=1\×100+3\×10+5\×1=135,$ Obtain thus the picture element matrix of reductive water watermark image

$B_{2\×2}^o=\left[\begin{array}{cc}120& 13\\ 246& 135\end{array}\right]$

Step 3: relatively encrypted watermark image and reductive water watermark image: if the picture element matrix of encrypted watermark image equate with the picture element matrix of reductive water watermark image, illustrate that host image is not tampered, otherwise, illustrate that host image is tampered.Even B _{2 × 2}with equate, illustrate that host image is not tampered, otherwise, illustrate that host image is tampered.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, do not departing under the prerequisite of the technology of the present invention principle; can also make some improvement and distortion, these improvement and distortion also should be considered as protection scope of the present invention.

Claims (3)

1. the digital image tampering detection method with stealthy watermark, is characterized in that, comprises the steps:

Step 1: digital picture is carried out to stealthy watermark encrypting: host image and encrypted watermark image are represented with picture element matrix form respectively, the picture element matrix of encrypted watermark image is embedded in host image through watermark encrypting algorithm;

Step 2: the digital picture with stealthy watermark is decoded: the picture element matrix that extracts reductive water watermark image from the picture element matrix of host image through watermark decode algorithm;

Step 3: relatively encrypted watermark image and reductive water watermark image: if the picture element matrix of encrypted watermark image equate with the picture element matrix of reductive water watermark image, illustrate that host image is not tampered, otherwise, illustrate that host image is tampered.

2. the digital image tampering detection method of the stealthy watermark of band according to claim 1, is characterized in that, described watermark encrypting algorithm comprises the steps:

1) host image and encrypted watermark image are represented with picture element matrix form respectively:

If the picture element matrix of host image by N capable × a M row arrangement of subpixels forms, and is designated as A _nM, A _nMin the sub-pixel of capable, the j of i row be designated as a _ij; Wherein, 1≤i≤N, 1≤j≤M, 0≤a _ij≤ 255;

If the picture element matrix of encrypted watermark image by n capable × a m row arrangement of subpixels forms, and is designated as B _nm, B _nmin the sub-pixel of capable, the t of s row be designated as b _st; Wherein, 1≤s≤n, 1≤t≤m, 0≤b _st≤ 255;

Wherein, N >=n, M >=3m;

2) extract B _nmhundred, ten, individual position of sub-pixel: establish sub-pixel b _sthundred, ten, individual position be designated as respectively x, y, z;

3) by A _nMin the position of sub-pixel to be encrypted make zero: selected A _nMthe middle value of being expert at is not more than n, and the sub-pixel that place train value is not more than 3m is sub-pixel to be encrypted, made zero in a position for sub-pixel to be encrypted, and the sub-pixel a' after i is capable, j row make zero _i' _jrepresent;

4) encrypted watermark image is embedded to host image: by A _nMin the sub-pixel of capable, the j of i row after encrypting be designated as

By sub-pixel b _st'shundred x and a'' _{s (3t-2)}be added,

By sub-pixel b _stten y and a'' _{s (3t-1)}be added,

By sub-pixel b _stposition z and a'' _{s (3t)}be added,

The rest may be inferred, until by B _nmin all sub-pixels be embedded into A _nMin, A _nMin the sub-pixel that is not encrypted remain unchanged, obtain thus the image pixel matrix C after encrypting _nM.

3. the digital image tampering detection method of the stealthy watermark of band according to claim 2, is characterized in that, described watermark decode algorithm comprises the steps:

1) selected C _nMthe middle value of being expert at is not more than n, and the region that place train value is not more than 3m is region to be decoded;

2) in region to be decoded, with behavior unit, from left to right successively at C _nMin get three sub-pixels, and extract the units of three sub-pixels: establish from C _nMin _pthree sub-pixels that row is got are respectively wherein, units be designated as x ', units be designated as y ', units be designated as z ';

3) units of three sub-pixels is multiplied by respectively to 100,10,1, and summation, reduction draws the picture element matrix of reductive water watermark image in sub-pixel: $b_{p\left(\frac{q+2}{3}\right)}^o={100x}^{,}+{10y}^{,}+{1z}^{,},$ represent p is capable, the the sub-pixel of row.