CN103985079B - Digital image tampering detection method with stealthy watermark - Google Patents

Abstract

The invention discloses a kind of digital image tampering detection method with stealthy watermark, carries out stealthy watermark encrypting to digital picture first：Host image and encrypted watermark image are represented with picture element matrix form respectively, the picture element matrix Jing watermark encrypting algorithms of encrypted watermark image are embedded in host image；Secondly the digital picture of band stealth watermark is decoded：The picture element matrix of reduction watermarking images is extracted from the picture element matrix of host image through watermark decoding algorithm；Finally compare encrypted watermark image and reduction watermarking images：If the picture element matrix of encrypted watermark image is equal with the picture element matrix of reduction watermarking images, illustrates that host image is not tampered with, otherwise, illustrate that host image is tampered.Inventive algorithm is simple, easy to operation, can quickly judge whether image occurs tampering detection, beneficial to copyright protection.

Description

Digital image tampering detection method with invisible watermark

Technical Field

The invention relates to a digital image watermarking technology, in particular to a digital image tampering detection method with an invisible watermark, and belongs to the technical field of image processing.

Background

With the development of multimedia technology, people use digital products such as images and videos more and more frequently, and the application fields of the digital products are wider and wider, so that the original identification and the falsification detection of pictures become a prominent problem.

Disclosure of Invention

The invention aims to provide a digital image tampering detection method with an invisible watermark, which can effectively detect whether a host image is tampered.

The technical scheme adopted by the invention is as follows: the digital image tampering detection method with the invisible watermark comprises the following steps:

the method comprises the following steps: carrying out invisible watermark encryption on the digital image: respectively representing the host image and the encrypted watermark image in a pixel matrix form, and embedding the pixel matrix of the encrypted watermark image into the host image through a watermark encryption algorithm;

step two: decoding the digital image with the invisible watermark: extracting a pixel matrix of a restored watermark image from a pixel matrix of a host image through a watermark decoding algorithm;

step three: comparing the encrypted watermark image with the restored watermark image: if the pixel matrix of the encrypted watermark image is equal to the pixel matrix of the restored watermark image, the host image is not tampered, otherwise, the host image is tampered.

The watermark encryption algorithm comprises the following steps:

1) respectively representing the host image and the encrypted watermark image in a pixel matrix form:

let the pixel matrix of the host image be composed of an arrangement of N rows and × M columns of sub-pixels, denoted A_NM，A_NMThe sub-pixel of the ith row and the jth column is marked as a_ij(ii) a Wherein i is more than or equal to 1 and less than or equal to N, j is more than or equal to 1 and less than or equal to M, and a is more than or equal to 0_ij≤255；

Let the pixel matrix of the encrypted watermark image be composed of n rows and × m columns of sub-pixels, and be marked as B_nm，B_nmThe sub-pixel of the middle s-th row and t-th column is marked as b_st(ii) a Wherein s is more than or equal to 1 and less than or equal to n, t is more than or equal to 1 and less than or equal to m, and b is more than or equal to 0_st≤255；

Wherein N is more than or equal to N, and M is more than or equal to 3M;

2) extraction of B_nmSub-pixel hundredPosition, ten positions, unit position: let a sub-pixel b_stThe hundred, ten and ones are marked as x, y and z respectively;

3) a is to be_NMThe bit of the sub-pixel to be encrypted is zeroed: is selected from A_NMThe sub-pixel with the row value not more than n and the column value not more than 3m is the sub-pixel to be encrypted, the bit of the sub-pixel to be encrypted is reset to zero, and the sub-pixel after the zero reset of the ith row and the jth column is used as a ″_ijRepresents;

4) embedding the encrypted watermark image into the host image: a is to be_NMThe encrypted sub-pixels in the ith row and the jth column are recorded as

Sub-pixel b_stThe hundreds x and a ″)_s(3t-2)Add, then

Sub-pixel b_stThe ten positions y and a ″)_s(3t-1)Add, then

Sub-pixel b_stThe bits z and a ″)_s(3t)Add, then

And so on until B_nmIn which all sub-pixels are embedded in A_NMIn (A)_NMThe sub-pixels not subjected to the encryption processing are kept unchanged, thereby obtaining an encrypted image pixel matrix C_NM。

The watermark decoding algorithm comprises the following steps:

1) selecting C_NMTwo elements of which the row value is n, the column value is 3m, the row value is 1 and the column value is 1The rectangular area determined by the elements as the vertexes is an area to be decoded;

2) in the area to be decoded, the area is sequentially arranged at C from left to right in a row unit_NMTaking three sub-pixels, and extracting the single digit of the three sub-pixels: let a slave C_NMThe three sub-pixels taken from the middle p-th row are respectivelyWherein,the ones digit of (a) is marked as x',the ones digit of (a) is noted as y',the ones number of (c) is denoted as z'; q represents the column value of the first subpixel taken by p rows;

3) multiplying the single digits of the three sub-pixels by 100, 10 and 1 respectively, summing up, and restoring to obtain a pixel matrix for restoring the watermark imageThe sub-pixel of (1): to representIn the p th line, the thThe sub-pixels of a column.

Compared with the prior art, the invention has the following beneficial effects: the digital image tampering detection method with the invisible watermark is simple in algorithm, simple and easy to operate, capable of rapidly judging whether the image is tampered and detected and beneficial to copyright protection; the influence on the visual effect of the original image is small by adjusting unimportant data; in addition, the method has small calculation amount and meets the real-time requirement.

Drawings

FIG. 1 is a flow chart of the operation of the present invention.

Detailed Description

The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

As shown in fig. 1, the digital image tampering detection method with invisible watermarks includes the following steps:

the method comprises the following steps: carrying out invisible watermark encryption on the digital image: the host image and the encrypted watermark image are respectively expressed in a pixel matrix form, and the pixel matrix of the encrypted watermark image is embedded into the host image through a watermark encryption algorithm.

The watermark encryption algorithm comprises the following steps:

1) respectively representing the host image and the encrypted watermark image in a pixel matrix form:

let the pixel matrix of the host image be composed of an arrangement of N rows and × M columns of sub-pixels, denoted A_NM，A_NMThe sub-pixel of the ith row and the jth column is marked as a_ij(ii) a Wherein i is more than or equal to 1 and less than or equal to N, j is more than or equal to 1 and less than or equal to M, and a is more than or equal to 0_ij≤255；

Let the pixel matrix of the encrypted watermark image be composed of n rows and × m columns of sub-pixels, and be marked as B_nm，B_nmThe sub-pixel of the middle s-th row and t-th column is marked as b_st(ii) a Wherein s is more than or equal to 1 and less than or equal to n, t is more than or equal to 1 and less than or equal to m, and b is more than or equal to 0_st≤255；

Wherein N is more than or equal to N, and M is more than or equal to 3M;

2) extraction of B_nmHundred, ten, ones of the sub-pixels: let a sub-pixel b_stThe hundred, ten and ones are marked as x, y and z respectively;

3) a is to be_NMThe bit of the sub-pixel to be encrypted is zeroed: is selected from A_NMThe sub-pixel with the row value not more than n and the column value not more than 3m is the sub-pixel to be encrypted, the bit of the sub-pixel to be encrypted is reset to zero, and the sub-pixel after the zero reset of the ith row and the jth column is used as a ″_ijRepresents;

4) embedding the encrypted watermark image into the host image: a is to be_NMThe encrypted sub-pixels in the ith row and the jth column are recorded as

Sub-pixel b_stThe hundreds x and a ″)_s(3t-2)Add, then

Sub-pixel b_stThe ten positions y and a ″)_s(3t-1)Add, then

Sub-pixel b_stThe bits z and a ″)_s(3t)Add, then

And so on until B_nmIn which all sub-pixels are embedded in A_NMIn (A)_NMThe sub-pixels not subjected to the encryption processing are kept unchanged, thereby obtaining an encrypted image pixel matrix C_NM。

The above watermark encryption algorithm will now be further explained by way of example:the host image is represented in the form of a pixel matrix, assumed to be hypothesis A_NMFor an 8 row 8 column matrix:

similarly, the encrypted watermark image is represented in the form of a pixel matrix, assuming B_nmFor a 2 row 2 column matrix:

suppose a₁₁＝207，a₁₂＝143，a₁₃＝89，b₁₁120, extracting b₁₁Each of the hundred, ten and ones of (a) is represented by x, y and z, respectively, x is 1, y is 2, z is 0, and b₁₁The corresponding sub-pixel to be encrypted is a₁₁，a₁₂，a₁₃A is to₁₁，a₁₂，a₁₃Zero to obtain a ″)₁₁，a″₁₂，a″₁₃Then a ″)₁₁＝200，a″₁₂＝140，a″₁₃X is then combined with a ″', 80₁₁Add to obtainMixing y with a ″)₁₂Add to obtainMixing z with a ″)₁₃Add to obtainSame if a₁₄＝137，a₁₅＝123，a₁₆＝29，b₁₂When it is 13, thenIf a₂₁＝47，a₂₂＝142，a₂₃＝189，b₂₁246, thenIf a₂₄＝242，a₂₅＝172，a₂₆＝191，b₂₂135, thenA_8×8The sub-pixels not subjected to the encryption processing are kept unchanged, thereby obtaining an encrypted image pixel matrix C_8×8：

Step two: decoding the digital image with the invisible watermark: extracting a pixel matrix of a restored watermark image from a pixel matrix of a host image through a watermark decoding algorithm;

the watermark decoding algorithm comprises the following steps:

1) selecting C_NMA rectangular area determined by taking two elements with the row value of n, the column value of 3m and the row value of 1 as vertexes as an area to be decoded;

2) in the area to be decoded, the area is sequentially arranged at C from left to right in a row unit_NMTaking three sub-pixels, and extracting the single digit of the three sub-pixels: let a slave C_NMThe three sub-pixels taken from the middle p-th row are respectivelyWherein,the ones digit of (a) is marked as x',the ones digit of (a) is noted as y',the ones number of (c) is denoted as z'; q represents the column value of the first subpixel taken by p rows;

3) multiplying the single digits of the three sub-pixels by 100, 10 and 1 respectively, summing up, and restoring to obtain a pixel matrix for restoring the watermark imageThe sub-pixel of (1): to representIn the p th line, the thThe sub-pixels of a column.

Now with the encrypted image pixel matrix C_8×8For example, the following steps are carried out:

to C_8×8Performing decoding operation to obtain pixel matrix B of known encrypted watermark image_nmIs a 2-row and 2-column matrix, i.e. n-m-2, C_8×8The region with the middle row value not more than 2 and the column value not more than 6 is the region to be decoded, from C_8×8Starting in the first row, from left to right 3 subpixels are taken in a group, the first group being: the ones number of (a) is noted as x' ═ 1,the ones number of (a) is noted as y' ═ 2,the ones number of (a) is noted as z' ═ 0;the second group is: the ones 'number of (a) is noted as x' ═ 0,the ones number of (a) is noted as y' ═ 1,the ones number of (a) is 3;after the first row decoding is finished, the second row decoding is continued to obtain Thereby obtaining a pixel matrix for restoring the watermark image

Step three: comparing the encrypted watermark image with the restored watermark image: if the pixel matrix of the encrypted watermark image is equal to the pixel matrix of the restored watermark image, the host image is not tampered, otherwise, the host image is not tamperedThe host-clear image is tampered. If B is_2×2Andand if the two images are equal, the host image is not tampered, otherwise, the host image is tampered.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (2)

1. The digital image tampering detection method with the invisible watermark is characterized by comprising the following steps:

the method comprises the following steps: carrying out invisible watermark encryption on the digital image: respectively representing the host image and the encrypted watermark image in a pixel matrix form, and embedding the pixel matrix of the encrypted watermark image into the host image through a watermark encryption algorithm;

the watermark encryption algorithm comprises the following steps:

1) respectively representing the host image and the encrypted watermark image in a pixel matrix form:

let the pixel matrix of the host image be composed of an arrangement of N rows and × M columns of sub-pixels, denoted A_NM，A_NMThe sub-pixel of the ith row and the jth column is marked as a_ij(ii) a Wherein i is more than or equal to 1 and less than or equal to N, j is more than or equal to 1 and less than or equal to M, and a is more than or equal to 0_ij≤255；

Let the pixel matrix of the encrypted watermark image be composed of n rows and × m columns of sub-pixels, and be marked as B_nm，B_nmThe sub-pixel of the middle s-th row and t-th column is marked as b_st(ii) a Wherein s is more than or equal to 1 and less than or equal to n, t is more than or equal to 1 and less than or equal to m, and b is more than or equal to 0_st≤255；

Wherein N is more than or equal to N, and M is more than or equal to 3M;

2) extraction of B_nmHundred, ten, ones of the sub-pixels: let a sub-pixel b_stThe hundred, ten and ones are marked as x, y and z respectively;

3) a is to be_NMThe bit of the sub-pixel to be encrypted is zeroed: is selected from A_NMThe sub-pixel with the row value not more than n and the column value not more than 3m is the sub-pixel to be encrypted, the bit of the sub-pixel to be encrypted is reset to zero, and the sub-pixel after the zero reset of the ith row and the jth column is used as a ″_ijRepresents;

4) embedding the encrypted watermark image into the host image: a is to be_NMThe encrypted sub-pixels in the ith row and the jth column are recorded as

Sub-pixel b_stThe hundreds x and a ″)_s(3t-2)Add, then

Sub-pixel b_stThe ten positions y and a ″)_s(3t-1)Add, then

Sub-pixel b_stThe bits z and a ″)_s(3t)Add, then

And so on until B_nmIn which all sub-pixels are embedded in A_NMIn (A)_NMThe sub-pixels not subjected to the encryption processing are kept unchanged, thereby obtaining an encrypted image pixel matrix C_NM；

Step two: decoding the digital image with the invisible watermark: extracting a pixel matrix of a restored watermark image from a pixel matrix of a host image through a watermark decoding algorithm;

step three: comparing the encrypted watermark image with the restored watermark image: if the pixel matrix of the encrypted watermark image is equal to the pixel matrix of the restored watermark image, the host image is not tampered, otherwise, the host image is tampered.

2. The tamper detection method for digital images with invisible watermarks according to claim 1, wherein said watermark decoding algorithm comprises the steps of:

1) selecting C_NMA rectangular area determined by taking two elements with the row value of n, the column value of 3m and the row value of 1 as vertexes as an area to be decoded;

2) in the area to be decoded, the area is sequentially arranged at C from left to right in a row unit_NMTaking three sub-pixels, and extracting the single digit of the three sub-pixels: let a slave C_NMThe three sub-pixels taken from the middle p-th row are respectivelyWherein,the ones digit of (a) is marked as x',the ones digit of (a) is noted as y',the ones number of (c) is denoted as z'; q represents a p-line instituteTaking the column value of the first sub-pixel;

3) multiplying the single digits of the three sub-pixels by 100, 10 and 1 respectively, summing up, and restoring to obtain a pixel matrix for restoring the watermark imageThe sub-pixel of (1): to representIn the p th line, the thThe sub-pixels of a column.