CN111064859A

CN111064859A - Image information embedding method

Info

Publication number: CN111064859A
Application number: CN202010021400.6A
Authority: CN
Inventors: 冯丙文; 李彤; 翁健; 卢伟
Original assignee: Jinan University
Current assignee: Jinan University; University of Jinan
Priority date: 2020-01-09
Filing date: 2020-01-09
Publication date: 2020-04-24
Anticipated expiration: 2040-01-09
Also published as: CN111064859B

Abstract

The invention relates to an image information embedding method, which comprises the following steps: s1, acquiring an original carrier image and a secret message to be embedded, rearranging and dividing the original carrier image into carrier vectors x; segmenting the secret message into secret message blocks m; calculating an embedded disturbance value of each pixel in the original carrier image, and arranging and dividing the embedded disturbance values to obtain an embedded disturbance vector w corresponding to the carrier vector x; s2, sending the carrier vector x and the secret information block m into a steganographic encoder, and generating a corrected secret-containing carrier vector y through a check code; and S3, merging and rearranging all the secret carrier vectors to generate a secret image, and completing the embedding of the secret message. The invention obtains stronger error correction capability by correcting the steganographic vector instead of correcting the error in the decoded message. A good balance is achieved between robustness and embedding efficiency.

Description

Image information embedding method

Technical Field

The invention relates to the technical field of image information hiding, in particular to an image information embedding method.

Background

The adaptive steganographic coding STC technique is widely used because of its high embedding efficiency. May be embedded near the payload distortion boundary. However, as a side effect of high embedding efficiency, STC is very sensitive to channel interference, and a small corruption on the received payload will extend to a large range of message bits it carries, which is called corruption diffusion of STC. In actual covert communication, steganographic information may be affected by factors such as compression, channel noise, active attack and the like, published secret data may have information loss in practice, and an attacker may also want to destroy a covert communication channel through active attack. Despite the high embedding efficiency achieved, studies have shown that STC is poorly robust due to impairment dispersion, and that each bit error in the secret carrier vector results in a multiple bit error in the decoded message. Therefore, there is a need in the industry to develop an information embedding method that enables a sender to embed data on a carrier image at a high embedding rate and to obtain good robustness and anti-detection, i.e., a good balance between robustness and embedding efficiency.

Disclosure of Invention

Aiming at the problem of poor robustness in the prior art, the invention provides an image information embedding method.

The specific scheme of the application is as follows:

an image information embedding method, comprising:

s1, acquiring an original carrier image and a secret message to be embedded, rearranging and dividing the original carrier image into carrier vectors x; segmenting the secret message into secret message blocks m; calculating an embedded disturbance value of each pixel in the original carrier image, and arranging and dividing the embedded disturbance values to obtain an embedded disturbance vector w corresponding to the carrier vector x; wherein the length of the vector x is nl_ml_bThe length of the secret message block m is l_mThe length of the embedded perturbation vector w is nl_ml_b；

S2, sending the carrier vector x and the secret information block m into a steganographic encoder CCSTC, and generating a corrected secret carrier vector y through a check code; the length of the dense carrier vector is nl_ml_b；

And S3, merging and rearranging all the secret carrier vectors to generate a secret image, and completing the embedding of the secret message.

Preferably, the steganographic encoder CCSTC uses a vitebi algorithm to find a secret carrier vector y for the carrier vector x and the secret information block m; step S2 includes:

s21, generating a check matrix H required by the steganographic encoder;

s22, starting from the 0 th element of the carrier vector x and the 0 th bit of the secret message block m, constructing a Trellis block l according to the whole carrier vector x, the check matrix H and the secret message block m_mSplicing the Trellis blocks to form a Trellis diagram; wherein the Trellis block is composed of 2^lkThe row and the n columns of states;

and S23, backtracking in the Trellis diagram from the last column of the last Trellis block in the Trellis diagram to obtain a dense carrier vector y.

Preferably, step S21 includes:

s211, randomly generating a size l consisting of 0 and 1_k×l_aThe sub-matrix Hs of (a) is,

s212, splicing the sub-matrix Hs into a ladder shape with the size of (l)_k+l_m)×l_ml_aThe check matrix H.

Preferably, step S22 includes:

s221, initialize all 2 of the first column of the first Trellis block^lkA state; the state of the ith row and the jth column of one Trellis block is a five-tuple (c)_i，j，s1_i，j，s2_i，j，Ps_i，j，Po_i，j)，c_i，jTo reach the cost of this state s1_i，jIn the FCC state, s2_i，jIs in STC state, Ps_i，jFor STC state history matrix, Po_i，jAn output history matrix containing a dense carrier vector y, c_i，j∈[0，+∞)，

S222, according to the initialization state of the current Trellis block, the initial nl of the carrier vector x is used_bConstructing a Trellis block;

s223, connecting the Trellis block with the next Trellis block to be constructed;

s224, S222-S223 are repeatedly executed until all carrier vector elements and secret information block bits are processed.

Preferably, step S223 includes: if the 1 st bit to be embedded in the secret information block m is 0, reserving the even rows of the last 1 column of the Trellis block and using the even rows as the first 2 of the next Trellis block^lk-1A state; if the 1 st bit in the secret information block m is 1, reserving the odd rows of the last 1 column of the Trellis block and using the odd rows as the first 2 of the next Trellis block^lk-1One state, the remainder of the next Trellis block 2^lk-1The states are initialized to 0.

Preferably, if there are 8 rows of Trellis blocks and the secret message bit to be embedded is 0, the 2 nd, 4 th, 6 th, 8 th states of the last column of the Trellis block are reserved as the 1 st, 2 nd, 3 th, 4 th states of the next Trellis block, and the 5 th to 8 th states of the next Trellis block are reinitialized.

Preferably, all 2 of the first column of the first Trellis block are initialized^lkThe states include: for j ═ 1, c _1，10, for other j, c_1，1Infinity; for all j, s1_1，j＝0，s2_1，j＝0，Ps_1，j＝0，Po_1，j＝0。

Preferably, step S23 includes:

s231, making the index i of the secret message block m_msgThe last element pointing to the secret message block m starts to trace back from the last column of the last Trellis block, namely the first state of the jth column;

s232, the output history matrix Po of the first state_i，jBinary Bin (Po) corresponding to the jth element of (b)_i，j[j]) I.e. the last group l of dense carrier vectors y_bBit information; the STC state history matrix Ps of the first state_i，jThe jth element Ps of_i，j[j]The STC state, which is the state of the previous column connected to the first state;

s233, if the previous column connected with the first state is still in the currently processed Trellis block, finding the STC state in the previous columnIs Ps_i，j[j]The step S232 is executed again to obtain the second last group l of the secret carrier vector y_bBit information, analogizing in turn, and continuously finding the previous column of states until all l containing the dense carrier vector y are obtained_bBit information; if the previous column connected to the first state is not in the currently processed Trellis block, go to step S234;

s234, if m [ i ]_msg]When 0, let Ps_i，j[j]＝Ps_i，j[j]X 2, otherwise let Ps_i，j[j]＝Ps_i，j[j]X 2+1, and, in addition, let i_msg＝i_msg-l_mFinding the state with the STC state being the value in the last column of the last Trellis block, and starting with the state, resuming to execute step S232 to trace back the last Trellis block;

and S235, repeating the steps S232 to S234 until all the Trellis blocks are traced back, namely obtaining all the bit information containing the secret vector y.

Preferably, step S3 is followed by: s4, extracting the secret information in the secret image; wherein S4 includes:

s41, rearranging and dividing the dense images to obtain the length of ml_ml_bA dense carrier vector y of size;

s42, the vector y containing the secret is sent to an extractor corresponding to the steganographic encoder to generate a vector with length of l_mA secret message block m of size;

s43, all the secret message blocks m are combined to obtain the original embedded secret message in the secret image, and the secret message extraction is completed.

Preferably, step S42 includes:

s421, sending the vector y containing the dense carrier into an FCC decoder to obtain a decoded vector y';

s422, the vector y 'is sent to an STC extractor, and the secret message block y' can be obtained.

Compared with the prior art, the invention has the following beneficial effects:

according to the scheme, the carrier vector x and the secret information block m are sent to a steganographic encoder CCSTC, a corrected secret carrier vector y is generated through a check code, all the secret carrier vectors are combined and rearranged to generate a secret image, and the secret information is embedded. The scheme provides a fault-tolerant steganography of a robust check trellis code, and the ECC-based robust STC has high embedding rate of an STC frame and robustness which is not possessed by the STC frame. The scheme obtains stronger error correction capability by correcting the steganographic vector (containing the dense carrier vector) instead of correcting the error in the decoded message. A good balance is achieved between robustness and embedding efficiency, and a sender can embed data on a carrier image at a high embedding rate and can also obtain good robustness and anti-detection performance.

Drawings

Fig. 1 is a schematic flow chart of an image information embedding method of the present invention.

Fig. 2 is a frame diagram of the viterbi algorithm for the robust STC code of the present invention.

FIG. 3 is a diagram of a case of constructing a check grid by the image information embedding method of the present invention.

Detailed Description

The invention is further illustrated by the following figures and examples.

The image information embedding method provided by the invention is based on the robust STC (check lattice code) of the ECC (error check code), the ECC and the STC are combined, and the error correction coding is carried out on the STC input end by the scheme different from the error correction coding carried out on the existing robust steganographic code at the STC input end, the error correction coding is carried out on the STC output end, the check matrix structure of the STC is reserved, and all possible steganographic vectors can still be represented by a new check lattice.

For ECC:

suppose Hc ∈ {0,1}^n*qFor parity check matrix of error correcting code, the following embedding algorithm:

H·Hc y＝m

assume that each encoding l is made with an error correction code_aBit message bit, output l_bBit code words, then 1 st column to l_aThe path weights of the columns depend on the first l_bA bit carrier element. The number of paths into the node is equal to the radix of the set of error correction code messages used, 2^EaThen, againThe established path is given to the previously processed slice. According to the viterbi algorithm, the edge with the smallest total weight will be selected as the final incoming path for the node. Thus, the complexity of the algorithm varies with the length (l) of the ECC input_a) And the growth is exponential. In view of this, this scheme selects feed Forward Convolutional Codes (FCC) as error correcting codes because it can efficiently handle short inputs.

The ratio rate may be set to l_a/b_lThe FCC embedding function of (a) can be abbreviated as:

(code,state')＝CCEnc(info,Gc,state)

where info ∈ {0, …,2^a-1 represents an information bit, code ∈ {0, …,2^b-1} represents a codeword sequence, state/state' is the pre/post-embedding register state, Gc represents a codeword generator defined as: gc ═ Gc [: 0 [ ]]，…，Gc[:,b-1]]Wherein Gc [: i [ ]]∈{0，…，2^g,i}^a*1g, i specifies the delay of the i-th bit output of the encoder.

From the equation, the viterbi algorithm must store the FCC internal register state for each node in the check lattice. Furthermore, the width w of the STC sub-matrix ^ H should be a multiple of a.

The invention designs a robust adaptive steganography encoder and a corresponding extractor, wherein the adaptive steganography encoder is a central module for embedding image information, the extractor is a core module of a corresponding message extraction algorithm, the encoder keeps the structure of a check matrix and lattice (Trellis) of an original STC, but the FCC processing is further carried out when each edge in the Trellis is generated, so that the robustness of a finally generated dense image is ensured, and the ratio of the used FCC is set as l_a/b_lThe overall embedding flow of the scheme is as follows:

referring to fig. 1-2, an image information embedding method includes:

s1, acquiring an original carrier image and a secret message to be embedded, rearranging and dividing the original carrier image into carrier vectors x; segmenting the secret message into secret message blocks m; calculating the embedded disturbance value of each pixel in the original carrier image, and arranging and dividing the embedded disturbance values to obtain a carrier vector x corresponding to the carrier vector xThe embedded perturbation vector w of (a); wherein the length of the vector x is nl_ml_bThe length of the secret message block m is l_mThe length of the embedded perturbation vector w is nl_ml_b(ii) a Any embedded disturbance measurement method may be used to calculate the embedded disturbance value of each pixel in the original carrier image, which is not limited herein.

In this embodiment, the steganographic encoder CCSTC uses a vitebi algorithm to find a secret carrier vector y for the carrier vector x and the secret information block m; step S2 includes:

s21, generating a check matrix H required by the steganographic encoder; the check matrix H is used for constructing Trellis, and step S21 includes:

S22, starting from the 0 th element of the carrier vector x and the 0 th bit of the secret message block m, constructing a Trellis block l according to the whole carrier vector x, the check matrix H and the secret message block m_mSplicing the Trellis blocks to form a Trellis diagram; wherein the Trellis block is composed of 2^lkThe row and the n columns of states; step S22 includes the construction of each Trellis block and the connection method between Trellis blocks, and the specific steps are as follows:

s221, initialize all 2 of the first column of the first Trellis block^lkA state; the state of the ith row and the jth column of one Trellis block is a five-tuple (c)_i，j，s1_i，j，s2_i，j，Ps_i，j，Po_i，j)，c_i，jTo reach the cost of this state s1_i，jIn the FCC state, s2_i，jIn the STC state, Ps_i，jFor STC state history matrix, Po_i，jAn output history matrix containing a dense carrier vector y, c_i，j∈[0，+∞)，

Initialize all 2 of the first column of the first Trellis block^lkThe states include: for j ═ 1, c _1，10, for other j, c_1，1Infinity; for all j, s1_1，j＝0，s2_1，j＝0，Ps_1，j＝0，Po_1，j＝0。

S222, according to the initialization state of the current Trellis block, the initial nl of the carrier vector x is used_bConstructing a Trellis block; the construction of the Trellis block is intended to connect the state of each column in the Trellis block with the state of the previous column and determine the value of the quintuple of the state. The method comprises the following steps:

s2221, starting from column 2, for each

Check which of the ith state can be reached by which of the 1 st column states is reached by l for each possible combination of 0 and 1_aAnd e, calculating the candidate five-tuple corresponding to the e. The method is that the STC state s2 of the previous column state is calculated firstly_i′，j-1I' wherein

Where Dec is a conversion of a decimal number to a binary vector, Bin is a conversion of a binary vector to a decimal number, Hs [: and k represents the kth column of matrix Hs.

Since i' of the previous state is obtained, further other values of the quintuple that can be used to calculate the current state include calculating the FCC output

And FCC state s1_i，j

(o，s1_i，j)＝CCEnc(e，Gc，s1_i′，j-1)

Computing STC state history matrix

Ps_i，j＝[Ps_i′，j-1[1]，Ps_i′，j-1[2]，...，Ps_i′，j-1[j-1]，i′，0，...，0]

Computing an output history matrix

Po_i，j＝[Po_i′，j-1[1]，Po_i′，j-1[2]，...，Po_i′，j-1[j-1]，Dec(o)，0，...，0]

Calculating an embedding cost

S2222, after all possible vectors e are calculated, obtaining

Selecting the value of all the candidate quintuple of the current state, wherein c_i，jThe smallest five tuple serves as the final five tuple for the state. STC state s2 of the previous state corresponding to the five-tuple_i′，j-1The previous state of the connection is finally selected for the current state, and the connection line is e used for solving the quintuple.

S2223, after all the states in the 2 nd column continue, connect all the states in the 2 nd column with the previous column, and so on until all the columns of the Trellis block are connected with the previous column.

S223, connecting the Trellis block with the next Trellis block to be constructed; more further, step S223 includes: if the 1 st bit to be embedded in the secret information block m is 0, reserving the even rows of the last 1 column of the Trellis block and using the even rows as the first 2 of the next Trellis block^lk-1A state; if the 1 st bit in the secret information block m is 1, reserving the odd rows of the last 1 column of the Trellis block and using the odd rows as the first 2 of the next Trellis block^lk-1One state, the remainder of the next Trellis block 2^lk-1The states are initialized to 0. For example, if there are 8 rows of Trellis blocks and the secret message bit to be embedded is 0, the 2 nd, 4 th, 6 th, 8 th states of the last column of the Trellis block are reserved as the 1 st, 2 nd, 3 th, 4 th states of the next Trellis block, and the 5 th to 8 th states of the next Trellis block are reinitialized.

S224, repeatedly executing S222-S223 and processing the next nl of the carrier vector x_bAn element, and the remaining message bits of the secret information block m to be embedded. Until all carrier vector elements and secret information block bits have been processed.

And S23, backtracking in the Trellis diagram from the last column of the last Trellis block in the Trellis diagram to obtain a dense carrier vector y. The backtracking method in Trellis realizes the output of the output history matrix Po of one state_i，jThe corresponding output of the column and find the state of the previous column connected. Specifically, step S23 includes:

s232, the output history matrix Po of the first state (the first state of the jth column)_i，jBinary Bin (Po) corresponding to the jth element of (b)_i，j[j]) I.e. the last group l of dense carrier vectors y_bBit information; the STC state history matrix Ps of the first state_i，jThe jth element Ps of_i，j[j]The STC state, which is the state of the previous column connected to the first state;

s233, if the previous column connected with the first state is still in the currently processed Trellis block, finding out that the STC state in the previous column is Ps_i，j[j]The step S232 is executed again to obtain the second last group l of the secret carrier vector y_bBit information, analogizing, continuously finding the previous column state to obtain the l of the last third group, the fourth group and the like of the secret carrier vector y_bBit information until all the dense carrier vector y is obtainedl_bBit information; if the previous column connected to the first state is not in the currently processed Trellis block, go to step S234;

In this embodiment, step S3 is followed by: s4, extracting the secret information in the secret image; the confidential image may pass through the interference of the channel, wherein S4 includes:

s41, rearranging and dividing the dense images to obtain the length nl_ml_bA dense carrier vector y of size; wherein the rearrangement and division manner is the same as the rearrangement and division method similar to the embedding algorithm (image information embedding method) step S1.

S42, the vector y containing the secret is sent to an extractor corresponding to the steganographic encoder to generate a vector with length of l_mA secret message block m of size; wherein step S42 includes:

s422, the vector y' is sent to an STC extractor, and the secret message block m can be obtained.

Wherein, fig. 3 shows that given ^ H and Gc, the image information embedding method of the present invention constructs a case graph of check grids. It shows that the binary message sequence m ═ 0,1] is embedded into the bearer vector x ═ 1,1,0,1,0,1,0,0,0,0,0,1, with x having the corresponding weight w ═ 12,11,10,9,8,7,6,5,4,3,2, 1. Since the FCC employed receives a 2-bit input, there is no FCC output when the STC processes the first or third sub-matrix column. Thus, the grid contains only columns labeled 2 and 4. In fig. 3, the numbers assigned to each edge represent the FCC output, which is also a segment of the possible stego vector. Take STC state 01 in the column labeled 4 as an example. There are four edges into the node that correspond to

STC codewords

00, 01, 10, and 11. These edges come from the preceding STC states 01, 00, 10, and 11 in the column labeled 2, whose FCC states are stored as 4, 0, 16, and 20, respectively. Each STC codeword and associated FCC state are then input into the FCC, resulting in four dense carrier vector outputs, 010, 001, 111 and 100, respectively. Changing the original carrier vector 000 to these dense carrier vectors results in embedding distortions of 8,7, 24 and 9, respectively. By adding these distortion values to the path weights up to the corresponding previous STC state, we get the total weight of each path to be 21, 48, 39 and 28, respectively. Thus, the edge labeled 010 has the smallest weight and therefore remains in the Trellis diagram.

It should be noted that the embedding and the extraction in this scheme can be performed not only on the pixels of the image, but also on various transform domains of the image, such as DCT, DWT, and the like. The carrier vector is now composed of coefficients of the transform domain. The secret message can be embedded and extracted successfully and has high imperceptibility, and the effect is brought by the pixel suitable embedding degree measurement technology and the existing adaptive steganographic coding STC technology proposed by the secret. The technology combines the mask calculation technology proposed by the secret and the existing embedded disturbance measurement technology design based on image content.

The scheme provides a robust STC based on ECC, and a good balance is obtained between robustness and embedding efficiency. In order to improve the detection resistance, the scheme constructs the Trellis blocks according to the whole carrier vector x, the check matrix H and the secret message block m, backtracks in the Trellis diagram from the last column of the last Trellis block in the Trellis diagram to obtain the dense carrier vectors y, combines and rearranges all the dense carrier vectors to generate a dense image, and completes the embedding of the secret message, so that the scheme corrects errors in the hidden vector rather than in the decoded message. Since the impairment gain grows exponentially, correcting steganographic vector errors is more efficient than correcting decoded message errors. Therefore, a strong error correction capability can be obtained in this way. Due to similarity with the original STC form, the scheme can replace an encoder in an STC frame, and the robustness of the existing steganographic scheme is enhanced.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An image information embedding method, comprising:

S2, sending the carrier vector x and the secret information block m into a steganographic encoder CCSTC, and generating a corrected secret carrier vector y through a check code; the length of the dense carrier vector is nl_ml_b，

2. The image information embedding method of claim 1, wherein the steganographic encoder CCSTC finds a secret carrier vector y for a carrier vector x and a secret information block m using a vitebi algorithm; step S2 includes:

s21, generating a check matrix H required by the steganographic encoder;

3. The image information embedding method according to claim 2, wherein step S21 includes:

4. The image information embedding method according to claim 2, wherein step S22 includes:

5. The image information embedding method according to claim 4, wherein step S223 includes: if the 1 st bit to be embedded in the secret information block m is 0, reserving the even rows of the last 1 column of the Trellis block and using the even rows as the first 2 of the next Trellis block^lk-1A state; if the 1 st bit in the secret information block m is 1, reserving the odd rows of the last 1 column of the Trellis block and using the odd rows as the first 2 of the next Trellis block^lk-1One state, the remainder of the next Trellis block 2^lk-1The states are initialized to 0.

6. An image information embedding method according to claim 5, wherein if there are 8 rows of Trellis blocks and the secret message bit to be embedded is 0, then the 2 nd, 4 th, 6 th, 8 th states of the last column of Trellis blocks are reserved as the 1 st, 2 nd, 3 th, 4 th states of the next Trellis block, respectively, and the 5 th to 8 th states of the next Trellis block are reinitialized.

7. An image information embedding method according to claim 4, wherein all 2 of the first column of the first Trellis block are initialized^lkThe states include: for j ═ 1, c_1，10, for other j, c_1，1Infinity; for all j, s1_1，j＝0，s2_1，j＝0，Ps_1，j＝0，Po_1，j＝0。

8. The image information embedding method according to claim 4, wherein step S23 includes:

s231, making the index i of the secret message block m_msgThe last element pointing to the secret message block m is then from the last column of the last Trellis block, i.e. the jth columnThe first state of (2) starts backtracking;

s233, if the previous column connected with the first state is still in the currently processed Trellis block, finding out that the STC state in the previous column is Ps_i，j[j]The step S232 is executed again to obtain the second last group l of the secret carrier vector y_bBit information, analogizing in turn, and continuously finding the previous column of states until all l containing the dense carrier vector y are obtained_bBit information; if the previous column connected to the first state is not in the currently processed Trellis block, go to step S234;

9. The image information embedding method according to claim 1, further comprising, after step S3: s4, extracting the secret information in the secret image; wherein S4 includes:

s41, rearranging and dividing the dense images to obtain the length nl_ml_bA dense carrier vector y of size;

s42, the vector y containing the secret is sent to an extractor corresponding to the steganographic encoder to generate a vector with length of l_mSize secretA secret message block m;

10. The image information embedding method according to claim 9, wherein step S42 includes: