CN107146191A - An Efficient Information Hiding Method Introducing Auxiliary Pixels - Google Patents

Abstract

The present invention proposes a kind of efficient information hidden method for introducing auxiliary pixel, and hidden capacity is unrelated with the type of initial data, can be view data, can also be other data, hiding amount is fixed all the time, with big hidden capacity and Information Security, and is easy to software and hardware realization.This method realizes the Combined Treatment of secret information and key by the introducing of auxiliary pixel and data-optimized, and receiving terminal can Restore Secret information and high quality resume initial data completely.This method can carry out Information hiding in each pixel of raw image data, improve hiding efficiency, breach the limitation that current method is hidden in a pixel is to (two pixels), 1/2 hidden capacity can be met or exceeded to arbitrary image, recover carrier image PSNR during 1/2 hidden capacity more than 41dB, better than typical hidden method such as LSB and FEMD hidden methods.

Description

An Efficient Information Hiding Method Introducing Auxiliary Pixels

technical field

The invention relates to a data transmission method, in particular to an efficient information hiding method introducing auxiliary pixels, and belongs to the field of communication (such as data communication technology, etc.).

Background technique

Data transmission and image processing are important research topics in the field of communication at present. With the development of science and technology, people's demand for high-resolution images is increasing, and data compression is imperative. Without affecting the normal business of the image, if some secret data can be hidden in it for transmission, it is equivalent to a certain amount of data compression.

Information hiding, also known as steganography, can be divided into airspace information hiding and transformation domain information hiding. data, data uploaded on the ground, etc.) are hidden in the satellite remote sensing data and transmitted through the open satellite channel, to achieve the purpose of concealed communication or improve transmission efficiency without increasing the transmission rate, and provide a safe information transmission for satellite communication way.

Spatial steganography methods hide secret information by modifying carrier pixel values. Among them, the most representative algorithm is the least significant bit LSB substitution method, which directly replaces the lowest r bits of the carrier image pixel to embed information, and can obtain a higher embedding capacity, but the quality of the dense image decreases as the capacity increases obvious. In order to improve the visual quality of the image, someone proposed an improved method based on LSB, which improves the quality of the hidden image while maintaining the same embedding amount. These methods all utilize one pixel to hide multiple bits of secret information. Another type of spatial domain steganography method uses a pixel pair (two pixels) to complete information hiding, such as LSB matching revisited (LSBMR), EMD (exploiting modification direction) hiding method based on direction adjustment, and Fully EMD (FEMD) Concealment method. The FEMD method can hide a bit n binary (n ∈ N, n ≥ ² ) secret information in a carrier pixel pair (x, y), but its maximum embedding capacity cannot be increased.

The FEMD hiding method needs to hide information in a pixel pair composed of two pixels. Can the same information be hidden in one pixel, and it is not easy to crack. The hiding capacity performance is better than the LSB hiding method and the FEMD hiding method or the hiding capacity is better than the classic one. Hidden method, the answer is yes.

Contents of the invention

The technical problem solved by the present invention is to overcome the deficiencies of the prior art and provide an efficient information hiding method that introduces auxiliary pixels. It is not necessary to hide information in a pixel pair (two pixels), and the same information can be hidden in one pixel. There is a lot of information, and the information security is good, which can be used for efficient information hiding transmission in various data (especially image data) carriers.

The technical solution of the present invention is: an efficient information hiding method introducing auxiliary pixels, the steps are as follows:

¹ ) Convert the implicit binary secret information into n binary secret information, each secret information is s, and the value of s belongs to the set {0,1,2,...n ² -1}, n≥2;

2) Generate auxiliary pixel value y, y is a positive integer in [y ₀ , 255-y ₀ ], where y ₀ =n/2 is rounded; each pixel x in carrier image A and auxiliary pixel y form a pixel pair (x, y), calculate and obtain function value f=[(n-1)*x+n*y]mod n ² ;

3) Compare f with the secret information s to obtain a dense pixel pair (x’, y’);

4) If the dense pixel pair (x', y') overflows, adjust to get a new dense pixel pair (x, y), and then re-embed the secret information s;

5) Repeat step 3) to step 4) until all secret information s are embedded;

6) Compose all Δy into a set and perform lossless compression to obtain the compressed data set C0;

7) Generate a positive integer y=y ₀ +1 in [y ₀ , 255-y ₀ ] in order as the auxiliary pixel y, and continue to repeat steps 2) to 6) p times to obtain compressed data sets C1, C2...Cp, from C0, C1～Cp select C with the shortest data length, and write down the corresponding preferred auxiliary pixel value y; where p is an integer, and p=0 means no repetition;

8) Send the dense image A' composed of all x', the preferred auxiliary pixel y and the compressed data set C to the receiving end;

9) Receive the compressed data set C, decompress it to obtain a set of Δy, and use y to obtain a set of auxiliary pixels y', that is, y'=y+Δy;

10) The x' in the dense image A' and the dense auxiliary pixel y' are formed into a pixel pair (x', y');

11) For each pixel pair (x', y'), extract each n binary secret information according to s=[(n-1)*x'+n*y']modn ^{2 ;} repeat until n ^Binary secret information is extracted;

¹² ) Convert the extracted n binary secret information into binary secret information.

n=2 or 4 or 8 or 16.

The concrete process of step 3) is:

3.1) Compare f with the secret information s, if f=s, do not change the pixel pair (x, y), otherwise modify the pixel pair according to 3.2);

3.2) Search for a pixel pair (x+Δx, y+Δy) that satisfies f(x+Δx, y+Δy)=s, and select the pixel pair with the smallest modification (Δx, Δy) as the dense pixel pair (x' ,y').

The specific process of step 4) is: the specific method for adjusting and obtaining the new dense pixel pair (x, y) is:

The beneficial effect of the present invention compared with prior art is:

The present invention provides a high-efficiency information hiding method without increasing actual pixels and changing the amount of carrier data, introduces a key, and increases the security of hidden secret data.

Compared with the current background technology, the present invention has the following substantive differences and progress:

(1) This method first introduces an auxiliary pixel y to each pixel in the image, so that information can be hidden in each pixel, which overcomes the original problem of needing to hide information in two data, and improves the hiding efficiency .

(2) This method makes full use of the minimum correction amount of auxiliary data, optimizes the length of lossless compression based on the correction value set, improves the efficiency of hiding auxiliary pixel pairs, and achieves an unimaginable hiding effect.

(3) Compared with the EMD type of hiding method, this method has the key y while hiding, which increases the difficulty for the unauthorized receiver to crack the existing secret information, and has the effect of keeping secret while hiding.

(4) If this method only introduces an auxiliary pixel y to one of the two pixels in the image, the quality of the carrier image is improved because the amount of modification to the original image is small, for example, the PSNR value can be increased by 3dB.

Description of drawings

Figure 1(a)-Figure 1(f) are the standard grayscale images for simulation.

detailed description

While high-speed data is being transmitted, other low-speed data or part of high-speed data is often transmitted at the same time. In addition to transmitting images, other sensor data may also be transmitted. The invention provides a method for data transmission using information hiding technology, which has the characteristics of large hidden capacity, high performance and low complexity, and is practical in spacecraft engineering, ground information carrying transmission systems, and various image transmission systems. value.

The experiment uses the MATLAB2013a platform, and the carrier data uses 6 standard grayscale images of 512×512, as shown in Figure 1, and the secret information is generated by a pseudo-random number generator. If the algorithm needs to have higher security, the carrier can be preprocessed with chaotic sequences or some encryption algorithms.

The present invention introduces an efficient information hiding method of auxiliary pixels, the steps are as follows:

¹ ) Convert the binary secret information into n binary secret information, each secret information is s, and the value of s belongs to the set {0,1,2,...n ² -1}, n≥2; n can be 2, One of 4,8,16

2) Generate auxiliary pixel value y, y is a positive integer in [y ₀ ,255-y ₀ ], where y ₀ =n/2 is rounded;

Each pixel x and auxiliary pixel y in the carrier image A (size 512*512, 8 bits per pixel) form a pixel pair (x, y), and calculate the function value f=[(n-1)*x+n* y] mod n ² ;

3) Compare f with secret information s:

3.1) If f=s, then do not change the pixel pair (x, y), otherwise modify the pixel pair according to 3.2) rule;

3.2) Search for a pixel pair (x+Δx, y+Δy) that satisfies f(x+Δx, y+Δy)=s, and select the pixel pair with the smallest modification (Δx, Δy) as the dense pixel pair (x' ,y');

4) If the dense pixel pair (x', y') overflows, adjust according to formula (1) to get a new (x, y), and then re-embed the secret information s;

5) Repeat step 3) to step 4) until all secret information s are embedded;

6) Compose all Δy into a set and perform lossless compression to obtain the compressed data set C0;

7) Generate a positive integer y=y ₀ +1 in [y ₀ , 255-y ₀ ] in order as the auxiliary pixel y, and continue to repeat steps 2) to 6) p times to obtain compressed data sets C1, C2...Cp, from C0, C1～Cp select C with the shortest data length, and write down the corresponding preferred auxiliary pixel value y; p=0 means no repetition;

In this example p = 0;

8) Send the dense image A' composed of all x', the preferred auxiliary pixel y and the compressed data set C to the receiving end;

9) Receive the compressed data set C, decompress it to obtain a set of Δy, and use y to obtain a set of auxiliary pixels y', that is, y'=y+Δy;

10) The x' in the dense image A' and the dense auxiliary pixel y' are formed into a pixel pair (x', y');

11) For each pixel pair (x', y'), extract each n binary secret information according to the ^formula s=[(n-1)*x'+n*y']modn ² ; repeat until n ^Binary secret information has been extracted;

¹² ) Convert the extracted n binary secret information into binary secret information. n ² takes one of 4, 16, 64, 256.

Performance simulation of the present invention

Use peak signal to noise ratio (Peak Signal to Noise Ratio, PSNR), hidden capacity C and embedding rate E and other indicators to measure the performance of the hidden algorithm. For an 8bit digital image with a size of H×W, H and W are positive integers; PSNR is defined as follows:

In the formula, MSE is the mean square error between the original image and the dense image, and the calculation formula is

Here x _ij , Denote the pixel values at (i, j) of the original image and the hidden image respectively.

Hidden capacity, percentage increase in embedding rate

T=(V2-V1)/V1*100%=(U2-U1)/U1*100% (2)

In the formula, V1 represents the embedding rate of the comparison method, V2 represents the embedding rate of the present invention; U1 represents the hidden capacity of the comparative method, and U2 represents the hidden capacity of the present invention.

Concealment capacity U: the number of hidden bits (bpp) per pixel (8 bits). If Q bits are hidden in Z bits, then the concealment capacity U=8*Q/Z bpp.

Embedding rate V: relative hidden capacity or hidden capacity relative value V, the ratio of the number of hidden bits to the number of carrier bits, if Q bits are hidden in Z bits, then the relative hidden capacity is V=Q/Z.

1) Embedding rate and hidden capacity comparison

In the FEMD method, the parameter n affects the information hiding capacity and embedding rate, and the present invention can further improve the embedding rate by adding auxiliary pixels and optimizing them.

The FEMD method hides an n binary number in an average of ² pixels (each uses 8 bits, 16 bits in total), and the number of bits is K=log ₂ (n ² ); the hidden capacity U1=8K/16=K/2bpp, Embedding rate V1=K/16;

The present invention hides an n binary number in an average of ¹ pixel (8 bits) and 1 auxiliary pixel modification amount d bits, and the number of bits is K=log ₂ (n ² ); hidden capacity U2=8K/(8+d )bpp, embedded rate

V2=K/(8+d), d<8;

Table 1 shows the comparison results of the hidden capacity and embedding rate of the two methods under different n values. It can be seen that the hidden capacity U and embedding rate V of the two methods increase with the increase of n. When the value of n is When increasing from 2 to 16, the hidden capacity of the FEMD method increases to 4bpp from 1bpp, and the hidden capacity of the present invention increases to 4.9bpp from 1.6bpp; the embedding rate of the FEMD method increases to 1/2 from 1/8, and the inventive method The minimum embedding rate of 1/5 has been increased to 8/13, which is greater than 1/2.

Compared with FEMD, the minimum hidden capacity and embedding rate of this method are improved by 23%-60%. This is because for the same carrier, the auxiliary pixel value y is the same, and the number of coding bits of the auxiliary pixel after embedding the secret information is only determined by its modification value, which can be represented by (1+log ₂ n)bit, and the number of bits is obviously less than 8 bit.

Table 1 Hidden capacity U and embedding rate V of the two methods with different n values

Note: The calculation of the hidden capacity U and the embedding rate V does not consider the optimal compression, and the number of coding bits of the auxiliary pixel after the optimal compression is considered to be embedded with the secret information is only determined by its modification amount, and it is not represented by (1+log ₂ n)bit at all. The average number of bits is much smaller than the 8 bits of the carrier, and the total number of bits after compression may be reduced by several times to 100 times, or even tens of thousands of times. If the modification amount of auxiliary pixel y=0, the amount of auxiliary data compressed is very small. Equivalent to d=0. The hidden capacity can even be doubled.

2) PSNR comparison

In order to measure the degree of improvement of the present invention in terms of image quality, Table 2 shows the image quality respectively obtained by the present invention and the FEMD method under different embedding ratios V. On the whole, under the same or higher embedding rate or hidden capacity situation, PSNR of the present invention is all higher than FEMD method, as when same embedding rate (1/2), average PSNR improves to 41.97dB from 34.84dB, and average improvement 7.13dB.

In addition, even when embedding 8/13 (greater than 1/2) secret information, the PSNR of the present invention is still as high as 35.71dB, indicating that the method is an efficient information hiding algorithm, and the auxiliary pixel value as a key can ensure the security of secret information safety.

Table 2 PSNR (dB) of the two methods at different embedding rates

3) Compared with other similar methods

In order to compare this algorithm with other similar methods, the Lena image hiding effect is used for comparison, the present invention can realize more information hiding with different embedding rates, and the PSNR of the present invention is better than the LSB method, such as when n=2, PSNR increases by at least 2.0dB.

The reason for the improvement of image quality is that the present invention can greatly increase the information embedding rate by adding auxiliary pixels. Compared with the FEMD method, when embedding the same proportion of secret information, the present invention needs to use a lower pixel contrast ratio, thus reducing the modification rate of the carrier. small.

In a word, the present invention proposes a high-efficiency information hiding method by introducing auxiliary pixels. The hiding capacity has nothing to do with the type of original data. It can be image data or other data. The hiding amount is always fixed, with large hiding capacity and information security , and easy to realize by software and hardware. Its characteristics are: the method realizes the joint processing of secret information and key through the introduction of auxiliary pixels and data optimization, and the receiving end can completely restore the secret information and restore the original data with high quality.

This method can hide information in each pixel of the original image data, improves the hiding efficiency, breaks through the limitation of the current method for hiding in a pixel pair (two pixels), and can reach or exceed 1/2 of any image Hiding capacity, when the hiding capacity is 1/2, the PSNR of the recovered cover image exceeds 41dB, and the performance is better than typical hiding methods such as LSB and FEMD hiding methods.

Parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims (4)

1. a kind of efficient information hidden method for introducing auxiliary pixel, it is characterised in that step is as follows：

1) implicit binary system secret information is converted into n²The secret information of system, each secret information is s, and s values belong to set {0,1,2,…n²-1},n≥2；

2) it is [y to produce auxiliary pixel value y, y₀,255-y₀] in positive integer, wherein y₀=n/2 is rounded；Will be every in carrier image A Individual pixel x and auxiliary pixel y constitutes pixel to (x, y), calculates and obtains functional value f=[(n-1) * x+n*y] mod n²；

3) f and secret information s are compared, obtained containing close pixel to (x ', y ')；

If 4) overflowed containing close pixel to (x ', y '), then adjustment obtain it is new containing close pixel to (x, y), it is then again embedded secret Information s；

5) step 3 is repeated) to step 4), until all secret information s insertions are finished；

6) all Δ y composition set is carried out obtaining compressed data set C0 after Lossless Compression；

7) [y is produced in order₀,255-y₀] interior positive integer y=y₀+ 1 as auxiliary pixel y, continues repeat step 2) to 6) p times, Compressed data set C1, C2 ... Cp is obtained, from C0, C1~Cp selects data length most short C, writes down corresponding preferred auxiliary picture Plain value y；Wherein p is integer, and p=0 represents not repeat；

8) all x ' stego-image A ', preferably auxiliary pixel y and compressed data set C constituted is sent to receiving terminal；

9) receiving compressed data set C, decompression obtains Δ y set, and auxiliary pixel y ' set, i.e. y '=y+ are obtained using y Δy；

10) pixel is constituted to (x ', y ') by the x ' in stego-image A ' and containing close auxiliary pixel y '；

11) to each pixel to (x ', y '), according to s=[(n-1) * x '+n*y '] modn²Extract each n²System secret information； Repeat, until n²System secret information is extracted and finished；

12) by the n of extraction²System secret information switchs to binary system secret information.

2. a kind of efficient information hidden method for introducing auxiliary pixel according to claim 1, it is characterised in that：N=2 or 4 or 8 or 16.

3. a kind of efficient information hidden method for introducing auxiliary pixel according to claim 1 or 2, it is characterised in that：Step Rapid detailed process 3) is：

3.1) f and secret information s are compared, if f=s, do not change pixel to (x, y), otherwise repaiied by 3.2) rule Change pixel pair；

3.2) search meet f (x+ Δs x, y+ Δ y)=s pixel to (x+ Δs x, y+ Δ y), select wherein modification amount (Δ x, Δ Y) minimum pixel to as containing close pixel to (x ', y ').

4. a kind of efficient information hidden method for introducing auxiliary pixel according to claim 3, it is characterised in that：Step 4) Detailed process be：Adjustment is obtained：

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