A method for realizing covert communication by using terahertz high-speed data transmission

Abstract

The application discloses a method for realizing covert communication by using a terahertz high-speed data transmission, which combines information hiding technology with a terahertz high-speed data transmission system, uses original data of a terahertz high-speed data transmission channel as a carrier, carries out digital sampling on an analog signal which needs to be separately transmitted, modifies values of a data part of the carrier, matches the data to be hidden with a function value of the carrier data, hides marking information in the data containing the hidden information, and further improves quality of the carrier data at a receiving end, and saves channel resources for transmitting the analog signal. The information hiding process is carried out at a front end of the terahertz high-speed data transmission system, and does not change a terahertz wireless communication system. The hiding method is simple and flexible, and PSNR is improved by 3 dB compared with a least significant bit replacement method under the condition of the same hiding capacity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wireless communication, and particularly relates to a method for realizing covert communication by using terahertz high-speed data transmission. BACKGROUND

[0002] The terahertz wave band (THz) refers to electromagnetic waves with a frequency in the range of 0.1-10 THz, which is between the microwave and infrared wave bands, and has the characteristics of both microwaves and light waves, such as large bandwidth, high security and strong directivity. In view of the many advantages of terahertz waves in the field of communication, terahertz wireless communication is one of the most promising applications of terahertz technology. Terahertz waves can theoretically support high-speed data transmission of several tens of Gbit / s to several Tbit / s, which is much higher than the wireless communication in the microwave and millimeter wave bands. At the same time, compared with optical wireless communication, terahertz waves are less affected by the atmosphere and are easier to track, and therefore have a broader application prospect.

[0003] The energy of the terahertz signal is mainly concentrated on the communication link with strong directivity, which greatly increases the difficulty for an illegal eavesdropper to eavesdrop on the terahertz signal. Therefore, terahertz waves are widely considered to have broad application prospects in the field of secure and private communication. However, in recent years, research on terahertz secure communication technology has found that terahertz communication still faces security problems in information interaction such as eavesdropping and attack. Encryption, spread spectrum communication, burst communication and direction modulation technologies can be used to ensure the security of wireless communication, among which encryption technology is mainly used to protect the plaintext information of the communication content, spread spectrum communication technology and burst communication technology are used to reduce the probability of signal interception, and direction modulation technology is used to degrade the quality of the signal intercepted by a third party. These technologies can ensure the security of wireless communication from different angles and can be used in combination in many scenarios. In recent years, some researchers have introduced the covert channel technology in information hiding into the field of wireless communication and proposed a wireless covert channel, which has brought more technical options for the security of wireless communication. SUMMARY

[0004] The technical purpose of the present application is to overcome the shortcomings of the prior art, and to provide a method for realizing covert communication by using terahertz high-speed data transmission, to realize a terahertz wireless covert communication system based on information hiding, and to improve the utilization rate of the terahertz high-speed data transmission channel.

[0005] The technical solution of the present application is a method for realizing covert communication by using terahertz high-speed data transmission, comprising:

[0006] (1) AD sampling is performed on an analog signal to be transmitted in the communication system to obtain quantized data as secret information, denoted as S=S1, S2, …, Sn. n , wherein S i is a binary number, i=1, 2, …n; wherein n represents the number of samples.

[0007] (2) Set the original data of the terahertz wireless communication front end as C = C1, C2, …, C n , where C i is an 8-bit sampled binary number, represented as C i = c i,8 , c i,7 , c i,6 , c i,5 , c i,4 , c i,3 , c i,2 , c i,1 ;

[0008] (3) Divide the original data C of the terahertz wireless communication front end into a group of every two (C i , C i+1 ) as a carrier data pair, and calculate the modulus function f of the carrier data pair;

[0009] (4) Divide the secret information S into a group of every two (S i , S i+1 ) as a secret information bit, convert it to a quaternary number Q j = 2S i + S i+1 , and calculate the difference value d according to the modulus function f;

[0010] (5) According to the difference value d, judge the matching degree of the carrier data pair (C i , C i+1 ) and the secret information bit (S i , S i+1 ), embed (S i , S i+1 ) into (C i , C i+1 ) according to the matching degree, obtain the secret-containing data pair (SP i , SP i+1 ), and mark the modification of C i+1 in the carrier data pair using the marking information L, where L = L1, L2, …, L n / 2 , L i is a binary number with values of 0 and 1;

[0011] (6) Repeat steps (3) to (5) until all carrier data pairs are embedded with secret information, obtain the secret-containing data SP and the marking information L; losslessly compress the marking information L to obtain new marking information Lc, and the length is recorded as k;

[0012] (7) Use the secret-containing data SP as a carrier, hide the marking information Lc using the difference between adjacent two numbers, obtain the secret-containing data SP'; transmit the secret-containing data SP' through the terahertz high-speed data transmission channel.

[0013] The calculation formula of the module function is f = (C i +2C i+1 )mod 4; wherein mod 4 represents the remainder obtained by dividing the value by 4.

[0014] The calculation formula of the difference value d is d = (f-Q j )mod 4.

[0015] The matching degree of the carrier data pair (C i ,C i+1 ) and the secret information bit (S i ,S i+1 ) is judged according to the difference value d, (S i ,S i+1 ) is embedded into (C i ,C i+1 ) according to the matching degree, the secret-containing data pair (SP i ,SP i+1 ) is obtained, and the modification of C i+1 in the carrier data pair is marked by using the marking information L, including:

[0016]

[0017] When d = 0, the carrier data pair (C i ,C i+1 ) does not need to be modified, the information hiding is completed, and L i is marked as 0;

[0018] When d = 1, C i in the carrier data is reduced by 1 to obtain a new data pair (C i -1,C i+1 ), the information hiding is completed, and L i is marked as 0;

[0019] When d = 2, C i+1 in the carrier data is increased by 1 to obtain a new data pair (C i ,C i+1 +1), the information hiding is completed, and L i is marked as 1;

[0020] When d = 3, C i in the carrier data is increased by 1 to obtain a new data pair (C i +1,C i+1 ), the information hiding is completed, and L i is marked as 0.

[0021] The difference value between two adjacent secret data SPs is used to hide the mark information Lc to obtain the secret data SP', including:

[0022] The difference value between two adjacent secret data SPs is used to hide the mark information Lc to obtain the secret data SP', including: i , SP i+1 The difference value D=(D1, D2,..., D n / 2 ) between two adjacent secret data SPs is calculated, wherein SP i is expressed as [sp i,8 , sp i,7 , sp i,6 , sp i,5 , sp i,4 , sp i,3 , sp i,2 , sp i,1 ];

[0023] The number of data pairs corresponding to the difference absolute value |D| from 0 to the maximum value is counted

[0024] R=(R0, R1,..., R max );

[0025] The sum of the number of data pairs corresponding to the difference absolute value |D| from 0 to x is calculated, so that it satisfies The difference value x is obtained by solving, wherein k represents the length of the mark information Lc;

[0026] The difference value D is preprocessed, the difference value with a value of-128±x in the difference value D is left shifted by u bits, and the difference value with a value of 128±x in the difference value D is right shifted by u bits, so that the new difference value-128±x and 128±x generated after the mark information is embedded do not overlap with the original difference value;

[0027] The mark information Lc is embedded from the data pair (SP i , SP i+1 ) with the difference value D=0 i , and when embedding, the binary highest bit sp i+1,8 of SP i+1 is replaced by Lc i , until the mark information is completely embedded, and the final secret data SP' is obtained.

[0028] The k<n / 2, 0<x<128 and u>2x.

[0029] The secret data SP is the same size as the original data C.

[0030] The proportion of 0 and 1 in the mark information L is 3:1.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] (1) This invention utilizes the matching degree between the carrier data modal function value and the data to be hidden to hide secret information. At the same time, the generated marker information is hidden in the data containing secret information to further improve the carrier quality. Through the information hiding method, a terahertz high-speed data transmission wireless covert communication system with better performance is realized.

[0033] (2) This invention combines a terahertz high-speed data transmission system with an information hiding method, giving full play to the advantages of the information hiding method, so that the transmission of secret information does not occupy the data transmission channel. While transmitting high-speed terahertz data, it also conceals the transmission of an analog signal, which saves communication channels and improves the transmission efficiency of the terahertz high-speed data transmission system.

[0034] (3) This invention utilizes the matching of the modulus function values ​​of the data to be hidden and the carrier data to achieve information hiding, and uses the cryptic data to hide the marker information again to improve the PSNR of the decoded data and the original data at the receiving end. Compared with the hiding result of the LSB replacement method, the PSNR can be improved by 3dB under the same hiding capacity.

[0035] (4) The information hiding process of this invention is carried out at the front end of the terahertz high-speed data transmission system without changing the terahertz wireless communication system. The hiding method is simple, flexible and versatile, and can be adjusted according to the actual situation. Attached Figure Description

[0036] Figure 1 This is a flowchart of a terahertz wireless covert communication method.

[0037] Figure 2 This is a test image. Detailed Implementation

[0038] This invention proposes a method for covert communication using a terahertz high-speed data transmission channel. It combines information hiding technology with a terahertz high-speed data transmission system. Using the original data of the terahertz high-speed data transmission channel as a carrier, the analog signal that needs to be transmitted separately is digitally sampled. After modifying the numerical values ​​of the carrier data, the data to be hidden matches the value of the carrier data modulus function. The marking information is hidden in the dense data for the receiver to further improve the carrier data quality. The PSNR is better than the traditional LSB method, while saving channel resources for transmitting the analog signal.

[0039] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0040] like Figure 1 As shown, this invention provides a method for covert communication using a terahertz high-speed data transmission channel, with the following steps:

[0041] (1) Perform AD sampling on one analog signal to be transmitted in the communication system, and obtain the quantized data as secret information, denoted as S = (S1, S2, ..., S...). n ), where S i The number is a binary number, i = 1, 2, ..., n; n represents the number of samples.

[0042] (2) Assume the original data of the terahertz wireless communication front end is C = (C1, C2, ..., C n ), where C i For an 8-bit sampled binary number, C i Represented as C i =[c i,8 ,c i,7 ,c i,6 ,c i,5 ,c i,4 ,c i,3 ,c i,2 ,c i,1 ], C i The value range is [0, 255];

[0043] (3) Divide the original data C from the terahertz wireless communication front end into two (C i C i+1 The data is divided into a group as a carrier data pair, and the modulus function f of the data pair is calculated using the formula f = (C i +2C i+1 mod 4, where mod4 represents the remainder when the value is divided by 4;

[0044] (4) Group the secret information S into pairs of (Si, Si+1) as secret information bits, and convert them into quaternary number Qj = 2S. i +S i+1 The difference d is calculated based on the modulus function f, and the formula is d = (fQ) / (fQ) j )mod 4;

[0045] (5) Determine the carrier data pair (C) based on the difference d. i C i+1 ) and secret information bits (S i ,S i+1 The degree of matching is used to determine the secret information bits (S). i ,S i+1 Embedded into (C i C i+1 In ), the dense data pair (SP) is obtained. i SP i+1 ), and use the tagging information L to tag the carrier data in C i+1 The modification details, where L = (L1, L2, ..., L n / 2 ), Li is a binary number with value 0 or 1, and the specific method is as follows:

[0046]

[0047] case1: when d = 0, the carrier data pair (C i ,C i+1 ) does not need to be modified, the information hiding is completed, and L i is marked as 0;

[0048] case2: when d = 1, the new data pair (C i -1,C i ) is obtained by subtracting 1 from C i+1 in the carrier data, the information hiding is completed, and L i is marked as 0;

[0049] case3: when d = 2, the new data pair (C i+1 ,C i +1) is obtained by adding 1 to C i+1 in the carrier data, the information hiding is completed, and L i is marked as 1;

[0050] case4: when d = 3, the new data pair (C i +1,C i ) is obtained by adding 1 to C i+1 in the carrier data, the information hiding is completed, and L i is marked as 0.

[0051] (6) Repeat steps 3 to 5 until all carrier data pairs are embedded with secret information, to obtain the secret data SP (with the same size as the original data C) and the marking information L;

[0052] (7) The ratio of 0 and 1 in the marking information L is 3:1, and the lossless compression is performed on L to obtain the new marking information Lc, and the length of Lc is k (k < n / 2);

[0053] (8) Using the difference between adjacent two numbers to hide the marking information Lc, the secret data SP' is obtained, and the specific hiding process is as follows:

[0054] The difference D = (D1, D2, …, D n / 2 ) between adjacent two secret data (SP i ,SP i+1 ) in the secret data SP is calculated, wherein SP i can be expressed as [sp i,8 ,sp i,7 ,sp i,6 ,sp i,5 ,spi,4 ,sp i,3 ,sp i,2 ,sp i,1 The absolute value of the statistical difference |D| ranges from 0 to its maximum value, corresponding to the number of data pairs R = (R0, R1, ..., R...). max );

[0055] Calculate the sum of the number of data pairs corresponding to the absolute value of the difference |D| from 0 to x, such that it satisfies The difference x is obtained by solving for k, where k represents the length of the tag information Lc, and k <n / 2,0<x<128;

[0056] The difference D is preprocessed by shifting the difference value of -128±x to the left by u positions and shifting the difference value of 128±x to the right by u positions to ensure that the new difference values ​​-128±x and 128±x generated after embedding the tag information do not overlap with the original difference values, where u>2x;

[0057] From the data pairs with difference D = 0 (SP) i SP i+1 Embedding tag information Lc in ) i When embedding, use Lc i Replace SP i+1 The highest bit of the binary number sp i+1,8 This continues until all the labeled information is embedded, resulting in the final encrypted data SP'.

[0058] (9) The encrypted data SP' is transmitted through the terahertz high-speed data transmission channel.

[0059] like Figure 2 As shown, six 512×512 natural images were used as the original data for terahertz transmission, and the data from another analog signal quantized by AD was used as the secret information, replaced by binary random numbers for simulation testing. The method of this invention was compared with the classic LSB and EMD methods to test the image quality of different methods with a hiding capacity of 1 bpp. Table 1 shows the PSNR performance comparison results of the three algorithms on different images without hiding the marker information. Table 2 shows the PSNR performance comparison results of the three algorithms on different images with the marker information hidden.

[0060] Table 1. Performance Comparison of Different Hiding Methods When Markers Are Not Hidden (PSNR)

[0061] Hiding method Lena Baboon Peppers Boats Goldhill Airplane Mean LSB 51.14 51.12 51.15 51.13 51.15 51.15 51.14 EMD 52.11 52.10 52.11 52.12 52.11 52.12 52.11 The method 52.40 52.39 52.40 52.39 52.38 52.40 52.39

[0062] Table 2. Performance Comparison of Different Hiding Methods After Marking and Hiding (PSNR)

[0063] Hiding method Lena Baboon Peppers Boats Goldhill Airplane Mean LSB 51.14 51.12 51.15 51.13 51.15 51.15 51.14 EMD 52.11 52.10 52.11 52.12 52.11 52.12 52.11 The method 54.17 54.13 54.17 54.15 54.13 54.16 54.15

[0064] It can be seen that the hiding capacity of the present application can reach 1 / 8 (1bpp), and the PSNR between the carrier data and the original data after the first information hiding is better than that of the classical LSB and EMD methods without hiding the mark information, and the average PSNR of the data containing secret information can reach 52.4dB; the modification of the second value in each group of numbers during the first hiding is marked as secret information for the second hiding, so that the receiver can modify the corresponding data by using the mark information, further improve the recovered carrier data, and make the PSNR further increase by about 1.8dB, with an average of 54.2dB, which is 3dB higher than the LSB replacement method.

[0065] The hiding method of the present application is used in the front-end processing of the terahertz transmission system, and does not need to modify the terahertz high-speed data transmission system, and the hiding method is simple, flexible and changeable, can adapt to the requirements of the original data quality of the carrier in different occasions, improve the covert transmission performance, has practical value in the terahertz wireless communication system, and has application prospect in various other data transmission systems.

[0066] The contents not described in detail in the specification of the present application belong to the known technology of those skilled in the art.

Claims

1. A method for covert communication using terahertz high-speed data transmission, characterized in that, The method comprises the steps of: (1) AD sampling to a analog signal to be transmitted, get quantized data as secret information, recorded as S = S1, S2, …, S n , where S i is a binary number, i = 1, 2, … n; Where n represents the number of samples; (2) Set the original data of the terahertz wireless communication front end as C=C1, C2, …, C n , where C i is an 8-bit sampling binary number, represented as C i =c i,8 , c i,7 , c i,6 , c i,5 , c i,4 , c i,3 , c i,2 , c i,1 ; (3) divide the raw data C of the terahertz wireless communication front end into a group of carrier data pairs every two (C i ,C i+1 ) and calculate the modulus function f of the carrier data pairs; (4) The secret information S is converted into a quaternary number Q i = 2S i+1 + S j every two bits (S i , S i+1 ) of the secret information bits, and the difference d is calculated according to the modulo function f. (5) judging the matching degree of the carrier data pair (C i ,C i+1 ) and the secret information bits (S i ,S i+1 ) according to the difference d, embedding (S i ,S i+1 ) into (C i ,C i+1 ) according to the matching degree, obtaining the secret-containing data pair (SP i ,SP i+1 ), and marking the modification of C i+1 in the carrier data pair by using the marking information L, wherein L=L1, L2, …, L n / 2 , L i is a binary number with values of 0 and 1; judging the matching degree of the carrier data pair (C i ,C i+1 ) with the secret information bits (S i ,S i+1 ) according to the difference d, embedding (S i ,S i+1 ) into (C i ,C i+1 ) according to the matching degree, obtaining the secret-containing data pair (SP i ,SP i+1 ), and marking the modification of C i+1 in the carrier data pair by using the marking information L, comprising: When d = 0, the carrier data pair (C i ,C i+1 ) does not need to be modified at all, the completion information is hidden, and L i is marked as 0. When d = 1, C i -1, C i i+1 ), completing information hiding, L i is marked as 0;​ When d=2, the C in the carrier data i+1 Adding 1 results in a new data pair (C) i C i+1 +1), complete information hiding, L i Marked as 1; When d = 3, C i +1, C i +1, C i+1 ), the information hiding is completed, and L i is marked as 0. (6) repeating steps (3)-(5) until all carrier data pairs are embedded with secret information, obtaining secret data SP and label information L; losslessly compressing the label information L to obtain new label information Lc, and the length is recorded as k; (7) using the secret data SP as a carrier, hiding the label information Lc by using the difference between two adjacent numbers to obtain secret data SP'; transmitting the secret data SP' through a terahertz high-speed data transmission channel.

2. The method for covert communication using terahertz high-speed data transmission according to claim 1, characterized in that: The calculation formula of the module function is f=(C i +2C i+1 )mod4; wherein, mod4 represents the remainder obtained by dividing the value by 4.

3. The method for covert communication using terahertz high-speed data transmission according to claim 2, characterized in that: The difference d is calculated as d = (f - Q j ) mod 4.

4. The method for covert communication using terahertz high-speed data transmission according to claim 3, characterized in that: The method of using the secret data SP as a carrier, hiding the label information Lc by using the difference between two adjacent numbers to obtain secret data SP' comprises the steps of: Computing the difference D = (D1, D2,..., D i , between two adjacent secret data-containing SPs in a secret data-containing SP i+1 n / 2 i i,8 i,7 i,6 i,5 i,4 i,3 i,2 i,1 ]​​​​​​​​​​ The statistical difference absolute value |D| takes values from 0 to the maximum value corresponding to the number of data pairs R=(R0, R1, …, R max ). The sum of the number of data pairs corresponding to the difference value absolute value |D| from 0 to x is made to satisfy The difference value x is solved; wherein k represents the length of the mark information Lc. Preprocessing the difference value D, left shifting the difference value D with a value of-128±x by u bits, and right shifting the difference value D with a value of 128±x by u bits, so as to ensure that the new difference value-128±x and 128±x generated after embedding the label information do not overlap with the original difference value; From the data pair (SP i , SP i+1 ) with difference D = 0, the mark information Lc i is embedded, replacing the binary highest bit sp i+1,8 of SP i+1 with Lc i until the mark information is completely embedded, obtaining the final data with secret SP'.

5. The method for covert communication using terahertz high-speed data transmission according to claim 4, characterized in that: The k is less than n / 2, the x is greater than 0 and less than 128, and the u is greater than 2x.

6. The method according to any one of claims 1-5, wherein the method is characterized in that: The secret data SP is the same size as the original data C.

7. The method according to any one of claims 1-5, wherein the method is characterized in that: The proportion of 0 and 1 in the label information L is 3:1.

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