An artificial noise secure communication method not limited to the null space of the legitimate channel

Abstract

An artificial noise-based secure communication method not limited to the null space of the legitimate channel, adding a first type of artificial noise w to the information signal s k and a second type of artificial noise w m to form the transmission signal x1, where w k is located in the null space of the legitimate channel matrix. If there is no channel null space, then there is no w component in the transmission signal x1 k component, and w m is located in the column space of the legitimate channel matrix. The present invention can adopt two-stage communication, and the receiver adds the two received signals; the transmission signal in the first stage is x1, and the transmission signal in the second stage is x2. The communication system applying the artificial noise-based secure communication method of the present invention not limited to the null space of the legitimate channel can be a MIMO communication system or a SISO communication system or a MISO communication system. The present invention hides the transmission of the secure information through two types of artificial noise, and further eliminates the interference of the artificial noise to the legitimate users through two-stage signals.

Description

Technical Field

[0001] The present invention belongs to the technical field of encrypted communication, and particularly relates to an artificial noise secure communication method that is not limited by the null space (NS) of a legitimate channel. Background Art

[0002] With the advent of high-computing-power computers and the continuous update of advanced eavesdropping technologies, traditional key-based encryption technologies can no longer ensure information security, and problems such as the complexity of their encryption algorithms and the custody and distribution of keys have gradually phased out key-based encryption technologies. At the same time, it has been found from the perspective of information theory that it is entirely possible to achieve secure communication using physical layer technologies. Physical layer security technology has thus become a new opportunity in the field of wireless communication. Physical layer security technology is independent of higher layers and does not rely on higher-layer encryption means to achieve the secure transmission of information in a wireless channel. Its basic principle is to utilize the inherent characteristic information (noise, fading, etc.) of the wireless channel to achieve the secure transmission of information through reasonable design. Even if the eavesdropper's computing power is not limited, the number of bits that the eavesdropper can obtain can be restricted, deteriorating the quality of the eavesdropping channel without any impact on legitimate users.

[0003] Physical layer secure communication technology uses the inherent characteristic information endogenous security mechanism of the wireless channel to ensure the security of information during the communication process. Physical layer security technology is mainly divided into the following categories: 1. Information-theory-based physical layer security; 2. Artificial noise-assisted security; 3. Security-oriented beamforming technology; 4. Physical layer key generation technology; 5. Physical layer encryption technology. Among the existing physical layer secure communication technologies, the most frequently used and effective solution is the artificial noise scheme. There are two methods for generating artificial noise: the multi-antenna method and the relay simulation method. The AN scheme generated by multi-antennas designs the artificial noise (AN) in the null space (NU) of the legitimate channel, that is, the artificial noise is orthogonal to the legitimate channel. The transmission in the legitimate channel is eliminated because it is orthogonal to the legitimate channel, achieving the purpose of having no impact on legitimate users while seriously affecting the eavesdropping of eavesdroppers.

[0004] The design principle of this artificial noise is that while the transmitter sends confidential information, it uses part of the available power to send artificial noise. The artificial noise w k , satisfies H k w k = 0. The specific transmission process is as follows:

[0005] The transmitter sends s + w k to the user, and the receiver and the eavesdropper receive respectively:

[0006] y b = H AB (s + w k ) + n b = HAB s + n b

[0007] y e = H AE (s + w k ) + n b = H AE s + H AE w k + n e

[0008] where s is the transmission signal, H AB is the legitimate channel matrix, H AE is the eavesdropping channel matrix, n b and n e are white noises.

[0009] For legitimate users, the artificial noise is eliminated in the legitimate channel because it is orthogonal to the channel. For eavesdroppers, the artificial noise seriously affects the eavesdropping and decryption of eavesdroppers.

[0010] However, not all channels have a null space. The channel null space is defined as the matrix composed of the orthogonal basis perpendicular to the channel matrix H k , that is, H k w k = 0, and all w k constitute the null space of the channel. H k w k = 0 can be equivalent to the homogeneous equation system Ax = 0 in linear algebra. Whether the channel matrix has a null space is equivalent to whether the homogeneous equation system H k w k = 0 has a solution. In fact, this equation always has a solution, that is, the all-zero solution. However, designing all-zero artificial noise for the channel null space is meaningless, so only the case of non-zero solutions is discussed. In linear algebra, the necessary and sufficient condition for the homogeneous linear equation system to have a non-zero solution is that the rank of the coefficient matrix of the equation system is less than the number of unknowns, that is, r(H k ) < n, where n is the dimension number of w k , that is, the number of unknowns, and is also the number of columns of H k . Therefore, the necessary and sufficient condition for the existence of non-zero solutions is that r(H k ) is less than the number of columns of H k , that is, the condition for the channel to have a null space is that the rank of the channel matrix is less than its number of columns. From the above analysis, it can be seen that not all channels have a channel null space. Therefore, the design and use of traditional artificial noise have certain requirements for the channel matrix, that is, the design of traditional artificial noise has limitations, and its application scope is limited by the channel matrix and is not applicable to communication systems without a channel null space. On the other hand, if the eavesdropping end is located near the receiver and the eavesdropping channel is highly similar to the legitimate channel, this scheme cannot guarantee the security of information. Summary of the Invention

[0011] To overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an artificial noise secure communication method that is not limited to the null space of the legitimate channel. The transmission of the confidential information is hidden by two kinds of artificial noise, and the interference of the artificial noise to the legitimate users is further cancelled through two-stage signal transmission, so that the artificial noise is no longer limited to the channel null space. Even if there is no channel null space, the secure transmission of information can be realized; even if the eavesdropping end is located near the receiver, it is impossible to decrypt the information.

[0012] To achieve the above purpose, the technical solution adopted by the present invention is:

[0013] An artificial noise secure communication method that is not limited to the null space of the legitimate channel, adding a first kind of artificial noise w to the information signal s k and a second kind of artificial noise w m to form the transmission signal x 1 , x 1 = s + w k + w m , where w k is located in the null space of the legitimate channel matrix. If there is no channel null space, then there is no w 1 component in the transmission signal x k , w m is located in the column space of the legitimate channel matrix.

[0014] In one embodiment, each component of v k is selected to be a Gaussian distribution with independent mean of 0 and variance of to construct the first kind of artificial noise w k :

[0015] w k = Z k v k

[0016] Each component of V m is selected to be a Gaussian distribution with independent mean of 0 and variance of to construct the second kind of artificial noise w m :

[0017] w m = Γ m V m

[0018] Z k is the basis vector in the null space of the legitimate channel matrix, and Γ m is the basis vector in the column space of the legitimate channel matrix.

[0019] That is, vk Each component of is an independent variable following a Gaussian distribution with a mean of 0 and a variance of , and V m Each component of is an independent variable following a Gaussian distribution with a mean of 0 and a variance of .

[0020] In one embodiment, the communication method uses two - stage communication, and the receiver adds the two received signals; the transmission signal in the first stage is x 1 , and the transmission signal in the second stage is x 2 , which is expressed as:

[0021]

[0022] In the formula, H AB,1 is the legitimate channel matrix in the first stage, H AB,2 is the legitimate channel matrix in the second stage, and H AB,1 ≠H AB,2 .

[0023] The communication system applying the present invention is not limited to the communication method of artificial - noise - based secure communication in the null space of the legitimate channel, and can be a MIMO communication system or a SISO communication system or a MISO communication system.

[0024] For a MIMO communication system, when there is a null space in the legitimate channel, the form of the two - stage transmission signal is designed to eliminate the interference of the two kinds of artificial noise on the legitimate user; when there is no null space in the legitimate channel, only the second kind of artificial noise w m is used to achieve secure transmission of information in a two - stage manner.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention designs two kinds of artificial noise. One is the artificial noise designed in the null space of the legitimate channel, and the other is the randomly generated artificial noise designed in the column space of the legitimate channel. The transmission of the confidential information is hidden by the two kinds of artificial noise, and further, the interference of the artificial noise on the legitimate user is eliminated by the two - stage signal. It has the following advantages:

[0027] First: The design of the two kinds of artificial noise makes the artificial noise no longer limited to the null space of the channel, and this method can be adopted for communication systems with or without a null space in the channel to achieve secure information communication.

[0028] Second: Due to the design and calculation of the two - stage signal, even if the eavesdropping end is near the receiver and the legitimate channel has a high similarity with the eavesdropping end, the eavesdropping end cannot decrypt the two different signals received in the two stages.

[0029] Third: The artificial noise scheme designed in the null space (NS) of the legitimate channel in NS only involves one-stage artificial noise designed in the null space of the legitimate channel, while the present invention involves two-stage hybrid artificial noise. For eavesdroppers, the impact on them is greater, the interference is stronger, and the communication system is more secure.

[0030] Fourth: Even if the computing power of the eavesdropping end is not limited, no matter what receiving method the eavesdropping end adopts, the two types of artificial noise are always embedded in the confidential information and cannot be demodulated by the eavesdropping end, ensuring the security of the confidential information.

[0031] Fifth: Strong scalability. In terms of the design principle of this method, it is completely possible to design multiple types of hybrid artificial noise to hide the transmission of private information, and to offset the interference of artificial noise on legitimate users by reasonably designing multi-stage signal transmission, so as to achieve the secure reach of information. Brief Description of the Drawings

[0032] Figure 1 It is a system model diagram applicable to the present invention.

[0033] Figure 2 It is a flowchart for implementing the present invention. Detailed Embodiment

[0034] The following will describe in detail the implementation manner of the present invention in conjunction with the drawings and embodiments.

[0035] In the physical layer security technology, the artificial noise scheme is most frequently used and has remarkable effects. However, most of the artificial noise schemes are designed according to the channel characteristics and are designed in the null space (NS) of the legitimate channel. During the transmission on the legitimate channel, it is eliminated because it is orthogonal to the legitimate channel, so as not to interfere with the legitimate receiver and achieve the secure transmission of information. However, not all channels have a null space, so the artificial noise designed in NS has limitations, and its scheme application range is limited by the channel matrix. The present invention needs to solve the limitations of artificial noise design, so that secure communication of information can be achieved even if the channel does not have a null space.

[0036] The present invention is implemented through the following system design and transmission mechanism:

[0037] In one embodiment, the present invention designs for the MISO communication scenario, as Figure 1 shown. The transmitter (Alice) has N T antennas, the legitimate user (Bob) has N R antennas (N R =1), and the eavesdropping end (Eve) has N E antennas (N E=1). Taking two - stage communication as an example, the present invention will be described in detail. Considering that the channel matrix varies in different stages in the actual scenario, it is assumed that the same channel state information is different in the two stages, that is, the legitimate channel matrix H AB,1 in the first stage and the legitimate channel matrix H AB,2 in the second stage are different, H AB,1 ≠H AB,2 .

[0038] First stage: The transmission signal from the transmitter to the legitimate user is x 1 , so the signal y b,1 received by Bob and the signal y e,1 received by Eve are respectively:

[0039] y b,1 =H AB,1 x 1 +n b,1 (1 - 1)

[0040] y e,1 =H AE,1 x 1 +n e,1 (1 - 2)

[0041] where n b,1 and n e,1 are independent additive white Gaussian noises with a mean of 0 and variances of and H AE,1 is the eavesdropping channel matrix in the first stage. The transmission signal x 1 is composed of the information signal s, the first artificial noise w k , and the second artificial noise w m , that is

[0042] x 1 =s + w k +w m (1 - 3)

[0043] where w k is in the null space of the legitimate channel matrix H AB,1 in the first stage, that is, H AB,1 w k =0. If there is no channel null space, then there is no w 1 component in the x k signal, and w m is in the column space of the legitimate channel matrix H AB,1 in the first stage.

[0044] In the embodiments of the present invention, the first artificial noise w k and the second artificial noise wm Construction formula: w k = Z k v k 、w m = Γ m V m . Where Z k is the basis vector in the null space of the legitimate channel matrix, and Γ m is the basis vector in the column space of the legitimate channel matrix. If fixed w k and w m are selected, and ||G k w k || or ||G k w m || is very small, the interference caused to the eavesdropper is very small and easy to remove. To avoid this situation, in the embodiments of the present invention, w k and w m are selected as complex Gaussian random vectors in the null space and column space of the main channel, while Z k 、Γ m are the basis vectors of the null space and column space of the main channel, and v k and V m are responsible for making w k and w m not fixed. They are complex Gaussian random vectors, and each component is an independent Gaussian distribution with a mean of 0 and variances of and

[0045] Substitute equations (1-3) into (1-1) and (1-2) respectively, the signals y b,1 received by the legitimate user and the signal y e,1 received by the eavesdropper can be expressed as:

[0046] y b,1 = H AB,1 (s + w m ) + n b,1 (1-4)

[0047] y e,1 = H AE,1 (s + w k + w m ) + n e,1 (1-5)

[0048] According to the above scheme, the present invention uses two kinds of artificial noise, which are respectively designed in the null space and column space of the channel. Since the design of artificial noise is not limited to the null space of the channel, even if the channel has no null space, secure transmission of information can still be achieved.

[0049] ​Furthermore, the communication method of the present invention further includes a second stage: the signal transmitted by the transmitter to the legitimate user, i.e., the transmission signal in the second stage, is x 2 , x 2 It is designed according to the characteristics of the legitimate channel matrix in two stages, expressed as:

[0050]

[0051] Therefore, the signal y received by Bob in the second stage can be obtained b,2 and the signal y received by Eve e,2 are respectively:

[0052]

[0053]

[0054] where n b,2 and n e,2 are independent additive white Gaussian noises with a mean of 0 and variances of and H AE,2 is the eavesdropping channel matrix in the second stage, defined as

[0055]

[0056] Therefore, the signals received by Bob and Eve in two stages can be sorted out as:

[0057] y b,1 = H AB,1 (s + w m ) + n b,1 (1 - 10)

[0058] y b,2 = H AB,1 (s - w m ) + n b,2 (1 - 11)

[0059] y e,1 = H AE,1 (s + w k + w m ) + n e,1 (1 - 12)

[0060] y e,2 = G AE,2 (s + w k - w m ) + n e,2 (1 - 13)

[0061] For legitimate users, y b,1 + yb,2 Filter out the artificial noise w m , while the eavesdropper cannot. Since the legitimate channel matrices are independent and not equal in different stages, i.e., H AB,1 ≠H AB,2 . Therefore, from (1-9), it can be seen that G AE,2 ≠H AE,1 . In this case, even if Eve passes through y e,1 +y e,2 , it is impossible to eliminate the artificial noise w m . Moreover, the first kind of artificial noise w k is designed within the legitimate channel H AB,1 . No matter what operations are performed at the eavesdropping end, it is impossible to eliminate the artificial noise w k . Therefore, no matter how the eavesdropping end operates, it is impossible to eliminate the interference of the two kinds of artificial noise on it.

[0062] Therefore, in this embodiment, the transmission of the confidential information is hidden by two kinds of artificial noise, and the interference of the artificial noise is cancelled by two-stage signal transmission. The double interference of the two-stage signal and the two kinds of artificial noise exacerbates the difficulty for the eavesdropping end to demodulate the confidential information and enhances the security of the system.

[0063] If for a channel without a channel null space, such as a SISO communication system, this system can also use this transmission mechanism for secure communication. The transmission mechanism for the SISO communication system is as follows:

[0064] The first stage: The transmitter transmits the signal x 1 =s - w m to the legitimate user. The signals received by the legitimate user Bob and the eavesdropping end Eve are:

[0065] y b,1 =h AB,1 (s + w m ) + n b,1 (1-14)

[0066] y e,1 =h AE,1 (s + w m ) + n e,1 (1-15)

[0067] The second stage: The transmitter transmits the signal x 2 to the legitimate receiver. The signal x 2 is designed as:

[0068]

[0069] So we can obtain the signals received by Bob and Eve in the second stage as:

[0070]

[0071]

[0072] Among them

[0073] The definitions of the parameters in the above formulas (1-14) to (1-18) can refer to the parameter definitions in the MISO communication system. The difference is only that in the SISO communication system, there is no matrix involved and it is only a variable.

[0074] Similarly, for the MIMO communication system, when there is a channel null space in the legitimate channel, this secrecy scheme can be adopted for secure information transmission. Only the signals transmitted in two stages need to be reasonably designed to eliminate the interference of the two kinds of artificial noise on the legitimate users; when there is no channel null space in the legitimate channel, it is also possible to only use the second randomly generated artificial noise w m to achieve secure transmission of information in two stages. The reasonable design here is to design the form of the signals transmitted in two stages, as long as the interference of the noise can be eliminated at the receiving end, so that the artificial noise does not interfere with the legitimate users.

[0075] The present invention is designed for the MISO communication system, but the SISO and MIMO communication systems can still adopt the design principle of the present invention and reasonably design the two-stage signals to achieve secure information reach.

[0076] Reference Figure 2 , when the present invention adopts two-stage communication, the complete steps are as follows:

[0077] Step 1: Obtain the legitimate channel matrix H of the first stage AB,1 .

[0078] Step 2: Perform singular value decomposition on H AB,1 to obtain its null space and column space.

[0079] Step 3: Select a basis vector in the null space as Z k , and select a basis vector in the column space as Γ m .

[0080] Step 4: Select the components of v k to be independent Gaussian distributions with a mean of 0 and a variance of , and construct the artificial noise w k = Z k v k .

[0081] Step 5: Select the components of V m to be independent Gaussian distributions with a mean of 0 and a variance of Construct artificial noise w according to the Gaussian distribution m = Γ m V m .

[0082] Step 6: Construct the signal x transmitted in the first stage 1 = s + w k + w m . Superimpose the private information s and the two kinds of artificial noise

[0083] Step 7: The transmitter sends x 1 to the receiver

[0084] Step 8: Obtain the legitimate channel gain matrix H in the second stage AB,2 .

[0085] Step 9: Construct the signal transmitted in the second stage

[0086] Step 10: The receiver adds the two received signals

Claims

1. An artificial noise secure communication method not limited to the null space of the legitimate channel, Characterized in that, Add the first type of artificial noise w to the information signal s k and the second type of artificial noise w m to form the transmission signal x 1 , x 1 = s + w k + w m , where w k is located in the null space of the legitimate channel matrix. If there is no channel null space, then there is no w 1 component in the transmission signal x k , and w m is located in the column space of the legitimate channel matrix; Select v k whose components are independent Gaussian distributions with a mean of 0 and a variance of to construct the first type of artificial noise w k : w k = Z k v k Select V m whose components are independent Gaussian distributions with mean 0 and variance to construct the second type of artificial noise w m : w m = Γ m V m Z k is a basis vector in the null space of the legitimate channel matrix, Γ m is a basis vector in the column space of the legitimate channel matrix; The communication method adopts two-stage communication, and the receiver adds the two received signals; where the transmission signal in the first stage is x 1 , and the transmission signal in the second stage is x 2 , which is expressed as: Where, H AB,1 is the legitimate channel matrix in the first stage, and H AB,2 is the legitimate channel matrix in the second stage, where H AB,1 ≠ H AB,2 .

2. A communication system using the artificial noise secure communication method not limited to the null space of the legitimate channel according to claim 1.

3. The communication system according to claim 2, Characterized in that, The communication system is an MIMO communication system or a SISO communication system or a MISO communication system.

4. The communication system according to claim 3, Characterized in that, For the MIMO communication system, when there is a null space in the legitimate channel, a two-stage transmission signal form is designed to eliminate the interference of two kinds of artificial noise on legitimate users; when there is no null space in the legitimate channel, only the second kind of artificial noise w is used m , and secure transmission of information is achieved in a two-stage manner.

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