Channel reciprocity enhancement method and system for physical layer key generation

Abstract

The present invention relates to a channel reciprocity enhancement method and system for physical layer key generation, which combines a dual-band closed-loop feedback mechanism with a preset error compensation formula to determine the complex scalar of each subcarrier of the channel prediction. Due to the dual-band closed-loop feedback mechanism, the first communication device and the second communication device can obtain each other's CSI parameters, which can eliminate the CSI non-reciprocity caused by hardware fingerprint interference. At the same time, since the complex scalar of each subcarrier based on the channel prediction is used when performing non-reciprocity compensation, the incomplete channel reciprocity caused by the random interference launched by the phase shift matrix of the intelligent hyperplane in the reflection link is compensated. Therefore, not only can the CSI non-reciprocity caused by hardware fingerprint interference be eliminated, but also the incomplete channel reciprocity caused by the random interference launched by the attacker based on the phase shift matrix of the intelligent hyperplane in the reflection link can be compensated.

Description

Technical Field

[0001] The present invention relates to the field of wireless communications, and in particular to a channel reciprocity enhancement method and system for physical layer key generation. Background Art

[0002] The proliferation of wireless communications has driven a steady increase in the number of internet-connected devices and has also heightened awareness of the importance of network security. Physical layer key generation (PKG) based on precise channel reciprocity, with its low complexity and low management costs, effectively complements existing secure key sharing encryption techniques. However, compared to traditional encryption techniques, PKG is more susceptible to interference attacks. Even a small amount of non-reciprocal channel can cause a significant mismatch in the key sources between communicating parties, leading to key negotiation failure. Therefore, improving channel compensation for reciprocity between key exchange partners, thereby effectively mitigating the damage caused by interference, is of great research significance. Summary of the Invention

[0003] The present invention provides a channel reciprocity enhancement method and system for physical layer key generation, which is used to solve the problem in the prior art that a small amount of non-reciprocal channels can cause serious mismatches in the key sources of the communicating parties during the physical layer key generation process, resulting in key negotiation failure. The method realizes channel compensation that improves the reciprocity between the key interacting parties during the physical layer key generation process, thereby effectively reducing the damage caused by interference.

[0004] A channel reciprocity enhancement method for physical layer key generation is applied to a channel reciprocity enhancement system for physical layer key generation, the method comprising: a first communication device and a second communication device mutually transmit pilot sequences in a direct link and a reflection link via a first frequency band within a first coherent time period; the first communication device determines a second joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission, and the second communication device determines a first joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission; the first communication device and the second communication device mutually transmit pilot sequences in a direct link and a reflection link via a second frequency band within a second coherent time period, and the first communication device determines a third joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission, and the second communication device determines a third joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission. The fourth joint channel estimate of each subcarrier when receiving the pilot sequence under the dual-band receiving mode is determined by the first communication device; for each subcarrier, the first communication device determines the first loop channel estimate of the subcarrier under the dual-band based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier; the second communication device determines the second loop channel estimate of the subcarrier under the dual-band based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier; the first communication device and the second communication device determine the complex scalar of each subcarrier of the channel prediction based on a preset error compensation formula, the first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier; wherein the complex scalar of each subcarrier is used to perform incomplete channel reciprocity compensation caused by target interference, wherein the target interference is the active interference of the smart reflecting surface in the reflection link.

[0005] In one embodiment, the preset error compensation formula is a preset minimum mean square error compensation formula, and the complex scalar of each subcarrier predicted by the channel is determined based on the preset error compensation formula, the first loop channel estimate of each subcarrier, and the second loop channel estimate of each subcarrier, including: substituting the first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier into the preset minimum mean square error compensation formula to determine the complex scalar of each subcarrier predicted by the channel.

[0006] In one embodiment, the preset minimum mean square error compensation formula is: or Where Γ(k) represents the complex-valued scalar of the k-th subcarrier of the channel prediction; represents the first loop channel estimate of the k-th subcarrier; represents the second loop channel estimate of the k-th subcarrier.

[0007] In one embodiment, the second communication device determines a first joint channel estimate for each subcarrier when receiving a pilot sequence under first frequency band transmission, including: the second communication device determines the first joint channel estimate for each subcarrier based on a first hardware deviation interference when receiving a pilot sequence from the first communication device under first frequency band transmission, a first channel estimate for each subcarrier in a direct link, a second channel estimate for each subcarrier in a reflected link, and a first phase shift matrix of an intelligent metasurface in the reflected link; the first communication device determines a second joint channel estimate for each subcarrier when receiving a pilot sequence under first frequency band transmission, including: the first communication device determines the second joint channel estimate for each subcarrier based on a second hardware deviation interference when receiving a pilot sequence from the second communication device under first frequency band transmission, a third channel estimate for each subcarrier in a direct link when receiving a pilot sequence under first frequency band transmission, a fourth channel estimate for each subcarrier in the reflected link, and a second phase shift matrix of an intelligent metasurface in the reflected link.

[0008] In one embodiment, the first joint channel estimate for the kth subcarrier is: Among them, F AB Indicates the first hardware deviation interference; represents the first channel estimate of the k-th subcarrier, represents the second channel estimate of the k-th subcarrier, represents the first phase shift matrix; n is the noise; the second joint channel estimate of the kth subcarrier is: Among them, F BA Indicates the second hardware deviation interference; represents the third channel estimate of the k-th subcarrier, represents the fourth channel estimate of the k-th subcarrier, represents the second phase shift matrix.

[0009] In one embodiment, the first communication device determines a third joint channel estimate for each subcarrier when receiving a pilot sequence under second frequency band transmission, including: the first communication device determines the third joint channel estimate for each subcarrier based on the first hardware deviation interference when receiving the pilot sequence from the second communication device under second frequency band transmission, the fifth channel estimate for each subcarrier in the direct link, the sixth channel estimate for each subcarrier in the reflection link, and the third phase shift matrix of the intelligent metasurface in the reflection link; the second communication device determines a fourth joint channel estimate for each subcarrier when receiving the pilot sequence under second frequency band transmission, including: the second communication device determines the fourth joint channel estimate for each subcarrier based on the second hardware deviation interference when receiving the pilot sequence from the first communication device under second frequency band transmission, the seventh channel estimate for each subcarrier in the direct link when receiving the pilot sequence under second frequency band transmission, the eighth channel estimate for each subcarrier in the reflection link, and the fourth phase shift matrix of the intelligent metasurface in the reflection link.

[0010] In one embodiment, the first communication device determines a first loop channel estimate for the subcarrier in the dual-band based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier, including: the first communication device determines the first loop channel estimate for the subcarrier in the dual-band based on the product of the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier; the second communication device determines a second loop channel estimate for the subcarrier in the dual-band based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier, including: the second communication device determines the second loop channel estimate for the subcarrier in the dual-band based on the product of the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier.

[0011] The present invention also provides a channel reciprocity enhancement system for physical layer key generation, the system comprising: a first communication device, a second communication device and an intelligent hyperplane for forming a reflection link; the first communication device and the second communication device directly transmit pilot signals to form a direct link; the first communication device and the second communication device transmit pilot signals through the intelligent hyperplane to form a reflection link; the first communication device and the second communication device are used to execute the corresponding steps in the above-mentioned channel reciprocity enhancement method for physical layer key generation.

[0012] The present invention also provides a computer device including a memory and a processor, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the processor executes the steps of the above-mentioned channel reciprocity enhancement method for physical layer key generation.

[0013] The present invention also provides a storage medium storing computer-readable instructions, which, when executed by one or more processors, causes the one or more processors to perform the steps of the above-mentioned channel reciprocity enhancement method for physical layer key generation.

[0014] The above-mentioned channel reciprocity enhancement method and system for physical layer key generation determines the complex scalar of each subcarrier of channel prediction by combining a dual-band closed-loop feedback mechanism with a preset error compensation formula. Due to the use of the dual-band closed-loop feedback mechanism, the first communication device and the second communication device can obtain each other's CSI parameters G A G B , it is easy to eliminate the CSI non-reciprocity caused by hardware fingerprint interference. At the same time, since the non-reciprocity compensation takes into account the compensation for the incomplete channel reciprocity caused by random interference launched based on the phase shift matrix of the intelligent hyperplane in the reflection link, that is, the complex scalar of each subcarrier determined by the channel prediction based on the first loopback channel estimation of each subcarrier and the second loopback channel estimation of each subcarrier is used to compensate for the incomplete channel reciprocity caused by the target interference. Therefore, it is possible to not only eliminate the CSI non-reciprocity caused by hardware fingerprint interference, but also compensate for the incomplete channel reciprocity caused by the random interference launched by the attacker based on the phase shift matrix of the intelligent hyperplane in the reflection link. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is one of the framework schematic diagrams of the channel reciprocity enhancement system for physical layer key generation provided by the present invention;

[0016] Figure 2 Schematic diagram of interaction between two communicating devices, Alice and Bob, provided by the present invention;

[0017] Figure 3 A schematic flow chart of a method for enhancing channel reciprocity for physical layer key generation provided by the present invention;

[0018] Figure 4 This is the second framework diagram of the channel reciprocity enhancement system for physical layer key generation provided by the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should have the usual meanings understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the embodiments of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative position relationships. When the absolute position of the described object changes, the relative position relationship may also change accordingly.

[0021] In order to facilitate understanding, the technical terms involved in the present invention are first explained.

[0022] (1) Time division duplex (TDD)

[0023] For TDD, uplink and downlink use the same frequency band. The time occupied by uplink and downlink in a frequency band can be adjusted as needed, and the time occupied by uplink and downlink is generally divided into several time periods at fixed intervals, called time slots.

[0024] In the TDD system, the base station can perform channel estimation using training pilots sent in the uplink, and then use channel reciprocity to obtain downlink channel state information (CSI).

[0025] (2) Channel reciprocity

[0026] Channel reciprocity means that uplink and downlink signals are transmitted in different time slots on the same frequency resource. Therefore, within a relatively short period of time (the coherence time of channel propagation), the uplink and downlink signals can be considered to experience the same channel fading. The coherence time is the maximum time difference within which the channel remains constant. If the same signal from the transmitter reaches the receiver within the coherence time, the fading characteristics of the signals are completely similar and the receiver perceives them as a single signal.

[0027] (3) Orthogonal frequency division multiplexing (OFDM)

[0028] OFDM is actually a type of multi-carrier modulation. It uses frequency division multiplexing to achieve parallel transmission of high-speed serial data. It has good resistance to multipath fading and can support multi-user access. It divides the channel into several orthogonal sub-channels, converting the high-speed data signal into parallel, low-speed sub-data streams, which are modulated and transmitted on each sub-channel. Orthogonal signals can be separated by using correlation techniques at the receiver, reducing mutual interference between sub-channels. Using sub-channels to divide the wireless channel allows different users to communicate simultaneously using the same frequency band, thereby improving network throughput and coverage. OFDM uses sub-carriers to increase data transmission rates and resist interference.

[0029] Subchannels divide a large channel into multiple smaller channels, each capable of independently transmitting data. The use of subchannels improves spectrum efficiency, allowing multiple users to communicate simultaneously within the same frequency band. Subcarriers, on the other hand, divide a broadband signal into multiple narrowband signals for transmission. Each user is assigned multiple subcarriers, thereby increasing data rates and system capacity.

[0030] (4) Reconfigurable intelligent surface (RIS)

[0031] The smart hyperplane consists of multiple identical RIS units. Each RIS unit consists of multiple PIN diodes connected to multiple metal patches, printed on a dielectric substrate. Each diode can be switched between two states: on and off, resulting in different reflection coefficients for the RIS unit. Assuming each RIS unit has a different reflection coefficient, these different reflection coefficients have the same amplitude gain but different phase shifts.

[0032] (5) Physical layer key generation

[0033] Physical-layer key generation leverages the inherent randomness of the wireless channel response in amplitude and phase to generate high-entropy symmetric shared keys. This provides information-theoretic security and is an attractive alternative to public-key technologies. In current research, the typical process for obtaining physical-layer shared keys consists of four steps: channel detection, key bit quantization, consensus negotiation, and privacy amplification.

[0034] Typically, during channel sounding, the first and second communications devices transmit pilot signals to each other within the relevant time interval of the channel. The resulting measurements, such as the received signal strength, channel impulse response, and channel phase, delay, and envelope, can be used as a random source for key generation. During quantization, both communicating parties convert the channel measurements into a bit sequence of 0s and 1s. This shared random source quantization, while taking into account the randomness of the quantization sequence, seeks to achieve more quantization bits and lower the quantization bit error rate. Common methods include single-threshold quantization, dual-threshold quantization, multi-bit adaptive quantization thresholds, cumulative distribution function-based quantization, and vector quantization. During consistency negotiation, discrepancies between key bit streams caused by device differences or additive noise are discarded or corrected using a message coordination protocol to reduce the inconsistency rate. During privacy amplification, the key is compressed through a mapping to discard inconsistent bits, preventing Eve from inferring any key information based on the existing messages, thereby strengthening key consistency.

[0035] Since key generation methods based on channel reciprocity are more vulnerable to interference attacks than traditional encryption technologies and are highly dependent on the accuracy of wireless channels, even partially non-reciprocal channels can cause serious mismatches in the generated key materials, leading to key negotiation failure.

[0036] The existing technology only has relatively mature methods for addressing CSI non-reciprocity caused by hardware fingerprint interference and synchronization offset. However, in real-world scenarios, the impact of interference in both the uplink and downlink is not a fixed value like a hardware fingerprint, but rather varies randomly over time. For example, the interference caused by an attacker attacking a Reconfigurable Intelligent Surface (RIS) varies randomly. Although some articles have addressed solutions for generating physical layer keys when an RIS is attacked, there are no clear solutions for the channel non-reciprocity caused by an attacker attacking the RIS. Therefore, the present invention's channel reciprocity enhancement method for physical layer key generation is used to effectively compensate for the incomplete channel reciprocity caused by interference caused by an attacker attacking the RIS.

[0037] The channel reciprocity enhancement method and system for physical layer key generation provided by the present invention will be described below with reference to the accompanying drawings.

[0038] For ease of understanding, the following Figure 1The channel reciprocity enhancement system for physical layer key generation is described. The channel reciprocity enhancement system for physical layer key generation provided by the present invention has two different frequency bands (BAND 1 and BAND 2), and the transceiver can selectively turn on or off several subcarriers for each transmission, thereby transmitting through different frequency bands. This is applicable to multi-carrier modulation TDD systems. The present invention uses channel sounding values ​​CSI (channel state information) as a key source. Figure 1 As shown, the channel reciprocity enhancement system for physical layer key generation provided by the present invention includes: a first communication device, a second communication device and a RIS for forming a reflection link; wherein the first communication device and the second communication device directly transmit pilot signals to form a direct link; the first communication device and the second communication device transmit pilot signals through an intelligent hyperplane to form a reflection link; the first communication device and the second communication device are used to perform the steps of the channel reciprocity enhancement method for physical layer key generation of the present invention. In the present invention, the first communication device can be called Alice and the second communication device can be called Bob. A RIS composed of N reflection units is used to improve the channel randomness. It is assumed that all units are independent and the state value can be set to "on" or "off" by the controller. The phase shift matrix Φ=[ω1φ1,φ2φ2,ω3φ3,...ω is changed in real time. N φ N ] T ,ω i ∈{0,1}, where φ i ∈(0,2π) represents the random phase shift corresponding to each RIS unit. The inevitable hardware deviation interference is also a factor that causes CSI non-reciprocity, which is written as F in this invention. direction , where direction is the signal transmission direction, for example F AB represents a hardware deviation interference when transmitting signals from Alice to Bob, F BA represents a hardware deviation interference when transmitting signals from Bob to Alice.

[0039] In the invention, by adopting It represents the channel estimation of the direct link from Alice to Bob when BAND1 transmits the pilot sequence. Indicates the channel estimation of the direct link from Bob to Alice when BAND1 transmits the pilot sequence. Similarly, using It represents the channel estimation of the direct link from Alice to Bob when BAND1 transmits the pilot sequence. It represents the channel estimation of the direct link from Bob to Alice when BAND1 transmits the pilot sequence. Indicates the channel estimation of the reflection link from Alice to RIS when BAND1 transmits the pilot sequence, and adopts Indicates the channel estimation of the reflection link from RIS to bob when BAND1 transmits the pilot sequence, using Indicates the channel estimation of the reflection link from Alice to RIS and then from RIS to bob when BAND1 transmits the pilot sequence. Similarly, using Indicates the channel estimation of the reflection link from RIS to Alice when BAND1 transmits the pilot sequence, and adopts Indicates the channel estimation of the reflection link from bob to RIS when BAND1 transmits the pilot sequence, using It represents the channel estimation of the reflection link from Bob to RIS and then from RIS to Alice when BAND1 transmits the pilot sequence.

[0040] Similar to BAND1, using It represents the channel estimation of the direct link from Alice to Bob when BAND2 transmits the pilot sequence. Indicates the channel estimation of the direct link from Bob to Alice when BAND2 transmits the pilot sequence. Similarly, It represents the channel estimation of the direct link from Alice to Bob when BAND2 transmits the pilot sequence. It represents the channel estimation of the direct link from Bob to Alice when BAND2 transmits the pilot sequence. Indicates the channel estimation of the reflection link from Alice to RIS when BAND2 transmits the pilot sequence, and adopts Indicates the channel estimation of the reflection link from RIS to bob when BAND2 transmits the pilot sequence, using Indicates the channel estimation of the reflection link from Alice to RIS and then from RIS to bob when BAND2 transmits the pilot sequence. Similarly, using Indicates the channel estimation of the reflection link from RIS to Alice when BAND2 transmits the pilot sequence, and adopts Indicates the channel estimation of the reflection link from bob to RIS when BAND2 transmits the pilot sequence, using It represents the channel estimation of the reflection link from bob to RIS and then from RIS to Alice when BAND2 transmits the pilot sequence.

[0041] Combine Figure 1For the system shown in the figure, assume that a malicious external attacker Mallory launches active interference by randomly changing the RIS reflection matrix in the uplink and downlink RIS induction links, causing Φ A ≠Φ B As long as the RIS configuration update rate is higher than the channel sampling rate, the observed RIS-induced link CSI will differ, thus violating the total reciprocity of the channel. The attacked RIS matrix will randomly change over time, while the hardware deviation parameter is a constant value.

[0042] Figure 2 This is a schematic diagram of the interaction between the communicating devices Alice and Bob in the application scenario of the present invention. It can be understood that Figure 2 In the interaction process between Alice and Bob shown in the figure, the transmission of the pilot signal goes through the following steps: Figure 1 The direct link and the reflected link are shown, that is, the channel estimation includes the estimation of the direct link and the joint estimation of the reflected link.

[0043] In step 200, Alice and Bob respectively generate corresponding OFDM pilot sequences.

[0044] In step 201, Alice sends a pilot sequence to Bob via band 1. After receiving the pilot sequence, Bob estimates the channel and obtains the first joint channel estimate of the kth subcarrier.

[0045] In step 202, during the first coherent time period of the pilot sequence sent in step 201, Bob sends a pilot sequence to Alice via frequency band 1. After receiving the pilot sequence, Alice estimates the channel and obtains the second joint channel estimate of the k-th subcarrier

[0046] In step 203, Bob sends a pilot sequence to Alice via frequency band 2 and uses the first joint channel estimate of the kth subcarrier obtained in step 201 as Alice receives the pilot sequence sent via band 2 and the first joint channel estimate Based on Estimation of the channel, get the first loop channel estimation of the kth subcarrier in dual band

[0047] In step 204, during the second coherent time period of the pilot sequence sent in step 203, Alice sends a pilot sequence to Bob via frequency band 2 and uses the second joint channel estimate of each subcarrier obtained in step 201 as Bob receives the pilot sequence sent via band 2 and the second joint channel estimate Based on The channel estimation is used to obtain the second loop channel estimation of the kth subcarrier in the dual-band

[0048] In step 205, based on the minimum mean square error (MMSE) compensation formula, the complex-valued scalar Γ(k) corresponding to the k-th subcarrier is determined so that the first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier are equal, thereby compensating for the incomplete channel reciprocity caused by random interference caused by the phase shift matrix of the smart hyperplane in the reflection link.

[0049] Figure 3 This is a flow chart of a method for enhancing channel reciprocity for physical layer key generation provided by the present invention. It is understood that this method for enhancing channel reciprocity for physical layer key generation can be performed by a channel reciprocity enhancement system for physical layer key generation. The channel reciprocity enhancement system for physical layer key generation can be a computer device.

[0050] like Figure 3 As shown, in one embodiment, a channel reciprocity enhancement method for physical layer key generation is proposed, which may specifically include the following steps:

[0051] In step 310, the first communication device and the second communication device transmit pilot sequences to each other in both the direct link and the reflected link via the first frequency band within a first coherent time period; and the first communication device determines a second joint channel estimate for each subcarrier when receiving the pilot sequence under the first frequency band transmission, and the second communication device determines a first joint channel estimate for each subcarrier when receiving the pilot sequence under the first frequency band transmission.

[0052] Specifically, the step 310 may refer to the relevant descriptions of the above steps 200 to 202.

[0053] The process of determining the first joint channel estimate of each subcarrier specifically includes:

[0054] The second communication device determines the first joint channel estimate of each subcarrier based on the first hardware deviation interference when receiving the pilot sequence from the first communication device under the first frequency band transmission (at time t), the first channel estimate of each subcarrier in the direct link, the second channel estimate of each subcarrier in the reflection link, and the first phase shift matrix of the intelligent metasurface in the reflection link.

[0055] Specifically, the expression of the first joint channel estimate of the k-th subcarrier is: Among them, F AB Indicates the first hardware deviation interference; represents the first channel estimate of the k-th subcarrier, represents the second channel estimate of the k-th subcarrier, represents the first phase shift matrix; n is the noise.

[0056] The process of determining the second joint channel estimate of each subcarrier specifically includes:

[0057] The first communication device determines a second joint channel estimate for each subcarrier based on the second hardware deviation interference when receiving the pilot sequence from the second communication device under the first frequency band transmission (at time t), the third channel estimate of each subcarrier in the direct link when receiving the pilot sequence under the first frequency band transmission, the fourth channel estimate of each subcarrier in the reflection link, and the second phase shift matrix of the intelligent metasurface in the reflection link.

[0058] Specifically, the second joint channel estimate of the k-th subcarrier is: Among them, F BA Indicates the second hardware deviation interference; represents the third channel estimate of the k-th subcarrier, represents the fourth channel estimate of the k-th subcarrier, represents the second phase shift matrix.

[0059] It can be understood that, first, considering the frequency band selection, it can be defined that the sub-channel CSIs in different frequency bands i and j are not equal. Second, in TDD systems, channel variations between measurements are difficult to model accurately, so for simplicity, we can assume that the CSI variations are continuously integrable. In addition, the legitimate communication parties only send a pilot signal once during each coherence time {t, t+τ}, then receive the pilot and estimate the channel. Assuming that the channel remains unchanged during the coherence time, the legitimate communication channel satisfies reciprocity: that is, Therefore, based on the above conditions, the above

[0060] In step 320, the first communication device and the second communication device transmit pilot sequences to each other in both the direct link and the reflected link via the second frequency band during the second coherent time period, and the first communication device determines a third joint channel estimate for each subcarrier when receiving the pilot sequence under the second frequency band transmission, and the second communication device determines a fourth joint channel estimate for each subcarrier when receiving the pilot sequence under the second frequency band transmission.

[0061] Specifically, step 320 corresponds to steps 203 to 204 above. It should be noted that, in conjunction with step 203, while the second communication device transmits a pilot sequence to the first communication device via the second frequency band in the direct link and the reflection link, it also transmits a first joint channel estimate of the k-th subcarrier to the first communication device, thereby preparing for the first communication device to subsequently determine the first loopback channel estimate of the k-th subcarrier based on the first joint channel estimate and the third joint channel estimate of the k-th subcarrier. Similarly, in conjunction with step 204, it can be seen that, while the first communication device transmits a pilot sequence to the second communication device via the second frequency band in the direct link and the reflection link, it also transmits a second joint channel estimate of the k-th subcarrier to the second communication device, thereby preparing for the second communication device to subsequently determine the second loopback channel estimate of the k-th subcarrier based on the second joint channel estimate and the fourth joint channel estimate of the k-th subcarrier.

[0062] The process of determining the third joint channel estimate of each subcarrier specifically includes:

[0063] The first communications device determines, based on a first hardware deviation interference when receiving a pilot sequence from the second communications device under second frequency band transmission, a fifth channel estimate for each subcarrier in the direct link, a sixth channel estimate for each subcarrier in the reflection link, and a third phase shift matrix of the smart metasurface in the reflection link, a third joint channel estimate for each subcarrier;

[0064] Specifically, the expression of the third joint channel estimate of the k-th subcarrier is: Among them, F AB Indicates the first hardware deviation interference; represents the fifth channel estimate of the k-th subcarrier, represents the sixth channel estimate of the k-th subcarrier, represents the third phase shift matrix.

[0065] The process of determining the fourth joint channel estimate of each subcarrier specifically includes:

[0066] The second communication device determines the fourth joint channel estimate of each subcarrier based on the second hardware deviation interference when receiving the pilot sequence from the first communication device under the second frequency band transmission, the seventh channel estimate of each subcarrier in the direct link when receiving the pilot sequence under the second frequency band transmission, the eighth channel estimate of each subcarrier in the reflection link, and the fourth phase shift matrix of the intelligent metasurface in the reflection link.

[0067] Specifically, the fourth joint channel estimate of the k-th subcarrier is: Among them, F BA Indicates the second hardware deviation interference; represents the seventh channel estimate of the k-th subcarrier, represents the eighth channel estimate of the k-th subcarrier, represents the first phase shift matrix; n is the noise.

[0068] In step 330, for each subcarrier, the first communication device determines a first loopback channel estimate for the subcarrier in the dual-band based on the first joint channel estimate for the subcarrier and the third joint channel estimate for the subcarrier; and the second communication device determines a second loopback channel estimate for the subcarrier in the dual-band based on the second joint channel estimate for the subcarrier and the fourth joint channel estimate for the subcarrier.

[0069] The process of estimating the first loop channel of the subcarrier includes: the first communication device determines the first loop channel estimate of the subcarrier in the dual-band based on the product of the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier.

[0070] Combining the above and channel reciprocity, we can know that the first loop channel estimation of the kth subcarrier is

[0071]

[0072] Similarly, the process of estimating the first loop channel of the subcarrier includes: the second communication device determines the second loop channel estimate of the subcarrier in the dual band based on the product of the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier.

[0073] Combining the above and channel reciprocity, we can know that the second loop channel estimation of the kth subcarrier is

[0074] The present invention adopts and Serves as a key source for future key generation steps. and It can be seen from the expression that by sharing the cross term F AB and F BA The common randomness of , eliminates the non-reciprocity caused by hardware bias. and It can be seen that due to the malicious attack of the active interferer, the manipulated RIS matrix Φ A and Φ B The RIS interference is unpredictable and completely independent, so the influence of the RIS interference still exists. Therefore, in order to eliminate the above RIS interference, a complex-valued scalar of each subcarrier of the appropriate channel prediction is selected based on the following step 340.

[0075] In step 340, the first communication device and the second communication device determine a complex-valued scalar for each subcarrier of the channel prediction based on a preset error compensation formula, a first loopback channel estimate for each subcarrier, and a second loopback channel estimate for each subcarrier; wherein the complex-valued scalar for each subcarrier is used to compensate for incomplete channel reciprocity caused by target interference, wherein the target interference is the active interference of the smart reflecting surface in the reflection link.

[0076] The preset error compensation formula is used to minimize the error between the channel prediction and the original channel estimation.

[0077] In one embodiment, the preset error compensation formula is a preset minimum mean square error compensation formula, and step 340 includes: substituting the first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier into the preset minimum mean square error compensation formula to determine the complex scalar of each subcarrier of the channel prediction.

[0078] Specifically, the preset minimum mean square error compensation formula is:

[0079] Where Γ(k) represents the complex-valued scalar of the k-th subcarrier of the channel prediction; represents the first loop channel estimate of the k-th subcarrier; represents the second loop channel estimate of the k-th subcarrier.

[0080] in, It can be understood as the channel estimation prediction value at the second communication device when sending the kth subcarrier, that is, The actual channel measurement value at the first communication device when the k-th subcarrier is transmitted is determined as the predicted channel estimation value.

[0081] The minimum mean square error in channel prediction is: In the case of , the minimum mean square error of channel prediction can be derived as: in, E[] represents the expectation operator, while a and b are the statistical averages of the RIS matrix in the uplink and downlink, σ ARB and σ AB represents the standard deviation of the distribution corresponding to the reflection link channel estimation and the direct link channel estimation respectively.

[0082] In the present invention, Γ(k)=p+jq. This means that E[ε(k) 2 ] The derivatives of p and q must be zero to minimize the square error with respect to Γ(k), that is: and,

[0083] The predicted scalar of the last k-th subcarrier can be derived as:

[0084] The channel reciprocity enhancement method for physical layer key generation of the present invention combines a dual-band closed-loop feedback mechanism with a preset error compensation formula to determine the complex scalar of each subcarrier of the channel prediction. Due to the use of the dual-band closed-loop feedback mechanism, the first communication device and the second communication device can obtain each other's CSI parameters G A G B , it is easy to eliminate the CSI non-reciprocity caused by hardware fingerprint interference. At the same time, since the non-reciprocity compensation takes into account the compensation for the incomplete channel reciprocity caused by random interference launched based on the phase shift matrix of the intelligent hyperplane in the reflection link, that is, the complex scalar of each subcarrier determined by the channel prediction based on the first loopback channel estimation of each subcarrier and the second loopback channel estimation of each subcarrier is used to compensate for the incomplete channel reciprocity caused by the target interference. Therefore, it is possible to not only eliminate the CSI non-reciprocity caused by hardware fingerprint interference, but also compensate for the incomplete channel reciprocity caused by the random interference launched by the attacker based on the phase shift matrix of the intelligent hyperplane in the reflection link.

[0085] The channel reciprocity enhancement system for physical layer key generation provided by the present invention is described below. The channel reciprocity enhancement system for physical layer key generation described below and the channel reciprocity enhancement method for physical layer key generation described above can refer to each other.

[0086] like Figure 4 As shown, in one embodiment, a channel reciprocity enhancement system for physical layer key generation is provided, and the channel reciprocity enhancement system for physical layer key generation may include: a first communication device 410, a second communication device 420, and a smart hyperplane 430 for forming a reflection link;

[0087] The first communication device 410 and the second communication device 420 directly transmit pilot signals to form a direct link;

[0088] The first communication device 410 and the second communication device 420 transmit pilot signals through the smart hyperplane 430 to form a reflection link;

[0089] The first communication device 410 and the second communication device 420 are configured to execute corresponding steps in the above-mentioned channel reciprocity enhancement method for physical layer key generation.

[0090] The channel reciprocity enhancement system for physical layer key generation provided by the present invention combines a dual-band closed-loop feedback mechanism with a preset error compensation formula to determine the complex scalar of each subcarrier of the channel prediction. Due to the use of the dual-band closed-loop feedback mechanism, the first communication device and the second communication device can obtain each other's CSI parameters G A G B , it is easy to eliminate the CSI non-reciprocity caused by hardware fingerprint interference. At the same time, since the non-reciprocity compensation takes into account the compensation for the incomplete channel reciprocity caused by random interference launched based on the phase shift matrix of the intelligent hyperplane in the reflection link, that is, the complex scalar of each subcarrier determined by the channel prediction based on the first loopback channel estimation of each subcarrier and the second loopback channel estimation of each subcarrier is used to compensate for the incomplete channel reciprocity caused by the target interference. Therefore, it is possible to not only eliminate the CSI non-reciprocity caused by hardware fingerprint interference, but also compensate for the incomplete channel reciprocity caused by the random interference launched by the attacker based on the phase shift matrix of the intelligent hyperplane in the reflection link.

[0091] In one embodiment, a computer device is proposed, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the following steps corresponding to the channel reciprocity enhancement method for physical layer key generation are implemented: a first communication device and a second communication device mutually transmit pilot sequences in a direct link and a reflection link via a first frequency band within a first coherent time period; and the first communication device determines a second joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission, and the second communication device determines a first joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission; the first communication device and the second communication device mutually transmit pilot sequences in a direct link and a reflection link via a second frequency band within a second coherent time period, and the first communication device determines a second joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission. The third joint channel estimate of the subcarrier, the second communication device determines the fourth joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission; for each subcarrier, the first communication device determines the first loop channel estimate of the subcarrier under the dual frequency band based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier; the second communication device determines the second loop channel estimate of the subcarrier under the dual frequency band based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier; the first communication device and the second communication device determine the complex scalar of each subcarrier of the channel prediction based on a preset error compensation formula, the first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier; wherein the complex scalar of each subcarrier is used to perform incomplete channel reciprocity compensation caused by target interference, wherein the target interference is the active interference of the smart reflecting surface in the reflection link.

[0092] On the other hand, the present invention also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the channel reciprocity enhancement method for physical layer key generation provided by the present invention, and the channel reciprocity enhancement method for physical layer key generation includes: the first communication device and the second communication device send pilot sequences to each other in a direct link and a reflection link through a first frequency band within a first coherent time period; and the first communication device determines the second joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission, and the second communication device determines the first joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission; the first communication device and the second communication device send pilot sequences to each other in a direct link and a reflection link through a second frequency band within a second coherent time period, and the first communication device determines The first communication device determines a third joint channel estimate for each subcarrier when receiving a pilot sequence under second frequency band transmission, and the second communication device determines a fourth joint channel estimate for each subcarrier when receiving a pilot sequence under second frequency band transmission; for each subcarrier, the first communication device determines a first loopback channel estimate for the subcarrier under dual frequency bands based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier; the second communication device determines a second loopback channel estimate for the subcarrier under dual frequency bands based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier; the first communication device and the second communication device determine a complex scalar for each subcarrier of channel prediction based on a preset error compensation formula, the first loopback channel estimate for each subcarrier, and the second loopback channel estimate for each subcarrier; wherein the complex scalar for each subcarrier is used to perform incomplete channel reciprocity compensation caused by target interference, wherein the target interference is the active interference of the smart reflecting surface in the reflection link.

[0093] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to execute the channel reciprocity enhancement method for physical layer key generation provided by the present invention, wherein the channel reciprocity enhancement method for physical layer key generation includes: a first communication device and a second communication device mutually transmit pilot sequences in a direct link and a reflection link via a first frequency band within a first coherent time period; and the first communication device determines a second joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission, and the second communication device determines a first joint channel estimate of each subcarrier when receiving the pilot sequence under the first frequency band transmission; the first communication device and the second communication device mutually transmit pilot sequences in a direct link and a reflection link via a second frequency band within a second coherent time period, and the first communication device determines a second joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission. The third joint channel estimate of the carrier, the second communication device determines the fourth joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission; for each subcarrier, the first communication device determines the first loop channel estimate of the subcarrier under the dual frequency band based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier; the second communication device determines the second loop channel estimate of the subcarrier under the dual frequency band based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier; the first communication device and the second communication device determine the complex scalar of each subcarrier of the channel prediction based on a preset error compensation formula, the first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier; wherein the complex scalar of each subcarrier is used to perform incomplete channel reciprocity compensation caused by target interference, wherein the target interference is the active interference of the smart reflecting surface in the reflection link.

[0094] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0095] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0096] It can be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A channel reciprocity enhancement method for physical layer key generation, characterized in that: Applied to a channel reciprocity enhancement system for physical layer key generation, the method comprises: The first communication device and the second communication device transmit pilot sequences to each other in a direct link and a reflected link via the first frequency band during a first coherent time period; the first communication device determines a second joint channel estimate for each subcarrier when receiving the pilot sequence in the first frequency band transmission, and the second communication device determines a first joint channel estimate for each subcarrier when receiving the pilot sequence in the first frequency band transmission; The first communication device and the second communication device transmit pilot sequences to each other in both the direct link and the reflected link via the second frequency band during the second coherence time period, and the first communication device determines a third joint channel estimate for each subcarrier when receiving the pilot sequence under the second frequency band transmission, and the second communication device determines a fourth joint channel estimate for each subcarrier when receiving the pilot sequence under the second frequency band transmission; For each subcarrier, the first communication device determines, based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier, a first loopback channel estimate of the subcarrier in the dual-band; the second communication device determines, based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier, a second loopback channel estimate of the subcarrier in the dual-band; The first communication device and the second communication device determine a complex scalar of each subcarrier of the channel prediction based on a preset error compensation formula, a first loop channel estimate of each subcarrier, and a second loop channel estimate of each subcarrier; wherein the complex scalar of each subcarrier is used to compensate for incomplete channel reciprocity caused by target interference, wherein the target interference is the active interference of the smart reflective surface in the reflection link; wherein, The preset minimum mean square error compensation formula is: or Where Γ(k) represents the complex-valued scalar of the k-th subcarrier of the channel prediction; represents the first loop channel estimate of the k-th subcarrier; represents the second loop channel estimate of the k-th subcarrier; The first joint channel estimate for the kth subcarrier is: Among them, F AB Indicates the first hardware deviation interference; represents the first channel estimate of the k-th subcarrier, represents the second channel estimate of the k-th subcarrier, represents the first phase shift matrix; n is the noise; The second joint channel estimate for the kth subcarrier is: Among them, F BA Indicates the second hardware deviation interference; represents the third channel estimate of the k-th subcarrier, represents the fourth channel estimate of the k-th subcarrier, represents the second phase shift matrix; The first communication device determines, based on the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier, a first loopback channel estimate of the subcarrier in the dual-band, including: the first communication device determines, based on the product of the first joint channel estimate of the subcarrier and the third joint channel estimate of the subcarrier, the first loopback channel estimate of the subcarrier in the dual-band; The second communication device determines, based on the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier, a second loopback channel estimate of the subcarrier in the dual-band, including: the second communication device determines, based on the product of the second joint channel estimate of the subcarrier and the fourth joint channel estimate of the subcarrier, the second loopback channel estimate of the subcarrier in the dual-band; The expression of the third joint channel estimate of the kth subcarrier is: Among them, F AB Indicates the first hardware deviation interference; represents the fifth channel estimate of the k-th subcarrier, represents the sixth channel estimate of the k-th subcarrier, represents the third phase shift matrix; The fourth joint channel estimate for the kth subcarrier is: Among them, F BA Indicates the second hardware deviation interference; represents the seventh channel estimate of the k-th subcarrier, represents the eighth channel estimate of the k-th subcarrier, represents the first phase shift matrix; n is the noise.

2. The channel reciprocity enhancement method for physical layer key generation according to claim 1, wherein: The preset error compensation formula is a preset minimum mean square error compensation formula, and determining the complex scalar of each subcarrier of the channel prediction based on the preset error compensation formula, the first loop channel estimate of each subcarrier, and the second loop channel estimate of each subcarrier includes: The first loop channel estimate of each subcarrier and the second loop channel estimate of each subcarrier are substituted into a preset minimum mean square error compensation formula to determine a complex scalar of each subcarrier of channel prediction.

3. The channel reciprocity enhancement method for physical layer key generation according to claim 1, wherein: The second communication device determines a first joint channel estimate for each subcarrier when receiving a pilot sequence under first frequency band transmission, including: The second communication device determines a first joint channel estimate for each subcarrier based on a first hardware deviation interference when receiving a pilot sequence from the first communication device under first frequency band transmission, a first channel estimate for each subcarrier in the direct link, a second channel estimate for each subcarrier in the reflection link, and a first phase shift matrix of the smart metasurface in the reflection link; The first communication device determines a second joint channel estimate for each subcarrier when receiving a pilot sequence under first frequency band transmission, including: The first communication device determines a second joint channel estimate for each subcarrier based on a second hardware deviation interference when receiving a pilot sequence from the second communication device under first frequency band transmission, a third channel estimate for each subcarrier in the direct link when receiving the pilot sequence under first frequency band transmission, a fourth channel estimate for each subcarrier in the reflection link, and a second phase shift matrix of the intelligent metasurface in the reflection link.

4. The channel reciprocity enhancement method for physical layer key generation according to claim 1, wherein: The first communication device determines a third joint channel estimate for each subcarrier when receiving a pilot sequence under second frequency band transmission, including: the first communication device determines the third joint channel estimate for each subcarrier based on a first hardware deviation interference when receiving a pilot sequence from a second communication device under second frequency band transmission, a fifth channel estimate for each subcarrier in a direct link, a sixth channel estimate for each subcarrier in a reflection link, and a third phase shift matrix of the smart metasurface in the reflection link; The second communication device determines the fourth joint channel estimate of each subcarrier when receiving the pilot sequence under the second frequency band transmission, including: the second communication device determines the fourth joint channel estimate of each subcarrier based on the second hardware deviation interference when receiving the pilot sequence from the first communication device under the second frequency band transmission, the seventh channel estimate of each subcarrier in the direct link when receiving the pilot sequence under the second frequency band transmission, the eighth channel estimate of each subcarrier in the reflection link, and the fourth phase shift matrix of the intelligent metasurface in the reflection link.

5. A channel reciprocity enhancement system for physical layer key generation, characterized in that: The system includes: a first communication device, a second communication device, and an intelligent hyperplane for forming a reflection link; The first communication device and the second communication device directly transmit a pilot signal to form a direct link; The first communication device and the second communication device transmit pilot signals through the smart hyperplane to form a reflection link; The first communication device and the second communication device are configured to execute corresponding steps in the channel reciprocity enhancement method for physical layer key generation according to any one of claims 1 to 4.

6. A computer device comprising a memory and a processor, characterized in that: The memory stores computer-readable instructions, which, when executed by the processor, enable the processor to perform the steps of the channel reciprocity enhancement method for physical layer key generation according to any one of claims 1 to 4.

7. A storage medium storing computer-readable instructions, characterized in that: When the computer-readable instructions are executed by one or more processors, the one or more processors are caused to perform the steps of the channel reciprocity enhancement method for physical layer key generation according to any one of claims 1 to 4.

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