Construction of a wireless multipath grid and its application method for secure communication

Abstract

This invention discloses the construction of a wireless multipath grid and its application method for secure communication, comprising the following steps: Both parties in the wireless communication acquire wireless channel state information through channel measurement. After preprocessing to improve the reciprocity of uplink and downlink wireless channel state information, a complex sequence of wireless channel impulse responses is extracted, possessing the following characteristics: 1. In terms of amplitude, it exhibits a time-domain sparse and random multipath fading pulse sequence; 2. For both parties in the wireless communication, the number, delay, amplitude, and phase of the pulses in this complex sequence all possess short-term reciprocity, long-term uncorrelation, and spatial uniqueness. Using the sparse multipath fading pulses in the complex sequence of wireless channel impulse responses possessing the above characteristics, a symmetrical three-dimensional wireless multipath grid is constructed for both parties in the wireless communication, used for key generation or key distribution. This invention serves as a covert communication channel, enabling terminal devices to securely generate or distribute key information while conducting normal wireless communication, thus achieving secure communication.

Description

Technical Field

[0001] This invention belongs to the field of information security technology, and in particular relates to the construction of a wireless multipath grid and its application method for secure communication. Background Technology

[0002] With the rapid development of technology, wireless communication technology is leading the trend of the digital age. From mobile communication to the Internet of Things, wireless communication is permeating every aspect of our lives, bringing unprecedented convenience and innovation to society. However, because the data transmitted in wireless communication may involve sensitive information such as user privacy and trade secrets, attackers may take advantage of the open and transparent nature of wireless communication to attempt to eavesdrop, intercept, or tamper with this data. Therefore, ensuring the confidentiality of wireless communication data transmitted in open channels has become a significant challenge.

[0003] Traditional methods rely on cryptographic techniques to generate keys, which are then distributed to legitimate communicating parties to encrypt and decrypt transmitted data using the symmetric key. However, this approach is limited by the development of computing, communication, and trust infrastructure resources, resulting in high complexity.

[0004] The dynamic changes in wireless channels under environmental influences offer a new solution to this problem: by utilizing the short-term reciprocity, long-term variation, and spatial uniqueness of uplink and downlink channel state information in wireless communication, their characteristic parameters can be used to dynamically and in real-time generate symmetric keys during wireless communication, which can then be used for information encryption with low complexity. Simultaneously, this scheme can reduce the amount of information that can be eavesdropped on by third parties beyond the coherent distance to near zero, thereby achieving secure communication.

[0005] Channel State Information (CSI) can be described from both frequency and time domain perspectives, and can be categorized into Channel Frequency Response (CFR) and Channel Impulse Response (CIR). Current research on physical layer secure communication focuses on using CFR as a key generation source. However, the inherent correlation of CFR introduces the possibility of key cracking. Furthermore, research on key generation and distribution for the more random sparse impulse sequences generated by wireless multipath effects, specifically CIR, has yet to develop a universally applicable, mature, and highly usable solution. Therefore, a new secure communication method is needed. Summary of the Invention

[0006] The purpose of this invention is to provide a construction method for a wireless multipath grid and its application in secure communication. The invention involves measuring the wireless channel frequency response between legitimate communication parties, preprocessing the signal, extracting the complex sequence of the wireless channel impulse response, and using the sparse multipath fading pulses in the sequence to construct a symmetrical three-dimensional wireless multipath grid for secure communication, thereby solving the technical problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0008] A method for constructing a Radio Multipath Fence (RMF) and its application in secure communications includes the following steps:

[0009] Step 1, Wireless Channel Measurement: Two wireless communication partners, A and B, conduct a wireless communication operation. Based on channel estimation techniques, they obtain the channel frequency response of the uplink and downlink wireless channel state information.

[0010] Step 2, Wireless Channel State Information Preprocessing: The wireless channel frequency response described in Step 1 is preprocessed with amplitude energy normalization, phase relativization and moving average smoothing schemes to improve the reciprocity of uplink and downlink wireless channel state information.

[0011] Step 3, Wireless Channel Impulse Response Extraction: Wireless communication parties A and B use the wireless channel frequency response described in Step 2 to extract the complex sequence h(n) of the wireless channel impulse response. h(n) has the following characteristics: a) In terms of amplitude, it is a time-domain sparse and random multipath fading pulse sequence; b) For both wireless communication parties, the number of pulses, delay, amplitude, and phase in this complex sequence all have short-term reciprocity, long-term uncorrelation, and spatial uniqueness.

[0012] Step 4, Wireless Multipath Grid Construction: Wireless communication parties A and B use the delay, amplitude, and phase of equal amount of sparse multipath fading pulses in the complex sequence h(n) of the wireless channel impulse response extracted in Step 3 to construct a three-dimensional symmetrical wireless multipath grid.

[0013] Step 5, Wireless Multipath Grid Secure Communication: The three-dimensional spatially symmetrical wireless multipath grid constructed by the wireless communication parties A and B in Step 4 serves as a covert communication channel for generating or distributing key information.

[0014] Furthermore, in step 1, the two wireless communication parties use the least squares or least mean square error general channel estimation technique to obtain wireless channel state information; let the original channel frequency response obtained from the channel estimation be:

[0015]

[0016] in, a represents the influence coefficient of sampling frequency offset on the phase of channel frequency response at different frequencies, b represents the influence factors of phase offset and noise on the phase of channel frequency response, and θ(k) represents the phase of channel frequency response. The channel frequency response phase is represented by denoted by , K represents the length of the channel frequency response, e is the exponential basis, j is the general unit in the exponential expression of complex numbers, and k is the general independent variable symbol in the frequency domain expression.

[0017] Furthermore, in step 2, the uplink and downlink wireless channel frequency response is improved through preprocessing. The reciprocity of the frequency response of the channel after amplitude normalization and phase relativization is H(k), and the frequency response of the wireless channel after moving average smoothing is H. 1 (k) specifically includes the following steps:

[0018] S21, Amplitude Energy Normalization:

[0019] S22, Phase relativization:

[0020]

[0021]

[0022] S23, Moving Average Smoothing:

[0023]

[0024] Furthermore, in step 3, the wireless channel frequency response H described in step 2 is utilized. 1 (k) Extract the complex sequence h(n) of the wireless channel impulse response corresponding to the sparse state; wireless channel frequency response H 1 The relationship between (k) and the complex sequence of impulse response h(n) of the wireless channel satisfies:

[0025]

[0026] Converting to matrix form yields the following relationship:

[0027]

[0028] The left side of the above equation represents the baseband wireless channel frequency response H. 1 (k); The first matrix on the right side of the equation is the relationship matrix between the baseband wireless channel frequency response and the wireless channel impulse response in radio frequency multipath attenuation coefficients, where ω k τ represents the corresponding frequency domain carrier frequency. nThis represents the corresponding time-domain delay; the second matrix on the right side of the equation is the multipath attenuation coefficient of the wireless channel impulse response in radio frequency, and the sequence h(n) to be solved is given, with the length of h(n) being N; to better distinguish sparse pulses, for τ n Quantization is performed using upsampling intervals, i.e., N > K;

[0029] Solving this relationship yields the wireless channel impulse response. Where a n Indicates amplitude. Indicates phase.

[0030] Furthermore, in step 4, the wireless communication parties A and B utilize the delay i and amplitude a of each sparse pulse set I in the complex sequence h(n) of the wireless channel impulse response extracted in step 3. i and phase Constructing a symmetrical wireless multipath grid RMF in three-dimensional space:

[0031]

[0032] Let the wireless multipath grid constructed by A be RMF. A The wireless multipath grid constructed by B is an RMF. B That is, there is RMF at this time. A ≈RMF B .

[0033] Furthermore, step 5, generating key information, specifically includes the following steps:

[0034] The feature parameters of the wireless multipath grid in step 4, including quantity, delay, amplitude, and phase, are extracted and combined using linear and nonlinear processing methods to form a sequence of combined feature parameters. This sequence generates a symmetric key for encrypted communication between wireless communication parties A and B. The key generation method includes a true random number generation scheme or a pseudo random number generation scheme. The true random number generation scheme directly quantizes the sequence of combined feature parameters to generate random key bits. The pseudo random number generation scheme uses the sequence of combined feature parameters as a random source and generates a pseudo random key bit sequence using a cryptographically secure random number generation algorithm.

[0035] Furthermore, step 5, distributing the key information, specifically includes the following steps:

[0036] Using the symmetrical wireless multipath grid described in step 4, Party A modulates the key bits to be distributed onto the RMF. A This includes parameters such as quantity, delay, amplitude, and phase characteristics; and RMF analysis is performed on the phase. A PSK phase modulation with a zero-phase reference yields a sequence containing secret information. Party B receives Then, according to RMFB right Demodulation is performed; RMF is applied to the phase correspondence. B PSK phase demodulation with zero phase reference yields the corresponding key bits.

[0037] The present invention provides a construction method for a wireless multipath grid and its application in secure communication, which has the following advantages:

[0038] (1) Extracting the impulse response of the wireless channel in a random discrete state as a random source overcomes the inherent correlation defect of using the original wireless channel frequency response as a random source.

[0039] (2) A three-dimensional wireless multipath grid with symmetry between the two parties in wireless communication is constructed by using the sparse multipath fading pulses in the complex sequence of impulse response of wireless channel for secure communication, thereby further improving the security characteristics such as concealment, randomness and confidentiality.

[0040] (3) It can be used in conjunction with existing wireless communication protocols without changing the established modulation and demodulation process. It has low computational complexity and high universality and feasibility.

[0041] The present invention proposes a construction method for a wireless multipath grid and its application method for secure communication, which can be used as a covert communication channel in wireless communication for key generation and distribution to achieve secure communication. Attached Figure Description

[0042] Figure 1 This is a schematic diagram illustrating the construction of a wireless multipath grid and its application method for secure communication according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of the preprocessing flow of the original wireless channel frequency response according to an embodiment of the present invention;

[0044] Figure 3 This is a schematic diagram of the wireless channel frequency response extracted after preprocessing in an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram illustrating the extraction of the impulse response amplitude of the wireless channel according to an embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram illustrating secure communication using a constructed wireless multipath grid, as described in an embodiment of the present invention. Detailed Implementation

[0047] To better understand the purpose, structure, and function of this invention, the following detailed description, in conjunction with the accompanying drawings, describes the construction of a wireless multipath grid and its application method for secure communication.

[0048] This invention can be implemented in many different forms and should not be considered as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art.

[0049] like Figure 1 The diagram shown illustrates the construction of a wireless multipath grid and its application method for secure communication proposed in this invention. The method specifically includes the following steps:

[0050] Step 1, Wireless Channel Measurement: The ESP32 module manufactured by ESPRESSIF is used as the wireless communication partners A and B, and wireless communication is performed using the IEEE 802.11g ERP-OFDM physical layer specification. Under the IEEE 802.11g ERP-OFDM physical layer specification: the center frequency of channel 13 is f. c =2.472GHz, signal transmission bandwidth is 20MHz; one OFDM symbol frequency domain includes 64 subcarriers, of which 52 are effective data carrier subcarriers, time domain symbol length is T = 3.2µs, frequency domain frequency point spacing Δf = 0.3125MHz. Based on the least squares channel estimation technique, A and B use the 52-bit effective long training field LTF in the signal preamble to perform channel estimation, i.e., K = 52, to obtain frequency domain wireless channel state information.

[0051]

[0052] Step 2, Wireless Channel State Information Preprocessing: The wireless channel frequency response described in Step 1 is preprocessed using at least the following methods: amplitude energy normalization, phase relativization, and least squares smoothing, to improve the reciprocity of uplink and downlink wireless channel state information.

[0053] Specifically, the following three steps of data preprocessing are performed:

[0054] S21, Amplitude energy normalization processing:

[0055]

[0056] S22, Phase relativization processing:

[0057]

[0058]

[0059] S23, Moving average smoothing, here the moving average window length is m=4, with the following expression:

[0060]

[0061] This example illustrates the preprocessing flow diagram for the raw wireless channel frequency response acquired by the ESP32, as shown below. Figure 2 As shown. Let Ap and Sta be the legitimate communicating parties, and Eve be the eavesdropper. The preprocessed CFRs of the three parties are as follows: Figure 3 As shown.

[0062] Step 3, extraction of wireless channel impulse response: Wireless communication parties A and B extract the wireless channel impulse response h(n) using the wireless channel frequency response described in step 2. h(n) has at least the following characteristics: (1) In terms of amplitude, it is a time-domain sparse random multipath fading pulse sequence, that is, most elements in the amplitude sequence are close to zero, and only a few non-zero elements correspond to the main reflection or scattering paths experienced by the signal during propagation; (2) For both wireless communication parties, the number, delay, amplitude, and phase of the pulses in this complex sequence all have short-term reciprocity, long-term uncorrelation, and spatial uniqueness.

[0063] Specifically, using the wireless channel frequency response H described in step 2 1 (k) Extract the wireless channel impulse response h(n) corresponding to the sparse state. The relationship between the wireless channel frequency response and the wireless channel impulse response satisfies:

[0064]

[0065] Furthermore, converting to matrix form yields the following relationship:

[0066]

[0067] The left side of the above equation is the baseband wireless channel frequency response channel estimation sequence H. 1 (k). The first matrix on the right side of the equation is the relationship matrix between the baseband wireless channel frequency response and the wireless channel impulse response in radio frequency multipath attenuation coefficients: where ω k =2π(f c +k·Δf) corresponds to the subcarrier frequency of the wireless channel frequency response; in order to obtain the sparse and random multipath pulse of the time-domain wireless channel impulse response, the time-domain sampling rate is increased to f. s =200MHz, then the sampling time interval Δt = 1 / f s N = T / Δt, corresponding to the time domain delay τ n =Δt·n, n∈[0,N-1]. The second matrix on the right side of the equation is the sequence h(n) to be solved for the multipath attenuation coefficients of the wireless channel impulse response at radio frequency.

[0068] Furthermore, the above matrix relationships constitute an underdetermined system of equations. Based on the prior knowledge of the sparse nature of h(n), and using the minimization of the l1 norm as a constraint, this system of equations can be solved to obtain the following: Figure 4The amplitude shown is a time-domain sparse and random multipath fading pulse sequence.

[0069] Step 4, Wireless Multipath Grid Construction: Wireless communication parties A and B use the delay, amplitude, and phase of equal amount of sparse multipath fading pulses in the complex sequence of wireless channel impulse response extracted in Step 3 to construct a three-dimensional symmetrical wireless multipath grid.

[0070] Furthermore, the wireless communication parties A and B utilize the sparse pulse set I in the complex sequence h(n) of the wireless channel impulse response extracted in step 3, along with the delay i and amplitude a, to obtain the values ​​of each pulse. i and phase Constructing a symmetrical wireless multipath grid RMF in three-dimensional space:

[0071]

[0072] That is, at this time there is RMF A ≈RMF B .

[0073] Step 5, Wireless Multipath Grid Secure Communication: The three-dimensional spatially symmetrical wireless multipath grid constructed by the wireless communication parties A and B in Step 4 can be used as a covert communication channel for generating or distributing key information.

[0074] Furthermore, key information is generated or distributed using the three-dimensional spatial symmetric wireless multipath grid constructed by the wireless communication parties A and B as described in step 4:

[0075] S51 Key Generation: Extract the characteristic parameters of the wireless multipath grid described in step 4, including at least the quantity, delay, amplitude, and phase. Combine these parameters using linear and nonlinear processing methods to form a sequence of combined characteristic parameters, generating a symmetric key for encrypted communication between wireless communication parties A and B. The key generation method includes at least the following:

[0076] S511 True Random Number Generation Scheme: Directly quantizes the combined feature parameter sequence to generate random key bits;

[0077] The S512 pseudo-random number generation scheme uses a sequence of combined feature parameters as a random source to generate a pseudo-random key bit sequence through a cryptographically secure random number generation algorithm.

[0078] S52 Key Distribution: Using the symmetrical wireless multipath grid described in step 4, Party A modulates the key bits to be distributed onto the RMF. A This includes parameters such as quantity, delay, amplitude, and phase characteristics; and RMF analysis is performed on the phase. A PSK phase modulation with a zero-phase reference yields a sequence containing secret information. Party B receives Then, according to RMFB right Demodulation is performed; RMF is applied to the phase correspondence. B PSK phase demodulation with zero phase reference yields the corresponding key bits.

[0079] Furthermore, based on the short-term reciprocity and spatial uniqueness of the uplink and downlink wireless channel characteristics of legitimate communicating parties, this invention can be used to continuously generate and distribute symmetric keys for further secure communication, such as... Figure 5 As shown.

[0080] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A construction method for a wireless multipath grid and its application in secure communication, characterized in that, Includes the following steps: Step 1, Wireless Channel Measurement: Both wireless communication parties and In a single wireless communication operation, both parties obtain the wireless channel frequency response based on channel estimation techniques to obtain uplink and downlink wireless channel state information. ; Step 2, Wireless Channel State Information Preprocessing: The wireless channel frequency response described in Step 1 is preprocessed with amplitude energy normalization, phase relativization and moving average smoothing schemes to improve the reciprocity of uplink and downlink wireless channel state information. Step 3, Wireless Channel Impulse Response Extraction: Both wireless communication parties and Extract the complex sequence of the wireless channel impulse response using the wireless channel frequency response described in step 2. , It has the following characteristics: a) In terms of amplitude, it is a time-domain sparse and random multipath fading pulse sequence; b) For both parties in wireless communication, the number of pulses, delay, amplitude, and phase in this complex sequence all have short-term reciprocity, long-term uncorrelation, and spatial uniqueness. Step 4, Wireless Multipath Grid Construction: Wireless Communication Between Two Parties and Using the complex sequence of wireless channel impulse response extracted in step 3 The delay, amplitude, and phase of moderately sparse multipath fading pulses are used to construct a three-dimensional symmetrical wireless multipath grid. Step 5, Wireless Multipath Grid Secure Communication: The wireless communication between the two parties in Step 4 and A symmetrical wireless multipath grid in three-dimensional space is constructed as a covert communication channel for generating or distributing key information.

2. The construction of the wireless multipath grid according to claim 1 and its application method for secure communication, characterized in that, In step 1, both wireless communication parties use the least squares or least mean square error general channel estimation technique to obtain wireless channel state information; let the original channel frequency response obtained from the channel estimation be: ； in, , This represents a coefficient indicating the influence of sampling frequency offset on the phase of the frequency response of channels at different frequencies. Factors representing the influence of phase offset and noise on the phase of the channel frequency response. Indicates the channel frequency response phase. This represents the channel frequency response phase obtained from channel estimation. This indicates the length of the channel frequency response.

3. The construction of the wireless multipath grid according to claim 2 and its application method for secure communication, characterized in that, In step 2, the uplink and downlink wireless channel frequency response is improved through preprocessing. The reciprocity of the frequency response of the channel after amplitude normalization and phase relativization is: The frequency response of the wireless channel after moving average smoothing is Specifically, it includes the following steps: S21, Amplitude Energy Normalization; ; S22, Phase relativization: ； ； S23, Moving Average Smoothing: 。 4. The construction of the wireless multipath grid according to claim 3 and its application method for secure communication, characterized in that, In step 3, the wireless channel frequency response described in step 2 is utilized. Extract the complex sequence of the wireless channel impulse response corresponding to the sparse state. Wireless channel frequency response Complex sequence of impulse response of wireless channel The relationship satisfies: ； Converting to matrix form yields the following relationship: ； The left side of the above equation represents the baseband wireless channel frequency response. The first matrix on the right side of the equation is the relationship matrix between the baseband wireless channel frequency response and the wireless channel impulse response in radio frequency multipath attenuation coefficients, where... This indicates the corresponding frequency domain carrier frequency. This represents the corresponding time-domain delay; the second matrix on the right-hand side of the equation is a complex sequence of the wireless channel impulse response. ,make The length is ;against Quantization is performed using upsampling intervals, i.e. ; Solving this relationship yields the complex sequence of impulse response of the wireless channel. ,in Indicates amplitude. Indicates phase.

5. The construction of the wireless multipath grid according to claim 4 and its application method for secure communication, characterized in that, In step 4, the two wireless communication parties and Using the complex sequence of wireless channel impulse response extracted in step 3 Medium sparse pulse set Each delay Amplitude and phase Constructing a symmetrical wireless multipath grid in three-dimensional space : ； make The constructed wireless multipath grid is , The constructed wireless multipath grid is That is, at this time there is .

6. The construction of the wireless multipath grid according to claim 5 and its application method for secure communication, characterized in that, Step 5, generating key information, specifically includes the following steps: The feature parameters of the wireless multipath grid in step 4, including quantity, delay, amplitude, and phase, are extracted and combined using linear and nonlinear processing methods to form a sequence of combined feature parameters, which is then used to generate a sequence for wireless communication between the two parties. and Symmetric keys for encrypted communication; key generation methods include true random number generation schemes or pseudo random number generation schemes; true random number generation schemes directly quantize the combined feature parameter sequence to generate random key bits; pseudo random number generation schemes use the combined feature parameter sequence as a random source and generate a pseudo random key bit sequence through a cryptographically secure random number generation algorithm.

7. The construction of the wireless multipath grid according to claim 5 and its application method for secure communication, characterized in that, Step 5, distributing the key information, specifically includes the following steps: Using the symmetrical wireless multipath grid described in step 4, The party modulates the key bits to be distributed onto... This includes parameters such as quantity, delay, amplitude, and phase characteristics; focusing on the phase... PSK phase modulation with a zero-phase reference yields a sequence containing secret information. , Fang received Afterwards, according to right Demodulation is performed; based on phase correspondence, [the following is done / implemented]... PSK phase demodulation with zero phase reference yields the corresponding key bits.

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