Key generation method and system based on OTFS

Abstract

The invention provides an OTFS-based secret key generation method and system, and relates to the field of physical layer security, and the method comprises the steps that based on multiple rounds of channel detection between a master node and a slave node, the two nodes respectively execute the following operations by using respective received signals: based on the received signals, channel estimation is performed, and by using a channel estimation result, a secret key is generated; estimating a channel state information vector of the delay Doppler domain; performing decorrelation transformation on the estimated channel state information vector; and mapping the channel state information vector subjected to decorrelation transformation into a corresponding quantization interval, dynamically generating a coding index by adopting a self-adaptive index adjustment mechanism according to an index of the quantization interval, extracting high-order bits from a Gray code corresponding to the coding index, and generating a local shared key. According to the method, OTFS modulation and demodulation are used for physical layer key generation, autocorrelation caused by OTFS is solved through decorrelation transformation, and the efficiency, robustness and consistency of key generation in a mobile communication scene are improved.

Description

Technical Field

[0001] The present disclosure relates to the field of physical layer security, and in particular to an OTFS-based key generation method and system. Background Art

[0002] The rapid development of mobile communications technology is profoundly changing our daily lives. Mobile communications connect devices through wireless channels, but the broadcast nature of these channels exposes users to privacy risks. In wireless communications applications, many small devices (such as drones) have limited computing resources and power output due to their small size and limited power resources, making traditional encryption schemes that rely heavily on computing resources difficult to apply.

[0003] Physical layer key generation technology is becoming increasingly important in wireless communications, especially in enhancing communication security and protecting privacy. Unlike traditional encryption technologies, physical layer key generation methods dynamically generate shared keys based on the characteristics of wireless channels. Specifically, physical layer key generation utilizes the randomness and reciprocity of wireless channels to dynamically generate shared keys, which is particularly suitable for resource-constrained scenarios. This method can enhance the confidentiality of communications without relying on high computing resources. The process is lightweight and efficient, and can dynamically generate keys to effectively prevent attacks, thereby significantly improving system security and privacy in resource-constrained wireless communication environments.

[0004] However, in high-mobility communication scenarios, the channel estimation performance in Orthogonal Frequency Division Multiplexing (OFDM) degrades dramatically due to the loss of subcarrier orthogonality, which leads to a reduction in the Signal to Interference plus Noise Ratio (SINR). In this case, ensuring the reliability and consistency of the key generation process becomes an urgent issue to be addressed. In addition, rapidly time-varying channels can cause loss of synchronization between legitimate parties, further complicating the key generation process.

[0005] To address these issues, key generation techniques based on Orthogonal Time-Frequency Space (OTFS) have emerged. However, existing work has not considered the lack of randomness caused by the slowly varying nature of DD-domain channels. This slowly varying nature of DD-domain channels leads to stronger autocorrelation between adjacent channel measurements, potentially reducing the entropy of generated keys. Furthermore, since the number of multipaths in real wireless channels is limited and the delay and Doppler shift of each multipath are discrete, the channel response is sparse, i.e., there are only a few non-zero elements in the delay-Doppler domain, which results in a low key generation rate.

[0006] Therefore, the key generation technology in existing mobile communication scenarios is affected by the particularity of the scenarios and has deficiencies in efficiency, robustness, and consistency. Summary of the Invention

[0007] To address the above issues, this paper proposes an OTFS-based key generation method and system. OTFS modulation and demodulation are used for physical layer key generation, and decorrelation transformation is used to resolve the autocorrelation caused by OTFS, thereby improving the efficiency, robustness, and consistency of key generation in mobile communication scenarios.

[0008] According to some embodiments, the present disclosure adopts the following technical solutions:

[0009] An OTFS-based key generation method is based on multiple rounds of channel detection between a master node and a slave node. Using the signals received by each node, the two nodes perform the following operations:

[0010] Based on the received signal, channel estimation is performed, and the channel state information vector in the delay-Doppler domain is estimated using the channel estimation result;

[0011] Performing decorrelation transformation on the estimated channel state information vector;

[0012] The decorrelation-transformed channel state information vector is mapped to the corresponding quantization interval. Based on the index of the quantization interval, an adaptive index adjustment mechanism is used to dynamically generate a coding index. The high-order bits are extracted from the Gray code corresponding to the coding index to generate a local shared key.

[0013] The multi-round channel detection utilizes OTFS modulation and demodulation, where the master node and the slave node alternately send pilot signals and receive signals sent by the other party.

[0014] According to some embodiments, the present disclosure adopts the following technical solutions:

[0015] An OTFS-based key generation system, based on multiple rounds of channel detection between a master node and a slave node, uses the signals received by each node to perform key generation operations, including:

[0016] The estimation module is configured to: perform channel estimation based on the received signal, and estimate the channel state information vector in the delay-Doppler domain using the channel estimation result;

[0017] The decorrelation module is configured to: perform decorrelation transformation on the estimated channel state information vector;

[0018] a generation module configured to: map the decorrelation transformed channel state information vector to a corresponding quantization interval, dynamically generate a coding index based on the index of the quantization interval using an adaptive index adjustment mechanism, extract high-order bits from the Gray code corresponding to the coding index, and generate a local shared key;

[0019] The multi-round channel detection utilizes OTFS modulation and demodulation, where the master node and the slave node alternately send pilot signals and receive signals sent by the other party.

[0020] According to some embodiments, the present disclosure adopts the following technical solutions:

[0021] A computer program product includes a computer program, wherein when the computer program is executed by a processor, the computer program implements the OTFS-based key generation method.

[0022] According to some embodiments, the present disclosure adopts the following technical solutions:

[0023] A non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the OTFS-based key generation method is implemented.

[0024] According to some embodiments, the present disclosure adopts the following technical solutions:

[0025] An electronic device includes: a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement the OTFS-based key generation method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This disclosure proposes a key generation method and system based on OTFS, which avoids complex calculation processes and improves the practicality, operability, efficiency, and robustness of key generation. Specifically:

[0028] (1) OTFS modulation and demodulation are used for physical layer key generation, and decorrelation transform is used to resolve the autocorrelation caused by OTFS, ensuring the reliability and consistency of the key generation process.

[0029] (2) By using the high-order bits of the Gray code to extract the key, the interference of low-order bit noise is effectively reduced.

[0030] (3) The adaptive index adjustment mechanism can flexibly handle boundary conditions and ensure the consistency of keys. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute a part of the present disclosure, are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure.

[0032] Figure 1 This is an application scenario diagram of Example 1;

[0033] Figure 2 This is an example diagram of a sending frame in Example 1;

[0034] Figure 3 This is a flowchart of key generation in Example 1. DETAILED DESCRIPTION

[0035] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0036] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "comprising" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] The present invention uses a transmission system built on OTFS for physical layer key generation. Compared with traditional time-frequency domain modulation schemes, the use of the OTFS transmission system for key generation significantly reduces the bit disparity rate (BDR). OTFS is designed for high-mobility communications and can convert fast-changing time-frequency domain signals into slowly varying delay-Doppler (DD) domain signals. It can effectively enhance the correlation of estimated channel state information and improve the signal-to-noise ratio, thereby significantly reducing the bit disparity rate during the key generation process.

[0039] Example 1

[0040] In one embodiment of the present disclosure, a key generation method based on OTFS is provided. Based on multiple rounds of channel detection between a master node and a slave node, the two nodes respectively perform the following operations using the signals received by each node: Figure 1 The operations shown are:

[0041] Step S1: performing channel estimation based on the received signal, and using the channel estimation result to estimate the channel state information vector in the delay-Doppler domain;

[0042] Step S2: Perform a decorrelation transformation on the estimated channel state information vector;

[0043] Step S3: Map the decorrelated channel state information vector to the corresponding quantization interval. According to the index of the quantization interval, adopt an adaptive index adjustment mechanism to dynamically generate a coding index, and extract high-order bits from the Gray code corresponding to the coding index to generate a local shared key;

[0044] Among them, the multi-round channel sounding uses OTFS modulation and demodulation, and the pilot signals are alternately sent between the master node and the slave node, and the signals sent by the other party are received.

[0045] As an embodiment, a key generation method based on OTFS of the present disclosure generates a shared key at the physical layer between legitimate communication nodes A and B. Among them, node A is the master node and B is the slave node. The specific implementation process is as follows:

[0046] 1. The legitimate communication nodes A and B alternately send pilot signals to perform multi-round channel sounding;

[0047] In the application scenario of this embodiment, there are legitimate communication nodes A and B and an eavesdropper E. Using OTFS modulation and demodulation, the legitimate communication nodes A and B alternately act as the transmitter and the receiver to perform the following process:

[0048] Assume that the parameters of the transmission system constructed based on OTFS modulation and demodulation are as follows: A transmission signal frame X DD has M×N symbols, the duration of one time slot of the transmission signal is T, and the subcarrier spacing is Δf, and they satisfy The maximum delay τ max <T, the maximum Doppler shift And it satisfies τ max ν max <<1; The frame length T of the transmission signal f = NT.

[0049] At the transmitter, use an OTFS frame as shown in Figure 2 for channel sounding. An OTFS frame consists of a pilot symbol and MN - 1 protection symbols. Among them, the red small grid is the pilot symbol, and the rest are protection symbols, which is expressed by the formula:

[0050]

[0051] Among them, x p represents the pilot symbol, and 0 represents the protection symbol.

[0052] The received signal is expressed by the formula:

[0053]

[0054] Where h[l, k] represents the DD domain channel impulse response, and z[l, k] represents the noise.

[0055] 2. The legitimate communication nodes A and B use the received signal to perform channel estimation;

[0056] At the receiving end, the received signal Y DD [l, k], perform threshold-based channel estimation, which is expressed as:

[0057] Y T [l, k] = b(l, k)Y DD [l, k]

[0058] Among them, Y T [l, k] is the estimated channel, l, k satisfy l∈{l p -l max , l p -l max}, k∈{k p -2k max , k p -2k max}, b(l, k) represents the threshold function

[0059]

[0060] in, is the threshold value of the threshold function, at this time, Y T Most elements in [l, k] are zero, and only the elements in the path are non-zero.

[0061] 3. Use the estimation results to estimate the channel state information vector, including the delay index Doppler shift index and channel coefficients

[0062] First make a preliminary estimate, expressed as follows:

[0063]

[0064] For delay offset and Doppler shift For the path, the discrete delay-Doppler channel coefficient is estimated as:

[0065]

[0066] In order to reduce the bit inconsistency rate, this embodiment uses Model Generate a key.

[0067] Since M is usually large and N is relatively small in OTFS transmission systems, in typical broadband systems, the channel path delay can be approximated as an integer multiple of T / M without loss of accuracy, so the delay estimate is an integer, so the final estimate of the delay index is The Doppler shift index estimated by the receiving end based on these discrete points is usually a non-integer. Therefore, in order to obtain a more accurate Doppler shift index estimate, this embodiment uses a cross-correlation method to improve the estimation accuracy and calculates the cross-correlation function:

[0068]

[0069] in, is the impulse function of the DD domain channel along the Doppler dimension, and the final estimate of the Doppler shift index is:

[0070]

[0071] 4. Perform decorrelation transformation on the estimated channel state information;

[0072] Channel State Information or Perform decorrelation transformation one by one, use x to represent the channel state information to be transformed, divide x into C vectors, each vector length is L, and the mean of x is expressed as

[0073] Use KLT transformation to transform each subvector x i Do decorrelation transform:

[0074] y i =U H (x i -μ x )

[0075] Where H is the conjugate transpose, and U is the autocorrelation matrix R of x. x The orthogonal matrix obtained by SVD decomposition is R x =USU H In this example, the autocorrelation matrix is ​​estimated using the following formula:

[0076]

[0077] By estimating the autocorrelation matrix Perform SVD decomposition and get U H Estimates

[0078] exist Only some of the principal components are suitable for generating keys, while other principal components are seriously interfered by noise. The first L in T Column vector to construct the transformation matrix U H .

[0079] Finally, the legitimate communication nodes A and B respectively obtain the channel state information vector y after decorrelation transformation A and y B , where y A and y B By C sub-vectors y i composition.

[0080] 5. Map the channel state information vector after decorrelation transformation to the corresponding quantization interval. According to the index of the quantization interval, an adaptive index adjustment mechanism is used to dynamically generate a coding index. The high-order bits are extracted from the Gray code corresponding to the coding index to generate a local shared key, such as Figure 3 As shown, specifically:

[0081] (1) Generate several quantization intervals with equal probability for the elements in the sub-vector, each quantization interval has a unique index and quantization threshold.

[0082] According to the distribution of elements in the sub-vector, give the sub-vector y i The element allocation in K=2 m+2 =4×2 m There are quantization intervals with equal probability, and the quantization threshold of the kth quantization interval is:

[0083]

[0084] Among them, F -1 is the probability distribution function of y, and k is the index of the quantization interval.

[0085] Let η0 = -∞, η K =+∞, then the kth quantization interval is (η K-1 , η K ], k=1,…,K.

[0086] (2) Based on the quantization threshold of each quantization interval, each element value in the sub-vector is mapped to the corresponding quantization interval.

[0087] According to the above quantization threshold, the legal communication nodes A and B traverse each subvector y i For each element in , subvector y i Each element value in is mapped to the corresponding quantization interval to obtain the corresponding index k.

[0088] (3) Generate a shared key based on the index k of the mapped quantization interval.

[0089] First, the master node generates a key generation strategy sequence number based on the index k of the quantization interval where the current element is located and sends it to the slave node;

[0090] Specifically, use e k Indicates the Gray code corresponding to index k, e k (i) means e k The i-th position of .

[0091] Let k′=k-1, and communication node A will convert the least significant bit e of the Gray code corresponding to k′ into k′ (0)∈{0, 1} is used as the key generation strategy sequence number and sent to the communication node B.

[0092] Then, communication node A and communication node B generate a policy sequence number e based on the key. k′ (0), dynamically generate coding indexes, and extract keys based on the coding indexes using high-order bits of Gray code, effectively reducing the interference of low-order bit noise.

[0093] The generation rule of the coding index is:

[0094] When e k′ (0) = 1: coding index k″ = k′;

[0095] When e k′ When (0)=0: the coding index is dynamically adjusted to k″=((k+1)mod K).

[0096] Based on the above encoding index k″, extract e k″ The first m most significant bits of are the key S.

[0097] Finally, it will be or The concatenation of each generated key is the final generated key.

[0098] Example 2

[0099] In one embodiment of the present disclosure, a key generation system based on OTFS is provided. Based on multiple rounds of channel detection between a master node and a slave node, the two nodes respectively perform key generation operations using their respective received signals, including:

[0100] The estimation module is configured to: perform channel estimation based on the received signal, and estimate the channel state information vector in the delay-Doppler domain using the channel estimation result;

[0101] The decorrelation module is configured to: perform decorrelation transformation on the estimated channel state information vector;

[0102] a generation module configured to: map the decorrelation transformed channel state information vector to a corresponding quantization interval, dynamically generate a coding index based on the index of the quantization interval using an adaptive index adjustment mechanism, extract high-order bits from the Gray code corresponding to the coding index, and generate a local shared key;

[0103] The multi-round channel detection utilizes OTFS modulation and demodulation, where the master node and the slave node alternately send pilot signals and receive signals sent by the other party.

[0104] Example 3

[0105] In one embodiment of the present disclosure, a computer program product is provided, including a computer program. When the computer program is executed by a processor, the computer program implements the OTFS-based key generation method.

[0106] Example 4

[0107] In one embodiment of the present disclosure, a non-transitory computer-readable storage medium is provided, wherein the non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the OTFS-based key generation method is implemented.

[0108] Example 5

[0109] In one embodiment of the present disclosure, an electronic device is provided, comprising: a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device implements the OTFS-based key generation method.

[0110] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0111] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0112] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Those skilled in the art should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A key generation method based on OTFS, characterized in that: Based on multiple rounds of channel detection between the master node and the slave node, the two nodes perform the following operations respectively using the signals they receive: Based on the received signal, channel estimation is performed, and the channel state information vector in the delay-Doppler domain is estimated using the channel estimation result; Performing decorrelation transformation on the estimated channel state information vector; The decorrelation-transformed channel state information vector is mapped to the corresponding quantization interval. Based on the index of the quantization interval, an adaptive index adjustment mechanism is used to dynamically generate a coding index. The high-order bits are extracted from the Gray code corresponding to the coding index to generate a local shared key. The multi-round channel detection utilizes OTFS modulation and demodulation, where the master node and the slave node alternately send pilot signals and receive signals sent by the other party.

2. The OTFS-based key generation method according to claim 1, wherein: The alternate transmission of the pilot signal is that the master node and the slave node take turns as the transmitter and the receiver, and the transmitter sends an OTFS frame consisting of a pilot symbol and several protection symbols to the receiver.

3. The OTFS-based key generation method according to claim 1, wherein: The decorrelation transformation is to divide the channel state information vector into a number of sub-vectors of equal length, and perform decorrelation transformation on each sub-vector through KLT transformation based on the autocorrelation matrix of the channel state information vector.

4. The OTFS-based key generation method according to claim 3, wherein: The channel state information vector after decorrelation transformation is mapped to the corresponding quantization interval, specifically: Generate a number of quantization intervals with equal probability for the elements in the subvector, each quantization interval has a unique index and quantization threshold; Based on the quantization threshold of each quantization interval, each element value in the subvector is mapped to the corresponding quantization interval.

5. The OTFS-based key generation method according to claim 1, wherein: The adaptive index adjustment mechanism is used to dynamically generate the coding index, specifically: The master node generates a key generation strategy sequence number based on the index of the quantization interval where the current element is located and sends it to the slave node; The master and slave nodes generate strategy numbers based on the key and dynamically generate coding indexes.

6. The OTFS-based key generation method according to claim 5, wherein: The key generation strategy sequence number is specifically: k is the index of the quantization interval where the current element is located, let k ′ =k-1, k ′ The corresponding Gray code e k′ The least significant bit e k′ (0)∈{0, 1} is used as the key generation strategy sequence number.

7. A key generation system based on OTFS, characterized in that: Based on multiple rounds of channel detection between the master node and the slave node, the two nodes perform key generation operations using the signals they receive, including: The estimation module is configured to: perform channel estimation based on the received signal, and estimate the channel state information vector in the delay-Doppler domain using the channel estimation result; The decorrelation module is configured to: perform decorrelation transformation on the estimated channel state information vector; a generation module configured to: map the decorrelation transformed channel state information vector to a corresponding quantization interval, dynamically generate a coding index based on the index of the quantization interval using an adaptive index adjustment mechanism, extract high-order bits from the Gray code corresponding to the coding index, and generate a local shared key; The multi-round channel detection utilizes OTFS modulation and demodulation, where the master node and the slave node alternately send pilot signals and receive signals sent by the other party.

8. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the OTFS-based key generation method according to any one of claims 1 to 6 is implemented.

9. A non-transitory computer-readable storage medium, characterized in that The non-transitory computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by the processor, the OTFS-based key generation method according to any one of claims 1 to 6 is implemented.

10. An electronic device, characterized in that: include: A processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement an OTFS-based key generation method as described in any one of claims 1 to 6.

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