Physical layer key generation and integrated transmission of one-time pad encryption method and system

Abstract

The present application relates to the technical field of physical layer security and cryptography, and particularly relates to a physical layer key generation and one-time pad encryption integrated transmission method and system, wherein an original key is generated in a coherent block at a transmitting end, and an encryption key is obtained through a cascade hash operation; a data symbol is obtained through encoding modulation after the original key is XORed with the encryption key; the original key is mapped to a key symbol through a designed key constellation, and the key symbol is phase and power constrained; a precoding vector containing key symbol information and artificial noise in a legal channel null space is constructed to realize synchronous transmission of the key and the data; a legal receiving end demodulates the data symbol, recovers the key through zero-forcing equalization and Voronoi decision, reconstructs the encryption key and decrypts the ciphertext. The present application saves a time slot for independent key generation, improves transmission efficiency and reduces time delay; artificial noise and cascade hash are used for composite protection, and the one-time pad information theory security requirement is still met in a strong eavesdropping scene, and the present application is compatible with mainstream modulation and easy to deploy.

Description

Technical Field

[0001] This invention relates to the field of physical layer security and cryptography, specifically to a method and system for integrating physical layer key generation and one-time pad encryption. Background Technology

[0002] One-time pad is the only encryption scheme proven to possess information-theoretic security. Its security requires that the key be completely random, the same length as the plaintext, and used only once. However, deploying one-time pad in practical wireless communication systems faces two major challenges: first, it requires establishing a high-speed key distribution link that matches the data rate; second, it is essential to ensure the security of the key distribution process itself.

[0003] Physical layer key generation (PLD) technology leverages the reciprocity, randomness, and time-varying nature of wireless channels to enable legitimate communicating parties to generate a consistent random key, while preventing eavesdroppers in different locations from obtaining the same key. This is considered an ideal approach to achieving one-time pad encryption. Existing PLD-based one-time pad methods generally employ a "time-sharing" model, where communication time is divided into alternating key generation and encrypted data transmission phases. This time-sharing approach results in significant communication latency and system resource overhead, making it difficult to deploy in latency-sensitive or resource-constrained mainstream communication systems.

[0004] Furthermore, most existing research is based on the assumption that eavesdroppers have limited capabilities (such as unknown channel state information or the presence of received noise), lacking rigorous security analysis and defense mechanisms against powerful eavesdroppers with prior knowledge (such as knowing all channel state information and protocol details). Without instantaneous knowledge of the eavesdropper's channel information, relying solely on physical layer techniques such as artificial noise is insufficient to guarantee absolute key security from an information theory perspective, posing a risk of key information leakage. Therefore, there is an urgent need for an efficient and secure integrated transmission method capable of simultaneously generating keys and transmitting data, while also resisting attacks from powerful eavesdroppers. Summary of the Invention

[0005] To address the problems of low efficiency, high latency, and inability to withstand strong eavesdroppers in existing technologies that employ time-sharing key generation and data transmission, thus failing to meet the one-time pad information theory security requirements, this invention proposes an integrated physical layer key generation and one-time pad encryption transmission method and system. Through integrated key and data transmission and composite protection using artificial noise and cascaded keys, it achieves efficient and low-latency transmission while still meeting the one-time pad information theory security requirements under extreme conditions.

[0006] To achieve the above objectives, the technical solution adopted is:

[0007] This invention provides a method for integrating physical layer key generation and one-time pad encryption for transmission, comprising the following steps:

[0008] Step 1: Within each coherent block, the transmitter uses a true random number generator to generate the original key sequence, and uses a cryptographic hash function to perform a concatenated hash operation on the original key of the current block, the encryption key of the previous coherent block, and the coherent block number to generate the encryption key of the current block.

[0009] Step 2: The transmitting end performs an XOR operation between the plaintext and the encryption key to obtain the ciphertext, and then performs channel coding and modulation on the ciphertext to obtain a data symbol sequence;

[0010] Step 3: The transmitter designs a key constellation and maps the original key to key symbols according to the key constellation; the phase of the key symbols is constrained within the phase decision region of the data symbols, and the amplitude is constrained within the power range that meets the communication quality requirements;

[0011] Step 4: The transmitter constructs a precoding vector so that the equivalent response of the legitimate channel carries key symbol information, and injects artificial noise into the null space of the legitimate channel to achieve synchronous transmission of key information and data symbols;

[0012] Step 5: The legitimate receiver demodulates the data symbols from the received signal, extracts the key symbol estimate through zero-forcing equalization, recovers the key symbol sequence through Voronoi region decision, and then obtains the original key estimate. The encryption key is then reconstructed through concatenated hashing, and the ciphertext is decrypted to recover the plaintext.

[0013] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, the formula for the concatenated hash operation in step 1 is further as follows: ,in For cryptographic hash functions, This is the original key for the current block. is the encryption key for the previous coherent block, and n is the coherent block number. This indicates the initial key used in the splicing operation, specifically the first coherent block. This can be the user's root key or a pre-negotiated symmetric key.

[0014] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, step 3, mapping the original key to key symbols according to the key constellation, further includes: key symbols It is at every moment, from a fixed key constellation In this context, a specific key constellation point is selected based on the original key bits at that moment.

[0015] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, the key constellation is further obtained by solving an optimization problem with the objective of minimizing the key symbol error rate and constraints of symbol power and phase range, wherein the phase constraint is: Where M is the modulation order, Pi Indicates phase, Indicates the key constellation point; the power range is the minimum transmit power required to ensure data demodulation. to ,in Additional power budget allocated to the key generation process.

[0016] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, the key symbol error rate is further: ,in, The key symbol error rate, For Hamming distance, It is a Gaussian Q-function. Let be the noise variance, and i and j be the indices of the key constellation points. For key constellation points The corresponding bit tag.

[0017] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, the precoding vector construction in step 4 is further described as follows: ,in, For a valid channel vector, For their conjugate, For its norm, For key symbols, for The null space matrix, and satisfying , Given an artificial noise vector, the total power of the precoded vector satisfies , This represents the maximum transmission power of the transmitter. This represents the power of artificial noise.

[0018] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, the power of the artificial noise is further... It can be adaptively adjusted to the maximum transmission power at the transmitting end. Under constraints, the goal is to maximize the eavesdropper's uncertainty about the key symbol while ensuring the quality of legitimate communication.

[0019] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, in step 5, the key symbol estimate is extracted through zero-forcing equalization, satisfying: ,in, In order to receive signals, Symbol estimation for the demodulated data.

[0020] According to the integrated physical layer key generation and one-time pad encryption transmission method of the present invention, further, in the extreme case where the eavesdropper knows all channel state information and protocol details and there is no received noise, the encryption density increases with the number of coherent blocks. The leakage of encryption key information is approaching zero, which meets the security requirements of one-time pad information theory.

[0021] Furthermore, the present invention also provides an integrated physical layer key generation and one-time pad encryption transmission system for implementing the integrated physical layer key generation and one-time pad encryption transmission method described above. The system includes:

[0022] A transmitting device equipped with multiple antennas for performing key generation, encryption, modulation, and precoding operations;

[0023] A legitimate receiving device equipped with one or more antennas, used to perform data demodulation, key extraction and decryption operations;

[0024] The security performance of the system does not depend on obtaining the instantaneous channel state information of the eavesdropper.

[0025] The beneficial effects achieved by adopting the above technical solution are:

[0026] 1. This invention embeds the physical layer key generation process into the data transmission process, and achieves synchronous transmission of key information and encrypted data through randomized precoding, completely eliminating the independent key generation time slot, significantly improving the system's spectrum efficiency and transmission efficiency, greatly reducing communication latency and resource overhead, and solving the bottleneck problems of low efficiency and high latency in the traditional time-sharing mode.

[0027] 2. For extreme eavesdropping scenarios where all channel state information and protocol details are known and there is no received noise, this invention adopts a composite security mechanism of "artificial noise interference at the signal layer + concatenated hashing at the key layer". At the signal layer, artificial noise is used to interfere with the eavesdropper's reception, and at the key layer, a concatenated structure based on cryptographic hash functions is used to post-process the original key. Theoretically, this can guarantee that the information leakage of the encryption key asymptotically approaches zero as the number of coherent blocks increases. Even under the worst eavesdropping conditions, it still meets the information theory security requirements of one-time pad, and the security level far exceeds that of traditional physical layer security schemes.

[0028] 3. The method proposed in this invention is fully compatible with mainstream modulation methods such as M-PSK, without requiring any changes to the existing communication underlying architecture. The precoding logic can be directly implemented in multi-antenna systems, resulting in low deployment costs, strong adaptability, and convenient application to various practical wireless communication security scenarios.

[0029] 4. This invention designs a key constellation by minimizing the key symbol error rate and combining power and phase constraints to ensure that the legitimate receiving end can stably and accurately extract key information without interfering with data demodulation. This significantly improves the reliability of key transmission and ensures the stable operation of the integrated transmission process.

[0030] 5. Compared with the traditional time-sharing physical layer key generation-one-time pad scheme (PLSKG-OTP), the communication time cost of this invention is only 26% of the traditional scheme, and the transmission efficiency is significantly improved. At the same time, under strong eavesdropping conditions, the leakage of key information can be asymptotically approached to zero. It achieves breakthroughs in both efficient low-latency transmission and high-level security against leakage, taking into account both practicality and security. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0032] Figure 1 This is a flowchart illustrating the integrated physical layer key generation and one-time pad encryption transmission method according to an embodiment of the present invention.

[0033] Figure 2 This is a framework diagram of the physical layer key generation and one-time pad encryption integrated transmission method according to an embodiment of the present invention. Detailed Implementation

[0034] The exemplary solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art.

[0035] First, construct the system model. Consider a system containing multiple antennas (let the number of antennas be ). Imagine a communication system consisting of a base station (Alice), a single-antenna legitimate user (Bob), and a single-antenna eavesdropper (Eve). Assume the channel exhibits flat fading over a length of... The symbols remain unchanged within the coherent block. Within the nth coherent block, the channel vectors from the base station to the user and from the base station to the eavesdropper are denoted as follows: and Assume Alice can accurately estimate the channel reciprocity (via pilots sent by Bob) at the beginning of each coherent block. The received noise levels for Bob and Eve are respectively... and In the system model, the transmitted signal at time t within the nth coherent block is: ,in For the pre-coding vector to be designed, It is a unity-power M-PSK data symbol from ciphertext modulation, i.e. The precoding vector power constraint is ,in This represents the maximum transmit power of the transmitter. Bob and Eve's received signals are respectively:

[0036]

[0037] The core of this invention lies in designing randomized precoding vectors. This makes its equivalent response to that of a legitimate channel. While carrying key information, the data symbols are not affected. The correct demodulation.

[0038] Based on the above system model, this invention discloses an integrated physical layer key generation and one-time pad encryption transmission method. It employs a composite security mechanism of signal layer artificial noise protection and a cascaded key structure based on cryptographic hash functions. The system's security performance does not depend on obtaining the eavesdropper's instantaneous channel state information and is compatible with all orders of M-PSK phase shift keying modulation technology. Figure 1 and Figure 2 As shown, the specific implementation process is as follows:

[0039] Step S1: System initialization and key generation (transmitter): In each coherent block, the transmitter uses a true random number generator to generate the original key sequence, and uses a cryptographic hash function to perform concatenated hash operation on the original key of the current block, the encryption key of the previous coherent block and the coherent block number to generate the encryption key of the current block.

[0040] Before communication begins, the transmitter (Alice) and receiver (Bob) generate an initial key using a root key or a pre-negotiated symmetric key. Within each coherent block n, the transmitter uses a true random number generator to generate a uniformly random raw key sequence. The encryption key is generated using a cascaded hash structure. For the first coherent block, a cryptographic hash function is used. Initial key The original key of the current block and the sequence number of the coherent block 1 are used to perform a concatenated hash operation to generate the encryption key for the first coherent block; for subsequent coherent blocks, a cryptographic hash function is used... The concatenated hash operation is performed on the original key of the current block, the encryption key of the previous coherent block, and the coherent block number to generate the encryption key of the current block. The concatenated hash operation is to convert the original key of the current block into a hash value. The encryption key of the previous coherent block After concatenating the coherent block sequence number n, it is then processed using a cryptographic hash function. The calculation formula is as follows:

[0041]

[0042] in, This indicates a splicing operation. For cryptographic hash functions, SHA-256 is selected. This is the original key for the current block. is the encryption key for the previous coherent block, and n is the coherent block number. The use of a concatenated key structure improves long-term security.

[0043] Step S2: Data Encryption and Modulation (Transmitter): The transmitter performs an XOR operation on the plaintext and the encryption key to obtain the ciphertext, and performs channel coding and modulation on the ciphertext to obtain a data symbol sequence.

[0044] The transmitter sends a plaintext bit sequence of length L. Perform a bit-by-bit XOR operation with the encryption key to obtain the ciphertext. The ciphertext is channel-coded to obtain a coded bit stream, which is then mapped to a data symbol sequence via M-PSK modulation. ,in This is a unit power symbol. In this embodiment, 4-PSK modulation (M=4) is used, and LDPC code (code rate 1 / 2) is selected for channel coding, with L value being 128 bits.

[0045] Step S3: Key constellation design (transmitter): The transmitter designs the key constellation and maps the original key to key symbols according to the key constellation; the phase of the key symbols is constrained within the phase decision region of the data symbols, and the amplitude is constrained within the power range that meets the communication quality requirements.

[0046] First, define the key symbol sequence. Key symbol It is at every moment, from a fixed key constellation In this context, a specific key constellation point is selected based on the original key bits at that moment; the key constellation is... The cardinality is the same as the modulation order, that is... In short, a key constellation maps the raw key bits to specific complex key symbols used to carry and transmit key information. The key constellation is obtained by solving an optimization problem with the objective of minimizing the key symbol error rate, constrained by symbol power and phase range.

[0047]

[0048] in, The key symbol error rate, For Hamming distance, It is a Gaussian Q-function. Let be the noise variance, and i and j be the indices of the key constellation points. For key constellation points The corresponding bit tag. M is the modulation order. Pi Indicates phase, Indicates the key constellation point; It is the minimum transmit power required to ensure data demodulation. Additional power budget allocated to the key generation process.

[0049] The optimization objective is to minimize the bit error rate of the key symbol while ensuring communication reliability, and to constrain the key symbol phase to not exceed the phase decision region of the M-PSK symbol. This is to ensure that key perturbation does not affect the correct demodulation of data symbols. In this embodiment, The value is set to 5dBm to ensure (set up for ).

[0050] Step S4: Secure Precoding and Transmission (Transmitter): The transmitter constructs a precoding vector so that the equivalent response of the legitimate channel carries key symbol information, and injects artificial noise into the null space of the legitimate channel to achieve synchronous transmission of key information and data symbols. The transmitter transmits signals through multiple antennas so that the equivalent channel response carries key information, and the artificial noise does not affect the demodulation of data symbols by the legitimate receiver.

[0051] To achieve an equivalent channel response carrying key information (i.e. To prevent eavesdropping, this embodiment employs a secure precoding design based on artificial noise. At each time t, according to the key symbol... Design precoding vectors This results in two components: one aligned with the key symbol, and the other an artificial noise component injected into the null space of the legitimate channel. Specifically, it takes the following form:

[0052]

[0053] in, For a valid channel vector, For their conjugate, For its norm, For key symbols, for The null space matrix, and satisfying , To distribute artificial noise power evenly The artificial noise vector on the disk, the total power of the precoded vector satisfies , This represents the maximum transmission power of the transmitter. This represents the power of the artificial noise. The first term is the key symbol. Linear mapping to equivalent channel The second item is artificial noise, because... Therefore, artificial noise has no impact on the legitimate user (Bob). In this embodiment, The value range is 0-10 dBm. Set it to 20dBm.

[0054] Power of artificial noise It can be adaptively adjusted to the maximum transmission power at the transmitting end. Under constraints, the goal is to maximize the eavesdropper's uncertainty about the key symbol while ensuring the quality of legitimate communication.

[0055] Step S5: Signal Reception and Decryption (Legitimate Receiver): The legitimate receiver first performs data symbol judgment on the received signal to recover the data symbols; then, it uses the error-free data symbols to perform zero-forcing equalization on the received signal to obtain the key symbol estimate; subsequently, it performs Voronoi region judgment on the key symbol estimate to recover the key symbol sequence and the original key estimate; finally, it reconstructs the encryption key through concatenated hashing and decrypts the ciphertext to recover the plaintext.

[0056] The legitimate receiver receives the signal as follows: ,because The phase is constrained to Within the judgment area, the legitimate receiving end first... The phase is used for maximum likelihood determination to recover the estimated data sign value. (in (where i represents the constellation point index), the ciphertext estimate is obtained after demapping and decoding. At high signal-to-noise ratios, it can be considered that... .

[0057] The user used the error-free Perform zero-forcing equalization on the received signal and extract key symbol estimation:

[0058]

[0059] in, In order to receive signals, For symbol estimation of the demodulated data, Then The judgment was issued to the nearest Voronoi region. Corresponding key constellation points This allows the key symbol sequence to be recovered, and thus the original key estimate can be obtained. Finally, the cascaded hash operation at the transmitting end is repeated to generate an estimated encryption key. and ciphertext XOR to recover plaintext .

[0060] Under the worst-case eavesdropping conditions where the eavesdropper knows all channel state information and protocol details and there is no received noise, the number of coherent blocks varies. The information leakage of encryption keys is close to zero, which meets the security requirements of one-time pad information theory.

[0061] This invention also discloses an integrated physical layer key generation and one-time pad encryption transmission system for implementing the above-mentioned integrated physical layer key generation and one-time pad encryption transmission method. The system includes:

[0062] A transmitting device equipped with multiple antennas for performing key generation, encryption, modulation, and precoding operations;

[0063] A legitimate receiving device equipped with one or more antennas, used to perform data demodulation, key extraction and decryption operations;

[0064] The security performance of the system does not depend on obtaining the instantaneous channel state information of the eavesdropper.

[0065] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for integrating physical layer key generation and one-time pad encryption for transmission, characterized in that, Includes the following steps: Step 1: Within each coherent block, the transmitter uses a true random number generator to generate the original key sequence, and uses a cryptographic hash function to perform a concatenated hash operation on the original key of the current block, the encryption key of the previous coherent block, and the coherent block number to generate the encryption key of the current block. Step 2: The transmitting end performs an XOR operation between the plaintext and the encryption key to obtain the ciphertext, and then performs channel coding and modulation on the ciphertext to obtain a data symbol sequence; Step 3: The transmitter designs a key constellation and maps the original key to key symbols according to the key constellation; the phase of the key symbols is constrained within the phase decision region of the data symbols, and the amplitude is constrained within the power range that meets the communication quality requirements; Step 4: The transmitter constructs a precoding vector so that the equivalent response of the legitimate channel carries key symbol information, and injects artificial noise into the null space of the legitimate channel to achieve synchronous transmission of key information and data symbols; Step 5: The legitimate receiver demodulates the data symbols from the received signal, extracts the key symbol estimate through zero-forcing equalization, recovers the key symbol sequence through Voronoi region decision, and then obtains the original key estimate. The encryption key is then reconstructed through concatenated hashing, and the ciphertext is decrypted to recover the plaintext.

2. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 1, characterized in that, The formula for the concatenated hash operation described in step 1 is: ,in For cryptographic hash functions, This is the original key for the current block. is the encryption key for the previous coherent block, and n is the coherent block number. This indicates the initial key used in the splicing operation, specifically the first coherent block. This can be the user's root key or a pre-negotiated symmetric key.

3. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 1, characterized in that, Step 3, which involves mapping the original key to key symbols according to the key constellation, includes: key symbols It is at every moment, from a fixed key constellation In this context, a specific key constellation point is selected based on the original key bits at that moment.

4. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 3, characterized in that, The key constellation is obtained by solving an optimization problem with the objective of minimizing the key symbol error rate, constrained by symbol power and phase range. The phase constraint is as follows: Where M is the modulation order, Pi Indicates phase, Indicates the key constellation point; the power range is the minimum transmit power required to ensure data demodulation. to ,in Additional power budget allocated to the key generation process.

5. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 4, characterized in that, The key symbol error rate is: ,in, The key symbol error rate, For Hamming distance, It is a Gaussian Q-function. Let be the noise variance, and i and j be the indices of the key constellation points. For key constellation points The corresponding bit tag.

6. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 1, characterized in that, The precoding vector construction in step 4 is as follows: ,in, For a valid channel vector, For their conjugate, For its norm, For key symbols, for The null space matrix, and satisfying , Given an artificial noise vector, the total power of the precoded vector satisfies , This represents the maximum transmission power of the transmitter. This represents the power of artificial noise.

7. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 6, characterized in that, The power of the artificial noise It can be adaptively adjusted to the maximum transmission power at the transmitting end. Under constraints, the goal is to maximize the eavesdropper's uncertainty about the key symbol while ensuring the quality of legitimate communication.

8. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 1, characterized in that, In step 5, the key symbol estimate is extracted through zero-forcing equalization, satisfying the following: ,in, In order to receive signals, Symbol estimation for the demodulated data.

9. The integrated physical layer key generation and one-time pad encryption transmission method according to claim 1, characterized in that, In the extreme case where the eavesdropper knows all channel state information and protocol details and there is no received noise, the number of coherent blocks varies. The leakage of encryption key information is approaching zero, which meets the security requirements of one-time pad information theory.

10. A physical layer key generation and one-time pad encryption integrated transmission system, characterized in that, For implementing the integrated physical layer key generation and one-time pad encryption transmission method as described in any one of claims 1-9, the system comprises: A transmitting device equipped with multiple antennas for performing key generation, encryption, modulation, and precoding operations; A legitimate receiving device equipped with one or more antennas, used to perform data demodulation, key extraction and decryption operations; The security performance of the system does not depend on obtaining the instantaneous channel state information of the eavesdropper.

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