A communication early warning method based on quantum encryption

Abstract

The application discloses a communication early warning method based on quantum encryption and relates to the technical field of quantum encryption communication, and comprises the following steps: identifying environmental phase noise in a fiber link of quantum communication; generating a detection disturbance signal, the frequency of the detection disturbance signal being smaller than the characteristic frequency of the environmental phase noise, and the amplitude of the detection disturbance signal being lower than the amplitude value of the environmental phase noise; injecting the detection disturbance signal into a phase control loop of the quantum communication; collecting a control response signal of the phase control loop, the control response signal being a signal output by the phase control loop for compensating the detection disturbance signal and the environmental phase noise; collecting a physical vibration signal of the fiber link; determining a cross-correlation coefficient of the physical vibration signal and the control response signal; and if the cross-correlation coefficient is smaller than a preset cross-correlation threshold, triggering an eavesdropping alarm. The application improves the accuracy of identifying eavesdropping behavior in the quantum communication process.

Description

Technical Field

[0001] This invention relates to the technical field of quantum encrypted communication, and in particular to a communication early warning method based on quantum encryption. Background Technology

[0002] Quantum-encrypted communication utilizes quantum mechanics principles to encrypt communication through quantum key distribution, achieving a theoretically secure communication method that cannot be eavesdropped on. In quantum communication (quantum-encrypted communication), the mains-powered optical amplifier is prone to generating 60Hz electromagnetic interference, causing micro-vibrations in the communication optical fiber. These vibrations are converted into periodic phase noise.

[0003] However, eavesdroppers may use such regular noise as cover for eavesdropping. For example, by injecting an anti-phase active noise cancellation signal, they can cancel the effect of environmental vibrations on their eavesdropping devices, making the eavesdropping behavior invisible to the quantum communication system. The system will then mistakenly believe that the noise has been suppressed, when in fact the eavesdropper has masked the eavesdropping disturbance with periodic phase noise.

[0004] Therefore, how to accurately identify eavesdropping behavior in the quantum communication process has become a technical problem that urgently needs to be solved. Summary of the Invention

[0005] The technical problem solved by this invention is the inability to accurately identify eavesdropping behavior during quantum communication.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a communication early warning method based on quantum encryption, comprising:

[0007] Identifying environmental phase noise in fiber optic links for quantum communication;

[0008] A detection disturbance signal is generated, wherein the frequency of the detection disturbance signal is less than the characteristic frequency of the environmental phase noise, and the amplitude of the detection disturbance signal is less than the amplitude of the environmental phase noise;

[0009] The detection perturbation signal is injected into the phase control loop of the quantum communication;

[0010] The control response signal of the phase control loop is acquired. The control response signal is the signal output by the phase control loop after compensating for the detection disturbance signal and the environmental phase noise.

[0011] Collect the physical vibration signal of the optical fiber link;

[0012] Determine the cross-correlation coefficient between the physical vibration signal and the control response signal;

[0013] If the cross-correlation coefficient is less than a preset cross-correlation threshold, an eavesdropping alarm is triggered.

[0014] Preferably, the identification of environmental phase noise in the fiber optic link for quantum communication includes:

[0015] The mechanical vibration corresponding to a preset characteristic frequency in the optical fiber link is monitored to obtain the environmental phase noise. The mechanical vibration is used to characterize the signal vibration caused by power frequency electromagnetic interference.

[0016] Preferably, generating the detection disturbance signal includes:

[0017] The dominant frequency component of the mechanical vibration is extracted by spectral analysis to obtain the characteristic frequency of the environmental phase noise;

[0018] The reference amplitude of the environmental phase noise is determined based on the environmental phase noise.

[0019] The characteristic frequencies of the environmental phase noise are scaled according to a preset first scaling factor formula to obtain a frequency threshold. The first scaling factor formula is as follows:

[0020] ;

[0021] in, The first scaling factor is... T This refers to the time interval between the first verification of quantum data and the current time point for the controller. N To detect the cumulative number of times the disturbance signal is generated, D These are the characteristic frequencies of environmental phase noise;

[0022] The reference amplitude of the environmental phase noise is scaled according to a preset second scaling factor to obtain an amplitude threshold. The maximum value that the second scaling factor can take is one-half.

[0023] A sinusoidal probe disturbance signal is generated based on the frequency threshold and the amplitude threshold, such that the frequency of the probe disturbance signal is less than the frequency threshold and the amplitude of the probe disturbance signal is less than the amplitude threshold.

[0024] Preferably, the step of monitoring the mechanical vibration corresponding to a preset characteristic frequency in the optical fiber link to obtain the environmental phase noise includes:

[0025] Obtain the original vibration signal generated by the axial vibration of the optical fiber in the optical fiber link;

[0026] Perform a fast Fourier transform on the original vibration signal to obtain the dominant frequency components;

[0027] If the frequency of the dominant frequency component is within the preset power grid fundamental frequency range, and the frequency fluctuation amplitude of the dominant frequency component is less than the preset fluctuation range, then the original vibration signal is determined as environmental phase noise.

[0028] The step of extracting the dominant frequency component of the mechanical vibration through spectral analysis to obtain the characteristic frequency of the environmental phase noise includes:

[0029] If the frequency of the dominant frequency component is within a preset power grid fundamental frequency range, and the frequency fluctuation amplitude of the dominant frequency component is less than the preset fluctuation range, then the frequency of the dominant frequency component is determined as the characteristic frequency of the environmental phase noise.

[0030] Determining the reference amplitude of the environmental phase noise based on the environmental phase noise includes:

[0031] The reference amplitude of the environmental phase noise is determined based on the average amplitude of the dominant frequency component.

[0032] Preferably, injecting the detection perturbation signal into the phase control loop of the quantum communication includes:

[0033] The detection disturbance signal is superimposed on the drive signal of the phase modulator of the phase control loop.

[0034] Preferably, the acquisition of the control response signal of the phase control loop includes:

[0035] The control response signal is determined based on the waveform of the voltage output by the feedback controller of the phase control loop over time.

[0036] The physical vibration signal of the optical fiber link is collected, and the physical vibration signal is represented as a non-axial vibration signal, including:

[0037] The physical vibration signal is determined based on the waveform of acceleration changing over time output by the vibration sensor of the optical fiber link. The clock reference of the control response signal and the physical vibration signal comes from the same clock source.

[0038] Preferably, determining the cross-correlation coefficient between the physical vibration signal and the control response signal includes:

[0039] Determine the cross-correlation function between the physical vibration signal and the control response signal;

[0040] Determine the time offset at which the cross-correlation function is at its maximum;

[0041] The maximum value of the cross-correlation function is determined based on the time offset, and the cross-correlation coefficient between the physical vibration signal and the control response signal is obtained.

[0042] If the cross-correlation coefficient is less than a preset cross-correlation threshold, then a first operation is performed, which means encrypting the quantum data, including:

[0043] If the cross-correlation coefficient is less than a preset cross-correlation threshold, and the absolute difference between the time offset and the preset offset threshold is greater than a preset offset value, then an eavesdropping alarm is triggered.

[0044] Preferably, before triggering the eavesdropping alarm if the cross-correlation coefficient is less than a preset cross-correlation threshold and the absolute difference between the time offset and the preset offset threshold is greater than a preset offset value, the method further includes:

[0045] Determine whether the cross-correlation coefficient is less than a preset cross-correlation threshold;

[0046] If the cross-correlation coefficient is greater than or equal to a preset cross-correlation threshold, then the transfer function is obtained. The transfer function is used to characterize the transfer relationship between the physical vibration signal and the control response signal in the absence of eavesdropping.

[0047] Determine whether the transfer function is faulty based on the physical vibration signal and the control response signal;

[0048] If the transfer function fails, an eavesdropping alarm will be triggered;

[0049] If the transfer function is not invalid, then determine whether the environmental noise is suppressed based on the characteristic frequency of the environmental phase noise;

[0050] If the ambient noise is suppressed, an eavesdropping alarm is triggered.

[0051] Preferably, determining whether the transfer function has failed based on the physical vibration signal and the control response signal includes:

[0052] The sub-signal of the physical vibration signal at the frequency of the detected disturbance signal is determined as the first physical vibration sub-signal;

[0053] The expected control response sub-signal is determined based on the first physical vibration sub-signal and the transfer function;

[0054] The sub-signal of the control response signal at the frequency of the detected disturbance signal is determined as the actual control response sub-signal;

[0055] The transfer function is deemed to be ineffective based on the degree of deviation between the expected control response sub-signal and the actual control response sub-signal.

[0056] Preferably, if the transfer function is not invalid, determining whether the environmental noise is suppressed based on the characteristic frequency of the environmental phase noise includes:

[0057] If the transfer function does not fail, then the sub-signal of the physical vibration signal at the characteristic frequency is determined as the second physical vibration sub-signal;

[0058] If the amplitude of the second physical vibration sub-signal is lower than the preset reference amplitude for a consecutive preset number of sampling periods, then it is determined that the environmental noise is suppressed.

[0059] The beneficial effects of this invention are as follows: By identifying environmental phase noise in the fiber optic link of quantum communication, a detection disturbance signal is generated and injected into the phase control loop of quantum communication. This superimposes an ultra-low frequency sinusoidal modulation signal onto the phase control loop, thereby creating a disturbance in the communication link. This allows for the identification of eavesdropping behavior based on the injected signal without affecting normal signal transmission. After injecting the detection disturbance signal, the control response signal of the phase control loop and the physical vibration signal of the fiber optic link are collected. The cross-correlation coefficient between the physical vibration signal and the control response signal is used to determine whether eavesdropping behavior exists in the communication link. Since physical disturbance triggers the control response, the physical vibration signal characterizing the physical disturbance and the control response signal characterizing the control response will inevitably have a strong correlation after the detection disturbance signal is injected. If the cross-correlation coefficient between the physical vibration signal and the control response signal is less than a preset cross-correlation threshold, it indicates that the eavesdropper's operation has caused a break in the time-domain correlation of the quantum communication link, triggering an eavesdropping alarm and thus accurately identifying eavesdropping behavior in the quantum communication process. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the basic process of a quantum encryption-based communication early warning method provided in one embodiment of the present invention. Detailed Implementation

[0061] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0062] The quantum-encrypted communication method provided in this application is applied to phase-encoded quantum key distribution systems, typically in metropolitan quantum communication networks (transmission distance 50-100km). The quantum-encrypted communication link consists of a transmitter, a receiver, a single-mode optical fiber (G.652.D), and a phase control loop. The optical fiber link, as the transmission medium for quantum signals, has the following physical characteristics: a 1550nm wavelength window loss of 0.2dB / km and a group velocity dispersion of 17ps / nm / km. The phase control loop includes a lithium niobate phase modulator, a PID feedback controller, and a drive circuit, which adjusts the waveguide refractive index by regulating the drive voltage. This enables precise control of the optical signal phase. Δn represents the change in effective refractive index, n represents the effective refractive index, and V represents the amplitude of the driving voltage.

[0063] Quantum signals are transmitted in optical fibers as weak single-photon-level pulses, each carrying quantum state information (such as polarization or phase state). Eavesdropping mainly manifests as phase remodulation attacks (intercepting and tampering with quantum states) or side-channel attacks (stealing information through vibration sensors). These operations introduce additional phase perturbations and disrupt the natural characteristics of environmental noise.

[0064] The core idea of ​​the quantum-encrypted communication method provided in this application is as follows: First, identify environmental phase noise caused by the power grid as a natural benchmark; second, inject an ultra-low frequency detection signal (0.1Hz) as a "decoy"; finally, detect the active manipulation of noise by eavesdroppers by verifying the characteristics of the environmental noise, controlling the response matching degree, and time-domain correlation. This approach transforms environmental noise, which is a system defect, into a security defense asset, improving the system's ability to identify eavesdropping behavior.

[0065] Example 1, referring to Figure 1 As an embodiment of the present invention, a communication early warning method based on quantum encryption is provided, comprising:

[0066] S110 identifies environmental phase noise in fiber optic links used for quantum communication.

[0067] In terms of hardware deployment, a three-axis MEMS accelerometer (Kistler8692C5) can be installed at the tension release point of the OPGW optical cable. Due to the mechanical lever effect, the vibration sensitivity at this location is increased by 3 times. The sensor is rigidly connected by a titanium alloy clamp, and the contact surface is coated with thermal conductive silicone grease (Dow Corning DC-340) to ensure consistent heat transfer. The sampling rate is configured to 5kHz (to meet the Nyquist theorem for capturing 300Hz power frequency harmonics).

[0068] The signal processing chain includes: pre-filtering, using an 8th-order elliptic filter (Q=50), with a passband of 59.5-60.5Hz and a stopband attenuation >80dB; lock-in amplification, using a Stanford Research SR830 digital lock-in amplifier, with the reference signal source connected to the power grid phase synchronization module (accuracy 0.001°); and temperature compensation, with a built-in Pt1000 temperature sensor, real-time correction using the formula V_corr=V_raw*[1+0.00385*(T-25)], where Q represents the quality factor, V_corr represents the final voltage after temperature drift correction, V_raw represents the uncorrected voltage output by the lock-in amplifier, and T represents the real-time measured probe temperature.

[0069] The physical mechanism by which power grid frequency vibrations are transmitted to optical cables involves three layers of coupling: electromagnetic induction, alternating magnetic field generated by 50Hz power frequency current, and electromagnetic induction. Magnetostriction; the steel armor of the optical cable undergoes [restriction / expansion] in a magnetic field. Periodic deformation; stress-light coupling, deformation via the Poisson effect. Converted into fiber refractive index change B represents the magnetic flux density, μ0 represents the free magnetic permeability, I represents the instantaneous current in the conductor, r represents the perpendicular distance from any point in the magnetic field to the conductor, λ represents the magnetostrictive strain, ΔL represents the absolute elongation of the steel armor, L represents the original length of the steel armor, and E represents the electrical energy.

[0070] Preferably, S110 includes sub-step S111, which monitors the mechanical vibration corresponding to a preset characteristic frequency in the optical fiber link to obtain the environmental phase noise. The mechanical vibration is used to characterize the signal vibration caused by power frequency electromagnetic interference.

[0071] Environmental phase noise specifically refers to the periodic phase jitter phenomenon induced by power frequency electromagnetic fields (50Hz or 60Hz) in optical fiber links. Its physical essence is that power frequency alternating current generates an alternating magnetic field. Magnetostriction effect induced by the steel armor of optical fibers This leads to axial strain in the optical fiber. This modulates the refractive index through the elasto-optic effect. Ultimately, this manifests as phase fluctuations in the optical signal. This noise exhibits strict periodicity (frequency fluctuation < ±0.1 Hz) and amplitude stability (fluctuation < 3%), serving as a natural fingerprint. Its necessity lies in: establishing a noise baseline for designing covert detection signals; eliminating the impact of phase noise on the bit error rate of qubits (measured to reduce QBER by 30%); and providing a non-replicable physical reference for eavesdropping detection. Let σ represent the Poisson term of the optical coefficient, σ represent the mechanical stress per unit area force, ε represent the axial strain of the optical fiber, Δφ represent the phase change of the optical signal, φ represent the phase of the optical signal, and QBER represent the bit error rate of the quantum bit.

[0072] During execution, a triaxial MEMS accelerometer (ADXL1002) is mounted on the fiber tension release point, with the sensing axis parallel to the fiber axis. A titanium alloy clamp applies a torque of 85 N·m to ensure rigid coupling, and the contact surface is coated with 50 μm of thermally conductive silicone grease (DowCorning DC-340) to optimize heat transfer. After preprocessing by a 4th-order Butterworth bandpass filter (45-65 Hz), the signal is digitized by a 16-bit ADC (ADS8860) at a sampling rate of 5 kHz. Finally, the dominant frequency component is extracted by a real-time FFT processor (Xilinx RFSoC), where FFT stands for Fast Fourier Transform.

[0073] Furthermore, S111 includes sub-steps S111a~S111c:

[0074] S111a: Obtain the original vibration signal generated by the axial vibration of the optical fiber in the optical fiber link.

[0075] Axial vibration refers to the periodic deformation of the optical fiber along its length (amplitude 0.1-1 μm), directly induced by the electromagnetic extensibility effect. A piezoelectric accelerometer (PCB 393B12) was used for capture, with the following core parameters: sensitivity 100 mV / g, range ±10g, and resonant frequency 22 kHz. During installation, the fiber axis must be strictly aligned (angular deviation <0.5°). The charge signal output from the sensor is converted into a voltage signal (conversion coefficient 1 V / pC) by a charge amplifier (PCB 482C15), and then filtered by an anti-aliasing filter (8th-order elliptic filter, cutoff frequency 500 Hz) to suppress high-frequency noise. ADC sampling uses a synchronous trigger mode (time base jitter <1 ns), with a sampling rate of 5 kHz satisfying the Nyquist theorem (maximum analysis frequency 2.5 kHz). Raw data is stored in a circular buffer (depth 10,000 points). This step preserves the complete vibration spectrum characteristics (0-2.5 kHz), avoiding information loss due to pre-filtering and laying the foundation for subsequent accurate spectrum analysis.

[0076] S111b performs a fast Fourier transform on the original vibration signal to obtain the dominant frequency component.

[0077] The Fast Fourier Transform (FFT) uses the Radix-2 algorithm. The execution flow of S111b includes: loading 1024 points of time-domain data; adding a Hanning window (w[n]=0.5-0.5cos(2πn / N)) to suppress spectral leakage; butterfly operation (5120 complex multiplications); calculating the modulus spectrum |X[k]|, where X[k] represents the complex spectrum.

[0078] The dominant frequency component is defined as a peak value that meets two conditions: amplitude > 3 times that of adjacent frequency points (ensuring significance); and frequency within the power frequency range (49.5-50.5Hz for a 50Hz system). The processor used is a Xilinx Zynq UltraScale+ RFSoC, with a computation time of 5μs (500MHz clock speed) and an output spectral resolution of 4.88Hz / bin. This step transforms the vibration time-domain characteristics into a frequency-domain energy distribution, accurately pinpointing power frequency interference as the core noise source.

[0079] S111c, if the frequency of the dominant frequency component is within the preset power grid fundamental frequency range, and the frequency fluctuation amplitude of the dominant frequency component is less than the preset fluctuation range, the original vibration signal is determined as environmental phase noise.

[0080] When the frequency of this component is detected to be constant within the power grid fundamental frequency range (50Hz or 60Hz, for example, [49.5, 50.5]Hz) and the frequency fluctuation amplitude is less than ±0.1Hz, this frequency is marked as the environmental characteristic frequency; the historical average amplitude of this component is recorded as a reference value.

[0081] S120 generates a detection disturbance signal. The frequency of the detection disturbance signal is lower than the characteristic frequency of the environmental phase noise, and the amplitude of the detection disturbance signal is lower than the amplitude of the environmental phase noise.

[0082] Configure the signal generator to output a sine wave signal with an amplitude of less than 5 milliradians, and set its frequency to less than one-thousandth of the characteristic frequency value (e.g., when the characteristic frequency is 60Hz, the detection frequency is ≤0.06Hz); connect this sine wave signal to the bias voltage control terminal of the phase modulator so that it modulates the optical phase together with the communication signal.

[0083] In the feedback control loop, an ultra-low frequency sinusoidal modulation signal is superimposed, that is, a configured sinusoidal signal. Its frequency is much lower than the ambient noise (60Hz), so it does not interfere with communication. Its amplitude is extremely small and does not affect the stability of the system. The generated detection disturbance signal is lower than the lower limit of the mechanical resonant frequency of the eavesdropping device actuator, making it difficult for the eavesdropper to separate and identify it.

[0084] Preferably, S120 includes sub-steps S121 to S125:

[0085] S121, the dominant frequency component of mechanical vibration is extracted through spectrum analysis to obtain the characteristic frequency of environmental phase noise.

[0086] The characteristic frequency is precisely located using the spectral centroid algorithm, and the FFT results of S111b are reused during execution to avoid redundant calculations. The characteristic frequency will serve as the design benchmark for the probe signal frequency, and its physical meaning is the accurate mapping of the power grid frequency in the optical fiber system with an error of <0.01Hz.

[0087] Specifically, S121 includes sub-step S121a: if the frequency of the dominant frequency component is within the preset power grid base frequency range, and the frequency fluctuation amplitude of the dominant frequency component is less than the preset fluctuation range, then the frequency of the dominant frequency component is determined as the characteristic frequency of the environmental phase noise.

[0088] S122, determine the reference amplitude of the environmental phase noise based on the environmental phase noise.

[0089] Specifically, S122 includes sub-step S122a, which determines the reference amplitude of the ambient phase noise based on the average amplitude of the dominant frequency component.

[0090] When the frequency of this component is detected to be constant within the power grid fundamental frequency range (50Hz or 60Hz) and the frequency fluctuation amplitude is less than ±0.1Hz, this frequency is marked as the environmental characteristic frequency; the historical average amplitude of this component is recorded as a benchmark reference value.

[0091] S123, the characteristic frequency of the environmental phase noise is scaled according to a preset first scaling factor formula to obtain a frequency threshold. The first scaling factor formula is:

[0092] ;

[0093] in, The first scaling factor is... T This refers to the time interval between the first verification of quantum data and the current time point for the controller. N To detect the cumulative number of times the disturbance signal is generated, D These are the characteristic frequencies of environmental phase noise;

[0094] S124, the reference amplitude of the environmental phase noise is scaled according to the preset second scaling factor to obtain the amplitude threshold. The maximum value that the second scaling factor can take is one-half.

[0095] S125 generates a sinusoidal probe disturbance signal based on a frequency threshold and an amplitude threshold, such that the frequency of the probe disturbance signal is less than the frequency threshold and the amplitude of the probe disturbance signal is less than the amplitude threshold.

[0096] The sine wave generation uses direct digital synthesis (DDS) technology, and the signal generator is configured to output a sine wave signal with an amplitude value of less than 5 milliradians, and its frequency is set to less than one-thousandth of the characteristic frequency value (e.g., when the characteristic frequency is 60Hz, the detection frequency is ≤0.06Hz).

[0097] S130 injects the probe perturbation signal into the phase control loop of quantum communication.

[0098] Preferably, S130 includes sub-step S131: superimposing the detected disturbance signal onto the drive signal of the phase modulator of the phase control loop.

[0099] The injection point is selected at the drive terminal of the phase modulator (iXblue MXER-LN-10), physically located between the PID controller output and the modulator's high-voltage amplifier. Signal superposition is achieved using an analog adder (ADI AD813).

[0100] S140, acquires the control response signal of the phase control loop. The control response signal is the signal output by the phase control loop to compensate for the detection disturbance signal and the environmental phase noise.

[0101] Preferably, S140 includes sub-step S141: determining the control response signal based on the waveform of the voltage output by the output terminal of the feedback controller of the phase control loop changing with time.

[0102] The control response signal refers to the voltage output by the PID controller to compensate for the total disturbance (ambient noise + detection signal). The acquisition point is located on the Vout pin of the PID controller (Analog Devices ADRC401), and it is captured using a 16-bit ADC (ADS8860) at a 1kHz sampling rate. The synchronization clock can be set to a Stanford Research FS725. This signal reflects the system's dynamic compensation behavior for phase disturbances and is one of the core inputs for eavesdropping detection.

[0103] S150 collects physical vibration signals from the fiber optic link.

[0104] Preferably, S150 includes sub-step S151: determining the physical vibration signal based on the waveform of acceleration changing with time output by the vibration sensor of the optical fiber link, and controlling the clock reference of the response signal and the physical vibration signal to originate from the same clock source.

[0105] Physical vibration signals are acquired via a MEMS accelerometer (Bosch BMA456), installed in the same location as the S110. The sensor output, after being conditioned via the IEPE interface, is acquired by a synchronous ADC channel (sampling rate 1kHz). The clock synchronization mechanism includes: a time base source, outputting a PPS (pulses per second) signal at the same clock; synchronization error <1ns (White Rabbit protocol); data alignment, and hardware-triggered sampling (trigger delay <5ns). This signal provides the physical vibration truth independent of the control loop, used to verify whether the natural characteristics of environmental noise have been disrupted. Quantum communication includes a receiver (sender) and a controller, where the receiver is also the sender. Quantum data is sent from any sender to any receiver, and the sent quantum data is verified by the controller. When interference occurs, the verification result does not match the measured value of the quantum data, so the quantum data is probabilistically collapsed and reconstructed, which takes longer. Therefore, it is possible to determine whether eavesdropping has occurred by the delay between the physical vibration signal and the control response signal, avoiding the need to perform unitary transformation and verification on massive amounts of quantum data one by one, enhancing the response speed for eavesdropping detection, and making the detection method simpler.

[0106] S160, determine the cross-correlation coefficient between the physical vibration signal and the control response signal, wherein the environmental phase noise is a normal signal extracted without eavesdropping, and the physical vibration signal is a normal signal extracted without eavesdropping or an abnormal signal extracted when eavesdropping is present.

[0107] A suspicious particle is intercepted. The suspicious particle is represented as arbitrary quantum data whose measured value does not match the preset measured value. When the controller receives the qubit state, it informs the eavesdropper of the exact location and measurement basis of the decoy state through a classical channel. The eavesdropper correctly measures the decoy state and sends the result to the controller. Then, the controller can determine whether the decoy state belongs to the eavesdropper based on the measurement result. If it belongs to the eavesdropper, the data is sent to the eavesdropper, and the quantum data of the channel where the eavesdropper is located is probabilistically collapsed and reconstructed. The quantum data transmission of that channel is restarted, and the delay time of the control response signal is sent. If it does not belong to the eavesdropper, the controller jumps to the next suspicious particle. The communication protocol of each channel adopts a common protocol based on the parity of the number of communicating parties.

[0108] Preferably, S160 includes sub-steps S161 to S163:

[0109] S161, Determine the cross-correlation function between the physical vibration signal and the control response signal. The calculation expression for the cross-correlation function is as follows:

[0110] ;

[0111] in, This represents the numerical value of the cross-correlation function between the physical vibration signal and the control response signal. The monitoring duration of any channel at the control side. The time delay between the physical vibration signal and the control response signal. This represents the value of the physical vibration signal at the end of the monitoring period. To control the value of the response signal at the end of the monitoring period, Represented as physical vibration signals, This is represented as a control response signal. Represented as discrete-time index, and It is a positive integer. It is represented by the differential symbol.

[0112] S162, determine the time offset when the cross-correlation function is at its maximum.

[0113] The time offset is the maximum point of the cross-correlation function.

[0114] S163, determine the maximum value of the cross-correlation function based on the time offset, and obtain the cross-correlation coefficient between the physical vibration signal and the control response signal.

[0115] The maximum value of the cross-correlation function is determined as the cross-correlation coefficient between the physical vibration signal and the control response signal.

[0116] Optionally, before S170, the method further includes S164~S169:

[0117] S164, determine whether the cross-correlation number is less than the preset cross-correlation threshold; if the cross-correlation number is greater than or equal to the preset cross-correlation threshold, jump to S165 and execute S165~S166; if the cross-correlation number is less than the preset cross-correlation threshold, execute S170.

[0118] Set a preset cross-correlation threshold, for example, 0.7.

[0119] S165, Obtain the transfer function, which is used to characterize the transfer relationship between the physical vibration signal and the control response signal in the absence of eavesdropping.

[0120] The transfer function H(f) = FFT[F(t)] / FFT[S(t)], where F(t) is the control response signal, S(t) is the physical vibration signal, and FFT is the Fast Fourier Transform.

[0121] S166, determine whether the transfer function has failed based on the physical vibration signal and the control response signal; if the transfer function has failed, proceed to S167; if the transfer function has not failed, proceed to S168.

[0122] The maximum value of the cross-correlation function represents the similarity between the physical vibration signal and the control response signal. The similarity is represented by the similarity in duration. When the similarity exceeds the preset cross-correlation value, the transfer function becomes time-sensitive. The time-sensitive transfer function represents the time-sensitive quantum data transmission of the channel. Then, the quantum data of the channel is probabilistically collapsed and reconstructed.

[0123] Preferably, S166 includes sub-steps S166a to S166d:

[0124] S166a, the sub-signal of the physical vibration signal at the frequency of the detected disturbance signal is determined as the first physical vibration sub-signal. The first physical vibration sub-signal is represented by the first scaling factor of the detected interference signal when the transfer function fails, based on the time point of failure, and the corresponding characteristic frequency is obtained.

[0125] S166b, determine the expected control response sub-signal based on the first physical vibration sub-signal and the transfer function;

[0126] S166c, the sub-signal of the control response signal at the frequency of the detected disturbance signal is determined as the actual control response sub-signal. The actual control response sub-signal is represented by the sum of the failure time point and the delay duration when the transfer function fails. The sum of the failure time point and the delay duration is set as the actual time point. The first scaling factor of the detected interference signal corresponding to the actual time point is calculated, and the corresponding characteristic frequency is obtained.

[0127] S166d determines whether the transfer function is faulty based on the degree of deviation between the expected control response sub-signal and the actual control response sub-signal.

[0128] There are several ways to implement the degree of deviation. For example, |expected control response sub-signal - actual control response sub-signal| / actual control response sub-signal. In this case, the output value can be set to less than 0.2 to indicate a low degree of deviation, and the transfer function will still be valid.

[0129] S170, triggering the eavesdropping alarm.

[0130] S168 determines whether environmental noise is suppressed based on the characteristic frequency of environmental phase noise.

[0131] Preferably, S168 includes sub-steps S168a~S168b:

[0132] S168a, the sub-signal of the physical vibration signal at the characteristic frequency is determined as the second physical vibration sub-signal;

[0133] S168b, if the amplitude of the second physical vibration sub-signal is lower than the preset reference amplitude for a consecutive preset number of sampling periods, then it is determined that the environmental noise is suppressed.

[0134] If the current amplitude is below 70% of the reference value for 10 consecutive sampling periods, it is considered that the environmental characteristics have been damaged, meaning that environmental noise has been suppressed. The reference value can be a preset value or a value set based on the average of historical amplitudes.

[0135] S169. If ambient noise is suppressed, an eavesdropping alarm will be triggered.

[0136] S170, triggering the eavesdropping alarm.

[0137] S170 includes sub-step S171: If the cross-correlation coefficient is less than the preset cross-correlation threshold, and the absolute difference between the time offset and the preset offset threshold is greater than the preset offset value, then trigger the eavesdropping alarm.

[0138] Example of the overall process:

[0139] 1. Identify environmental noise characteristics:

[0140] The vibration sensor is used to measure the axial vibration of the optical fiber and generate a raw vibration signal.

[0141] Perform a fast Fourier transform on the original vibration signal to locate the dominant frequency component;

[0142] When the frequency of this component is detected to be constant within the power grid fundamental frequency range (50Hz or 60Hz) and the frequency fluctuation amplitude is less than ±0.1Hz, this frequency is marked as the environmental characteristic frequency.

[0143] Record the historical average amplitude of this component as a benchmark reference value;

[0144] 2. Generate and inject detection signals:

[0145] Configure the signal generator to output a sine wave signal with an amplitude of less than 5 milliradians, and set its frequency to less than one-thousandth of the characteristic frequency value (e.g., when the characteristic frequency is 60Hz, the detection frequency is ≤0.06Hz).

[0146] The sinusoidal signal is connected to the bias voltage control terminal of the phase modulator so that it modulates the optical phase together with the communication signal.

[0147] 3. Dual-channel synchronous acquisition:

[0148] Channel 1 acquisition point: connected to the output terminal of the feedback controller, recording the waveform of its output voltage changing over time as the control response signal;

[0149] Channel 2 acquisition point: Connect to the output end of the vibration sensor and record the waveform of its output acceleration changing over time as a physical vibration signal;

[0150] Synchronization mechanism: The same clock source is used to provide a time base for both acquisition devices;

[0151] 4. Verification of the persistence of environmental characteristics (criterion 1):

[0152] Real-time calculation of the amplitude of physical vibration signals at environmental characteristic frequencies;

[0153] Judgment criteria: If the current amplitude is lower than 70% of the benchmark reference value for 10 consecutive sampling periods, it is considered that the environmental characteristics have been damaged.

[0154] 5. Control Response Matching Verification (Criterion Two):

[0155] Sub-step 1: During the system initialization phase, inject white noise test signals into the phase modulator and simultaneously acquire physical vibration signals and control response signals;

[0156] Sub-step 2: Calculate the amplitude-frequency response ratio and phase-frequency response difference between the physical vibration signal and the control response signal, and generate a frequency response table;

[0157] Sub-step 3: Real-time extraction of the amplitude and phase of the physical vibration signal at the detection frequency;

[0158] Sub-step 4: Query the frequency response table to obtain the expected control response amplitude and phase at this frequency point;

[0159] Sub-step 5: Real-time measurement of the actual amplitude and phase of the control response signal at the detection frequency;

[0160] Judgment criteria: If the actual amplitude deviates from the expected value by more than 15% or the actual phase deviates from the expected value by more than 20 degrees, it is considered an abnormal control response;

[0161] 6. Verification of dynamic coupling between physical and control signals (criterion three):

[0162] Real-time calculation of the cross-correlation coefficient between the control response signal and the physical vibration signal;

[0163] Find the time offset that maximizes the cross-correlation coefficient;

[0164] Judgment criterion: The maximum cross-correlation value is less than 0.7;

[0165] 7. Comprehensive assessment of eavesdropping behavior:

[0166] When any one of the criteria one, two, or three is met, the eavesdropping alarm protocol is triggered.

[0167] Upon alarm occurrence, immediately halt the current quantum key distribution session; send a switching command to the backup fiber optic link switching control module; locate the start time and duration of the abnormal change in the physical vibration signal; generate a security event log containing an abnormal timestamp, location identifier, and trigger criterion number; and push the alarm code and log file to the security operations and maintenance center via an encrypted network.

[0168] Periodic phase jitter at a fixed frequency (e.g., 60Hz) in quantum communication systems reduces the key generation rate (QBER increases). Traditional systems treat this as purely harmful noise. An eavesdropper (Eve) might exploit this regular noise as cover: by injecting an anti-phase active noise cancellation signal, they can counteract the effects of environmental vibrations on their eavesdropping equipment, making their eavesdropping "invisible" to the system—the system mistakenly perceives the noise as suppressed, when in fact it masks the eavesdropping disturbance.

[0169] Eve installs vibration sensors and piezoelectric actuators at the fiber optic eavesdropping points. It monitors the frequency and phase of environmental vibrations in real time; generates an inverse noise-canceling signal to drive the actuator; and precisely cancels out local vibrations, preventing additional phase disturbances caused by eavesdropping. The system only detects the original environmental noise and cannot detect the presence of eavesdropping (traditional monitoring fails).

[0170] The technical solution of this application transforms the control system itself into an eavesdropping detector—by actively injecting detection disturbances and verifying physical responses, the eavesdropper's noise reduction behavior is exposed.

[0171] The logic for the establishment of criterion one is as follows: This application uses the 60Hz peak that is stably present in the physical vibration signal S(f) as an environmental feature to identify eavesdropping behavior. Eve must suppress this noise in order to hide, and the operation will destroy the original fingerprint (this environmental feature).

[0172] The logic for the second criterion is that Eve cannot accurately counteract the injected probe signal, and its operation causes a significant deviation in the real-time measurement control response signal of the abnormal control response.

[0173] The logic for the validity of criterion three is that Eve's operation would disrupt the system chain that leads to control response due to physical disturbances.

[0174] In practical use, if Eve suppresses the 60Hz component of the original ambient noise, the 60Hz peak that is stable in the physical vibration signal S(f) will disappear or be distorted, thus triggering the above-mentioned criteria one and criteria three; if Eve compensates for the original ambient noise, then the above-mentioned criteria two and criteria three will be triggered.

[0175] Therefore, when system resources are scarce, eavesdropping behavior can be quickly determined based on criterion three, while when system resources are sufficient, a more accurate determination can be made based on criteria one, two, and three.

[0176] This application embodiment identifies environmental phase noise in the fiber optic link of quantum communication, generates a detection disturbance signal, and injects the detection disturbance signal into the phase control loop of quantum communication to superimpose an ultra-low frequency sinusoidal modulation signal into the phase control loop, thereby creating a disturbance in the communication link. This allows for the identification of eavesdropping behavior based on the injected signal without affecting normal signal transmission. After injecting the detection disturbance signal, the control response signal of the phase control loop and the physical vibration signal of the fiber optic link are collected. The cross-correlation coefficient between the physical vibration signal and the control response signal is used to determine whether eavesdropping behavior exists in the communication link. Since physical disturbance triggers control response, the physical vibration signal characterizing the physical disturbance and the control response signal characterizing the control response will necessarily have a strong correlation after the detection disturbance signal is injected. If the cross-correlation coefficient between the physical vibration signal and the control response signal is less than a preset cross-correlation threshold, it indicates that the eavesdropper's operation has caused a break in the time-domain correlation of the quantum communication link, triggering an eavesdropping alarm and thus accurately identifying eavesdropping behavior in the quantum communication process.

[0177] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media containing computer-usable program code. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0178] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A communication warning method based on quantum encryption, characterized in that, The method comprises: identifying environmental phase noise in a fiber link of quantum communication; generating a probe disturbance signal, a frequency of the probe disturbance signal being less than a characteristic frequency of the environmental phase noise, an amplitude of the probe disturbance signal being lower than an amplitude value of the environmental phase noise; injecting the probe disturbance signal into a phase control loop of the quantum communication; collecting a control response signal of the phase control loop, the control response signal being a signal output by the phase control loop for compensating the probe disturbance signal and the environmental phase noise; collecting a physical vibration signal of the fiber link; determining a cross-correlation coefficient of the physical vibration signal and the control response signal; if the cross-correlation coefficient is less than a preset cross-correlation threshold, triggering an eavesdropping alarm.

2. The method of claim 1, wherein, The identifying environmental phase noise in a fiber link of quantum communication comprises: monitoring mechanical vibration corresponding to a preset characteristic frequency in the fiber link to obtain the environmental phase noise, the mechanical vibration being used to represent signal vibration caused by power frequency electromagnetic interference.

3. The method of claim 2, wherein, The generating a probe disturbance signal comprises: extracting a main frequency component of the mechanical vibration by spectrum analysis to obtain the characteristic frequency of the environmental phase noise; determining a reference amplitude of the environmental phase noise according to the environmental phase noise; scaling the characteristic frequency of the environmental phase noise according to a preset first scaling coefficient formula to obtain a frequency threshold, the first scaling coefficient formula being: ； wherein, is a first scaling coefficient, T is a time point interval from a time point when the control party first verifies the quantum data to a current time point, N is a cumulative number of times of generating the detection disturbance signal, D is a characteristic frequency of the environmental phase noise; scaling the reference amplitude of the environmental phase noise according to a preset second scaling coefficient to obtain an amplitude threshold, a maximum value that the second scaling coefficient can take being one half; generating a probe disturbance signal in a sine wave form according to the frequency threshold and the amplitude threshold, so that the frequency of the probe disturbance signal is less than the frequency threshold, and the amplitude of the probe disturbance signal is less than the amplitude threshold.

4. The method of claim 3, wherein, The monitoring mechanical vibration corresponding to a preset characteristic frequency in the fiber link to obtain the environmental phase noise comprises: obtaining an original vibration signal generated by axial vibration of an optical fiber in the fiber link; performing fast Fourier transform on the original vibration signal to obtain a main frequency component; if the frequency of the main frequency component is located in a preset power grid fundamental frequency range, and a frequency fluctuation amplitude of the main frequency component is less than a preset fluctuation range, and the original vibration signal is determined as the environmental phase noise; The extracting a main frequency component of the mechanical vibration by spectrum analysis to obtain the characteristic frequency of the environmental phase noise comprises: if the frequency of the main frequency component is located in a preset power grid fundamental frequency range, and a frequency fluctuation amplitude of the main frequency component is less than a preset fluctuation range, and the frequency of the main frequency component is determined as the characteristic frequency of the environmental phase noise; The determining a reference amplitude of the environmental phase noise according to the environmental phase noise comprises: determining the reference amplitude of the environmental phase noise according to an average amplitude of the main frequency component.

5. The method of claim 4, wherein, The injecting the probe disturbance signal into a phase control loop of the quantum communication comprises: superimposing the probe disturbance signal on a driving signal of a phase modulator of the phase control loop.

6. The method of claim 5, wherein, The method further comprises: acquiring a control response signal of the phase control loop, including: determining the control response signal according to a time-varying waveform of a voltage output by an output end of a feedback controller of the phase control loop; acquiring a physical vibration signal of the optical fiber link, the physical vibration signal being represented as a non-axial vibration signal, including:

7. The method of claim 6, wherein, determining the physical vibration signal according to a time-varying waveform of an acceleration output by an output end of a vibration sensor of the optical fiber link, the clock reference of the control response signal and the physical vibration signal being derived from a same clock source. The method further comprises: determining a cross-correlation coefficient of the physical vibration signal and the control response signal, including: determining a cross-correlation function of the physical vibration signal and the control response signal; determining a time offset at which the cross-correlation function is maximum; determining a maximum value of the cross-correlation function according to the time offset, to obtain the cross-correlation coefficient of the physical vibration signal and the control response signal.

8. The method of claim 7, wherein, The method further comprises: if the cross-correlation coefficient is less than a preset cross-correlation threshold, performing a first operation, the first operation being represented as encrypting quantum data, including: if the cross-correlation coefficient is less than the preset cross-correlation threshold, and an absolute difference between the time offset and a preset offset threshold is greater than a preset offset value, triggering an eavesdropping alarm. The method further comprises, before the step of if the cross-correlation coefficient is less than the preset cross-correlation threshold, and the absolute difference between the time offset and the preset offset threshold is greater than the preset offset value, triggering the eavesdropping alarm: determining whether the cross-correlation coefficient is less than the preset cross-correlation threshold; if the cross-correlation coefficient is greater than or equal to the preset cross-correlation threshold, acquiring a transfer function, the transfer function being used to represent a transfer relationship of transferring the physical vibration signal to the control response signal in a case of no eavesdropping; determining whether the transfer function is invalid according to the physical vibration signal and the control response signal; 9. The method of claim 8, wherein, if the transfer function is invalid, triggering the eavesdropping alarm; if the transfer function is not invalid, determining whether environmental noise is suppressed according to a characteristic frequency of the environmental phase noise; if the environmental noise is suppressed, triggering the eavesdropping alarm. The method further comprises: determining a first physical vibration sub-signal of the physical vibration signal at the frequency of the probe disturbance signal; 10. The method of claim 9, wherein, determining an expected control response sub-signal according to the first physical vibration sub-signal and the transfer function; determining an actual control response sub-signal of the control response signal at the frequency of the probe disturbance signal; determining whether the transfer function is invalid according to a deviation between the expected control response sub-signal and the actual control response sub-signal. The method further comprises: if the transfer function is not invalid, determining a second physical vibration sub-signal of the physical vibration signal at the characteristic frequency; if amplitudes of the second physical vibration sub-signal in a continuous preset number of sampling periods are all lower than a preset reference amplitude, determining that the environmental noise is suppressed.

Images