Bidirectional continuous variable quantum key distribution information negotiation method

Abstract

The invention discloses a bidirectional continuous variable quantum key distribution information negotiation method, which comprises the following steps that: a transmitting end and a receiving end respectively obtain corresponding coherent state information, map the corresponding coherent state information to a complex field, and screen to obtain a subset a and a subset b; the sending end and the receiving end jointly perform bidirectional processing based on the subset a and the subset b to obtain a key ma1 and a key ma2; wherein the bidirectional processing comprises first direction processing and second direction processing, and is used for carrying out joint decoding by sharing check bit information; performing privacy amplification based on the keys ma1 and ma2 to obtain a final key; according to the method, the key rate can be improved, the key inconsistency rate is not increased, and the security of CV-QKD is improved.

Description

Technical Field

[0001] The present invention relates to the field of quantum key distribution technology, and in particular to a bidirectional continuous variable quantum key distribution information negotiation method. Background Art

[0002] With the development of quantum computers, traditional encryption methods face security threats. Quantum Key Distribution (QKD) technology, based on the principles of quantum mechanics, has become one of the solutions. This technology allows two parties, the sender Alice and the receiver Bob, to securely share keys through the cooperation of quantum channels and classical channels in the presence of potential eavesdroppers. QKD technology is divided into two methods: discrete variable (Discrete Variable Quantum Key Distribution, DV-QKD) and continuous variable (Continuous-Variable Quantum Key Distribution, CV-QKD). CV-QKD encodes key information of continuous variables, such as the orthogonality of coherent states, and is particularly suitable for practical applications. With the development of technology, one-time pad technology has also been valued for its security, but the key rate of quantum key distribution is lower than that of normal communication. Therefore, in order to achieve one-time pad and improve the key generation rate, it is necessary to use all quantum signals as much as possible.

[0003] The key process of CV-QKD includes four steps: basis selection, parameter estimation, information negotiation, and privacy amplification. Among them, information negotiation is the focus of improving system performance, and the purpose is to extract consistent bit data from continuous variables. There are currently three mainstream negotiation methods: symbol negotiation, slice negotiation, and multi-dimensional negotiation. However, symbol negotiation and slice negotiation are suitable for high signal-to-noise ratio and short-distance communication; while multi-dimensional negotiation, through efficient error correction codes (such as low-density parity-check codes) to process low signal-to-noise ratio signals, is suitable for long-distance communication.

[0004] Existing quantum key distribution (QKD) protocols, while achieving high key generation rates, often face the problem of high key inconsistency rates; and the protocols mostly rely on one-way quantum signal processing, that is, the sender and receiver independently extract coherent state information from the quantum channel and perform one-way quantization and encoding. Although these protocols can generate keys, in actual applications, due to factors such as quantum channel noise, signal attenuation, and potential eavesdropping, the keys obtained by both parties are often different, resulting in a high key inconsistency rate. Summary of the invention

[0005] The purpose of the present invention is to provide a bidirectional continuous variable quantum key distribution information negotiation method, which enables the sender and the receiver to perform bidirectional processing on the coherent state information obtained through the quantum channel, and after verification, obtain the final sender and the receiver's consistent key, thereby improving the key rate without increasing the key inconsistency rate, thereby improving the security of CV-QKD.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a bidirectional continuous variable quantum key distribution information negotiation method, comprising:

[0008] The transmitting end and the receiving end respectively obtain corresponding coherent state information, and map the corresponding coherent state information to a complex domain, and filter out subset a and subset b;

[0009] The sender and the receiver perform two-way processing based on subset a and subset b to obtain the key. and ; Wherein, the bidirectional processing includes a first direction processing and a second direction processing, which is used to perform joint decoding by sharing check bit information;

[0010] Key-based and Perform privacy amplification and obtain the final key.

[0011] Optionally, the first direction processing process includes:

[0012] The receiving end quantizes the subset b and encodes it after interleaving to obtain the key. and check digit , based on the key Calculate the test sequence And the test sequence and check digit transmitting to the sender via a first error-free channel;

[0013] The sender quantizes and interleaves subset a and uses the received check bits The quantization results and test sequences after interleaving Decode and get ;Will De-interleave and extract the most reliable bits to get the key .

[0014] Optionally, the receiving end quantizes the subset b and encodes it after interleaving to obtain the key and check digit ,include:

[0015] The receiving end quantizes subset b and obtains the quantization result , and the quantitative results Split into most reliable bits and the least reliable bit ; Use a random interleaver to Perform interleaving to obtain And encode to get the key and check digit .

[0016] Optionally, the second direction processing process includes:

[0017] The receiving end generates a random key , and then set the check bit As a frozen bit pair key After encoding, modulation is performed to obtain the modulation result ; The receiving end will normalize the subset b and the modulation result Perform M mapping transformation to obtain result S, and transmit it to the sender through the second channel;

[0018] The sender performs an inverse transformation on the subset a and the result received from the second error-free channel, and then demodulates to obtain the demodulation result , and based on the check digit The demodulation result Decode to get the key .

[0019] Optionally, the second direction processing process further includes:

[0020] The receiving end generates a random key , and then set the check bit As a frozen bit pair key After encoding, modulation is performed to obtain the modulation result ; The receiving end combines subset b and the modulation result The result S is obtained by performing a sign extension transformation and transmitted to the sender through an AWGN channel;

[0021] The sender performs an inverse transformation on the subset a and the result received from the AWGN channel, and then demodulates the result to obtain the demodulation result. , and based on the check digit The demodulation result Decode to get the key .

[0022] Optionally, the transmitting end and the receiving end respectively obtain corresponding coherent state information, and map the corresponding coherent state information to a complex domain, and filter to obtain a subset a and a subset b, including:

[0023] The coherent state information of the transmitter and the coherent state information of the receiver are mapped to the complex domain to obtain set A and set B respectively;

[0024] Calculate the modulus of the coherent state elements in set A and set B respectively, and use the probability density function to obtain the probability density value corresponding to the coherent state element;

[0025] Based on the set threshold, the coherent state elements above the threshold are screened to obtain subsets a and subset b.

[0026] Optionally, the sender quantizes the subset a by calculating the log-likelihood ratio, and the calculation formula is as follows:

[0027] ;

[0028] in, is the quantized bit, i.e., the calculated codeword information is sent on the i-th channel; is the log-likelihood ratio corresponding to the i-th channel.

[0029] Optionally, the step of quantizing the subset b at the receiving end includes:

[0030] A quantization threshold is set according to the characteristics of the complex Gaussian variable in subset b, and a protection band is set according to the noise level, that is, an additional range is defined to reduce the erroneous judgment caused by noise, and the complex plane is evenly divided into Q quantization regions;

[0031] Gray code is used to map in the quantization area to obtain the quantization result.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a bidirectional continuous variable quantum key distribution information negotiation method, which enables a sender and a receiver to bidirectionally process coherent state information obtained through a quantum channel, and obtain a key that is consistent with that of the sender and the receiver after verification, thereby improving the key rate without increasing the key inconsistency rate, thereby improving the security of CV-QKD; by dynamically adjusting the quantization threshold, adopting polarization coding and soft decision decoding, and introducing a random interleaver, the key generation rate and robustness can be improved under different channel conditions, the influence of continuous errors can be reduced, and reliable consistent keys can be generated under high bit error rates and complex channel environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a schematic diagram of the key distribution information negotiation method flow in an embodiment of the present invention;

[0035] Figure 2 The figure is a schematic diagram of a bidirectional processing flow in an embodiment of the present invention;

[0036] Figure 3 The figure shows the key rate comparison of the two-way negotiation method under different code lengths and code rates;

[0037] Figure 4 The figure shows the comparison of key inconsistency rates of the two-way negotiation method under different code lengths and code rates. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0039] Example 1

[0040] like Figure 1 As shown, the embodiment of the present invention introduces a bidirectional continuous variable quantum key distribution information negotiation method, comprising the following steps:

[0041] S1: The transmitter and the receiver respectively obtain the corresponding coherent state information, and map the corresponding coherent state information to the complex domain, and filter out subsets a and subsets b;

[0042] S2: The sender and the receiver perform bidirectional processing based on subset a and subset b to obtain the key m a1 and m a2 ; Wherein, the bidirectional processing includes a first direction processing and a second direction processing, which is used to perform joint decoding by sharing check bit information;

[0043] S3: Based on key m a1 and m a2 Perform privacy amplification and obtain the final key.

[0044] A bidirectional continuous variable quantum key distribution information negotiation method provided by the present invention enables the sender and the receiver to perform bidirectional processing on the coherent state information obtained through the quantum channel, and obtain the final sender and the receiver's consistent key after verification, thereby improving the key rate without increasing the key inconsistency rate, thereby improving the security of CV-QKD.

[0045] In this embodiment, in step S1, the transmitting end and the receiving end respectively obtain corresponding coherent state information, and map the corresponding coherent state information to a complex domain, and filter out subsets a and subsets b, including:

[0046] S11: Map the coherent state information of the transmitter and the coherent state information of the receiver to the complex domain to obtain a set A and a set B respectively;

[0047] Specifically, first, the transmitter and receiver share coherent state information through the quantum channel. The coherent state information sent by the transmitter is xi , the coherent state information received by the receiver through the quantum channel is y i =x i +n, where n is noise and i is the index in the coherent state sequence, forming the coherent state sequence of the transmitter and the coherent state sequence of the receiver; then, the elements in the coherent state sequence of the transmitter and the coherent state sequence of the receiver are combined in pairs and mapped to the complex domain, , , is the code length, and we get the set A and set B ;

[0048] S12: Calculate the modulus of the coherent state elements in set A and set B respectively , and use the probability density function to obtain the probability density value corresponding to the coherent state element;

[0049] Specifically, the formula for calculating the modulus length is a conventional formula, which will not be described in detail here; in this embodiment, the formula of the probability density function is expressed as follows:

[0050]

[0051] in, is the mean of the modulus values, is the standard deviation of the modulus is the modulus of the coherent state element, which can be substituted here , calculated by the coherent state elements in set A or set B;

[0052] S13: Based on the set threshold, coherent state elements above the threshold are screened to obtain subset a and subset b.

[0053] In this embodiment, if Figure 2 As shown, the specific steps of the bidirectional processing in step S2 include:

[0054] (1) Processing in the first direction:

[0055] The receiving end Bob first performs a query on the subset b, which is the Quantify , and then Split into most reliable bits and the least reliable bit , and then use a random interleaver to Interleaving (i.e. Figure 2 ), we get And encode to get the key and check digit , based on the key Calculate the test sequence And the test sequence and check digit Transmitted to sender Alice via an error-free channel;

[0056] The sender Alice pairs the subset a, i.e. Quantize (LLR), calculate the LLR of the least reliable bit in subset a and get , using the same random interleaver pair Interleave processing is performed and the received check bit is used The quantization result after interleaving Check sequence Decode (CRC check successful) to get ,Will De-interlacing (i.e. Figure 2 The deinterleaver process shown in Figure 2 extracts the most reliable bits to obtain the key.

[0057] (2) Second direction processing:

[0058] Due to the diversity of channel environments for quantum key distribution, two schemes are designed for error-free channels and noisy channels to improve the adaptability and performance of the system. Scheme A optimizes data transmission through normalization and M mapping, which is suitable for error-free channels to maximize the key rate; while scheme B enhances noise resistance through sign extension transformation, which is suitable for noisy channels to ensure the reliability of key generation. The design of the two schemes enables the system to take into account both transmission efficiency and security under different channel conditions.

[0059] In summary, the second direction processing process can adopt scheme A and scheme B, which are as follows:

[0060] Option A:

[0061] The receiving end Bob randomly generates a key , and the check bit generated during the first direction processing As a frozen bit pair key Encode to get , and then the encoding result Modulate and get the modulation result ; The receiving end will normalize the subset b and the modulation result Perform M mapping transformation to obtain result S, and transmit it to the sender through the second channel;

[0062] The sender Alice combines the subset a and the result received from the second error-free channel After inverse transformation (reverse transformation), we get ,Will Demodulation to get the demodulation result , and based on the check digit The demodulation result Decode (CRC check successful) to get the key .

[0063] Specifically, Scheme A shows a higher key generation rate in error-free channels because the data is optimized through normalization and M-mapping, which reduces transmission redundancy and improves key generation efficiency. In a noise-free environment, a low key inconsistency rate is guaranteed, while greatly improving the efficiency of the system.

[0064] Option B:

[0065] The receiving end Bob randomly generates a key , and the check bit generated during the first direction processing As a frozen bit pair key Encode to get , and then the encoding result Modulate and get the modulation result ; The receiving end combines subset b and the modulation result The result S is obtained by performing a sign extension transformation and transmitted to the sender through an AWGN channel;

[0066] The sender Alice combines the subset a and the result received from the AWGN channel After inverse transformation (reverse transformation), demodulation obtains the demodulation result , and based on the check digit The demodulation result Decode (CRC check successful) to get the key .

[0067] Specifically, in the noisy AWGN channel, scheme B enhances the anti-noise capability through the symbol extension transformation, and can maintain a high key generation reliability even under complex channel conditions. While improving the channel adaptability, a certain key generation rate may be sacrificed, but the consistency and security of the data are guaranteed.

[0068] Specifically, the receiving end first performs a b Quantify The detailed process includes:

[0069] Based on step S1, After that, the corresponding amplitude and phase are calculated and the complex plane is evenly divided into 2 by setting the quantization threshold. 2quantized regions and uses Gray code mapping to allocate 2 bits in each region, which enables 2 bits to be generated from the phase information. Therefore, this process can be understood as a demodulation process similar to that of PSK modulation symbols.

[0070] Specifically, in the second direction processing, the scheme A: the receiving end combines the normalized subset b and the modulation result Perform M mapping transformation to obtain the result S, which specifically includes:

[0071] right Normalize:

[0072]

[0073] In the formula, is the norm of the corresponding data.

[0074] Using the reverse coordination framework, the receiving end Bob generates the original information, adds CRC check bits to the original information, widens the information length to K, and obtains the original key information , calculate the reliability of each channel through reliability estimation, sort the channels, and transmit data information to the channels with reliability higher than the first threshold , the channel with reliability lower than the first threshold transmits frozen bit information , when the codeword is initially generated, the frozen bit All are set to 0. Thus, the information and frozen bits are combined to form the original codeword ;

[0075] The channel coding in the present invention adopts the systematic polar coding (Systematic Polar Code) and uses the secondary coding method to encode the original codeword. First, the original codeword The first time it is fed into the encoder, the sequence b = uG is obtained. For the frozen bit position in sequence b, the frozen bit information is refilled , and get the sequence , convert the sequence Send it to the encoder again to calculate the final system codeword ; Where G is the generator matrix of the Polar code, which is calculated by the Kronecker product , ,

[0076] Codewords for the system Grouping, each d bit forms a group of vectors , and get the d-dimensional modulated sequence , the vector Perform d-dimensional mapping processing with the normalized coherent state information at the receiving end to obtain the mapping relationship between the two , and satisfies , where is a vector, is the normalized coherent state information at the receiving end;

[0077] Based on the mapping relationship between the two , and get the result S.

[0078] Specifically, the sender Alice quantizes the subset a, i.e., Za in the figure (LLR) to obtain , including:

[0079] The transmitter (Alice) calculates the channel log likelihood ratio according to the mapping relationship and sends the channel log likelihood ratio to the system code decoder to obtain the decoding result , the specific steps are:

[0080] The sender Alice receives the mapping relationship , calculate codeword information , and calculate the maximum likelihood ratio corresponding to the channel. The specific formula of the channel log likelihood ratio is:

[0081]

[0082] in, is the quantized bit, i.e., the codeword information calculated at the transmitting end of the i-th channel; is the log-likelihood ratio corresponding to the i-th channel.

[0083] Alice, the transmitter, decodes the system code according to the channel log-likelihood ratio (LLR) information. System code decoding needs to be completed through a decoder and an encoder. The channel log-likelihood ratio (LLR) is sent to the decoder to obtain the decoded information. , the decoded information It is sent to the encoder again to obtain information m, and the information of the information bit position in information m is taken out. After passing the CRC check, the final decoding result, i.e. the key, is formed. .

[0084] Example 2

[0085] The embodiment of the present invention provides a simulation comparison experiment. After simulating the two-way negotiation method proposed by the present invention and the traditional multi-dimensional negotiation method under different code lengths N and code rates K, the following results are obtained: Figure 3 The key rate comparison diagram of the two-way negotiation method under different code lengths shown in FIG. Figure 4 The figure shows a comparison of key inconsistency rates of the two-way negotiation method under different code lengths.

[0086] The two-way negotiation method (a two-way continuous variable quantum key distribution information negotiation method) proposed in the present invention selects the corresponding negotiation method, M mapping or sign extension transformation, according to different channel conditions. Therefore, the present invention conducts simulation experiments on two-way negotiation using M mapping in an error-free channel and two-way negotiation using sign extension in an AWGN channel for these two situations, and obtains the following results: Figure 3 Figure 4 The simulation results are as follows. Specifically, the bidirectional M mapping and bidirectional sign extension transformation in the figure represent the bidirectional negotiation method proposed in the present invention. From the analysis of the simulation results shown in the figure, it can be concluded that the use of the bidirectional negotiation method significantly improves the key generation efficiency of continuous variable quantum key distribution while maintaining a low key inconsistency rate.

[0087] Specifically, compared with the traditional M-mapping method, the two-way negotiation can achieve nearly twice the key rate (SKR) when the signal-to-noise ratio increases without increasing the key inconsistency rate (KIR). In addition, the two-way method combined with sign extension further reduces the amount of information that needs to be transmitted on the error-free channel. Although this improvement comes at the cost of a slight increase in the inconsistency rate, it provides additional advantages by reducing communication costs and improving system adaptability. The simulation results verify the performance improvement of the two-way negotiation method and show that it can flexibly balance the key generation rate, consistency and communication efficiency under different channel conditions, providing an effective solution for the practical application of CV-QKD systems.

[0088] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A bidirectional continuous variable quantum key distribution information negotiation method, characterized in that: include: The transmitting end and the receiving end respectively obtain corresponding coherent state information, and map the corresponding coherent state information to a complex domain, and filter out subset a and subset b; The sender and the receiver perform two-way processing based on subset a and subset b to obtain the key. and ; Wherein, the bidirectional processing includes a first direction processing and a second direction processing, which is used to perform joint decoding by sharing check bit information; Key-based and Perform privacy amplification and obtain the final key.

2. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 1, characterized in that: The first direction processing process includes: The receiving end quantizes the subset b and encodes it after interleaving to obtain the key. and check digit , based on the key Calculate the test sequence And the test sequence and check digit transmitting to the sender via a first error-free channel; The sender quantizes and interleaves subset a and uses the received check bits The quantization results and test sequences after interleaving Decode and get ;Will De-interleave and extract the most reliable bits to get the key .

3. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 2, characterized in that: The receiving end quantizes the subset b and encodes it after interleaving to obtain the key and check digit ,include: The receiving end quantizes subset b and obtains the quantization result , and the quantitative results Split into most reliable bits and the least reliable bit ; Use a random interleaver to Perform interleaving to obtain And encode to get the key and check digit .

4. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 3, characterized in that: The second direction processing process includes: The receiving end generates a random key , and then set the check bit As a frozen bit pair key After encoding, modulation is performed to obtain the modulation result ; The receiving end will normalize the subset b and the modulation result Perform M mapping transformation to obtain result S, and transmit it to the sender through the second channel; The sender performs an inverse transformation on the subset a and the result received from the second error-free channel, and then demodulates to obtain the demodulation result , and based on the check digit The demodulation result Decode to get the key .

5. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 2, characterized in that: The second direction processing process further includes: The receiving end generates a random key , and then set the check bit As a frozen bit pair key After encoding, modulation is performed to obtain the modulation result ; The receiving end combines subset b and the modulation result The result S is obtained by performing a sign extension transformation and transmitted to the sender through an AWGN channel; The sender performs an inverse transformation on the subset a and the result received from the AWGN channel, and then demodulates the result to obtain the demodulation result. , and based on the check digit The demodulation result Decode to get the key .

6. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 1, characterized in that: The transmitting end and the receiving end respectively obtain corresponding coherent state information, and map the corresponding coherent state information to a complex domain, and screen to obtain a subset a and a subset b, including: The coherent state information of the transmitter and the coherent state information of the receiver are mapped to the complex domain to obtain set A and set B respectively; Calculate the modulus of the coherent state elements in set A and set B respectively, and use the probability density function to obtain the probability density value corresponding to the coherent state element; Based on the set threshold, the coherent state elements above the threshold are screened to obtain subsets a and subset b.

7. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 2, characterized in that: The sender quantifies the subset a by calculating the log-likelihood ratio. The calculation formula is as follows: ； in, is the quantized bit, i.e., the calculated codeword information is sent on the i-th channel; is the log-likelihood ratio corresponding to the i-th channel.

8. The bidirectional continuous variable quantum key distribution information negotiation method according to claim 2, characterized in that: The steps of quantizing subset b at the receiving end include: A quantization threshold is set according to the characteristics of the complex Gaussian variable in subset b, and a protection band is set according to the noise level, that is, an additional range is defined to reduce the erroneous judgment caused by noise, and the complex plane is evenly divided into Q quantization regions; Gray code is used to map in the quantization area to obtain the quantization result.

Images