Low complexity continuous variable quantum key distribution information negotiation method

Abstract

The application discloses a low-complexity continuous variable quantum key distribution information negotiation method, and relates to the technical field of quantum communication.The method comprises the following steps: generating a random Gaussian sequence at a Bob end; adding the random Gaussian sequence to an original Gaussian sequence at the Bob end and sending the added Gaussian sequence to an Alice end; quantizing the random Gaussian sequence into multiple slices; directly sending a low-bit slice to the Alice end; and sending a high-bit slice to the Alice end; calculating an estimation function and a log-likelihood ratio of each layer according to received data at the Alice end; decoding according to the calculated log-likelihood ratio and the check sub calculated at the Bob end; leaving a decoded successful key string as a key of the Alice end after multiple iterations; and discarding a decoded failed key string and a directly sent low-bit key string.The method provided by the application is suitable for a reverse negotiation mechanism.

Description

Technical Field

[0001] This invention relates to quantum communication technology, and in particular to a low-complexity continuous-variable quantum key distribution information negotiation method. Background Technology

[0002] The CV-QKD (Continuous Variable Quantum Key Distribution) system solves the problem of non-unconditionally secure key distribution in classical cryptography, enabling real-time one-time pad unconditionally secure key distribution between legitimate communicating parties.

[0003] Post-processing in CV-QKD systems is crucial for improving key rates. Information negotiation is a vital step in post-processing, primarily used to correct inconsistencies in keys between legitimate communicating parties using error-correcting codes. However, this error correction process requires both parties to transmit data over a public channel, making them vulnerable to collective attacks by eavesdroppers.

[0004] Traditional information negotiation algorithms mainly include two types: multidimensional negotiation algorithms and slice negotiation algorithms. Among them, multidimensional negotiation algorithms can achieve high negotiation efficiency in long-distance CV-QKD systems with extremely low signal-to-noise ratios, but their post-processing algorithms are complex, and they extract less than 1 bit of key information per pulse, resulting in a low key rate. The key rate refers to the success rate of key string decoding. Slice negotiation algorithms can extract more than 1 bit of key information per pulse, but they are greatly affected by noise, and their key rate decreases significantly with increasing communication distance.

[0005] To address the aforementioned issues, Chinese patent document CN112886970B discloses a negotiation method for continuous variable quantum key distribution. This method uses the highest-order bit for multi-dimensional negotiation and the remaining bits for slice negotiation. Compared to traditional multi-dimensional negotiation algorithms and slice negotiation algorithms, this composite negotiation method improves information negotiation efficiency and final key rate. However, due to the significantly increased complexity of data post-processing, its information negotiation efficiency remains relatively poor. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, the technical problem to be solved by the present invention is to provide a low-complexity continuous-variable quantum key distribution information negotiation method with high final key rate, low data post-processing complexity, and high information negotiation efficiency.

[0007] To address the aforementioned technical problems, this invention provides a low-complexity continuous-variable quantum key distribution information negotiation method. This negotiation method includes a reverse negotiation mechanism, characterized by the following specific steps:

[0008] Step 1: In the reverse negotiation mechanism, after quantum transmission and basis comparison, Alice's end and Bob's end obtain a pair of original Gaussian sequences that follow a Gaussian distribution, where Alice's end is the sender and Bob's end is the receiver.

[0009] The original Gaussian sequence at the Alice end is , among them The modulation variance at the Alice end;

[0010] The noise of the quantum channel is , The noise variance of the quantum channel;

[0011] The original Gaussian sequence at Bob's end is y = x + z, which satisfies ;

[0012] Step 2: Randomly generate a Gaussian sequence at the Bob end. And send c+y to Alice's end;

[0013] Step 3: Bob's end quantizes and splits the Gaussian sequence c into m original key strings. and will the former Original key string It is sent directly to Alice, and calculated according to the pre-set error correction code. Original key string Proofreading and the calculated The checksum of the original key string Send to Alice;

[0014] Step 4: Alice subtracts its original Gaussian sequence x from the received c+y to obtain c', sets an inter-layer iteration threshold T=1, and constructs an initially empty key string sequence U. The received original key string... Included in the key string sequence U;

[0015] Step 5: Let ;

[0016] Step 6: Alice calculates the result using c' and all the keys in the key string sequence U. The estimated function of the layer is calculated, and the calculated function is used to calculate the layer. The log-likelihood ratio of the layer;

[0017] Then based on the calculation The layer log-likelihood ratio and the checksum sent by Bob's end conduct Layer decoding, after which Alice's end is obtained. Layer decoding key string ;

[0018] Then use the Alice side Layer decoding key string Calculate Alice's end Layer checker And calculate the Alice end's Layer checker The verification code sent by Bob Compare them; if they match, then determine... If the layer decoding is successful, then Alice's end will be... Layer decoding key string Define it as a valid key string for decoding; otherwise, determine... If layer decoding fails, then Alice's end will be... Layer decoding key string

[0019] Defined as an invalid key string for decoding;

[0020] Step 7: If Then the Alice end obtained from step 6 will be decoded. Layer decoding key string Substitute into the key string sequence U, so that the decoding key string Become the last key in the key string sequence U, and let Then proceed to step 6;

[0021] if Then, delete the last key string from the key string sequence U, and then decode the Alice end obtained in step 6. Layer decoding key string Substitute into the key string sequence U, so that the decoding key string Become the last key in the key string sequence U, and let Then proceed to step 6;

[0022] if Then proceed to step 8;

[0023] Step 8: If Alice successfully decodes each layer, Alice sets all valid decoded key strings as its key, so that Alice and Bob obtain a symmetric key, and this round of information negotiation ends. Otherwise, proceed to step 9.

[0024] Step 9: If the value of the inter-layer iteration threshold T is less than the preset iteration upper limit, then let T = T + 1, clear the key string sequence U, and then go to step 5; otherwise, go to step 10.

[0025] Step 10: Alice sets all valid decoded key strings to Alice's key, and this round of information negotiation ends.

[0026] The present invention provides a low-complexity continuous-variable quantum key distribution information negotiation method. Bob's end uses a quantum random number generator to generate a new random Gaussian sequence, adds it to the quantum sequence, and sends it to Alice's end. Simultaneously, Bob's end quantizes and segments the new Gaussian sequence to obtain the key string, then sends the low-order slices to Alice's end, and sends the checksums calculated from the high-order slices to Alice's end. Alice's end first estimates each layer of slices, and then completes decoding based on the checksums. Compared with existing information negotiation algorithms, this method treats the original quantum sequence as known noise, and by adding a new Gaussian sequence, the generated key sequence has a higher variance, thereby reducing the noise impact in information negotiation. It achieves a low frame error rate under a high signal-to-noise ratio, improving the final key rate of the system. Furthermore, the addition operation between the quantum sequence and the key sequence effectively reduces the complexity of data post-processing, and the information negotiation efficiency is relatively high. Attached Figure Description

[0027] Figure 1 This is a negotiation diagram of the low-complexity continuous variable quantum key distribution information negotiation method according to an embodiment of the present invention. Detailed Implementation

[0028] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. However, these embodiments are not intended to limit the present invention. Any similar structures or variations thereof that adopt the present invention should be included in the protection scope of the present invention. The commas in the present invention all indicate the relationship between and. The English letters in the present invention are case-sensitive.

[0029] Information negotiation methods are generally divided into forward negotiation and reverse negotiation. Forward negotiation uses the data of the sending end Alice as a reference to correct the data of the receiving end Bob, while reverse negotiation uses the data of the receiving end Bob as a reference to correct the data of the sending end Alice.

[0030] like Figure 1 As shown in the embodiment of the present invention, a low-complexity continuous-variable quantum key distribution information negotiation method is provided. This negotiation method includes a reverse negotiation mechanism, and its specific steps are as follows:

[0031] Step 1: In the reverse negotiation mechanism, after quantum transmission and basis comparison, Alice's end and Bob's end obtain a pair of original Gaussian sequences that follow a Gaussian distribution, where Alice's end is the sender and Bob's end is the receiver.

[0032] The original Gaussian sequence at the Alice end is , among them The modulation variance at the Alice end. Indicates that x follows a sequence from 0 to 1. Gaussian distribution;

[0033] The noise of the quantum channel is , Let V be the noise variance of the quantum channel. This means that z follows a sequence from 0 to 1. Gaussian distribution;

[0034] The original Gaussian sequence at Bob's end is y = x + z, which satisfies , This means that y follows a sequence from 0 to 1. Gaussian distribution;

[0035] Quantum transport and basis comparison at the Alice and Bob ends are existing technologies;

[0036] During quantum transmission, Alice generates n coherent states, each consisting of a pair of amplitude and phase orthogonal operators. The orthogonal operators are randomly selected by a quantum random number generator according to a Gaussian distribution with an expected value of 0. Alice sends these coherent states to Bob through a quantum channel with noise following a Gaussian distribution. Bob measures the orthogonality of each incoming pulse using a zero-difference or heterodyne detector.

[0037] During the basis comparison process, Bob tells Alice the orthogonal operator to be randomly selected for each measurement. Alice retains the positions that use the same orthogonal operator according to Bob's notification. Thus, after the basis comparison, Alice and Bob have a pair of Gaussian sequences that follow a Gaussian distribution, and the corresponding positions use the same orthogonal operator.

[0038] The quantum channel used in this embodiment is an AWGN channel, but other quantum channels can also be used in other embodiments.

[0039] Step 2: Randomly generate a Gaussian sequence at the Bob end. And send c+y (that is, add c and y together) to Alice's end;

[0040] Step 3: Bob's end quantizes and splits the Gaussian sequence c into m original key strings. and will the former Original key string It is sent directly to Alice, and calculated according to the pre-set error correction code. Original key string Proofreading and the calculated The checksum of the original key string Send to Alice;

[0041] The method for calculating the checksum is existing technology.

[0042] Step 4: Alice subtracts its original Gaussian sequence x from the received c+y to obtain c', sets an inter-layer iteration threshold T=1, and constructs an initially empty key string sequence U. The received original key string... Included in the key string sequence U;

[0043] Step 5: Let ;

[0044] Step 6: Alice calculates the result using c' and all the keys in the key string sequence U. The estimated function of the layer is calculated, and the calculated function is used to calculate the layer. The log-likelihood ratio of the layer (the method for calculating the estimation function and the log-likelihood ratio is existing technology);

[0045] Then based on the calculation The layer log-likelihood ratio and the checksum sent by Bob's end conduct Layer decoding, after which Alice's end is obtained. Layer decoding key string ;

[0046] Then use the Alice side Layer decoding key string Calculate Alice's end Layer checker And calculate the Alice end's Layer checker The verification code sent by Bob Compare them; if they match, then determine... If the layer decoding is successful, then Alice's end will be... Layer decoding key string Define it as a valid key string for decoding; otherwise, determine... If layer decoding fails, then Alice's end will be... Layer decoding key string

[0047] Defined as an invalid key string for decoding;

[0048] Step 7: If Then the Alice end obtained from step 6 will be decoded. Layer decoding key string Substitute them into the key string sequence U, so that the number of key strings in the key string sequence U becomes One, decoding key string Become the last key in the key string sequence U, and let Then proceed to step 6;

[0049] if Then, the last key string is deleted from the key string sequence U, making the number of key strings in the key string sequence U become... Then decode the Alice end obtained in step 6. Layer decoding key string Substitute them into the key string sequence U, so that the number of key strings in the key string sequence U becomes One, decoding key string Become the last key in the key string sequence U, and let Then proceed to step 6;

[0050] if Then proceed to step 8;

[0051] Step 8: If each layer on the Alice end (total) If all layers are successfully decoded, Alice sets all valid decoded key strings as her key, so that Alice and Bob obtain symmetric keys, and this round of information negotiation ends; otherwise, proceed to step 9.

[0052] Step 9: If the value of the inter-layer iteration threshold T is less than the preset iteration upper limit, then let T = T + 1, clear the key string sequence U, and then go to step 5; otherwise, go to step 10.

[0053] In this embodiment, the upper limit of iterations is set to 20 times. In other embodiments, the upper limit of iterations can also be set to other values, such as 10 times, 15 times, etc.

[0054] Step 10: Alice sets all valid decoded key strings to Alice's key, and this round of information negotiation ends.

Claims

1. A low-complexity continuous-variable quantum key distribution information negotiation method, the negotiation method comprising a reverse negotiation mechanism, characterized in that, The specific steps are as follows: Step 1: In the reverse negotiation mechanism, after quantum transmission and basis comparison, Alice and Bob obtain a pair of original Gaussian sequences conforming to Gaussian distribution, wherein Alice is the sending end and Bob is the receiving end; The original Gaussian sequence at Alice's end is where is the modulation variance at Alice's end; The noise of the quantum channel is , is the variance of the noise of the quantum channel; The original Gaussian sequence at Bob's end is y = x + z, which satisfies ; Step 2: Bob randomly generates a Gaussian sequence and sends c+y to Alice. Step 3: Bob's end quantizes and splits the Gaussian sequence c into m original key strings. and will the former Original key string It is sent directly to Alice, and calculated according to the pre-set error correction code. Original key string Proofreading and the calculated The checksum of the original key string Send to Alice; Step 4: Alice end will receive the c + y minus its own original Gaussian sequence x after c', and build an initial empty key string sequence U, will receive the original key string into the key string sequence U; Step 5: Let ; Step 6: Alice calculates the result using c' and all the keys in the key string sequence U. The estimated function of the layer is calculated, and the calculated function is used to calculate the layer. The log-likelihood ratio of the layer; According to the calculated layer log-likelihood ratio and the check sub-packet sent by the Bob terminal Perform layer decoding, and obtain the Alice terminal's layer decoding key string ; Then use the Alice side Layer decoding key string Calculate Alice's end Layer checker And calculate Alice's end Layer checker The verification code sent by Bob Compare them; if they match, then determine... If the layer decoding is successful, then Alice's end will be... Layer decoding key string Define it as a valid key string for decoding; otherwise, determine... If layer decoding fails, then Alice's end will be... Layer decoding key string Defined as an invalid key string for decoding; Step 7: If Then the Alice end obtained from step 6 will be decoded. Layer decoding key string Substitute it into the key string sequence U, so that the decoding key string Become the last key in the key string sequence U, and let Then proceed to step 6; If then the last key string in the sequence U of key strings is deleted and the decoded layer key string from step 6 is added to the sequence U of key strings so that the decoded key string becomes the last key string in the sequence U of key strings and is set to and the process returns to step 6. If then go to step 8; Step 8: If each layer of Alice is successfully decoded, Alice sets all the decoded valid key strings to the key of Alice, so that Alice and Bob obtain symmetric keys, and the information negotiation of this round ends.

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