CN101599826A - Scalable multi-user quantum key distribution network system and its key distribution method - Google Patents

Abstract

The invention discloses an expandable multi-user quantum key distribution network system and its key distribution method. The system includes a point-to-multipoint quantum key distribution composed of a quantum key transmitter and a plurality of quantum key receivers. system. The steps of the key distribution method are as follows: 1. The quantum key transmitter, that is, the transmitter, and multiple quantum key receivers, that is, the receiver, perform quantum key distribution, and the transmitter and each receiver share a random quantum key ; 2. Any two receivers send requests to the transmitter, and the transmitter compares it bit by bit with the two quantum keys shared by the two receivers and tells the two receivers the comparison result, and the two receivers combine themselves with the transmitter The quantum key shared by the other party and the comparison result can be used to deduce the quantum key shared by the other party and the transmitter. The invention has the advantages of reasonable design, convenient use and operation, strong user capacity expansion capability, long transmission distance, good user functionality, and key sharing between any two legal receivers.

Description

Scalable multi-user quantum key distribution network system and its key distribution method

technical field

The invention belongs to the technical field of quantum key distribution, and in particular relates to an expandable multi-user quantum key distribution network system and a key distribution method thereof.

Background technique

Quantum key distribution provides an absolutely secure random sequence for both sides of legal communication in different places, usually called quantum key. The security of quantum key is proved to be absolutely safe in theory, even if the advent of quantum computer does not pose a threat to it . This is because a single quantum state is used as an information carrier to transmit information, usually called a qubit. The security of this qubit is guaranteed by the uncertainty principle in quantum mechanics and the no-cloning theorem of unknown quantum states. therefore. This absolutely secure quantum key will first be used in military, national security and other fields, and become a new battlefield for scientists from all over the world.

The "point-to-point" quantum key distribution technology has been extensively studied. With the continuous development of network technology, the integration of quantum key distribution and classical communication network system has become a new research goal, and the quantum key distribution network system among multiple users has become a current research hotspot. The quantum key distribution network can provide quantum keys to legitimate users in the network. However, due to the uniqueness of qubits, the routing technology supporting quantum key distribution in the network is different from the implementation of classical communication, so quantum routing technology has become a key technology in quantum key distribution networks.

At present, according to the routing characteristics of the quantum key distribution network, it can be divided into three categories: the first category, the trusted party is the node for routing; the second category, the optical device is the node for routing; the third category, the quantum repeater is the node for routing.

Among them, the trusting party performs routing for the nodes, which essentially uses the mature "point-to-point" quantum key distribution device as the basic link, and uses the trusted relay party to perform "routing" at the node to form a quantum key. Distribution network, in which each pair of quantum keys is independently distributed between two adjacent nodes. Use the quantum key generated on each node to sequentially perform "encryption-decryption-encryption-...-decryption" operations on the classical information to be sent. In this way, long-distance key transmission is realized by using multiple "point-to-point" links for encryption and decryption. The advantage of this type of network is that the quantum key distribution network composed of trusting parties as nodes can easily realize quantum key distribution between long distances under the existing technical conditions, and can serve a wide area. The disadvantage is that the security of the network system depends on the trustworthiness of the nodes, that is, each node is trustworthy. This is because the information passed (keys or important information) will remain in the memory of any one node, and this information can be copied many times without being discovered. As the transmission distance increases, the number of nodes increases, and the safety and reliability guarantee coefficient decreases, so these are extremely unfavorable aspects for the absolutely confidential communication system.

In addition, the nodes of the quantum key distribution network can be realized by using optical switches or wavelength division multiplexing devices or optical beam splitters. ① The quantum key distribution network system based on optical switches or wavelength division multiplexers has the following advantages: 1. Easy technical implementation: this kind of quantum key distribution network is easy to realize under the current technical conditions; 2. Good security: quantum The information will not be destroyed during the transmission process, and the security is good; third, the user functionality is good: key distribution can be realized between any two users in the network. However, its disadvantages are as follows: First, the service scope is small: nodes do not have the relay amplification function, and can only serve metropolitan or local areas; Second, the network capacity is poorly scalable: the network capacity is limited by device parameters, Moreover, these two types of optical devices have a large insertion loss. As the capacity of network users increases, they can only be expanded by cascading optical devices, so the insertion loss also increases, which will shorten the quantum key distribution transmission. distance, and to reduce the rate at which quantum keys are generated. ② Quantum key distribution network based on optical beam splitter. Its advantages: 1. Easy technical implementation: this quantum key distribution network is easy to realize under the current technical conditions; 2. Good security: quantum information will not be destroyed during transmission, and the security is good. Disadvantages: 1. Small service range: nodes do not have relay amplification function, and can only serve metropolitan or local areas; 2. Poor user functions: only one-to-multi-point key distribution can be realized in the network; , the expansion performance is poor, and the expansion of the user capacity of the network seriously affects the transmission distance and distribution rate of the quantum key. Since the eavesdropper can eavesdrop on all ports of the beam splitter at the same time, the average number of photons μ emitted by the sender Alice should be equal to η, where η is the total qubit transmission efficiency between Alice and each receiving end Bob (channel transmission efficiency and the detection efficiency). After passing through the 1×n beam splitter, the average number of photons between Alice and Bob at each receiving end is actually μ/n. As the number of users increases, n increases, and the safe transmission distance and key generation rate decrease sharply.

For quantum nodes based on the characteristics of quantum entanglement, the advantages are: 1. Wide range of services: quantum nodes have the function of relay amplification and can serve local, urban, and wide areas. Second, good security: Quantum information will not be destroyed during the transmission process, and the security is good; Third, user functionality is good: key distribution can be realized between any two users in the network. Disadvantages: There are currently difficulties in technical implementation. Although the principle experimental research has proved its feasibility, the realization of quantum devices depends on the existing manufacturing process and level. At present, it seems that high-precision quantum components with nano-microstructures will be possible to build efficient quantum information systems. , that is to say, only the development of nanotechnology can ensure that the successfully developed quantum router has the required parameters. However, under the existing experimental conditions, this is not yet possible.

In summary, the existing multi-user quantum key distribution system based on optical beam splitters has the following disadvantages: 1. Poor user functions: only one-to-multi-point key distribution can be realized in the network; 2. User capacity expansion performance Poor: The expansion of capacity reduces the transmission distance and generation efficiency of the key; three, the transmission distance is short.

Contents of the invention

The technical problem to be solved by the present invention is to provide a scalable multi-user quantum key distribution system with reasonable design, convenient use and operation, strong user capacity expansion capability, long transmission distance and good user functionality in view of the above-mentioned deficiencies in the prior art. Network Systems.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an expandable multi-user quantum key distribution network system, including a quantum key transmitter and a plurality of quantum key transmitters respectively connected to the quantum key transmitter A point-to-multipoint quantum key distribution system composed of the receiving end, the quantum key information distributed by the quantum key transmitting end to the multiple quantum key receiving ends corresponds to multiple random binary sequences; the multiple quantum key Any two quantum key receiving ends in the key receiving end can realize key sharing after comparing, analyzing and judging the shared quantum key information between them and the quantum key transmitting end through the quantum key transmitting end.

The quantum key transmitting end is composed of a weak coherent pulse light source capable of preparing a coherent pulse sequence, and the coherent pulse sequence generated by the weak coherent pulse light source is divided into n weak coherent pulses corresponding to the plurality of quantum key receiving ends A sequence of 1×n beam splitters is respectively connected to the n outlets of the 1×n beam splitter, and the phases of the weak coherent pulse sequences emitted by each outlet are randomly encoded and correspondingly prepared n random quantum n phase modulators of the bit sequence and n attenuators respectively attenuating the n random qubit sequences and correspondingly sending them to the receiving end of the quantum key, the number of receiving ends of the plurality of quantum keys is n; the quantum cryptography The receiving end of the key is correspondingly equipped with a decoder that demodulates the received random qubit sequence and obtains a corresponding random binary sequence; the 1×n optical beam splitter is arranged at the light exit of the weak coherent pulse light source, and the attenuator Arranged at the exit of the phase modulator; the qubit sequence is an optical qubit sequence, and the coherent pulse sequence is a coherent optical pulse sequence.

The attenuator is connected to the receiving end of the quantum key through a communication optical fiber.

The present invention also provides a method for key distribution using an expandable multi-user quantum key distribution network system with simple steps, easy implementation and good use effect, which is characterized in that the method includes the following steps:

Step 1, the quantum key transmitter and the plurality of quantum key receivers perform quantum key distribution respectively, that is, the quantum key transmitter sends a random quantum key information to each quantum key receiver respectively; After the key distribution is completed, a random quantum key in the random quantum key information, that is, a random binary sequence, is shared between the quantum key transmitter and each quantum key receiver, and the quantum key transmitter and each quantum key receiver share The length, that is, the number of bits, of a section of random quantum keys shared among the multiple quantum key receiving ends is the same;

Step 2. When any two quantum key receiving ends in the plurality of quantum key receiving ends, that is, Bobi and Bobj, want to establish a shared key, the establishment process is as follows:

201. Bobi and Bobj respectively send a request to the quantum key transmitter to establish a shared key with the other party;

202. After receiving the request from Bobi and Bobj, the quantum key transmitter compares it bit by bit with the two quantum keys shared by Bobi and Bobj respectively, and obtains the comparison result accordingly: when the two quantum keys When the values on the corresponding bits of the key are the same, the quantum key transmitter will take "Y" for the comparison result on this bit; The comparison result takes "N";

203. The quantum key transmitter informs Bobi and Bobj of the obtained comparison result through an open channel;

204. According to the quantum key shared by himself and the quantum key transmitter, and combined with the comparison result notified by the quantum key transmitter, Bobi can deduce the quantum key shared by Bobj and the quantum key transmitter; Therefore, Bobj can also deduce the quantum key shared by Bobi and the quantum key transmitter, then a shared key is established between Bobi and Bobj, that is, Bobi and Bobj share each other’s quantum key;

Neither Bobi nor Bobj can share the shared key with any third quantum key receiver.

When the quantum key transmitting end described in the above step 1 and the multiple quantum key receiving ends respectively perform quantum key distribution, the quantum key distribution protocol is the BB84 protocol, the phase difference quantum key distribution protocol or the B92 protocol .

Before the quantum key transmitting end described in the above step 202 compares it bit by bit with the two quantum keys shared by Bobj and Bobj, the two quantum keys are correspondingly numbered step by step. The bits corresponding to the same number in the segment quantum key are the same.

Compared with the prior art, the present invention has the following advantages:

1. The scalable multi-user quantum key distribution network system can realize the key distribution between any two legal quantum key receiving ends, that is, between any two users in the network.

2. The expansion of user capacity no longer affects the transmission distance of the key and the key distribution rate, and theoretically speaking, the expansion of user capacity is not limited; and the expansion of user capacity does not affect the performance of other users.

3. Under the existing technical conditions and without changing the network system and its related equipment parameters, the scalable multi-user quantum key distribution network system can expand the transmission distance to 2 times the original, and its The ultimate transmission distance can reach more than 200km, so it can completely serve the metropolitan area.

4. Low technical difficulty and engineering cost.

In summary, the present invention mainly improves the existing multi-user quantum key distribution system based on optical beam splitters, and proposes a star-shaped quantum key distribution network system correspondingly, which is reasonable in design, easy to use and operate, and Strong user capacity expansion capability, long transmission distance, and good user functionality. After the transmitter and each receiver complete quantum key distribution, keys can be shared between any two receivers.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a schematic structural diagram of the scalable multi-user quantum key distribution network system of the present invention.

Fig. 2 is a flow chart of the scalable multi-user quantum key distribution method of the present invention.

Explanation of reference signs:

1-quantum key transmitter; 1-1-weak coherent pulse light source; 1-2-1×n optical beam splitter;

1-3-phase modulator; 1-4-attenuator; 2-quantum key receiver;

3-Communication optical fiber.

Detailed ways

As shown in Figure 1, the scalable multi-user quantum key distribution network system of the present invention includes a quantum key transmitter 1 (i.e. Alice) and a plurality of quantum keys respectively connected to the quantum key transmitter 1 A point-to-multipoint quantum key distribution system composed of receivers 2. The quantum key information distributed by the quantum key transmitter 1 to the multiple quantum key receivers 2 corresponds to multiple random binary sequences. Any two quantum key receiving ends 2 in the plurality of quantum key receiving ends 2 can compare the shared quantum key information between each of them and the quantum key transmitting end 1 through the quantum key transmitting end 1 Realize key sharing after analysis and judgment.

In this embodiment, the quantum key transmitter 1 is composed of a weak coherent pulse light source 1-1 (that is, WCP) capable of preparing a coherent pulse sequence, and divides the coherent pulse sequence generated by the weak coherent pulse light source 1-1 into 1×n optical beam splitters 1-2 (ie, Beam-splitter) corresponding to n weak coherent pulse sequences corresponding to the plurality of quantum key receiving ends 2, respectively corresponding to the 1×n optical beam splitters 1-2 n outlets of each outlet and correspondingly randomly encode the phases of the weak coherent pulse sequences sent by each outlet and correspondingly prepare n random qubit sequences n phase modulators 1-3 (ie φ1, φ2... . ..φn) and respectively attenuating the n random qubit sequences and correspondingly sending them to the n attenuators 1-4 (namely ATT1, ATT2...ATTn) at the receiving end 2 of the quantum key. The number of the plurality of quantum key receiving terminals 2 is n, specifically Bob1, Bob2... Bobn. The quantum key receiving end 2 is correspondingly provided with a decoder for demodulating the received random qubit sequence and obtaining a corresponding random binary sequence. The 1×n optical beam splitter 1-2 is arranged at the light exit of the weak coherent pulse light source 1-1, and the attenuator 1-4 is arranged at the exit of the phase modulator 1-3; the qubit sequence is an optical quantum A bit sequence, the coherent pulse sequence is a coherent light pulse sequence.

The attenuator 1-4 is connected to the quantum key receiving end 2 through a communication optical fiber 3 .

In conjunction with Fig. 2, the scalable multi-user quantum key distribution method of the present invention comprises the following steps:

Step 1. The quantum key transmitter 1 and the plurality of quantum key receivers 2 respectively perform quantum key distribution, that is, the quantum key transmitter 1 sends a random quantum key to each quantum key receiver 2 respectively. key information. After the quantum key distribution is completed, a random quantum key in the random quantum key information is shared between the quantum key transmitter 1 and each quantum key receiver 2, that is, a random binary sequence, and the quantum key transmits The length, that is, the number of bits, of a piece of random quantum key shared between the terminal 1 and the plurality of quantum key receiving terminals 2 is the same.

In this embodiment, in the quantum key transmitter 1, a weak coherent pulse is firstly generated by a weak coherent pulse light source 1-1, specifically a weak coherent light pulse sequence; the generated weak coherent light pulse sequence passes through 1× After n optical beam splitters 1-2, obtain n weak coherent optical pulse trains; Simultaneously, by being connected to n phase modulators 1-3 (actual During the operation, each phase modulator 1-3 can be randomly modulated independently), that is, the number of light pulses in the n weak coherent light pulse trains corresponding to the 1-2n outlets of the 1×n beam splitter The phases are randomly encoded independently, so as to prepare n random qubit sequences, where the qubit is the basic information unit in the quantum computer; then, use n attenuators 1-4 to attenuate the n random qubit sequences , and finally sent to each quantum key receiving end 2 respectively through the communication optical fiber. In summary, the attenuated random qubit sequences sent from the n attenuators 1-4 to the n quantum key receivers 2 are the quantum key transmitter 1 to the n quantum key receivers 2 respectively. The random quantum key information sent. After the above-mentioned n random qubit sequences sent from the quantum key transmitter 1 respectively arrive at the quantum key receiving terminal 2, each quantum key receiving terminal 2 uses its internally set decoder to pair the arriving random quantum bit sequences. The bit sequence is decoded to obtain random quantum key information, thereby completing the quantum key distribution process from one quantum key transmitter 1 to n quantum key receivers 2.

When the quantum key transmitter 1 and the plurality of n quantum key receivers 2 respectively perform quantum key distribution, the quantum key distribution protocol is the BB84 protocol, the phase difference quantum key distribution protocol or the B92 protocol . In actual use, its quantum key distribution protocol can also be other than the BB84 protocol (using four polarization states for key distribution), the phase difference protocol (DPSK) and the B92 protocol (that is, the B92 quantum key agreement). some related agreements.

To sum up, in the present invention, the quantum key transmitting end 1 can implement quantum key distribution with any quantum key receiving end 2 independently. After the quantum key is distributed, the quantum key transmitter 1 shares a quantum key, that is, a random binary sequence, with each quantum key receiver 2 .

Step 2, when any two quantum key receiving ends 2 in the plurality of quantum key receiving ends 2, that is, Bobi and Bobj, want to establish a shared key, the establishment process is as follows:

201. Bobi and Bobj respectively send a request to the sub-key transmitter 1 to establish a shared key with the other party. Wherein, i≠j and neither of them is less than or greater than n, that is to say, Bobi and Bobj are any two quantum key receivers 2 among Bob1, Bob2... Bobn.

202. After receiving the request from Bobi and Bobj, the quantum key transmitter 1 compares it bit by bit with the two quantum keys shared by Bobi and Bobj respectively, and obtains the comparison result accordingly: when the two quantum keys When the values on the corresponding bits of the key are consistent, the quantum key transmitter (1) takes “Y” for the comparison result on this bit; when the values on the corresponding bits of the two quantum keys are inconsistent, the quantum key transmitter 1 Take "N" for the comparison result on this bit.

In this embodiment, before the quantum key transmitting end 1 compares it bit by bit with the two quantum keys shared by Bobi and Bobj, the two quantum keys are correspondingly numbered step by step, and the The bits corresponding to the same number in the two quantum keys are the same.

203. The quantum key transmitter 1 informs Bobi and Bobj of the obtained comparison result through an open channel.

204. According to the quantum key shared by himself and the quantum key transmitter 1, and combined with the comparison result notified by the quantum key transmitter 1, Bobi can infer the quantum key shared by Bobj and the quantum key transmitter 1. key; similarly, Bobj can also deduce the quantum key shared by Bobi and quantum key transmitter 1, then a shared key is established between Bobi and Bobj, that is, Bobi and Bobj share each other's quantum key.

It should be noted that neither Bobi nor Bobj can share the shared key with any third quantum key receiver 2 .

In this embodiment, the key sharing process list between Bobi and Bobj is shown in Table 1:

Table 1 List of key sharing process between Bobi and Bobj

As can be seen from Table 1, for the point-to-multipoint quantum key distribution (distribution) system described in the present invention, any two quantum key receiving ends 2 after completing the quantum key distribution between Alice, Both can share keys with each other. Moreover, for the sake of safety, the quantum key shared between two quantum key receiving terminals 2 , specifically between two users, cannot be shared with the third user, that is, the quantum key receiving terminal 2 . For example, if Bob1 and Bob2 share each other's quantum key, Bob1 can no longer use the above-mentioned shared key to share with Bob3. Because in this way, Bob3 knows the key information of Bob2, resulting in unsafe use. In addition, in order to ensure the security of the quantum key distribution process, it is necessary to identify the communication parties before the quantum key distribution to prevent counterfeiting.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technical aspects of the present invention. within the scope of protection of the scheme.

Claims (6)

1. An expandable multi-user quantum key distribution network system is characterized in that: comprising a plurality of quantum key receiving ends connected with the quantum key transmitting end (1) and respectively with the quantum key transmitting end (1) (2) A point-to-multipoint quantum key distribution system composed of, the quantum key information distributed by the quantum key transmitter (1) to the multiple quantum key receivers (2) is corresponding to a plurality of random binary sequences ; Between any two quantum key receiving ends (2) in the plurality of quantum key receiving ends (2), all can pass the quantum key transmitting end (1) pair respectively with the quantum key transmitting end (1) After comparing and analyzing the shared quantum key information among them, the key sharing is realized. 2. according to the described scalable multi-user quantum key distribution network system of claim 1, it is characterized in that: described quantum key transmitter (1) is by the weak coherent pulse light source (1-1 that can prepare coherent pulse sequence ), the coherent pulse sequence produced by the weak coherent pulse light source (1-1) is divided into a 1×n optical beam splitter ( 1-2), which are respectively connected to the n exits of the 1×n optical beam splitter (1-2), and correspondingly randomly encode the phases of the weak coherent pulse sequences emitted by each exit, and correspondingly prepare n random quantum The n phase modulators (1-3) of the bit sequence and the n attenuators (1-4) that respectively attenuate the n random qubit sequences and correspondingly send to the quantum key receiving end (2), so The number of multiple quantum key receiving ends (2) is n; the quantum key receiving end (2) is correspondingly provided with a decoder that demodulates the received random qubit sequence and obtains a corresponding random binary sequence; The 1×n beam splitter (1-2) is arranged at the light exit of the weak coherent pulse light source (1-1), and the attenuator (1-4) is arranged at the exit of the phase modulator (1-3); The qubit sequence is an optical qubit sequence, and the coherent pulse sequence is a coherent optical pulse sequence. 3. According to the scalable multi-user quantum key distribution network system according to claim 2, it is characterized in that: between the attenuator (1-4) and the quantum key receiving end (2) by communication optical fiber (3) to connect. 4. A method utilizing the scalable multi-user quantum key distribution network system claimed in claim 1 to carry out a method for key distribution, characterized in that the method comprises the following steps: Step 1, the quantum key transmitter (1) and the plurality of quantum key receivers (2) perform quantum key distribution respectively, that is, the quantum key transmitter (1) distributes quantum keys to each quantum key receiver respectively. (2) Send a random quantum key information; after the quantum key distribution is completed, a section of the random quantum key information is shared between the quantum key transmitting end (1) and each quantum key receiving end (2) The random quantum key is a random binary sequence, and the length of a random quantum key shared between the quantum key transmitting end (1) and the plurality of quantum key receiving ends (2) is the same as the number of bits; Step 2, when any two quantum key receiving ends (2) in the plurality of quantum key receiving ends (2) namely Bobi and Bobj want to set up a shared secret key, its establishment process is as follows: 201. Bobi and Bobj respectively send a request to the quantum key transmitter (1) to establish a shared key with the other party; 202. After receiving the request sent by Bobi and Bobj, the quantum key transmitter (1) compares it bit by bit with the two quantum keys shared by Bobi and Bobj respectively, and obtains the comparison result accordingly: when the two When the values on the corresponding bits of the quantum key are consistent, the quantum key transmitter (1) takes “Y” for the comparison result on this bit; when the values on the corresponding bits of the two quantum keys are inconsistent, the quantum key transmits Terminal (1) gets "N" for the comparison result on this bit; 203. The quantum key transmitter (1) tells Bobi and Bobj the obtained comparison result through an open channel; 204. According to the quantum key shared by himself and the quantum key transmitter (1), and combined with the comparison result informed by the quantum key transmitter (1), Bobi can deduce that Bobj and the quantum key transmitter (1) ) shared quantum key; similarly, Bobj can also deduce the quantum key shared by Bobi and the quantum key transmitter (1), then a shared key is established between Bobi and Bobj, that is, Bobi and Bobj Share each other's quantum key with each other; Neither Bobi nor Bobj can share the shared key with any third quantum key receiving end (2). 5. According to the scalable multi-user quantum key distribution method according to claim 4, it is characterized in that: the quantum key transmitting end (1) described in the step 1 and the described multiple quantum key receiving ends (2) When performing quantum key distribution separately, the quantum key distribution protocol is BB84 protocol, phase difference quantum key distribution protocol or B92 protocol. 6. According to the scalable multi-user quantum key distribution method according to claim 4 or 5, it is characterized in that: the quantum key transmitting end (1) described in the step 202 shares two sections with Bobi and Bobj respectively with it Before the quantum key is compared bit by bit, the two quantum keys are correspondingly numbered step by step, and the bits corresponding to the same number in the two quantum keys are the same.

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