KR102260714B1 - Method and Apparatus for Distributing Quantum Secure Key Based on Code - Google Patents

Abstract

The present invention relates to a code-based quantum cryptography key distribution method and apparatus, wherein the code-based quantum cryptography key distribution method in multi-qubit transmission and reception of the present invention detects bit information from a received quantum state in a receiver (Bob) to perform quantum cryptography In a discrete-variable quantum encryption key distribution protocol for calculating and sharing a key, in order to reduce the complexity of the receiver (Bob) side and improve the encryption key generation rate (Secure key rate), independent by a plurality of encoders It makes it possible to utilize a partial subspace of a multi-qubit bit string that can be generated by multiple encoding (for example, transmission/reception of a bit string with only 0 repetitions or 10,000 repetitions among bit strings) as encryption key information.

Description

Method and Apparatus for Distributing Quantum Secure Key Based on Code}

The present invention relates to a quantum cryptography key distribution method and apparatus, and more particularly, to a multi-qubit code-based quantum cryptography key distribution method and apparatus having multiple states in a discrete variable quantum cryptography key distribution protocol.

In general, in a quantum cryptography key distribution protocol (QKD, Quantum key distribution), for example, a transmitter (Alice) transmits a quantum state generated for coded key information through a quantum channel, and a receiver (Bob) ) informs the transmitter (Alice) of the reference information applied to the quantum state detection, the transmitter (Alice) detects the quantum state transmitted according to the reference information from the receiver (Bob), and error correction (error) based on the detected data correction) is applied to calculate a quantum encryption key.

On the other hand, in such a quantum state transmission/reception, encoding in transmission and decoding in reception of a single qubit or multi-qubit are successively performed. For example, the quantum cryptography BB84 protocol requires an encoder to transmit sequential single qubits, a decoder to receive sequential single qubits, and two photodetectors for two-state detection. However, in the quantum cryptography Multi-qubit QKD protocol to enhance security and extend data transmission rate, the number of combinations of multiple encoders for transmitting sequential multi-qubits, multiple decoders for receiving sequential multi-qubits, and multi-qubits A number of photodetectors are required to detect as many states.

Therefore, we propose a multi-qubit code-based quantum cryptographic key distribution method that can reduce the complexity of the receiver (Bob) side and improve the secure key rate by diversifying the types of multi-qubit transmission/reception methods. .

As a prior art document related to quantum cryptography key distribution, Wang, Jin-Dong, et al. "Efficient quantum key distribution via single-photon two-qubit states." Reference may be made to Journal of Physics B: Atomic, Molecular and Optical Physics 43.9 (2010) and the like.

Therefore, the present invention has been devised to solve the above problems, and an object of the present invention is to detect bit information from the received quantum state in the receiver (Bob) to calculate a quantum cryptography key and distribute the distributed variable quantum cryptography key In the protocol, to reduce the complexity of the receiver (Bob) side and to improve the encryption key generation rate (Secure key rate), to provide a code-based quantum encryption key distribution method and apparatus in the transmission and reception of multi-qubit.

First, to summarize the features of the present invention, the quantum cryptography key distribution method according to an aspect of the present invention for achieving the above object is sequentially coded using N encoders (N is a natural number of 2 or more) for the encryption key in the transmitter The multi-qubit quantum state is transmitted through the quantum channel, but each encoder selects one of M selectable (M is a natural number greater than or equal to 1) mutually unbiased basis, and selects a selectable number from all N encoders (2). ^MN) one small 2 ^K than (K is performed in such a manner that each of the encoder selects one of the two states in the selected basis such that the combination of the two conditions of small natural number more MN at 1), wherein the encoded multi- transmitting a qubit quantum state; and a receiver sequentially decodes the coded multi-qubit quantum state received through the quantum channel using a plurality of decoders to generate a single qubit, using N N-th decoders received from the N-1 th decoder. It generates the generated two-qubit quantum states, with a single-photon detector 2 ^K corresponding to a combination of the two states from the two-qubit quantum states comprises the step of performing each of the condition is detected.

By the transmitter receiving the information on the basis selection information and the 2 ^K, one of the state of the detected value of one of the one of the N decoders received over the public channel from the receiver, a corresponding basis of the state of the detected value matches , characterized in that the coded multi-qubit quantum state is used as an encryption key.

Each encoder of the transmitter is characterized in that it performs encoding on the characteristics of the quantum state, including the polarization or phase of the quantum state.

In addition, a transmitter for distributing a quantum cryptography key according to another aspect of the present invention includes a photon light source; and N encoders (N is a natural number greater than or equal to 2) for generating sequentially coded multi-qubit quantum states with respect to a cryptographic key from the quantum state emitted from the photon light source, wherein each of the N encoders includes M selectable (M is 1 selects one of at least a natural number) mutually unbiased basis, and such that the combination of the two states of less than the N number of encoders selected number possible for the entire (2 ^MN) 2 ^K pieces (K is a small natural number more MN from 1) For transmitting the coded multi-qubit quantum state in a manner that each encoder selects any one quantum state in the selected basis, the coded multi-qubit quantum state received through the quantum channel in the receiver A single qubit is generated by sequential decoding using a plurality of decoders, and a 2-qubit quantum state generated using N N-th decoders received from an N-1 th decoder is generated, and from the 2-qubit quantum state, the using the 2 ^K single-photon detector corresponding to the combination of the two states is characterized in that for performing the respective detection state.

In addition, a receiver for distributing a quantum cryptography key according to another aspect of the present invention sequentially decodes a coded multi-qubit quantum state received from a transmitter through a quantum channel to generate a single qubit, a plurality of sequentially connected decoder; And 2 ^K single performing the 2 ^K of each of the states corresponding to a detected combination of the two states from the N-th two-qubit quantum states generated by the decoder N dogs each received from the N-1 second decoder of the plurality of decoder It includes a photon detector, and transmits sequentially coded multi-qubit quantum states through a quantum channel using N encoders (N is a natural number greater than or equal to 2) for the encryption key in the transmitter, but each encoder selects M number of selectable (M is 1 selects one of at least a natural number) mutually unbiased basis, and the combination of the two states of less than the N number of encoders selected number possible for the entire (2 ^MN) 2 ^K pieces (K is a small natural number more MN from 1) It is characterized in that for receiving the coded multi-qubit quantum state, which is generated and transmitted in such a way that each of the encoders selects any one quantum state on a selected basis.

And, the quantum cryptography key distribution device for distributing the quantum cryptography key according to another aspect of the present invention is a quantum channel using N encoders (N is a natural number greater than or equal to 2) for the cipher key to sequentially coded multi-qubit quantum states. , where each encoder selects one of M selectable (M is a natural number greater than or equal to 1) mutually unbiased basis, and selects ^{2 K (2 MN} ) smaller than the selectable number (2 MN ) in all N encoders. a transmitter for transmitting the coded multi-qubit quantum state generated by selecting any one quantum state on a basis selected by each encoder so that K is a combination of quantum states from 1 to a natural number smaller than MN; and sequentially decoding the coded multi-qubit quantum state received through the quantum channel using a plurality of decoders to generate a single qubit, and using N N-th decoders received from the N-1 th decoder. generating a 2-qubit quantum states, with a single-photon detector 2 ^K corresponding to a combination of the two states from the two-qubit quantum state a receiver that performs each of the condition is detected.

According to the multi-qubit code-based quantum cryptography key distribution method and apparatus according to the present invention, in the discrete variable quantum cryptography key distribution protocol, the receiver Bob detects bit information from the received quantum state and performs error correction, In order to calculate and share a quantum encryption key through post-processing such as privacy amplification, it is possible to reduce the complexity of the photodetector on the receiver (Bob) side and improve the encryption key generation rate (Secure key rate).

Therefore, some combination (subspace) of bit strings of multi-qubits that can be generated by independent multi-encoding by a plurality of encoders (for example, transmission and reception of bit strings with only 0 repetitions or 10 repetitions among bit strings) Make it available as encryption key information.

1 is a block diagram of a quantum cryptography key distribution device according to a discrete variable quantum cryptography key distribution protocol according to an embodiment of the present invention.
2 is an implementation example of a quantum encryption key distribution device for K = 1 in FIG.
3 is an implementation example of a quantum cryptography key distribution device for 2-qubits with K = 1 and N = 2 in FIG. 1 .
FIG. 4 is an example of one fixed basis in the case of M=2 in the structure of FIG. 3, and is a diagram for explaining encoding and decoding processes for 2-qubits.
5 is a graph for explaining the cryptographic key generation rate performance of the quantum cryptographic key distribution device according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In this case, the same components in each drawing are denoted by the same reference numerals whenever possible. In addition, detailed descriptions of already known functions and/or configurations will be omitted. The content disclosed below will focus on parts necessary for understanding operations according to various embodiments, and descriptions of elements that may obscure the gist of the description will be omitted. Also, some components in the drawings may be exaggerated, omitted, or schematically illustrated. The size of each component does not fully reflect the actual size, so the contents described herein are not limited by the relative size or spacing of the components drawn in each drawing.

1 is a block diagram of a quantum cryptographic key distribution apparatus 100 according to a discrete variable quantum cryptographic key distribution protocol according to an embodiment of the present invention.

Referring to FIG. 1 , a quantum cryptography key distribution apparatus 100 according to a discrete variable quantum cryptography key distribution protocol according to an embodiment of the present invention transmits an optical signal for data transmission and reception through a quantum channel using an optical fiber in an optical communication network. It includes a transmitter (Alice) and a receiver (Bob) that send and receive.

The transmitter (Alice) and the receiver (Bob) may be included in various optical communication equipment on a network, that is, a network that provides a public channel, such as a wired/wireless Internet and a mobile communication network. For example, Ethernet equipment, L2/L3 equipment, and a server on a network provide or receive a quantum encryption key according to a discrete-variable quantum encryption key distribution protocol in order to transmit and receive data necessary for each other through optical communication (Alice) and a receiver Bob.

First, the operation of the transmitter (Alice) and the receiver (Bob) will be briefly described.

In the present invention, the transmitter (Alice) for distributing the quantum cryptography key and the receiver (Bob) for receiving the quantum cipher key can distribute and share the cipher key using a post-processing method. In the discrete variable quantum cryptography key distribution protocol of the present invention, the performance is the same whether in the forward or reverse direction.

To this end, the transmitter (Alice) sequentially coded multi-qubit (N-qubit) quantum while increasing the number of bits for the encryption key to be transmitted from the photon source 111 and the quantum state emitted from the photon light source to N. N encoders (N is a natural number greater than or equal to 2) 112 for generating a state, and each of the N encoders 112 is a random number generator (RNG, Random Number Generator) 113 according to a predetermined encryption algorithm or encoding algorithm. can be used to encode a multi-qubit (N-qubit) quantum state.

For example, the photon light source 111 may generate an entangled-state quantum with respect to a predetermined coded encryption key corresponding to the encryption key to be transmitted. Each of the N encoders 112 may perform encoding on characteristics of a quantum state, such as polarization and phase of the quantum state.

,

로 이루어지는 제1베이시스,

,

로 이루어지는 제2베이시스 등 다수의 베이시스들 중 하나의 베이시스가 사용될 수도 있고, 2이상의 베이시스가 사용될 수도 있으며, 각 인코더(112)는 베이시스의 선택 및 베이시스 요소 중 어느 하나의 선택을 통하여, N번째 인코더는 선택 가능한 수(2^MN)를 갖는다.Here, each of the N encoders 112 selects one of the M selectable (M is a natural number greater than or equal to 1) mutually unbiased basis, and is smaller than the ^{selectable number (2 MN ) in the entire N encoders 112 .} The coded multi-qubit (N-) in a manner that selects any one quantum state in the basis selected by each encoder 112 so as to be a combination of 2 ^{K quantum states (K is a natural number smaller than 1 to MN).} qubit) can generate and transmit a quantum state. For example, unbiased basis, generated according to the properties of entangled quantum states, such as spin states or energy states, are

,

A first basis consisting of

,

One basis among a plurality of basis, such as a second basis consisting of , may be used, or two or more basis may be used, and each encoder 112 performs the selection of the basis and the selection of any one of the basis elements through the Nth encoder. has a selectable number (2 ^MN ).

In the present invention, so that the combination of the two states of the N encoders 112, one small 2 ^K than the selection of the overall number of available (2 ^MN) (K is a small natural number more MN from 1), each encoder 112 is Any one quantum state in the selected basis can be selected. For example, if K=1, the N encoders 112 have two N-qubit quantum states (selected only on the first basis), eg |00...0> and |11...1> As such, a coded multi-qubit (N-qubit) quantum state consisting of N basis elements is generated. Such a K value is predetermined, and a corresponding rule may be set in advance so that the corresponding 2 ^{K N-qubit quantum states are generated from among the number (2 MN) that can be generated.}

The receiver (Bob) sequentially decodes the coded multi-qubit (N-qubit) quantum state received from the transmitter (Alice) through the quantum channel while decreasing the number of bits by one to generate a single qubit, sequentially connected decoders Including (121, 125), the number of N-th decoders 125 received from the N-1 th decoder is N. A receiver (Bob) is, N of the second decoder (125) N 2 ^K dog of the single photon detector for performing the 2 ^K of each of the states corresponding to a detected combination of the two states from the two-qubit quantum states generated respectively (SPD, Single Photon Detector) (129). Each of the decoders 121 and 125 may decode a multi-qubit (N-qubit) quantum state using a random number generator (RNG) 122 and 126 according to a predetermined encryption algorithm or encoding algorithm.

If the single-photon detector (129) performs the state detection on the output from the N decoders 125 of the second N, a predetermined processing unit in the receiver (Bob) it is to perform processing for the corresponding detection state 2 of ^{the K} An electrical signal corresponding to one corresponding state detected value, that is, bit information (digital code) is generated.

Since the receiver (Bob) transmits the information (bit information) for the basis selection information and the 2 ^K pieces of the state of the detected value from one of N decoders 125 through a public channel to the sender (Alice).

Transmitter (Alice) is a, the coded multi-match the information on the basis selection information and the 2 ^K, one of the state of the detected value of one of the N number of decoder 125 received through the public channel from a receiver (Bob) The qubit quantum state can be shared and used as an encryption key. For example, the transmitter (Alice) can maintain the coded multi-qubit quantum state transmitted to the receiver (Bob) in a quantum memory, etc. For this, it decodes itself using basis selection information from the receiver (Bob) and performs photodetection. By extracting the quantum state through the generated bit information, it is possible to determine whether the information matches the state detected value from the receiver Bob.

The transmitter (Alice) and the receiver (Bob) post-process the corresponding bit information generated by performing the state detection as described above in order to match the detected bit information as described above, that is, an error correction technique and confidentiality amplification. (privacy amplification) technique, etc. is applied to calculate and share a corrected quantum cryptography key. For example, the transmitter Alice receives the bit information detected by the receiver Bob through a public channel, etc., and performs error correction based on it, so that the bit information of the receiver Bob and its own bit information can be matched. have. Conversely, by receiving the bit information detected by the transmitter Alice from the receiver Bob and performing error correction based on the received bit information, the bit information of the transmitter Alice and its own bit information may be matched.

Figure 2 is an implementation example of the quantum encryption key distribution device 100 for K = 1 in Figure 1.

Referring to FIG. 2, when K = 1 in FIG. 1, each encoder 112 selects any one quantum state on the selected basis, but in this case, if it is selected only on the first basis, N encoders 112 Only two combinations of quantum states (e.g., |00...0>, |11...1>) are selected from the selectable number (2 ^{MN) in the whole, resulting in two coded multi-qubits (N-qubits).} ) to create a quantum state (eg, |00...0>, |11...1>).

3 is an implementation example of a quantum cryptography key distribution device for 2-qubits with K = 1 and N = 2 in FIG. 1 .

Referring to FIG. 3 , when K = 1 and N = 2 in FIG. 1 , each encoder 112 selects any one quantum state in the selected basis, but selectable from all of the two encoders 112 . In the number (2 ^2M ), only two combinations of quantum states are selected, producing two coded multi-qubit (2-qubit) quantum states.

FIG. 4 is a diagram for explaining encoding and decoding processes for 2-qubits in which M=1 in the structure of FIG. 3 .

As shown in FIG. 4 , if M = 1 in the structure of FIG. 3 , each encoder 112 selects any one quantum state on one basis, and the selectable number of all two encoders 112 ( 2 ² ) In , only two combinations of quantum states (eg, |00>, |11>) are selected to generate two coded multi-qubit (2-qubit) quantum states (eg, |00>, |11>).

5 is a graph for explaining the cryptographic key generation rate performance of the quantum cryptographic key distribution apparatus 100 according to an embodiment of the present invention. 5 is a result of an experiment under the conditions of the average number of photons as shown in the table below.

As shown in Figure 5, in the discrete variable quantum cryptographic key distribution protocol (QKD), the experimental results of the encryption key generation rate (Secure key rate) for the case of N = 2 and the BB84 protocol of the present invention as shown in Figure 1 It is shown by comparison. As shown in FIG. 5 , it was confirmed that the secure key rate was excellent in the case of the present invention, even if the noise due to the distance was greater than in the case of the BB84 protocol.

As described above, according to the multi-qubit code-based quantum encryption key distribution apparatus 100 according to the present invention, in the quantum encryption key distribution protocol, the receiver Bob detects bit information from the received quantum state and corrects the error ( To calculate and share a quantum encryption key through post-processing such as error correction and privacy amplification, it is possible to reduce the complexity of the photodetector on the receiver (Bob) side and improve the secure key rate. can Therefore, some combination (subspace) of bit strings of multi-qubits that can be generated by independent multi-encoding by a plurality of encoders (for example, transmission and reception of bit strings with only 0 repetitions or 10 repetitions among bit strings) Make it available as encryption key information.

As described above, the present invention has been described with specific matters such as specific components and limited embodiments and drawings, but these are provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments. , various modifications and variations will be possible without departing from the essential characteristics of the present invention by those of ordinary skill in the art to which the present invention pertains. Therefore, the spirit of the present invention should not be limited to the described embodiments, and all technical ideas with equivalent or equivalent modifications to the claims as well as the claims to be described later are included in the scope of the present invention. should be interpreted as

Transmitter (Alice)
Receiver (Bob)
Photon Light Source (111)
N encoders (112)
N decoders (121)
Nth decoder (125)
Single Photon Detector (129)

Claims (6)

The transmitter transmits sequentially coded multi-qubit quantum states using N encoders (N is a natural number greater than or equal to 2) for the encryption key through the quantum channel, but each encoder selects M (M is a natural number greater than or equal to 1) mutual ratio select one of the deflection basis, and to have each of the encoder selects one of the two states of the selected basis, the N encoders small 2 ^K than the selection of the overall number of available (2 ^MN) one (K 1 Transmitting the coded multi-qubit quantum state including a combination of quantum states (a natural number smaller than MN); and
The receiver sequentially decodes the coded multi-qubit quantum state received through the quantum channel using a plurality of decoders, and uses N N-th decoders connected to the N-1 th decoder to each 2-qubit quantum state. generate, and includes the step of performing each of the state detected from each of the 2-qubit quantum state with the 2 ^K single-photon detector corresponding to a combination of the two states,
According to a predetermined rule, by transmitting a multi-qubit quantum state corresponding to a combination of the N number of possible encoder the selection of the overall (2 ^MN) of 2 ^K of the quantum state,
A quantum encryption key distribution method implemented to use some combination of bit strings of the multi-qubit as encryption key information according to the preset rule. According to claim 1,
By the transmitter receiving the information on the basis selection information and the 2 ^K, one of the state of the detected value of one of the one of the N decoders received over the public channel from the receiver, a corresponding basis of the state of the detected value matches , Quantum encryption key distribution method, characterized in that for using the coded multi-qubit quantum state as an encryption key. According to claim 1,
Each encoder of the transmitter, quantum cryptography key distribution method, characterized in that to perform encoding for the characteristics of the quantum state, including the polarization or phase of the quantum state. photon light source; and N encoders (N is a natural number greater than or equal to 2) for generating sequentially coded multi-qubit quantum states with respect to a cryptographic key from the quantum states emitted from the photon light source,
Each of the N encoders selects one of the selectable M mutually unbiased basis (M is a natural number greater than or equal to 1), and selects any one quantum state in the basis selected by each of the N encoders. It serves to transmit a selected one smaller than the number of available 2 ^K (2 ^MN) of the coding including a combination of the two conditions of (K is a natural number smaller than MN from 1) a multi-qubit quantum state of the overall encoder,
The receiver sequentially decodes the coded multi-qubit quantum state received through the quantum channel using a plurality of decoders, and each 2-qubit quantum state is obtained using N N-th decoders connected to the N-1 th decoder. and performing the detection of each state from each of the 2-qubit quantum states ^{using 2 K single photon detectors corresponding to the combination of the quantum states,}
According to a predetermined rule, by transmitting a multi-qubit quantum state corresponding to a combination of the N number of possible encoder the selection of the overall (2 ^MN) of 2 ^K of the quantum state,
A transmitter for distributing a quantum cryptographic key, implemented to use some combination of the bit string of the multi-qubit as cryptographic key information according to the preset rule. a plurality of sequentially connected decoders for sequentially decoding a coded multi-qubit quantum state received from a transmitter through a quantum channel to generate a single qubit; and
Of the plurality of N-1-th decoder decoder N th decoder Dog N 2 ^K single-photon detector for performing the 2 ^K of each of the states corresponding to a detected combination of the two states from the two-qubit quantum states generated respectively connected to the including,
The transmitter transmits sequentially coded multi-qubit quantum states using N encoders (N is a natural number greater than or equal to 2) for the encryption key through the quantum channel, but each encoder selects M (M is a natural number greater than or equal to 1) mutual ratio select one of the deflection basis, and to have each of the encoder selects one of the two states of the selected basis, the N encoders small 2 ^K than the selection of the overall number of available (2 ^MN) one (K 1 To receive the coded multi-qubit quantum state including a combination of the quantum states of a natural number smaller than MN,
According to a predetermined rule, by transmitting a multi-qubit quantum state corresponding to a combination of the N number of possible encoder the selection of the overall (2 ^MN) of 2 ^K of the quantum state,
A receiver for receiving a quantum cryptographic key, implemented to use some combination of the bit string of the multi-qubit as cryptographic key information according to the preset rule. For the encryption key, sequentially coded multi-qubit quantum states are transmitted using N encoders (N is a natural number greater than or equal to 2) through a quantum channel, but each encoder selects M (M is a natural number greater than or equal to 1) mutually unbiased basis. select one of the, and to which the respective encoder select the quantum state of one of the selected basis, the N encoders small 2 ^K than the selection of the overall number of available (2 ^MN) pieces (K is from 1 MN a transmitter that transmits the coded multi-qubit quantum state comprising a combination of quantum states (smaller natural numbers); and
The coded multi-qubit quantum state received through the quantum channel is sequentially decoded using a plurality of decoders, and each 2-qubit quantum state is generated using N N-th decoders connected to the N-1 th decoder. and, and a receiver for performing each of the state detected from each of the 2-qubit quantum state with the 2 ^K single-photon detector corresponding to a combination of the two states,
According to a predetermined rule, by transmitting a multi-qubit quantum state corresponding to a combination of the N number of possible encoder the selection of the overall (2 ^MN) of 2 ^K of the quantum state,
A quantum cryptographic key distribution device implemented to use some combination of the bit string of the multi-qubit as cryptographic key information according to the preset rule.

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