Methods and systems for error correction in quantum cryptographic communication

Abstract

Provided are a quantum cryptographic communication method and system that reduce the time and cost associated with an error correction process and improve security by appropriately determining, according to the situation, the main bodies of the encoding process and the decoding process that are necessary when performing the error correction process. 【Solution means】A quantum cryptographic communication method between a first communication device and a second communication device according to the present invention includes a quantum communication step in which the first communication device transmits a first information sequence generated by randomly modulating the phase and polarization of photons to the second communication device, and the second communication device generates a second information sequence based on the first information sequence, and a post-processing step of making the first information sequence and the second information sequence identical and matching under an error correction mode selected based on a predetermined criterion, wherein the error correction mode is classified according to the main body of decoding of parity information.

Description

Technical Field

[0001] The present invention relates to a quantum cryptographic communication method and system.

Background Art

[0002] Quantum cryptography communication is a technology that uses the "particles" of light to generate indivisible quanta and creates and distributes a decryptable cryptographic key between a sender and a receiver to prevent hacking. Quantum cryptography communication is a technology that securely distributes cryptographic keys between a sender and a receiver through quantum communication, and is also called Quantum Key Distribution (QKD).

[0003] Quantum cryptography communication is composed of a quantum communication step in which a sender and a receiver generate their respective information sequences, and a post-processing step for making their respective information sequences match identically with each other. The quantum cryptography communication process will be described as follows with reference to FIGS. 1 and 2.

[0004] First, in the quantum communication step (S10), the sender Alice randomly generates an information sequence. When using light, information randomly modulated by phase, polarization, etc. is encoded to generate a first information sequence. The sender Alice transmits the first information sequence to the receiver Bob via a communication channel such as wired or wireless. The receiver Bob generates his own second information sequence based on the received first information sequence. As an example, the receiver Bob measures the first information sequence (by randomly selecting a polarization basis) to generate a second information sequence. That is, the receiver Bob will have an information sequence different from that of the sender Alice.

[0005] Next, the post - processing step (S20) is a process of making the different information sequences held by the sender and the receiver identical. The post - processing step includes a sifting process, an information reconciliation process, and a privacy amplification process. The sifting process is a process of leaving only the information sequences having the same basis using the basis used in generating each of the information sequences (the first information sequence and the second information sequence) of the sender Alice and the receiver Bob. The information reconciliation process is a process of making the information sequences remaining after the sifting process of the sender Alice and the receiver Bob identical using error - correcting codes. The privacy amplification process is a process of removing from the respective information sequences of the sender Alice and the receiver Bob the amount of information corresponding to the amount of information determined to be exposed to the eavesdropper Eve or the amount of information that should have been exposed in the quantum communication step or the post - processing step after the information reconciliation process is performed. The respective information sequences remaining after the privacy amplification process are the finally delivered encryption keys to Alice and Bob.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above - mentioned prior art, and an object of the present invention is to provide a quantum cryptographic communication method and system with improved security.

Means for Solving the Problems

[0007] A quantum key distribution method between at least one first communication device and at least one second communication device performed by at least one processor according to one aspect of the present invention made to achieve the above object includes: a quantum communication step in which the first communication device transmits a first information sequence generated by randomly modulating photons in terms of phase and polarization to the second communication device, and the second communication device generates a second information sequence based on the first information sequence; and a post-processing step of identically aligning the first information sequence and the second information sequence using parity information in an error correction mode selected based on a predetermined criterion. The error correction mode is either a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to identically align the second information sequence with the first information sequence, or a second error correction mode in which the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to identically align the first information sequence with the second information sequence. The predetermined criterion includes a first criterion in which the communication device where the detector is not located among the first communication device and the second communication device encodes the parity information, and the communication device where the detector is located among the first communication device and the second communication device decodes the parity information, and a second criterion in which either one of the first communication device and the second communication device decodes the parity information based on signaling information including information regarding the subject of decoding for the parity information.

[0008] The at least one second communication device includes a plurality of communication devices, and the post-processing step between the first communication device and the plurality of communication devices can be performed according to the first criterion. The at least one second communication device includes a plurality of communication devices, and the post-processing step between the first communication device and the plurality of communication devices can be performed according to the second criterion.

[0009] A quantum key distribution method between at least one first communication device and at least one second communication device performed by at least one processor according to another aspect of the present invention made to achieve the above object includes: a quantum communication step in which the first communication device transmits a first information sequence generated by randomly modulating photons in terms of phase and polarization to the second communication device, and the second communication device generates a second information sequence based on the first information sequence; and a post-processing step in which the first information sequence and the second information sequence are made identical and matched using parity information in an error correction mode selected based on a predetermined criterion. The error correction mode is either a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to make the second information sequence identical and matched to the first information sequence, or a second error correction mode in which the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to make the first information sequence identical and matched to the second information sequence. The predetermined criterion is such that when an eavesdropper is located closer to the second communication device than the first communication device, the error correction mode is selected as the first error correction mode, and when the eavesdropper is located closer to the first communication device than the second communication device, the error correction mode is selected as the second error correction mode. [[ID=],[1]] [[ID=],[2]]

[0010] [[ID=],[3]] A quantum key distribution system according to one aspect of the present invention made to achieve the above object includes a first communication device for transmitting a first information sequence generated by randomly modulating based on the phase and polarization of photons to a second communication device, and a second communication device for generating a second information sequence based on the received first information sequence. Quantum key distribution is performed by an error correction process of making the first information sequence and the second information sequence identical using parity information in an error correction mode selected based on a predetermined criterion. The error correction mode is a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to make the second information sequence identical to the first information sequence; and a second error correction mode in which the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to make the first information sequence identical to the second information sequence. The predetermined criterion includes a first criterion in which the communication device where the detector is not located among the first communication device and the second communication device encodes the parity information, and the communication device where the detector is located among the first communication device and the second communication device decodes the parity information; and a second criterion in which either one of the first communication device and the second communication device decodes the parity information based on signaling information including information regarding the subject of decoding for the parity information.

[0011] A quantum key distribution system according to another aspect of the present invention made to achieve the above object includes a first communication device for transmitting a first information sequence generated by randomly modulating according to the phase and polarization of photons to a second communication device, and a second communication device for generating a second information sequence based on the received first information sequence. Quantum key distribution is performed by an error correction process of making the first information sequence and the second information sequence identical using parity information in an error correction mode selected based on a predetermined criterion. The error correction mode is a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to make the second information sequence identical to the first information sequence, and the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to make the first information sequence identical to the second information sequence. The predetermined criterion is that when the eavesdropper is located closer to the second communication device than the first communication device, the error correction mode is selected as the first error correction mode, and when the eavesdropper is located even closer to the first communication device than the second communication device, the error correction mode is selected as the second error correction mode.

Advantages of the Invention

[0012] According to the present invention, by appropriately determining the main body of the encoding process and the decoding process required when performing the error correction process according to the situation, it is possible to provide a quantum key distribution method and system that reduce the time and cost required for the error correction process and improve security.

Brief Description of the Drawings

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BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, specific examples of embodiments for implementing the present invention will be described in detail with reference to the drawings.

[0015] Hereinafter, in order for those having ordinary knowledge in the technical field to which the present invention pertains (hereinafter referred to as ordinary technicians) to easily implement the present invention, several embodiments will be clearly and detailedly described with reference to the drawings.

[0016] FIG. 2 is a diagram showing a quantum key distribution communication system according to an embodiment.

[0017] Hereinafter, referring to FIG. 2, the above-mentioned Alice and Bob are the sender and receiver of the information sequence, respectively. Alice and Bob refer to the first communication device held by Alice and the second communication device held by Bob, respectively. As the communication device, all forms of electronic devices capable of communicating, such as telephones, computers, laptop computers, mobile devices, server devices, cloud devices, satellite devices, access points (APs), home appliances, and commercial electronic devices, are included. As an example, Alice is a smartphone and Bob is an ATM device.

[0018] Information correction or error correction in communication means the process of correcting information so that the same information can be possessed between the sender and the receiver.

[0019] FIG. 3 is a diagram showing an information correction process performed in ordinary mobile communication according to an embodiment.

[0020] Referring to FIG. 3, in ordinary mobile communication, the error correction process is a method in which additional information (for example, a parity bit or a syndrome) is added to an information sequence known only to the sender, and the information sequence (actual data) and the additional information (for example, a parity bit) are transmitted through a communication channel, and the receiver uses the received information to reconstruct its own information sequence to be the same as the information sequence possessed by the sender.

[0021] Such error correction is also performed in the quantum cryptographic communication system 100. Hereinafter, the additional information used for error correction is referred to as an "error correction code", and "parity information" is described as a typical embodiment of the error correction code, but the error correction code is not limited to parity information at all. In the quantum cryptographic communication system 100, such information correction is performed by transmitting additional information (i.e., parity information) to the information sequences (the first information sequence or the second information sequence) held by the sender and the receiver after the quantum communication step (step S10 in FIG. 1) is completed. That is, different from ordinary mobile communication, the error correction code in quantum cryptographic communication is utilized in a post-processing step after the quantum communication step is completed, and the error correction process is performed in a state where the sender and the receiver already have their own information sequences respectively. Therefore, the error correction process is performed on the premise that the communication channel is being eavesdropped by an eavesdropper. That is, since the communication channel is being eavesdropped, the information transmitted through the communication channel needs to be minimized.

[0022] FIG. 4 is a diagram showing a first error correction mode according to an embodiment, and FIG. 5 is a diagram showing a second error correction mode according to an embodiment. FIG. 6 is a diagram showing quantum cryptographic communication based on a one-way method according to an embodiment, and FIG. 7 is a diagram showing quantum cryptographic communication based on a two-way method according to an embodiment. FIG. 8 is a diagram showing quantum cryptographic communication between a smartphone and an ATM device according to an embodiment. FIG. 9 is a diagram showing a state where an eavesdropper Eve is near Alice according to an embodiment, and FIG. 10 is a diagram showing a state where an eavesdropper Eve is near Bob according to an embodiment.

[0023] FIG. 4 shows a first error correction mode in which, according to an embodiment, Alice encodes the parity information and Bob decodes the parity information. FIG. 5 shows a second error correction mode in which, according to an embodiment, Bob encodes the parity information and Alice decodes the parity information.

[0024] Parity information goes through the encoding process performed by the sender and the decoding process performed by the receiver. That is, when the sender of the parity information encodes the parity information and transmits it to the other party of the communication, the other party of the communication, that is, the receiver of the parity information, decodes the received parity information. Generally, the time taken for the decoding process is longer than the time taken for the encoding process, and the computational complexity is high. In ordinary mobile communication, the information sender Alice encodes the parity information, and the information receiver Bob decodes the parity information.

[0025] However, in the quantum cryptographic communication system 100, (after the quantum cryptographic step is completed), the sender Alice and the receiver Bob already possess their respective information sequences. Therefore, in the quantum communication step (S10), Alice is the sender of the information sequence and Bob is the receiver of the information sequence. However, separately from this, in the post-processing step (S20), Alice and Bob each become the receiver or the sender of the parity information.

[0026] According to one embodiment, after Alice encodes the parity information, the encoded parity information is transmitted to Bob via the communication channel. Bob uses the received parity information and the second information sequence that he already possesses to perform decoding, thereby aligning the second information sequence to be identical to the first information sequence. Bob transmits a feedback signal to Alice for the result of the decoding or the information that is additionally required. This is referred to as the first error correction mode (see FIG. 4).

[0027] In another embodiment, after Bob encodes the parity information, the encoded parity is transmitted to Alice via a communication channel. Alice aligns the first information sequence to be identical to the second information sequence by performing decoding using the received parity information and the first information sequence that she already has. Alice transmits a feedback signal to Bob regarding the result of the decoding or additional information required. This is referred to as the second error correction mode (see FIG. 5). Referring to FIGS. 5 and 6, in quantum cryptographic communication, after the quantum communication step is completed, it is not always necessary that the sender of the information sequence encodes and transmits the parity information, and the receiver of the information sequence decodes the received parity.

[0028] However, since the parity information transmitted in the first error correction mode is generated based on the first information sequence that Alice has, and the parity information transmitted in the second error correction mode is generated based on the second information sequence that Bob has, the parity information generated according to the error correction mode may be different from each other (the first parity in FIG. 4 and the second parity in FIG. 5 are different from each other).

[0029] Based on a predetermined criterion, one of the first error correction mode and the second error correction mode is determined. The following discloses a predetermined criterion for determining the subjects (Alice and Bob) who perform the encoding and decoding of the parity information.

[0030] The first criterion (the first criterion) is to make the subject having a better hardware device perform the decoding of the parity information in consideration of the high computational complexity of the decoding process.

[0031] The implementation of the quantum communication step in quantum cryptographic communication can be broadly divided into a one-way method and a two-way (two-way or plug and play) method. Referring to FIG. 6, in the one-way method, a laser for generating photons carrying information is located at the sender Alice, and a detector for detecting photons is located at the receiver Bob. In contrast, referring to FIG. 7, in the two-way method, a bulky and costly laser and detector are simultaneously located at either the sender Alice or the receiver Bob (Bob in FIG. 7). According to the first criterion, among Alice and Bob, the entity with better hardware devices performs the parity information decoding process.

[0032] Although the two-way method is used to compensate for polarization changes and path fluctuations that occur during quantum key distribution via optical fibers despite the reduction in transmission speed, for example, when quantum cryptographic communication is carried out between a portable (mobile) device such as a smartphone and a bank ATM device, since the portable device is a lightweight device with limitations in the performance of its memory and processor, the laser and detector are located at the ATM device.

[0033] According to one embodiment, it is determined that the entity where the detector is located among Alice and Bob has better performance of the hardware device. When Alice is a smartphone and Bob is an ATM device where the laser and detector are located, the parity information decoding is performed by Bob, and the encoding is performed by Alice (see FIG. 8).

[0034] The second criterion (the second standard) is such that among Alice and Bob, the entity closer to the eavesdropper decodes the parity information, and the remaining entity encodes the parity information. The communication channel (whether wired or wireless) generally has a high signal strength near the sender due to transmission loss, but the receiver may receive a weakened signal. If the eavesdropper Eve is located closer to either Alice or Bob, the eavesdropper Eve can eavesdrop on the parity signal from the nearby entity. If the sender of the parity information is Alice and the eavesdropper Eve is near Alice (see Figure 9), the eavesdropper Eve can receive the parity signal stronger than Bob, and there will be more eavesdropped information compared to when the eavesdropper Eve is near Bob (see Figure 10). That is, when the eavesdropper Eve is near Alice, by determining Bob as the sender of the parity information, the amount of information eavesdropped by the eavesdropper Eve decreases. That is, conclusively speaking, it is determined that the entity closer to the eavesdropper decodes the parity information, and the entity farther away encodes the parity information.

[0035] As an example of the second criterion, considering that it is difficult for a satellite to perform updates such as equipment in quantum cryptographic communication between a ground station and a satellite, the laser and detector are positioned at the ground station. However, since there may be an eavesdropping satellite around the communication target satellite, the ground station encodes the parity, and the satellite decodes the parity information. In such a situation, according to the first criterion, the ground station where the detector is located must decode the parity information, but according to the second criterion, the satellite decodes the parity information. That is, when the position of the eavesdropper is relatively clear, the second criterion takes precedence over the first criterion. When applying the second criterion, it must be considered that the position of the eavesdropper may be changed to determine the entity performing the decoding of the parity information.

[0036] The third criterion (the 3rd criterion) is that the entity for decrypting the parity information is designated by the quantum cryptographic communication system 100 or the communication entity or operator of the quantum cryptographic communication system 100 according to the situation. In such an embodiment, a protocol for the pre-agreed signaling information is specified, and based on the defined signaling information, the entity for decrypting the parity information and the entity for encoding are determined. Such signaling information is even more important because the error correction process does not end with a single transmission of parity information between Alice and Bob, and additional parity transmission may be further performed. For example, Alice encodes the parity information, Bob receives and decrypts the parity, Bob, who is the entity for decrypting, performs encoding to generate additional parity information, and the additional parity information is transmitted to Alice again. Alice decrypts the received additional parity information again. That is, signaling information indicating who is the entity for encoding the first parity information is required.

[0037] FIG. 11 is a diagram showing signaling information for distinguishing the entity for encoding parity information and the entity for decrypting parity information according to an embodiment.

[0038] The signaling information is information for indicating which of the sender and the receiver is the entity for decrypting (or encoding) the (first) parity. If no signaling information is transmitted between Alice and Bob, it is basically set that the entity having the detector performs the decryption of the parity (the 1st criterion).

[0039] The signaling information is composed of a bit string of size m (m is an integer). When m is 1, the signaling information is composed of 1 bit in size, and when m is 2, the signaling information is composed of 2 bits in size.

[0040] Signaling information is transmitted. When the signaling information is "0", the parity information is decoded by a party without a detector. When the signaling information is "1", the party for decoding the parity information is individually specified by the quantum cryptographic communication system 100. That is, the quantum cryptographic communication system 100 designates either Alice or Bob to decode the parity information. In such an embodiment, the signaling information further includes 1 bit as an additional bit, and thus has a total size of 2 bits. Based on the signaling information, the party that should decode the parity is designated. For example, when the value of the additional bit is "0", Alice decodes the parity information, and when it is "1", Bob decodes the parity information.

[0041] According to an embodiment, the signaling information basically has a size of 2 bits. For example, when the signaling information is "00", the party with a detector decodes the parity information. When it is "01", the party without a detector decodes the parity information. When the signaling information is "10", it indicates that both Alice and Bob can perform encoding or decoding. When the signaling information is "11", the party that performs the encoding or decoding of the first parity information is specified as either Alice or Bob.

[0042] For example, Alice first encodes parity information and Bob receives and decodes the parity. Then, Bob, who is the subject of decoding, performs encoding to generate additional parity information, and the additional parity information is transmitted back to Alice. Alice decodes the received additional parity information again. That is, assuming that the error correction process is not completed by a single parity transmission, the signaling information is composed of 2 bits. According to one embodiment, when the upper bit of the 2-bit signaling information is a specific value (e.g., 1), it means that the error correction process is not completed by a single parity transmission, and based on the value of the lower bit, it is determined which of Alice and Bob will perform encoding or decoding.

[0043] The signaling information is transmitted periodically or aperiodically between Alice and Bob during the implementation of the quantum cryptographic communication method. For example, when quantum key distribution is performed, the signaling is unconditionally transmitted, transmitted periodically according to the number of times of performing the quantum communication step (S10 in FIG. 1), or periodically transmitted for a certain period of time.

[0044] Those skilled in the art will understand that the size and rules of the above-described signaling information can be changed arbitrarily, and numerous embodiments will arise according to the agreement between Alice and Bob or the protocol of the quantum communication system 100. Therefore, it must be understood that the present invention is not limited to the embodiments described above with reference to FIG. 11. Note that the embodiments described above with reference to FIG. 11 relate to a one-to-one quantum cryptographic communication system, which is similarly applicable to one-to-many, many-to-one, or many-to-many quantum cryptographic communication systems.

[0045] FIG. 12 is a diagram showing a one-to-many quantum cryptographic communication system according to an embodiment.

[0046] One-to-many quantum cryptographic communication is a method in which one sender Alice communicates with multiple receivers (Bob1, Bob2, …, Bob N )(N is a positive number).

[0047] The one-to-many quantum cryptographic communication system 200 is composed of one-to-one quantum cryptographic communication between Alice and Bob1, one-to-one quantum cryptographic communication between Alice and Bob2, …, and one-to-one quantum cryptographic communication between Alice and Bob N That is, the one-to-many quantum cryptographic communication system 200 is composed of a plurality of one-to-one quantum cryptographic communications.

[0048] In the one-to-many quantum cryptographic communication system 200, as the signaling information indicating the subject of decoding of parity information, bits of size m×N are used. m bits is the size of the signaling information in one-to-one communication, and N is the number of one-to-one quantum cryptographic communications. That is, the one-to-many quantum cryptographic communication system 200 includes one-to-one quantum cryptographic communication between Alice and Bob1 performed via communication channel CH1, one-to-one quantum cryptographic communication between Alice and Bob2 performed via communication channel CH2, …, and communication channel CH N via which the one-to-one quantum cryptographic communication between Alice and Bob N is composed. Therefore, regarding the content of the signaling information described above with reference to FIG. 11, the same applies to the one-to-one quantum cryptographic communication via each communication channel.

[0049] According to one embodiment, in order to reduce the amount of bits transmitted for signaling information, all or at least some of the subjects participating in the one-to-many quantum cryptographic communication are set to be able to use the basic setting (that is, the subject having a detector decodes the parity information) without using the signaling information.

[0050] FIG. 13 is a diagram showing decoding of parity information using the basic setting without using the signaling information according to one embodiment (assuming that a detector is located at each of the receivers (Bob1, Bob2, …, Bob N )).

[0051] Unify the criteria for determining the entity responsible for decrypting parity information across the entire one-to-many quantum cryptographic communication system 200. In such an embodiment, instead of using m×N bits, it is possible to determine the entity responsible for decrypting parity information using only one bit. Across the entire one-to-many quantum cryptographic communication system 200 according to one embodiment, the signaling information is simply composed of only 1 bit in size, and either the sender Alice or the receiver group (Bob1, Bob2, …, Bob N ) is determined as the entity responsible for decrypting the parity information. For example, when the signaling information is "0", the sender Alice performs encoding, and the receiver group (Bob1, Bob2, …, Bob N ) performs decoding. When the signaling information is "1", the sender Alice performs decoding, and the receiver group (Bob1, Bob2, …, Bob N ) performs encoding.

[0052] FIG. 14 is a diagram showing the decryption of parity information using only one bit as signaling information according to one embodiment.

[0053] According to one embodiment, the signaling information is configured to be 2 bits in size, with a bit value indicating the unification of the criteria for determining the entity responsible for decrypting the parity information located in the upper bit, and a bit value specifying the entity responsible for decrypting the parity information located in the lower bit. However, since this can be freely configured, there is no limitation.

[0054] According to one embodiment, some of the one-to-one communications constituting the one-to-many quantum cryptographic communication system 200 unify the criteria for determining the entity responsible for decrypting the parity information, and the rest individually specify the entity responsible for decrypting the parity information. To individually specify the entity responsible for decrypting the parity information, the signaling information requires additional bits.

[0055] FIG. 15 is a diagram showing the decryption of parity information by individually specifying the entity responsible for decrypting the parity information using additional bits according to one embodiment.

[0056] Using additional bits will increase the size of the signaling information.

[0057] Many-to-one quantum cryptographic communication is a method in which multiple senders (Alice1, Alice2, …, Alice N ) communicate with a single receiver Bob (N is a positive number). Since many-to-one quantum cryptographic communication has a structure opposite to that of one-to-many quantum cryptographic communication, the content described above regarding one-to-many quantum cryptographic communication is similarly applicable to many-to-one quantum cryptographic communication, and thus its detailed description is omitted.

[0058] FIG. 16 is a diagram showing a many-to-many quantum cryptographic communication system according to an embodiment.

[0059] Many-to-many quantum cryptographic communication is a method in which multiple senders (Alice1, Alice2, …, Alice N ) communicate with multiple receivers (Bob1, Bob2, …, Bob K ) (N and K are positive numbers). As an example, the many-to-many quantum cryptographic communication system 300 includes one-to-one communication between Alice1 and Bob1, one-to-one communication between Alice1 and Bob2, one-to-one communication between Alice1 and Bob N , one-to-one communication between Alice2 and Bob1, one-to-one communication between Alice2 and Bob2, and one-to-one communication between Alice2 and Bob n . That is, the many-to-many quantum cryptographic communication system 300 is composed of N×K one-to-one quantum cryptographic communications.

[0060] Regarding the one-to-one quantum cryptographic communication via each communication channel, the content regarding the signaling information described above with reference to FIG. 11 is similarly applicable. In the many-to-many quantum cryptographic communication system 300, the signaling information indicating the subject of decoding the parity information is represented by bits of size m×N×K. The m bits are the size of the signaling information in one-to-one communication.

[0061] According to one embodiment, all or some of the entities participating in the many-to-many quantum cryptographic communication system 300 are configured to be able to use a basic setting (i.e., the entity having a detector performs parity decoding) without using signaling information.

[0062] According to one embodiment, the criteria for determining the entity for decoding parity information for the entire many-to-many quantum cryptographic communication system 300 are unified. Alternatively, in the many-to-many quantum cryptographic communication system 300, groups are divided for each sender (for example, the first communication group between Alice1 and the receivers (Bob1, Bob2,..., Bob K ) and the second communication group between Alice2 and the receivers (Bob1, Bob2,..., Bob K ), and different criteria for determining the entity for decoding parity information are applied for each group, but the criteria are unified within one group. Alternatively, in the many-to-many quantum cryptographic communication system 300, groups are divided for each receiver (for example, the first communication group between Bob1 and the senders (Alice1, Alice2), the second communication group between Bob2 and the senders (Alice1, Alice2), and the third communication group between Bob3 and the senders (Alice1, Alice2)), and different criteria for determining the entity for decoding parity information are applied for each group, but the criteria are unified within one group.

[0063] According to one embodiment, for some of the one-to-one communications constituting the many-to-many quantum cryptographic communication system 300, the criteria for determining the entity for decoding parity information are unified, and for the rest, the entity for parity decoding is specified individually. To specify the entity for parity decoding individually, the signaling information further requires additional bits for identifying the entity for decoding.

[0064] According to one embodiment, the above-described signaling information is transmitted between a sender and a receiver using methods such as a Physical Downlink Control Channel (PDCCH) such as 5G, LTE-A, LTE, Wi-Fi, an Enhanced PDCCH, a Physical Downlink Shared Channel (PDSCH), Cell specific high-layer signaling, and UE specific high-layer signaling.

[0065] According to one embodiment, the signaling information is part of the delivered quantum key. As an example, after step S10 in FIG. 1, the signaling information may be included in the second information sequence generated by Bob, but is not limited thereto.

[0066] This specification is intended to provide exemplary configurations and operations for implementing the present invention. The technical idea of the present invention includes not only the embodiments described above, but also implementations obtained by simply changing or modifying the above embodiments. Note that the technical idea of the present invention also includes implementations that can be easily changed or modified from the embodiments described above in the future.

Description of Reference Numerals

[0067] 100, 200, 300 Quantum Cryptographic Communication System

Claims

1. A quantum cryptographic communication method between at least one first communication device and at least one second communication device performed by at least one processor, comprising: a quantum communication step in which the first communication device transmits a first information sequence generated by randomly modulating photons in terms of phase and polarization to the second communication device, and the second communication device generates a second information sequence based on the first information sequence; a post-processing step of making the first information sequence and the second information sequence identical by using parity information in an error correction mode selected based on a predetermined criterion. The error correction mode is: a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to make the second information sequence identical to the first information sequence; either a second error correction mode in which the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to make the first information sequence identical to the second information sequence. The predetermined criterion includes: a first criterion in which the communication device where the detector is not located among the first communication device and the second communication device encodes the parity information, and the communication device where the detector is located among the first communication device and the second communication device decodes the parity information; a second criterion in which either one of the first communication device and the second communication device decodes the parity information based on signaling information including information regarding the subject of decoding of the parity information. A quantum cryptographic communication method characterized by including these.

2. The at least one second communication device includes a plurality of communication devices, The post-processing step between the first communication device and the plurality of communication devices is performed according to the first criterion. The quantum cryptographic communication method according to Claim 1.

3. The at least one second communication device includes a plurality of communication devices, The post-processing step between the first communication device and the plurality of communication devices is performed according to the second criterion. The quantum cryptographic communication method according to Claim 1.

4. A quantum cryptographic communication method between at least one first communication device and at least one second communication device performed by at least one processor, a quantum communication step in which the first communication device transmits a first information sequence generated by randomly modulating according to the phase and polarization of photons to the second communication device, and the second communication device generates a second information sequence based on the first information sequence; a post-processing step of making the first information sequence and the second information sequence identical and matching using parity information in an error correction mode selected based on a predetermined criterion, and the error correction mode is a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to make the second information sequence identical and matching with the first information sequence; either a second error correction mode in which the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to make the first information sequence identical and matching with the second information sequence, the predetermined criterion is when an eavesdropper is located closer to the second communication device than to the first communication device, the error correction mode is selected as the first error correction mode; when an eavesdropper is located closer to the first communication device than to the second communication device, the error correction mode is selected as the second error correction mode. A quantum cryptographic communication method characterized by this.

5. a first communication device for transmitting a first information sequence generated by randomly modulating according to the phase and polarization of photons to a second communication device; a second communication device for generating a second information sequence based on the received first information sequence, quantum key distribution is performed by an error correction process of making the first information sequence and the second information sequence identical and matching using parity information in an error correction mode selected based on a predetermined criterion, the error correction mode is a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to make the second information sequence identical and matching with the first information sequence; Either the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to align the first information sequence identically with the second information sequence, which is a second error correction mode, The predetermined criterion is a first criterion in which the communication device without a detector among the first communication device and the second communication device encodes the parity information, and the communication device with a detector among the first communication device and the second communication device decodes the parity information, a quantum key distribution communication system characterized by including a second criterion in which either one of the first communication device and the second communication device decodes the parity information based on signaling information including information regarding the subject of decoding for the parity information.

6. A first communication device for transmitting a first information sequence generated by randomly modulating according to the phase and polarization of photons to a second communication device, a second communication device for generating a second information sequence based on the received first information sequence, Quantum key distribution is performed by an error correction process of making the first information sequence and the second information sequence identical using parity information under an error correction mode selected based on a predetermined criterion, The error correction mode is a first error correction mode in which the first communication device encodes first parity information and transmits it to the second communication device, and the second communication device decodes the encoded first parity information to align the second information sequence identically with the first information sequence, Either the second communication device encodes second parity information and transmits it to the first communication device, and the first communication device decodes the encoded second parity information to align the first information sequence identically with the second information sequence, which is a second error correction mode, The predetermined criterion is when the eavesdropper is located closer to the second communication device than to the first communication device, the error correction mode is selected as the first error correction mode, a quantum key distribution communication system characterized in that when the eavesdropper is located closer to the first communication device than to the second communication device, the error correction mode is selected as the second error correction mode.

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