# US 12,003,624 B2 · Quantum cryptographic communication system, key management inspection device, key management inspection method, and computer program product

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- Number: US 12,003,624 B2
- Document ID: US12003624B2
- Status: Granted
- Kind: B2
- Application number: 17/651,200
- Filed: 2022-02-15
- Published: 2022-12-08
- Granted: 2024-06-04
- Earliest claimed: 2021-06-04
- Assignees: Kabushiki Kaisha Toshiba
- Applicants: Kabushiki Kaisha Toshiba
- Inventors: Kazuaki Doi; Yoshimichi Tanizawa; Toshiki Nakashima; Mari Matsumoto
- Web page: https://patentgrep.com/patent/US12003624B2

## CPC

- H04L 9/0852: {Quantum cryptography (transmission systems employing electromagnetic waves other than radio waves, e.g. light, infrared H04B10/00; wavelength-division multiplex systems H04J14/02; WDM arrangements H04J14/03)}
- H04L 9/002: {Countermeasures against attacks on cryptographic mechanisms (network architectures or network communication protocols for protection against malicious traffic H04L63/1441)}
- Y04S 40/20: Information technology specific aspects, e.g. CAD, simulation, modelling, system security
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- Y04S: SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS

## Abstract

A quantum-cryptographic-communication system according to an embodiment includes a key-integrated-management device, quantum-cryptography devices, and key-management-inspection devices. An inspection-target-value-calculating unit calculates an inspection-target value based on quantum-cryptography-device information related to a quantum-cryptography device. An expected-value-calculating unit calculates an expected value based on at least one of wiring information of a QKD link connected to the inspection-target-quantum-cryptography device; weather information of the site installed with the inspection-target-quantum-cryptography device; and the quantum-cryptography-device information. A permissible-value-calculating unit calculates a permissible value based on at least one of the wiring information, the weather information, and the quantum-cryptography-device information. A determining unit determines whether the inspection-target value is within the range of (expected value)−(permissible value) and within the range of (expected value)+(permissible value); and, when the inspection-target value is outside the range of (expected value)−(permissible value) and outside the range of (expected value)+(permissible value), transmits anomaly detection to a key integrated management device.

## Claims

### Claim 1

A quantum cryptographic communication system comprising:
a key integrated management device;
a plurality of quantum cryptography devices; and
a plurality of key management inspection devices, wherein
each of the plurality of key management inspection devices inspects a quantum cryptographic key generated by one of the plurality of quantum cryptography devices, and
each of the plurality of key management inspection devices includes one or more hardware processors configured to function at least as:
an inspection-target-value calculating unit that calculates an inspection target value based on quantum cryptography device information related to a quantum cryptography device,
an expected-value calculating unit that calculates an expected value based on at least one of
wiring information of a quantum cryptographic key distribution (QKD) link connected to the quantum cryptography device to be inspected,
weather information at a site installed with the quantum cryptography device to be inspected, and
the quantum cryptography device information,
a permissible-value calculating unit that calculates a permissible value based on at least one of the wiring information, the weather information, and the quantum cryptography device information, and
a determining unit that
determines whether or not the inspection target value is within a range of (the expected value)−(the permissible value) and within a range of (the expected value)+(the permissible value), and
when the inspection target value is outside the range of (the expected value)−(the permissible value) and outside the range of (the expected value)+(the permissible value), transmits anomaly detection to the key integrated management device.

### Claim 2 (depends on 1)

The quantum cryptography communication system according to claim 1, wherein
the quantum cryptography device information contains generation speeds of quantum cryptographic keys, and
the inspection-target-value calculating unit calculates an average value of the generation speeds as the inspection target value.

### Claim 3 (depends on 2)

The quantum cryptographic communication system according to claim 2, wherein
the wiring information contains
correspondence data indicating a correspondence of a propagation loss of entire optical fiber constituting the QKD link and the generation speed, and
the expected-value calculating unit calculates the expected value from the correspondence data.

### Claim 4 (depends on 2)

The quantum cryptographic communication system according to claim 2, wherein
the wiring information contains a wiring state indicating a ratio of an overhead wiring technique to an underground technique of optical fiber constituting the QKD link, and
the permissible-value calculating unit calculates the permissible value from the wiring state and the weather information.

### Claim 5 (depends on 4)

The quantum cryptographic communication system according to claim 4, wherein
the weather information contains wind force, and
the permissible-value calculating unit sets the permissible value to be large in proportion to proportion of the overhead wiring technique and in proportion to the wind force.

### Claim 6 (depends on 4)

The quantum cryptography communication system according to claim 4, wherein
the weather information contains an amount of rainfall, and
the permissible-value calculating unit sets the permissible value to be large in proportion to proportion of the overhead wiring technique and in proportion to the amount of rainfall.

### Claim 7 (depends on 1)

The quantum cryptographic communication system according to claim 1, wherein
the quantum cryptography device information contains generation speeds of quantum cryptographic keys, and
the inspection-target-value calculating unit calculates a dispersion value of the generation speeds as the inspection target value.

### Claim 8 (depends on 1)

The quantum cryptographic communication system according to claim 1, wherein
the quantum cryptography device information contains a Quantum bit error rate (QbER), and
the inspection-target-value calculating unit calculates a dispersion value of QbERs as the inspection target value.

### Claim 9 (depends on 7)

The quantum cryptographic communication system according to claim 7, wherein
the wiring information contains a wiring state indicating a ratio of an overhead wiling technique to an underground technique of the optical fiber constituting the QKD link,
the expected-value calculating unit calculates the expected value from the wiring state and the weather information, and
the permissible-value calculating unit calculates the permissible value from the wiring state and the weather information.

### Claim 10 (depends on 9)

The quantum cryptographic communication system according to claim 9, wherein
the weather information contains wind force,
the expected-value calculating unit sets the expected value to be large in proportion to proportion of the overhead wiring technique and in proportion to the wind force, and
the permissible-value calculating unit sets the permissible value to be large in proportion to proportion of the overhead wiring technique and in proportion to the wind force.

### Claim 11 (depends on 9)

The quantum cryptographic communication system according to claim 9, wherein
the weather information contains an amount of rainfall,
the expected-value calculating unit sets the expected value to be large in proportion to proportion of the overhead wiring technique and in proportion to the amount of rainfall, and
the permissible-value calculating unit sets the permissible value to be large in proportion to proportion of the overhead wiring technique and in proportion to the amount of rainfall.

### Claim 12

A key management inspection device that inspects a quantum cryptographic key generated by a quantum cryptography device, the key management inspection device comprising:
one or more hardware processors configured to function at least as:
an inspection-target-value calculating unit that calculates an inspection target value based on quantum cryptography device information related to the quantum cryptography device;
an expected-value calculating unit that calculates an expected value based on at least one of
the quantum cryptography device information,
wiring information of a quantum cryptographic key distribution (QKD) link connected to the quantum cryptography device, and
weather information of a site installed with the quantum cryptography device;
a permissible-value calculating unit that calculates a permissible value based on at least one of the quantum cryptography device information, the wiring information, and the weather information; and
a determining unit that
determines whether or not the inspection target value is within a range of (the expected value)−(the permissible value) and within a range of (the expected value)+(the permissible value), and
when the inspection target value is outside the range of (the expected value)−(the permissible value) and outside the range of (the expected value)+(the permissible value), transmits anomaly detection to a key integrated management device.

### Claim 13

A computer program product having a non-transitory computer readable medium including programmed instructions, wherein the instructions, when executed by a computer that inspects a quantum cryptographic key generated by a quantum cryptography device, cause the computer to function as:
an inspection-target-value calculating unit that calculates an inspection target value based on quantum cryptography device information related to the quantum cryptography device;
an expected-value calculating unit that calculates an expected value based on at least one of
wiring information of a quantum cryptographic key distribution (QKD) link connected to the quantum cryptography device to be inspected,
weather information of a site installed with the quantum cryptography device to be inspected, and
the quantum cryptography device information;
a permissible-value calculating unit that calculates a permissible value based on at least one of the wiring information, the weather information, and the quantum cryptography device information; and
a determining unit that
determines whether or not the inspection target value is within a range of (the expected value)−(the permissible value) and within a range of (the expected value)+(the permissible value), and
when the inspection target value is outside the range of (the expected value)−(the permissible value) and outside the range of (the expected value)+(the permissible value), transmits anomaly detection to a key integrated management device.