Quantum Key Management for Long-Distance Global Key Sharing

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Solution Overview

Problem

Existing quantum key distribution systems are limited by the distance over which encryption keys can be shared due to the use of single photons, and require a random number generator in the key management device for generating global encryption keys.

Innovation Solution

A quantum cryptography communication system that combines local keys shared via quantum key distribution with global keys, allowing for flexible system configuration without the need for a random number generator in the key management device, by using existing network technologies and components to manage and route encryption keys.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If quantum key distribution using single photons is used to share encryption keys, then secure key sharing is achieved, but the transmission distance is limited

Engineering Contradiction:
Improvesecurity of key sharingVSAvoidtransmission distance
Core Design Contradiction:
ReliabilityVSLength of moving object

Solution Approach 1:

The patent introduces a key management device as an intermediary between quantum key distribution devices. This device receives local keys from multiple QKD devices, generates global keys by combining these local keys, and distributes them to applications. This mediator architecture allows secure key sharing over extended distances by relaying and processing keys through intermediate nodes rather than requiring direct long-distance quantum transmission.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent divides the key management function into two parts: local keys generated by QKD devices for secure transmission, and global keys generated by the key management device for application use. This segmentation allows the system to maintain quantum security for key generation while using classical infrastructure for key distribution and management, thereby extending the effective transmission distance.

Inventive Principle:
Principle #1Segmentation

2Productivity

If a random number generator is added to the key management device for generating global encryption keys, then key generation capability is improved, but device complexity increases

Engineering Contradiction:
Improvekey generation capabilityVSAvoiddevice configuration
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The key management device utilizes the quantum random number generation capability already present in the connected QKD devices. Instead of adding its own random number generator, the device requests and processes random numbers from the QKD devices, which then uses these inputs along with other local keys to generate global keys. This self-service approach leverages existing resources to avoid increasing device complexity.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The key management device is designed to perform multiple functions: receiving local keys from multiple QKD devices, generating global keys, managing key distribution, and supporting various applications. By making the device universal and multi-functional, the patent avoids the need for separate dedicated random number generation hardware, as the key management device itself becomes the central hub for all key-related operations using existing quantum randomness.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If local keys from multiple quantum key distribution devices are combined to generate global keys, then key sharing flexibility is improved, but key management complexity increases

Engineering Contradiction:
Improvesystem configuration flexibilityVSAvoidkey management complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The key management device implements feedback mechanisms to track which local keys have been used for generating global keys, which applications are using which keys, and the status of key validity. This feedback system allows the device to automatically manage key lifecycles, revoke expired keys, and maintain security policies without manual intervention, thereby handling the increased complexity through automated control rather than manual processes.

Inventive Principle:
Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables efficient sharing of encryption keys over extended distances and flexible system configurations, ensuring secure encrypted data communication without the need for a random number generator in the key management device.

Implementation Method 1

quantum key distribution (QKD), of securely sharing an encryption key using a single photon successively transmitted between a transmission device and a reception device

Methodology Applied
Scientific EffectQuantum key distribution: Photoelectric Effect

Data Source

PatentEP4152684B1Quantum cryptography communication system, quantum cryptography communication device, key management device, and computer-readable medium
Publication Date: 2026.02.11 KK TOSHIBA
  • EP4152684B1 patent drawingFigure 1
  • EP4152684B1 patent drawingFigure 2
  • EP4152684B1 patent drawingFigure 3

AI summary

According to an arrangement, a quantum cryptography communication system includes a quantum cryptography communication device and a key management device (20). The quantum cryptography communication system includes a generated information supply unit, a reception unit (21), a determination unit, and a global key supply unit (24). The generated information supply unit is configured to supply generated information generated by quantum key distribution processing, to the key management device (20). The reception unit (21) is configured to receive the generated information from the quantum cryptography communication device. The determination unit is configured to determine a ratio at which the generated information is used for a global key random number for each encrypted data communication destination. The global key supply unit (24) is configured to supply a global key generated from the global key random number to an application connected to the key management device (20).