Quantum Key Relay Nodes for Long-Distance Transmission
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Solution Overview
Problem
Current quantum key distribution (QKD) systems are limited by the range of quantum key exchange, typically restricted to direct connections via radio links or fiber optic lines, with fiber optic connections limited to a few kilometers due to photon attenuation, necessitating the use of intermediate trusted nodes for key transmission, which requires complex security measures and raises concerns about key accessibility.
Innovation Solution
A method for transmitting quantum-secure keys between network nodes using an intermediate node without storing the key within that node, by forming a quantum channel between adjacent nodes on the transmission path and using Post Quantum Cryptography (PQC) and QKD keys to create a bit sequence for secure transmission, ensuring the key remains only accessible to the sending and receiving nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If intermediate trusted nodes are used for key transmission over long distances, then the transmission distance is extended, but the security risk and operational complexity increase due to key accessibility concerns
Solution Approach 1:
The transmission path is segmented into multiple quantum channels between adjacent network nodes. Each node performs local QKD with its neighbors, creating a chain of trusted quantum links rather than requiring a single long-distance quantum channel or a trusted intermediate node that stores the full key.
Solution Approach 2:
Quantum key relay nodes act as intermediaries that facilitate key distribution between distant nodes without storing the final communication key. These nodes perform local QKD operations and use quantum key aggregation to enable end-to-end secure communication while maintaining that the final key never resides in the intermediate nodes.
2Length of stationary object
If intermediate trusted nodes are used for key transmission, then long-distance key exchange is enabled, but the device complexity and security costs increase due to required monitoring and protection systems
Solution Approach 1:
The patent replaces the mechanical/physical security infrastructure (locking mechanisms, monitoring systems, protected facilities) required for trusted nodes with a quantum cryptographic approach. The security is achieved through quantum mechanical principles (no-cloning theorem, quantum entanglement) rather than physical security measures.
Solution Approach 2:
The quantum key relay nodes automatically perform local QKD operations and key aggregation through quantum protocols without requiring human intervention or external security monitoring. The quantum cryptographic protocols themselves provide the security guarantees, eliminating the need for manual security management.
3Reliability
If direct QKD connections are used between network nodes, then key security is maintained, but the transmission range is limited to a few kilometers due to photon attenuation
Solution Approach 1:
The long-distance transmission path is divided into multiple short-distance quantum channels between adjacent nodes. Each segment operates within the feasible QKD distance range, and the overall long-distance key distribution is achieved by combining these segments through quantum key aggregation at relay nodes.
Solution Approach 2:
Quantum key relay nodes serve as intermediaries that bridge long distances by performing local QKD with neighboring nodes. These relay nodes enable end-to-end key distribution between distant endpoints without requiring a single long-distance quantum channel, thus overcoming photon attenuation limitations.
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
This method enables secure key transmission over longer distances without compromising the key within intermediate nodes, reducing security costs and ensuring only the end nodes possess the quantum-secure key, maintaining confidentiality and authenticity against potential attackers.
Implementation Method 1
a communication system is considered quantum-safe if the confidentiality and (preferably, that is, essentially mandatory, verifiable) authenticity of transmitted data between a sender and a receiver cannot be compromised by quantum computers. According to the current state of the art, this is achieved by constructing a QKD system in which the sending and receiving entities have means for the quantum mechanical generation and exchange of shared cryptographic keys
Implementation Method 2
Regarding the latter, i.e., fiber optic connections, the range is limited by the attenuation to which the photons transmitted at low power for key exchange are subject in the optical fiber (the quantum channel)
Data Source
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AI summary
The invention relates to a method for transmitting quantum-safe keys between a first network node (1) and a second network node (2), each equipped with means (4, 5) for generating quantum-safe keys, but not directly connected to each other via a quantum channel. A random number RND generated as a quantum-safe user key in one of the network nodes (1, 2) is transmitted from the generating network node (1, 2) to the other network node (2, 1) via a transmission path with at least one intermediate network node (3), wherein a quantum channel (10, 11) for exchanging QKD keys is formed between network nodes that are immediately adjacent to each other on the transmission path.Between two network nodes that follow each other on the transmission path in the transmission direction, the user key is transmitted with a bit sequence that is formed by combining the user key with a PQC key previously negotiated between the network nodes (1, 2) according to a PQC procedure, and with a QKD key, namely a common quantum-safe key of the two consecutive network nodes.