Finite Key Security of Simplified Trusted Node Networks

TL;DR

This paper establishes finite-key security bounds for simplified trusted node networks in quantum key distribution, enabling practical assessment of their security and efficiency compared to traditional trusted nodes.

Contribution

It provides the first finite-key security proof for STN chains and introduces a cost function to evaluate their computational advantages.

Findings

Finite-key security bounds for STNs are now established.

A new cost function helps compare STNs and regular TNs in terms of computational efficiency.

STNs can be advantageous in scenarios with limited computational resources.

Abstract

Simplified trusted nodes (STNs) are a form of trusted node for quantum key distribution (QKD) networks which do not require running a full QKD stack every instance (i.e., they do not need to run error correction and privacy amplification each session). Such systems hold the advantage that they may be implemented with weaker computational abilities, than regular TNs, while still keeping up with key generation rate demands. The downside is that noise tolerance is lower. However, to get a better understanding of their suitability in various scenarios, one requires practical, finite-key security bounds for STN networks. So far, only theoretical asymptotic bounds are known. In this work we derive a new proof of security for STN chains in the finite key setting. We also derive a novel cost function allowing us to evaluate when STNs would be beneficial from a computational cost perspective, compared with regular TN networks.