Finite-Key Analysis for Coherent One-Way Quantum Key Distribution

TL;DR

This paper provides a rigorous finite-key security analysis for a variant of coherent-one-way quantum key distribution, extending secure transmission distances and ensuring security against coherent attacks with improved key rates.

Contribution

It introduces a tight finite-key security proof for COW-QKD using advanced statistical tools, enhancing practical security and performance over previous analyses.

Findings

Extended secure transmission distance in finite-key regime

Achieved higher key rates with Kato's inequality

Confirmed security against coherent attacks in practical settings

Abstract

Coherent-one-way (COW) quantum key distribution (QKD) is a significant communication protocol that has been implemented experimentally and deployed in practical products due to its simple equipment requirements. However, existing security analyses of COW-QKD either provide a short transmission distance or lack immunity against coherent attacks in the finite-key regime. In this paper, we present a tight finite-key security analysis within the universally composable framework for a variant of COW-QKD, which has been proven to extend the secure transmission distance in the asymptotic case. We combine the quantum leftover hash lemma and entropic uncertainty relation to derive the key rate formula. When estimating statistical parameters, we use the recently proposed Kato's inequality to ensure security against coherent attacks and achieve a higher key rate. Our paper confirms the security and feasibility of COW-QKD for practical application and lays the foundation for further theoretical study and experimental implementation.