Mitigating the source-side channel vulnerability by characterization of photon statistics

TL;DR

This paper focuses on characterizing photon statistics in practical quantum key distribution systems to detect side-channel attacks and improve security by accurately measuring photon properties and fluctuations.

Contribution

It introduces a rigorous method for photon source characterization, including mean photon number estimation and intensity fluctuation analysis, to mitigate source-side vulnerabilities in QKD.

Findings

Photon statistics characterization improves attack detection.

Multiple detectors provide more accurate photon number estimates.

Intensity fluctuation analysis helps identify state preparation flaws.

Abstract

Quantum key distribution (QKD) theoretically offers unconditional security. Unfortunately, the gap between theory and practice threatens side-channel attacks on practical QKD systems. Many well-known QKD protocols use weak coherent laser pulses to encode the quantum information. These sources differ from ideal single photon sources and follow Poisson statistics. Many protocols, such as decoy state and coincidence detection protocols, rely on monitoring the photon statistics to detect any information leakage. The accurate measurement and characterization of photon statistics enable the detection of adversarial attacks and the estimation of secure key rates, strengthening the overall security of the QKD system. We have rigorously characterized our source to estimate the mean photon number employing multiple detectors for comparison against measurements made with a single detector. Furthermore, we have also studied intensity fluctuations to help identify and mitigate any potential information leakage due to state preparation flaws. We aim to bridge the gap between theory and practice to achieve information-theoretic security.