Quantum key distribution component loopholes in 1500-2100 nm range perspective for Trojan-horse attacks

TL;DR

This paper investigates fiber optical component vulnerabilities in quantum key distribution systems within the 1500-2100 nm range, revealing spectral loopholes that could enable eavesdropping and proposing a passive countermeasure to enhance security.

Contribution

It identifies spectral transmission loopholes in fiber components used in QKD and proposes a simple passive countermeasure based on total internal reflection to mitigate Trojan-horse attacks.

Findings

Loopholes in fiber component transmission spectra between 1500-2100 nm.

Countermeasure causes at least 60 dB insertion loss for certain Trojan-horse pulses.

Potential for eavesdropping exploitation due to identified spectral vulnerabilities.

Abstract

Vulnerabilities of components used in quantum key distribution (QKD) systems affect its implementation security and must be taken into consideration during system development and security analysis. In this paper, we investigated transmission of fiber optical elements, which are commonly used in QKD systems for designing countermeasures against Trojan-horse attacks, in 1500-2100 nm range. As a result, we found loopholes in their transmission spectra which open possibilities for eavesdropping. We also suggested a simple passive countermeasure based on violation of total internal reflection in single-mode fiber, that leads to additional insertion losses of at least 60 dB for double-pass Trojan-horse probe pulses for wavelengths longer than 1830 nm.