Risk analysis of Trojan-horse attacks on practical quantum key distribution systems

TL;DR

This paper analyzes the security risks of Trojan-horse attacks on quantum key distribution systems through spectral measurements, identifying vulnerable wavelengths and proposing countermeasures to enhance security.

Contribution

It provides a detailed risk analysis of Trojan-horse attacks on QKD systems using spectral data and suggests effective countermeasures to mitigate these vulnerabilities.

Findings

Vulnerable wavelength regimes identified beyond 1550 nm

Spectral properties of components influence attack success

Countermeasures can significantly reduce attack risks

Abstract

An eavesdropper Eve may probe a quantum key distribution (QKD) system by sending a bright pulse from the quantum channel into the system and analyzing the back-reflected pulses. Such Trojan-horse attacks can breach the security of the QKD system if appropriate safeguards are not installed or if they can be fooled by Eve. We present a risk analysis of such attacks based on extensive spectral measurements, such as transmittance, reflectivity, and detection sensitivity of some critical components used in typical QKD systems. Our results indicate the existence of wavelength regimes where the attacker gains considerable advantage as compared to launching an attack at 1550 nm. We also propose countermeasures to reduce the risk of such attacks.