Protecting fiber-optic quantum key distribution sources against light-injection attacks

TL;DR

This paper proposes and experimentally validates a countermeasure for fiber-optic quantum key distribution sources against light-injection attacks, enhancing security by using sacrificial components like isolators or circulators.

Contribution

It introduces a practical countermeasure involving sacrificial components to protect QKD sources from high-power light-injection attacks, validated with off-the-shelf fiber-optic devices.

Findings

Off-the-shelf fiber-optic isolators and circulators can withstand high-power laser attacks.

The sacrificial component either attenuates or permanently breaks under attack.

The proposed method enhances the security of quantum key distribution sources.

Abstract

A well-protected and characterised source in a quantum key distribution system is needed for its security. Unfortunately, the source is vulnerable to light-injection attacks, such as Trojan-horse, laser-seeding, and laser-damage attacks, in which an eavesdropper actively injects bright light to hack the source unit. The hacking laser could be a high-power one that can modify properties of components via the laser-damage attack and also further help the Trojan-horse and other light-injection attacks. Here we propose a countermeasure against the light-injection attacks, consisting of an additional sacrificial component placed at the exit of the source. This component should either withstand high-power incoming light while attenuating it to a safe level that cannot modify the rest of the source, or get destroyed into a permanent high-attenuation state that breaks up the line. We demonstrate experimentally that off-the-shelf fiber-optic isolators and circulators have these desired properties, at least under attack by a continuous-wave high-power laser.