Ponosova A.Ruzhitskaya D.Chaiwongkhot P.Egorov V.Makarov V.Huang A.Mahidol University2023-06-182023-06-182022-10-01PRX Quantum Vol.3 No.4 (2022)https://repository.li.mahidol.ac.th/handle/20.500.14594/84249A well-protected and characterized 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.Computer ScienceArticleSCOPUS10.1103/PRXQuantum.3.0403072-s2.0-8514192532126913399