We propose a class of attacks on quantum key distribution (QKD) systems where an eavesdropper actively engineers new loopholes by using damaging laser illumination to permanently change properties of system components. This can turn a perfect QKD system into a completely insecure system. A proof-of-principle experiment performed on an avalanche photodiode-based detector shows that laser damage can be used to create loopholes. After about 1 W illumination, the detectors' dark count rate reduces 2 to 5 times, permanently improving single-photon counting performance. After about 1.5 W, the detectors switch permanently into the linear photodetection mode and become completely insecure for QKD applications.
@article{arxiv.1310.8384,
title = {Laser damage helps the eavesdropper in quantum cryptography},
author = {Audun N. Bugge and Sebastien Sauge and Aina M. M. Ghazali and Johannes Skaar and Lars Lydersen and Vadim Makarov},
journal= {arXiv preprint arXiv:1310.8384},
year = {2014}
}
Comments
Extended and improved discussions. This version is published in Phys. Rev. Lett. 5 pages, 4 figures