Source-linked AI summary
Hacking commercial quantum cryptography systems by tailored bright illumination
Lars Lydersen, Carlos Wiechers, Christoffer Wittmann, Dominique Elser, Johannes Skaar, Vadim Makarov
TL;DR
QKD security proofs assume device models that practical implementations may not fully satisfy. This paper experimentally shows that tailored bright illumination can remotely control detectors in two commercial QKD systems, enabling perfect eavesdropping.
Problem
Security proofs rely on device assumptions, while practical QKD components can deviate from those models, leaving implementation security requiring further evidence.
Method
The authors experimentally blind gated avalanche-photodiode detectors with bright illumination and control their clicks using tailored classical laser pulses.
Results
Two commercial QKD systems were fully cracked, with detector thresholds enabling perfect eavesdropping through remotely controlled measurements.
Takeaways & Limitations
Practical QKD security requires identifying and closing implementation loopholes and incorporating remaining imperfections into security proofs.
Takeaways & Limitations
The authors state that designing hack-proof detectors remains unclear and that future detectors must be tested for side channels.
Abstract
from arXiv · showhide
The peculiar properties of quantum mechanics allow two remote parties to communicate a private, secret key, which is protected from eavesdropping by the laws of physics. So-called quantum key distribution (QKD) implementations always rely on detectors to measure the relevant quantum property of single photons. Here we demonstrate experimentally that the detectors in two commercially available QKD systems can be fully remote-controlled using specially tailored bright illumination. This makes it possible to tracelessly acquire the full secret key; we propose an eavesdropping apparatus built of off-the-shelf components. The loophole is likely to be present in most QKD systems using avalanche photodiodes to detect single photons. We believe that our findings are crucial for strengthening the security of practical QKD, by identifying and patching technological deficiencies.