Source-linked AI summary
Quantum Hacking: Experimental demonstration of time-shift attack against practical quantum key distribution systems
Yi Zhao, Chi-Hang Fred Fung, Bing Qi, Christine Chen, Hoi-Kwong Lo
TL;DR
The paper addresses whether practical QKD systems can remain secure despite detector-efficiency mismatches and demonstrates a technologically feasible time-shift attack against a commercial system. The attack succeeds with current technology, showing that detection-efficiency loopholes affect both fundamental tests and QKD applications.
Problem
Practical QKD systems are widely believed secure, but detector-efficiency loopholes can violate fair-sampling assumptions relevant to security proofs.
Method
The paper experimentally applies a simple time-shift attack to a commercial QKD system without Eve measuring or preparing quantum states.
Results
The experiment provides the first demonstration of a technologically feasible attack that breaks a commercial QKD system using current technology.
Takeaways & Limitations
Practical QKD systems should be battle-tested, and security proofs should rely on testable assumptions addressing detection-efficiency and side-channel loopholes.
Takeaways & Limitations
The experiment manipulates the time variable in a practical detector-mismatch setting, while other variable domains are discussed as generalizations.
Abstract
from arXiv · showhide
Quantum key distribution (QKD) systems can send signals over more than 100 km standard optical fiber and are widely believed to be secure. Here, we show experimentally for the first time a technologically feasible attack, namely the time-shift attack, against a commercial QKD system. Our result shows that, contrary to popular belief, an eavesdropper, Eve, has a non-negligible probability (~4%) to break the security of the system. Eve's success is due to the well-known detection efficiency loophole in the experimental testing of Bell inequalities. Therefore, the detection efficiency loophole plays a key role not only in fundamental physics, but also in technological applications such as QKD.