Quantum Eavesdropping without Interception: An Attack Exploiting the Dead Time of Single Photon Detectors

TL;DR

This paper demonstrates a novel quantum eavesdropping attack exploiting detector dead time, allowing an eavesdropper to gain nearly complete key information without detection, highlighting a significant security vulnerability in QKD systems.

Contribution

The paper introduces and experimentally validates a simple attack exploiting detector dead time, revealing a critical security flaw in quantum key distribution protocols.

Findings

Eavesdropper inferred up to 98.8% of the key

Attack does not significantly increase error rate

Countermeasure to prevent this attack is proposed

Abstract

The security of quantum key distribution (QKD) can easily be obscured if the eavesdropper can utilize technical imperfections of the actual implementation. Here we describe and experimentally demonstrate a very simple but highly effective attack which even does not need to intercept the quantum channel at all. Only by exploiting the dead time effect of single photon detectors the eavesdropper is able to gain (asymptotically) full information about the generated keys without being detected by state-of-the-art QKD protocols. In our experiment, the eavesdropper inferred up to 98.8% of the key correctly, without increasing the bit error rate between Alice and Bob significantly. Yet, we find an evenly simple and effective countermeasure to inhibit this and similar attacks.