Real-time monitoring of single-photon detectors against eavesdropping in quantum key distribution systems

TL;DR

This paper presents a real-time monitoring method for single-photon detectors in quantum key distribution systems to detect practical eavesdropping attacks like after-gate and time-shift attacks by analyzing detection statistics.

Contribution

The authors introduce a real-time detection scheme based on statistical analysis of detection times, enabling practical identification of eavesdropping without detector modifications.

Findings

Successfully detects after-gate and time-shift attacks in real-time

Identifies changes in afterpulse probabilities during attacks

Distinguishes attack signatures through timing analysis

Abstract

By employing real-time monitoring of single-photon avalanche photodiodes we demonstrate how two types of practical eavesdropping strategies, the after-gate and time-shift attacks, may be detected. Both attacks are identified with the detectors operating without any special modifications, making this proposal well suited for real-world applications. The monitoring system is based on accumulating statistics of the times between consecutive detection events, and extracting the afterpulse and overall efficiency of the detectors in real-time using mathematical models fit to the measured data. We are able to directly observe changes in the afterpulse probabilities generated from the after-gate and faint after-gate attacks, as well as different timing signatures in the time-shift attack. We also discuss the applicability of our scheme to other general blinding attacks.