Resilience of gated avalanche photodiodes against bright illumination attacks in quantum cryptography

TL;DR

This paper demonstrates that properly operated gated avalanche photodiodes are resistant to bright illumination attacks in quantum cryptography, and monitoring photocurrent is an effective counter-measure against such attacks.

Contribution

The study provides a detailed analysis showing immunity of correctly operated gated APDs to continuous-wave attacks and proposes photocurrent monitoring as a simple countermeasure.

Findings

Gated APDs are immune to continuous-wave illumination attacks when correctly operated.

Monitoring photocurrent effectively detects attacks using temporally tailored light.

Proper operation and monitoring can secure quantum key distribution systems against bright illumination attacks.

Abstract

Semiconductor avalanche photodiodes (APDs) are commonly used for single photon detection in quantum key distribution. Recently, many attacks using bright illumination have been proposed to manipulate gated InGaAs APDs. In order to devise effective counter-measures, careful analysis of these attacks must be carried out to distinguish between incorrect operation and genuine loopholes. Here, we show that correctly-operated, gated APDs are immune to continuous-wave illumination attacks, while monitoring the photocurrent for anomalously high values is a straightforward counter-measure against attacks using temporally tailored light.