Attacking practical quantum key distribution system with wavelength dependent beam splitter and multi-wavelength sources

TL;DR

This paper reveals a vulnerability in practical quantum key distribution systems caused by wavelength-dependent beam splitters, demonstrating an attack that compromises security and emphasizing the need for stricter device security measures.

Contribution

The authors introduce a wavelength-dependent attack model exploiting beam splitter imperfections and experimentally demonstrate its effectiveness against real QKD systems.

Findings

The attack achieves nearly 100% success probability.

Practical QKD devices are vulnerable to side channel attacks.

Security protocols must account for wavelength-dependent imperfections.

Abstract

Unconditional security of quantum key distribution protocol can be guaranteed by the basic property of quantum mechanics. Unfortunately, the practical quantum key distribution system always have some imperfections, and the practical system may be attacked if the imperfection can be controlled by the eavesdropper Eve. Applying the fatal security loophole introduced by the imperfect beam splitter's wavelength dependent optical property, we propose wavelength-dependent attacking model, which can be applied to almost all practical quantum key distribution systems with the passive state modulation and photon state detection after the practical beam splitter. Utilizing our attacking model, we experimentally demonstrate the attacking system based on practical polarization encoding quantum key distribution system with almost 100% success probability. Our result demonstrate that all practical devices require tightened security inspection for avoiding side channel attacks in practical quantum key distribution experimental realizations.