# Exploiting Faraday Rotation to Jam Quantum Key Distribution via Polarized Photons

## TL;DR

This paper demonstrates that Faraday rotation can be exploited to jam quantum key distribution systems by rotating photon polarization, potentially disrupting secure communication without detection.

## Contribution

It analyzes the feasibility of Faraday rotation-based jamming attacks on fiber and free-space QKD, revealing vulnerabilities even with automated polarization calibration.

## Key findings

- Jamming attack can be effective against fiber-based QKD.
- Attack can be performed covertly and indefinitely.
- Potential to combine jamming with eavesdropping for security breaches.

## Abstract

Quantum key distribution (QKD) involving polarized photons could be vulnerable to a jamming (or denial-of-service) attack, in which a third party applies an external magnetic field to rotate the plane of polarization of photons headed toward one of the two intended recipients. Sufficiently large Faraday rotation of one of the polarized beams would prevent Alice and Bob from establishing a secure quantum channel. We investigate requirements to induce such rotation both for free-space transmission and for transmission via optical fiber, and find reasonable ranges of parameters in which a jamming attack could be successful against fiber-based QKD, even for systems that implement automated recalibration for polarization-frame alignment. The jamming attack could be applied selectively and indefinitely by an adversary without revealing her presence, and could be further combined with various eavesdropping attacks to yield unauthorized information.