A Static-Loop-Current Attack against the KLJN Secure Key Exchange System

TL;DR

This paper introduces a novel attack exploiting parasitic dc-voltage sources in the KLJN secure key exchange system, revealing vulnerabilities in practical low-frequency scenarios and proposing countermeasures.

Contribution

It presents a new attack method on the KLJN system using parasitic dc sources, which bypasses existing defenses and demonstrates the need for improved security measures.

Findings

The attack successfully compromises the KLJN system under certain conditions.

Traditional defense methods are ineffective against this parasitic dc-voltage-source attack.

Proposed defenses can mitigate the attack's effectiveness.

Abstract

A new attack against the Kirchhoff-Law-Johnson-Noise (KLJN) key distribution system is explored. The attack is based on utilizing a parasitic dc-voltage-source in the loop. Relevant situations often exist in the low-frequency limit in practical systems, especially when the communication is over a distance, due to a ground loop and/or electromagnetic interference (EMI). Surprisingly, the usual current/voltage comparison based defense method that exposes active attacks or parasitic features (such as wire resistance allowing information leak) does not function here. The attack is successfully demonstrated. Proposed defense methods against it are shown.