AC Loop Current Attacks Against The KLJN Secure Key Exchange Scheme

TL;DR

This paper introduces a novel AC loop current attack on the KLJN secure key exchange scheme, exploiting parasitic AC voltages caused by ground loops and EMI, with demonstrated effectiveness and proposed defenses.

Contribution

It presents the first attack exploiting parasitic AC voltages on KLJN, expanding understanding of potential vulnerabilities and proposing countermeasures.

Findings

Attack effective in low-frequency ground loop scenarios

High-frequency spectrum analysis reveals wire voltage vulnerabilities

Defense protocols can mitigate the attack

Abstract

A new attack against the Kirchhoff-Law-Johnson-Noise(KLJN) secure key exchange scheme is introduced. The attack exploits a parasitic (periodic) AC voltage-source at either Alice or Bob ends. Such situations exist due to AC ground loops and electromagnetic interference (EMI). In the low-frequency case, the procedure is the generalized form of the former DC ground loop based attack. In the high-frequency case, the power spectrum of the wire voltage is utilized. The attack is demonstrated in both the low and the high-frequency situations. Defense protocols against the attack are also discussed.