Quantum Backdoor – Performing Electronic Side-Channel Analysis on Quantum Key Distribution Systems

Maria Beatriz Soares Lopes da Costa

Key information

Authors:

Maria Beatriz Soares Lopes da Costa (Maria Beatriz Soares Lopes da Costa)

Supervisors:

Yasser Rashid Revez Omar (Yasser Rashid Revez Omar); João Carlos Carvalho de Sá Seixas (João Carlos Carvalho de Sá Seixas)

Published in

06/20/2024

Abstract

Over the last decades, Quantum Key Distribution (QKD) has risen as a promising solution for secure communications, a pressing subject in the aftermath of the security threat posed by Quantum Computers and the Shor's Algorithm. Offering a theoretically secure way to share secret keys between parties, QKD state-of-the-art has witnessed remarkable progress in the last years. Nonetheless, although theoretically secure, QKD is not implementation-secure and until now, the study of physical vulnerabilities in QKD setups has mainly focused on the optical channel. The concept of hacking a cryptographic system via its physical characteristics and associated leakages, known as side-channel analysis, was firstly introduced in classical cryptography, with the seminal work of Paul Kosher. Since then, power and electromagnetic side-channel analysis have become a staple in classical cryptanalysis. However, these concepts have hardly been applied to QKD. In this work we propose and implement a new method for side-channel analysis to QKD systems, by exploiting the power consumption of the electronic driver controlling the electro-optical components of the QKD transmitter. For high-rate transmission, QKD modules typically require electronic drivers, such as Field Programmable Gate Arrays (FPGAs). Here, we will show that the FPGA's power consumption can leak information about the QKD operation, and consequently the generated key. The analysis was performed on the QKD transmitter at the University of Padua. Our results are consistent and show critical information leakage, having reached a maximum accuracy of 73.35% in the prediction of the generated random keys at 100 MHz qubit repetition frequency.