The practical issues of side-channel-secure quantum key distribution

TL;DR

This paper discusses practical issues in implementing side-channel-secure quantum key distribution, addressing vulnerabilities and demonstrating that the protocol remains secure under certain attack conditions with minimal assumptions.

Contribution

It introduces a refined SCS protocol that accounts for correlated errors and Trojan-horse attacks, enhancing practicality without requiring full quantum state characterization.

Findings

Reflected light intensity below 10^{-6} limits Eve's information gain.

The SCS protocol effectively counters detection and source side attacks.

Numerical results support the protocol's robustness under realistic attack scenarios.

Abstract

Quantum Key Distribution (QKD) leverages the principles of quantum mechanics to provide theoretically unconditional security for cryptographic key sharing. However, practical implementations remain vulnerable due to non-ideal devices and potential security loopholes at both the source and detection sides of QKD systems. The side-channel-secure (SCS) protocol addresses these challenges by encoding bits in vacuum and non-vacuum states and introducing a third-party measurement node, thereby repelling attacks targeting the detection side as well as external lab attacks on the source side. In this work, we consider the state-dependent correlated errors and Trojan-horse attack while preserving the SCS protocol's key advantage-specifically, requiring only upper bounds on intensities characterization without needing a full description of quantum states in infinite dimensions. Numerical results demonstrate that when the reflected light intensity from Trojan-horse attacks falls below $10^{-6}$, Eve can scarcely extract additional key information from the reflections. This work makes the SCS protocol more practical.