Security analysis of orthogonal state attack on a high-speed quantum key distribution system

TL;DR

This paper presents a security analysis of orthogonal state attacks on high-speed quantum key distribution systems, demonstrating a feasible attack method that can compromise key security.

Contribution

It introduces a new security analysis model for orthogonal state attacks, including a practical muted attack verified experimentally on a 1 GHz QKD system.

Findings

Eve can control Bob's detection response by muting SPADs using orthogonal state attacks.

The attack enables Eve to learn nearly all the keys in the QKD system.

Simulation shows overestimated key rates are vulnerable under these attacks.

Abstract

High-speed quantum key distribution (QKD) systems have achieved repetition frequencies above gigahertz through advanced technologies and devices, laying an important foundation for the deployment of high-key-rate QKD system. Although these advanced systems may introduce potential loopholes, an eavesdropper Eve is challenging to exploit them by performing the intercept-resend attacks due to the limited time window under high repetition frequency. However, here, we propose a security analysis model of orthogonal state attacks that do not require intercept-resend operation on the key rate of a QKD system. Under this framework, we propose a muted attack and experimentally verify the feasibility of the attack using a 1 GHz single-photon avalanche detector (SPAD). By sending hundreds of photons each time, Eve can mute Bob's SPADs to control the overall detection response of the QKD receiver, allowing her to learn nearly all the keys. Furthermore, we use this security model to simulate the overestimated key rates of the QKD system under orthogonal state attacks, including both the muted attack and the dead-time attack. This work theoretically and experimentally shows a timely case of the security vulnerability in the high-speed QKD system.