Analysis of coherent quantum cryptography protocol vulnerability to an active beam-splitting attack

TL;DR

This paper introduces and analyzes a new active beam-splitting attack on the coherent one-way quantum key distribution protocol, demonstrating its effectiveness compared to standard attacks across various channel lengths.

Contribution

It presents a novel active attack method on the COW quantum cryptography protocol and provides an optimal parameter analysis for different channel lengths.

Findings

The active attack outperforms standard beam-splitting attacks in certain conditions.

Optimal attack parameters depend on channel length.

The attack can compromise the security of the COW protocol under specific settings.

Abstract

We consider a new type of attack on a coherent quantum key distribution protocol [coherent one-way (COW) protocol]. The main idea of the attack consists in measuring individually the intercepted states and sending the rest of them unchanged. We have calculated the optimum values of the attack parameters for an arbitrary length of a channel length and compared this novel attack with a standard beam-splitting attack.