Anonymous conference key agreement in linear quantum networks

TL;DR

This paper introduces a practical, anonymous conference key agreement protocol for three parties in linear quantum networks, leveraging repeater nodes and entanglement to enhance secure multi-party communication.

Contribution

It presents the first anonymous CKA protocol suitable for linear quantum networks using repeater nodes without a central server, ensuring participant anonymity and practical implementation.

Findings

Protocol protects participant identities from each other.

Achieves secure key agreement in a linear network setting.

Analyzes key rate in finite regimes for real-world feasibility.

Abstract

Sharing multi-partite quantum entanglement between parties allows for diverse secure communication tasks to be performed. Among them, conference key agreement (CKA), an extension of key distribution to multiple parties, has received much attention recently. Interestingly, CKA can also be performed in a way that protects the identities of the participating parties, therefore providing anonymity. In this work, we propose an anonymous CKA protocol for three parties that is implemented in a highly practical network setting. Specifically, a line of quantum repeater nodes is used to build a linear cluster state among all nodes, which is then used to anonymously establish a secret key between any three of them. The nodes need only share maximally entangled pairs with their neighbours, therefore avoiding the necessity of a central server sharing entangled states. This repeater setup makes our protocol an excellent candidate for implementation in future quantum networks. We explicitly prove that our protocol protects the identities of the participants from one another and perform an analysis of the key rate in the finite regime, contributing to the quest of identifying feasible quantum communication tasks for network architectures beyond point-to-point.