Scalable Mediated Semi-quantum Key Distribution

TL;DR

This paper introduces a scalable multi-party semi-quantum key distribution protocol using Bell states, demonstrating its security, efficiency, and potential for practical quantum communication networks.

Contribution

It presents the first circular M-SQKD protocol for multiple classical users, with a security proof and analysis of performance metrics.

Findings

Protocol is unconditionally secure in the asymptotic scenario.

Key rate and noise tolerance are derived from channel parameters.

Comparable security to fully quantum protocols with improved scalability.

Abstract

Mediated semi-quantum key distribution (M-SQKD) permits two limited "semi-quantum" or "classical" users to establish a secret key with the help of a third party (TP), in which TP has fully quantum power and may be untrusted. Several protocols have been studied recently for two-party scenarios, but no one has considered M-SQKD for multi-party scenarios. In this paper, we design a circular M-SQKD protocol based on Bell states, which offers an approach to realizing multiple "classical" users' key distribution. Then, we prove the protocol is unconditional security in the asymptotic scenario. The protocol's key rate and noise tolerance can be derived by utilizing the parameters observed in the channel. The results show that our protocol may hold similar security to a fully quantum one. We also compare the proposed protocol with similar protocols in terms of noise tolerance, qubit efficiency, communication cost, and scalability. Finally, the security proof method of this paper may contribute to studying the security of other circular semi-quantum cryptography protocols.