Lightweight Mediated Semi-Quantum Key Distribution Protocol with a Dishonest Third Party based on Bell States

TL;DR

This paper introduces a practical semi-quantum key distribution protocol using Bell states that eliminates the need for expensive detectors and can operate securely even if the third party is dishonest, enhancing practicality and security.

Contribution

It proposes a novel MSQKD protocol based on Bell states that is secure against known attacks and requires minimal quantum capabilities from classical participants.

Findings

Protocol is secure against well-known attacks.

Classical participants need only two quantum capabilities.

Does not require Trojan horse detectors or honest third party.

Abstract

The mediated semi-quantum key distribution (MSQKD) protocol is an important research issue that lets two classical participants share secret keys securely between each other with the help of a third party (TP). However, in the existing MSQKD protocols, there are two improvable issues, namely (1) the classical participants must be equipped with expensive detectors to avoid Trojan horse attacks and (2) the trustworthiness level of TP must be honest. To the best of our knowledge, none of the existing MSQKD protocols can resolve both these issues. Therefore, this study takes Bell states as the quantum resource to propose a MSQKD protocol, in which the classical participants do not need a Trojan horse detector and the TP is dishonest. Furthermore, the proposed protocol is shown to be secure against well-known attacks and the classical participants only need two quantum capabilities. Therefore, in comparison to the existing MSQKD protocols, the proposed protocol is better practical.