An Improved Asymptotic Key Rate Bound for a Mediated Semi-Quantum Key Distribution Protocol

TL;DR

This paper presents a new security proof and an improved asymptotic key rate bound for a mediated semi-quantum key distribution protocol, demonstrating higher error tolerance than previous results.

Contribution

It introduces a novel lower bound on the key rate for a mediated SQKD protocol, enhancing the understanding of its security and performance.

Findings

New lower bound on key rate derived

Protocol can tolerate higher error rates

Improved security proof for mediated SQKD

Abstract

Semi-quantum key distribution (SQKD) protocols allow for the establishment of a secret key between two users Alice and Bob, when one of the two users (typically Bob) is limited or "classical" in nature. Recently it was shown that protocols exists when both parties are limited/classical in nature if they utilize the services of a quantum server. These protocols are called mediated SQKD protocols. This server, however, is untrusted and, in fact, adversarial. In this paper, we reconsider a mediated SQKD protocol and derive a new proof of unconditional security for it. In particular, we derive a new lower bound on its key rate in the asymptotic scenario. Furthermore, we show this new lower bound is an improvement over prior work, thus showing that the protocol in question can tolerate higher rates of error than previously thought.