Double C-NOT attack on a single-state semi-quantum key distribution protocol and its improvement

TL;DR

This paper analyzes a semi-quantum key distribution protocol and reveals a vulnerability to a double C-NOT attack, proposing a modification to enhance its security against such attacks.

Contribution

It identifies a specific security flaw in a recent semi-quantum key distribution protocol and proposes an effective modification to prevent the double C-NOT attack.

Findings

Double C-NOT attack can compromise the protocol without detection.

Proposed modification effectively prevents the attack.

Enhanced security of the semi-quantum key distribution protocol.

Abstract

Recently, Zhang et al. proposed a single-state semi-quantum key distribution protocol (Int. J. Quantum Inf, 18, 4, 2020) to help a quantum participant to share a secret key with a classical participant. However, this study shows that an eavesdropper can use a double C-NOT attack to obtain parts of the final shared key without being detected by the participants. To avoid this problem, a modification is proposed here.