Permutation attack and counterattack on the two-party quantum key agreement over a collective noisy channel

TL;DR

This paper reveals a vulnerability in a two-party quantum key agreement protocol over noisy channels, demonstrating how a participant can manipulate the key, and proposes an improvement to prevent this attack.

Contribution

It identifies a permutation attack on a quantum key agreement protocol and introduces an enhancement to counteract this vulnerability.

Findings

The permutation attack allows a participant to manipulate the shared key.

The proposed improvement effectively prevents the attack.

The protocol's fairness can be compromised without the fix.

Abstract

Recently, Yang et al. (Quantum Inf Process 18, 74, 2019) proposed a two-party quantum key agreement protocol over a collective noisy channel. They claimed that their quantum key agreement protocol can ensure both of the participants have equal influence on the final shared key. However, this study shows that the participant who announces the permutation operation can manipulate the final shared key by himself/herself without being detected by the other. To avoid this loophole, an improvement is proposed here.