On the "Security analysis and improvements of arbitrated quantum signature schemes"

TL;DR

This paper critically examines recent arbitrated quantum signature schemes, revealing security flaws such as dispute arbitration issues and Trojan-horse attacks, which compromise unforgeability and undeniability.

Contribution

It identifies security vulnerabilities in proposed AQS schemes and demonstrates that these flaws undermine their core security properties.

Findings

Existing schemes are vulnerable to dispute arbitration failures.

Trojan-horse attacks can reveal secret keys undetected.

Core properties of quantum signatures may not be guaranteed.

Abstract

Recently, Zou et al. [Phys. Rev. A 82, 042325 (2010)] pointed out that two arbitrated quantum signature (AQS) schemes are not secure, because an arbitrator cannot arbitrate the dispute between two users when a receiver repudiates the integrity of a signature. By using a public board, they try to propose two AQS schemes to solve the problem. This work shows that the same security problem may exist in their schemes and also a malicious party can reveal the other party's secret key without being detected by using the Trojan-horse attacks. Accordingly, two basic properties of a quantum signature, i.e. unforgeability and undeniability, may not be satisfied in their scheme.