Security problem on arbitrated quantum signature schemes

TL;DR

This paper identifies security vulnerabilities in existing arbitrated quantum signature schemes that use quantum one-time encryption, demonstrating a forgery attack and proposing a method to enhance security.

Contribution

The paper reveals a security flaw in current quantum signature schemes and offers a straightforward approach to defend against the identified forgery attack.

Findings

Existential forgery attack on current schemes

Vulnerability due to reliance on quantum one-time encryption

Proposed method to recover security against forgery

Abstract

Until now, there have been developed many arbitrated quantum signature schemes implemented with a help of a trusted third party. In order to guarantee the unconditional security, most of them take advantage of the optimal quantum one-time encryption method based on Pauli operators. However, we in this paper point out that the previous schemes only provides a security against total break and actually show that there exists a simple existential forgery attack to validly modify the transmitted pair of message and signature. In addition, we also provide a simple method to recover the security against the proposed attack.