Analyses and improvement of a broadcasting multiple blind signature scheme based on quantum GHZ entanglement

TL;DR

This paper critically analyzes a quantum GHZ-based broadcasting multiple blind signature scheme, revealing security vulnerabilities and proposing an improved, more secure version against various participant and external attacks.

Contribution

It identifies security flaws in the existing scheme and introduces an improved protocol that resists multiple types of attacks, enhancing quantum signature security.

Findings

Original scheme vulnerable to intercept-resend attack

Signatory and sender impersonation attacks exist

Proposed scheme resists identified attacks and some collusion attacks

Abstract

A broadcasting multiple blind signature scheme based on quantum GHZ entanglement has been presented recently by Tian et al. It is said that the scheme's unconditional security is guaranteed by adopting quantum key preparation, quantum encryption algorithm and quantum entanglement. In this paper, we prove that each signatory can get the signed message just by an intercept-resend attack. Then, we show there still exists some participant attacks and external attacks. Specifically, we verify the message sender Alice can impersonate each signatory to sign the message at will, and so is the signature collector Charlie. Also, we demonstrate that the receiver Bob can forge the signature successfully, and with respect to the external attacks, the eavesdropper Eve can modify the signature at random. Besides, we discover Eve can change the signed message at will, and Eve can impersonate Alice as the message sender without being discovered. In particular, we propose an improved scheme based on the original one and show that it is secure against not only the attacks mentioned above but also some collusion attacks.