A note on a Code-Based Signature Scheme

TL;DR

This paper identifies a security flaw in a 2019 code-based signature scheme derived from McEliece, showing that the improved performance compromises security, highlighting the importance of careful parameter selection.

Contribution

The paper critically analyzes a recent code-based signature scheme, revealing security vulnerabilities caused by parameter choices and emphasizing the need for rigorous security evaluation.

Findings

The scheme's security is compromised despite longer public keys.

Parameter choices for efficiency introduce protocol vulnerabilities.

The scheme is not more secure than the standard McEliece cryptosystem.

Abstract

In this work, we exploit a serious security flaw in a code-based signature scheme from a 2019 work by Liu, Yang, Han and Wang. They adapt the McEliece cryptosystem to obtain a new scheme and, on top of this, they design an efficient digital signature. We show that the new encryption scheme based on McEliece, even if it has longer public keys, is not more secure than the standard one. Moreover, the choice of parameters for the signature leads to a significant performance improvement, but it introduces a vulnerability in the protocol.