Key Recovery Attack on Rank Quasi-Cyclic Code-based Signature Scheme

TL;DR

This paper demonstrates a practical key recovery attack on the Rank Quasi-Cyclic Signature scheme, showing that its secret key can be recovered efficiently within seconds at various security levels.

Contribution

It presents the first practical key recovery attack on RQCS, challenging its assumed security in the random oracle model.

Findings

Secret keys recovered in less than 41 seconds

Attack effective at 128-bit, 192-bit, and 256-bit security levels

Highlights vulnerabilities in RQCS scheme

Abstract

Rank Quasi-Cyclic Signature (RQCS) is a rank metric code-based signature scheme based on the Rank Quasi-Cyclic Syndrome Decoding (RQCSD) problem proposed by Song et al. in [2]. Their paper was accepted in the 22nd International Conference on Practice and Theory of Public Key Cryptography (PKC 2019). They have also shown that RQCS is EUF-CMA in the random oracle model. This short paper describes how to recover the secret key in RQCS with practical simulations. Our experimental results show that we are able to recover the secret key of RQCS in less than 41 seconds for all the proposed schemes at 128-bit, 192-bit and 256-bit security level.