International Association
for Cryptologic Research

MQ-Sign is a variant of the UOV singature scheme proposed by Shim et al. It has been suggested as a candidate for the standardization of post-quantum cryptography in Republic of Korea (known as KpqC). However, recently Aulbach et al. proposed a practical key recovery attack against MQ-Sign-RS and MQ-Sign-SS with a simple secret key $\mathcal{S}$. In this paper, we propose another attack that is valid for the case of a general secret key $\mathcal{S}$.