High-rank attack on HMFEv

Abstract

HMFEv is a new multivariate signature scheme proposed at PQCrypto 2017. This is a vinegar variant of multi-HFE (Chen et al., 2008). While the original multi-HFE is known to be insecure against the direct attack (Huang et al., 2015), the min-rank attack (Bettale et al., 2013) and the attack using a diagonalization approach (Hashimoto, 2017), HMFEv is considered to be secure enough against these attacks. However, the security against the high-rank attack had not been studied at all. In the present paper, we study the structure of HMFEv and discuss its security against the high-rank attack.