Degree of regularity for HFE Minus (HFE

In this paper, we prove a closed formula for the degree of regularity of the family of HFE- (HFE Minus) multivariate public key cryptosystems over a nite eld of size q. The degree of regularity of the polynomial system derived from an HFE- system is less than or equal to (q − 1)(⌊log q (D − 1)⌋ + a)