k != 0 { out.montgomeryMul(out, xR, m) } } return out.montgomeryReduction(m) } // InverseVarTime calculates x = a⁻¹ mod m and returns (x, true) if a is // invertible. Otherwise, InverseVarTime returns (x, false) and x is not // modified. // // a must be reduced modulo m, but doesn't need to have the same size. The // output will be resized to the size of m and overwritten. // //go:norace func (x *Nat) InverseVarTime(a *Nat, m *Modulus) (*Nat, bool) { u, A, err := extendedGCD(a, m.nat) if err != nil...