computes a * b / R) by R * R works out // to a multiplication by R, which takes the value out of the Montgomery domain. return x.montgomeryMul(x, m.rr, m) } // montgomeryReduction calculates x = x / R mod m, with R = 2^(_W * n) and // n = len(m.nat.limbs). // // This assumes that x is already reduced mod m. func (x *Nat) montgomeryReduction(m *Modulus) *Nat { // By Montgomery multiplying with 1 not in Montgomery representation, we // convert out back from Montgomery representation, because it works...