bytes long, ScalarMult returns an error // and the receiver is unchanged. func (p *P256Point) ScalarMult(q *P256Point, scalar []byte) (*P256Point, error) { s, err := new(p256OrdElement).SetBytes(scalar) if err != nil { return nil, err } // Start scanning the window from the most significant bits. We move by // 5 bits at a time and need to finish at -1, so -1 + 5 * 51 = 254. index := 254 sel, sign := boothW5(s.Rsh(index)) // sign is always zero because the boothW5 input here is at // most two bits...