type synthCombinedMult struct {
	Curve
}

func (s synthCombinedMult) CombinedMult(bigX, bigY *big.Int, baseScalar, scalar []byte) (x, y *big.Int) {
	x1, y1 := s.ScalarBaseMult(baseScalar)
	x2, y2 := s.ScalarMult(bigX, bigY, scalar)
	return s.Add(x1, y1, x2, y2)
}

func TestP256CombinedMult(t *testing.T) {
	type combinedMult interface {
		Curve
		CombinedMult(bigX, bigY *big.Int, baseScalar, scalar []byte) (x, y *big.Int)
	}

	if err != nil {
		panic("crypto/elliptic: nistec rejected normalized scalar")
	}
	return curve.pointToAffine(p)
}

// CombinedMult returns [s1]G + [s2]P where G is the generator. It's used
// through an interface upgrade in crypto/ecdsa.
func (curve *nistCurve[Point]) CombinedMult(Px, Py *big.Int, s1, s2 []byte) (x, y *big.Int) {
	s1 = curve.normalizeScalar(s1)
	q, err := curve.newPoint().ScalarBaseMult(s1)
	if err != nil {