= new ECPoint.F2m(curve, b.getX(), b.getY().negate(), withCompression);
= new ECPoint.F2m(curve, b.getX(), b.getX().add(b.getY()), withCompression);
        public ECPoint subtract(ECPoint b)        {            // Add -b            ECPoint.F2m minusB                = new ECPoint.F2m(curve, b.getX(), b.getY().negate(), withCompression);            return add(minusB);        }