return add(new ECPoint.Fp(curve, p2.x, p2.y.negate()));
return add(new ECPoint.Fp(curve, p2.x, p2.y.negate(), this.withCompression));
        public ECPoint subtract(ECPoint p2)        {            return add(new ECPoint.Fp(curve, p2.x, p2.y.negate()));        }