BestHTTP.SecureProtocol.Org.BouncyCastle.Math.EC.Custom.Sec.SecT163R2Point.TwicePlus C# (CSharp) Method

        public override ECPoint TwicePlus(ECPoint b)
        {
            if (this.IsInfinity)
            {
                return b;
            }
            if (b.IsInfinity)
            {
                return Twice();
            }

            ECCurve curve = this.Curve;

            ECFieldElement X1 = this.RawXCoord;
            if (X1.IsZero)
            {
                // A point with X == 0 is it's own Additive inverse
                return b;
            }

            ECFieldElement X2 = b.RawXCoord, Z2 = b.RawZCoords[0];
            if (X2.IsZero || !Z2.IsOne)
            {
                return Twice().Add(b);
            }

            ECFieldElement L1 = this.RawYCoord, Z1 = this.RawZCoords[0];
            ECFieldElement L2 = b.RawYCoord;

            ECFieldElement X1Sq = X1.Square();
            ECFieldElement L1Sq = L1.Square();
            ECFieldElement Z1Sq = Z1.Square();
            ECFieldElement L1Z1 = L1.Multiply(Z1);

            ECFieldElement T = Z1Sq.Add(L1Sq).Add(L1Z1);
            ECFieldElement A = L2.Multiply(Z1Sq).Add(L1Sq).MultiplyPlusProduct(T, X1Sq, Z1Sq);
            ECFieldElement X2Z1Sq = X2.Multiply(Z1Sq);
            ECFieldElement B = X2Z1Sq.Add(T).Square();

            if (B.IsZero)
            {
                if (A.IsZero)
                    return b.Twice();

                return curve.Infinity;
            }

            if (A.IsZero)
            {
                return new SecT163R2Point(curve, A, curve.B.Sqrt(), IsCompressed);
            }

            ECFieldElement X3 = A.Square().Multiply(X2Z1Sq);
            ECFieldElement Z3 = A.Multiply(B).Multiply(Z1Sq);
            ECFieldElement L3 = A.Add(B).Square().MultiplyPlusProduct(T, L2.AddOne(), Z3);

            return new SecT163R2Point(curve, X3, L3, new ECFieldElement[] { Z3 }, IsCompressed);
        }