C# ECPoint.Twice方法代码示例

		/**
		* Simple shift-and-add multiplication. Serves as reference implementation
		* to verify (possibly faster) implementations in
		* {@link org.bouncycastle.math.ec.ECPoint ECPoint}.
		* 
		* @param p The point to multiply.
		* @param k The factor by which to multiply.
		* @return The result of the point multiplication <code>k * p</code>.
		*/
		public ECPoint Multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo)
		{
			ECPoint q = p.Curve.Infinity;
			int t = k.BitLength;
			for (int i = 0; i < t; i++)
			{
				if (k.TestBit(i))
				{
					q = q.Add(p);
				}
				p = p.Twice();
			}
			return q;
		}

 /**
  * Simple shift-and-add multiplication. Serves as reference implementation
  * to verify (possibly faster) implementations in
  * {@link org.bouncycastle.math.ec.ECPoint ECPoint}.
  * 
  * @param p The point to multiply.
  * @param k The factor by which to multiply.
  * @return The result of the point multiplication <code>k * p</code>.
  */
 protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)
 {
     ECPoint q = p.Curve.Infinity;
     int t = k.BitLength;
     if (t > 0)
     {
         if (k.TestBit(0))
         {
             q = p;
         }
         for (int i = 1; i < t; i++)
         {
             p = p.Twice();
             if (k.TestBit(i))
             {
                 q = q.Add(p);
             }
         }
     }
     return q;
 }

        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 = curve.A.Multiply(Z1Sq).Add(L1Sq).Add(L1Z1);
            ECFieldElement T = Z1Sq.Add(L1Sq).Add(L1Z1);
            ECFieldElement L2plus1 = L2.AddOne();
            //ECFieldElement A = curve.A.Add(L2plus1).Multiply(Z1Sq).Add(L1Sq).MultiplyPlusProduct(T, X1Sq, Z1Sq);
            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, L2plus1, Z3);

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

		/**
		* Multiplies <code>this</code> by an integer <code>k</code> using the
		* Window NAF method.
		* @param k The integer by which <code>this</code> is multiplied.
		* @return A new <code>ECPoint</code> which equals <code>this</code>
		* multiplied by <code>k</code>.
		*/
		public ECPoint Multiply(ECPoint p, BigInteger k, PreCompInfo preCompInfo)
		{
			WNafPreCompInfo wnafPreCompInfo;

			if ((preCompInfo != null) && (preCompInfo is WNafPreCompInfo))
			{
				wnafPreCompInfo = (WNafPreCompInfo)preCompInfo;
			}
			else
			{
				// Ignore empty PreCompInfo or PreCompInfo of incorrect type
				wnafPreCompInfo = new WNafPreCompInfo();
			}

			// floor(log2(k))
			int m = k.BitLength;

			// width of the Window NAF
			sbyte width;

			// Required length of precomputation array
			int reqPreCompLen;

			// Determine optimal width and corresponding length of precomputation
			// array based on literature values
			if (m < 13)
			{
				width = 2;
				reqPreCompLen = 1;
			}
			else
			{
				if (m < 41)
				{
					width = 3;
					reqPreCompLen = 2;
				}
				else
				{
					if (m < 121)
					{
						width = 4;
						reqPreCompLen = 4;
					}
					else
					{
						if (m < 337)
						{
							width = 5;
							reqPreCompLen = 8;
						}
						else
						{
							if (m < 897)
							{
								width = 6;
								reqPreCompLen = 16;
							}
							else
							{
								if (m < 2305)
								{
									width = 7;
									reqPreCompLen = 32;
								}
								else 
								{
									width = 8;
									reqPreCompLen = 127;
								}
							}
						}
					}
				}
			}

			// The length of the precomputation array
			int preCompLen = 1;

			ECPoint[] preComp = wnafPreCompInfo.GetPreComp();
			ECPoint twiceP = wnafPreCompInfo.GetTwiceP();

			// Check if the precomputed ECPoints already exist
			if (preComp == null)
			{
				// Precomputation must be performed from scratch, create an empty
				// precomputation array of desired length
				preComp = new ECPoint[]{ p };
			}
			else
			{
				// Take the already precomputed ECPoints to start with
				preCompLen = preComp.Length;
//.........这里部分代码省略.........