C# BigInteger.GetMQuote方法代码示例

		public BigInteger ModPow(
			BigInteger exponent,
			BigInteger m)
		{
			if (m.sign < 1)
				throw new ArithmeticException("Modulus must be positive");

			if (m.Equals(One))
				return Zero;

			if (exponent.sign == 0)
				return One;

			if (sign == 0)
				return Zero;

			int[] zVal = null;
			int[] yAccum = null;
			int[] yVal;

			// Montgomery exponentiation is only possible if the modulus is odd,
			// but AFAIK, this is always the case for crypto algo's
			bool useMonty = ((m.magnitude[m.magnitude.Length - 1] & 1) == 1);
			long mQ = 0;
			if (useMonty)
			{
				mQ = m.GetMQuote();

				// tmp = this * R mod m
				BigInteger tmp = ShiftLeft(32 * m.magnitude.Length).Mod(m);
				zVal = tmp.magnitude;

				useMonty = (zVal.Length <= m.magnitude.Length);

				if (useMonty)
				{
					yAccum = new int[m.magnitude.Length + 1];
					if (zVal.Length < m.magnitude.Length)
					{
						int[] longZ = new int[m.magnitude.Length];
						zVal.CopyTo(longZ, longZ.Length - zVal.Length);
						zVal = longZ;
					}
				}
			}

			if (!useMonty)
			{
				if (magnitude.Length <= m.magnitude.Length)
				{
					//zAccum = new int[m.magnitude.Length * 2];
					zVal = new int[m.magnitude.Length];
					magnitude.CopyTo(zVal, zVal.Length - magnitude.Length);
				}
				else
				{
					//
					// in normal practice we'll never see this...
					//
					BigInteger tmp = Remainder(m);

					//zAccum = new int[m.magnitude.Length * 2];
					zVal = new int[m.magnitude.Length];
					tmp.magnitude.CopyTo(zVal, zVal.Length - tmp.magnitude.Length);
				}

				yAccum = new int[m.magnitude.Length * 2];
			}

			yVal = new int[m.magnitude.Length];

			//
			// from LSW to MSW
			//
			for (int i = 0; i < exponent.magnitude.Length; i++)
			{
				int v = exponent.magnitude[i];
				int bits = 0;

				if (i == 0)
				{
					while (v > 0)
					{
						v <<= 1;
						bits++;
					}

					//
					// first time in initialise y
					//
					zVal.CopyTo(yVal, 0);

					v <<= 1;
					bits++;
				}

				while (v != 0)
				{
					if (useMonty)
					{
//.........这里部分代码省略.........

        private static BigInteger ModPowMonty(BigInteger b, BigInteger e, BigInteger m, bool convert)
        {
            int n = m.magnitude.Length;
            int powR = 32 * n;
            bool smallMontyModulus = m.BitLength + 2 <= powR;
            uint mDash = (uint)m.GetMQuote();

            // tmp = this * R mod m
            if (convert)
            {
                b = b.ShiftLeft(powR).Remainder(m);
            }

            int[] yAccum = new int[n + 1];

            int[] zVal = b.magnitude;
            Debug.Assert(zVal.Length <= n);
            if (zVal.Length < n)
            {
                int[] tmp = new int[n];
                zVal.CopyTo(tmp, n - zVal.Length);
                zVal = tmp;
            }

            // Sliding window from MSW to LSW

            int extraBits = 0;

            // Filter the common case of small RSA exponents with few bits set
            if (e.magnitude.Length > 1 || e.BitCount > 2)
            {
                int expLength = e.BitLength;
                while (expLength > ExpWindowThresholds[extraBits])
                {
                    ++extraBits;
                }
            }

            int numPowers = 1 << extraBits;
            int[][] oddPowers = new int[numPowers][];
            oddPowers[0] = zVal;

            int[] zSquared = Arrays.Clone(zVal);
            SquareMonty(yAccum, zSquared, m.magnitude, mDash, smallMontyModulus);

            for (int i = 1; i < numPowers; ++i)
            {
                oddPowers[i] = Arrays.Clone(oddPowers[i - 1]);
                MultiplyMonty(yAccum, oddPowers[i], zSquared, m.magnitude, mDash, smallMontyModulus);
            }

            int[] windowList = GetWindowList(e.magnitude, extraBits);
            Debug.Assert(windowList.Length > 1);

            int window = windowList[0];
            int mult = window & 0xFF, lastZeroes = window >> 8;

            int[] yVal;
            if (mult == 1)
            {
                yVal = zSquared;
                --lastZeroes;
            }
            else
            {
                yVal = Arrays.Clone(oddPowers[mult >> 1]);
            }

            int windowPos = 1;
            while ((window = windowList[windowPos++]) != -1)
            {
                mult = window & 0xFF;

                int bits = lastZeroes + BitLengthTable[mult];
                for (int j = 0; j < bits; ++j)
                {
                    SquareMonty(yAccum, yVal, m.magnitude, mDash, smallMontyModulus);
                }

                MultiplyMonty(yAccum, yVal, oddPowers[mult >> 1], m.magnitude, mDash, smallMontyModulus);

                lastZeroes = window >> 8;
            }

            for (int i = 0; i < lastZeroes; ++i)
            {
                SquareMonty(yAccum, yVal, m.magnitude, mDash, smallMontyModulus);
            }

            if (convert)
            {
                // Return y * R^(-1) mod m
                MontgomeryReduce(yVal, m.magnitude, mDash);
            }
            else if (smallMontyModulus && CompareTo(0, yVal, 0, m.magnitude) >= 0)
            {
                Subtract(0, yVal, 0, m.magnitude);
            }

            return new BigInteger(1, yVal, true);
//.........这里部分代码省略.........