C# BigInteger.ShiftLeft方法代码示例

        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.........

        /*
         * Finds a pair of prime BigInteger's {p, q: p = 2q + 1}
         *
         * (see: Handbook of Applied Cryptography 4.86)
         */
        internal static BigInteger[] GenerateSafePrimes(int size, int certainty, SecureRandom random)
        {
            BigInteger p, q;
            int qLength = size - 1;
            int minWeight = size >> 2;

            if (size <= 32)
            {
                for (;;)
                {
                    q = new BigInteger(qLength, 2, random);

                    p = q.ShiftLeft(1).Add(BigInteger.One);

                    if (!p.IsProbablePrime(certainty))
                        continue;

                    if (certainty > 2 && !q.IsProbablePrime(certainty - 2))
                        continue;

                    break;
                }
            }
            else
            {
                // Note: Modified from Java version for speed
                for (;;)
                {
                    q = new BigInteger(qLength, 0, random);

                retry:
                    for (int i = 0; i < primeLists.Length; ++i)
                    {
                        int test = q.Remainder(BigPrimeProducts[i]).IntValue;

                        if (i == 0)
                        {
                            int rem3 = test % 3;
                            if (rem3 != 2)
                            {
                                int diff = 2 * rem3 + 2;
                                q = q.Add(BigInteger.ValueOf(diff));
                                test = (test + diff) % primeProducts[i];
                            }
                        }

                        int[] primeList = primeLists[i];
                        for (int j = 0; j < primeList.Length; ++j)
                        {
                            int prime = primeList[j];
                            int qRem = test % prime;
                            if (qRem == 0 || qRem == (prime >> 1))
                            {
                                q = q.Add(Six);
                                goto retry;
                            }
                        }
                    }

                    if (q.BitLength != qLength)
                        continue;

                    if (!q.RabinMillerTest(2, random))
                        continue;

                    p = q.ShiftLeft(1).Add(BigInteger.One);

                    if (!p.RabinMillerTest(certainty, random))
                        continue;

                    if (certainty > 2 && !q.RabinMillerTest(certainty - 2, random))
                        continue;

                    /*
                     * Require a minimum weight of the NAF representation, since low-weight primes may be
                     * weak against a version of the number-field-sieve for the discrete-logarithm-problem.
                     *
                     * See "The number field sieve for integers of low weight", Oliver Schirokauer.
                     */
                    if (WNafUtilities.GetNafWeight(p) < minWeight)
                        continue;

                    break;
                }
            }

            return new BigInteger[] { p, q };
        }

        public BigInteger Multiply(
            BigInteger val)
        {
            if (val == this)
                return Square();

            if ((sign & val.sign) == 0)
                return Zero;

            if (val.QuickPow2Check()) // val is power of two
            {
                BigInteger result = this.ShiftLeft(val.Abs().BitLength - 1);
                return val.sign > 0 ? result : result.Negate();
            }

            if (this.QuickPow2Check()) // this is power of two
            {
                BigInteger result = val.ShiftLeft(this.Abs().BitLength - 1);
                return this.sign > 0 ? result : result.Negate();
            }

            int resLength = magnitude.Length + val.magnitude.Length;
            int[] res = new int[resLength];

            Multiply(res, this.magnitude, val.magnitude);

            int resSign = sign ^ val.sign ^ 1;
            return new BigInteger(resSign, res, true);
        }