C# IBigInteger.Mod方法代码示例

        public static IBigInteger ValidatePublicValue(IBigInteger N, IBigInteger val)
        {
            val = val.Mod(N);

            // Check that val % N != 0
            if (val.Equals(BigInteger.Zero))
                throw new CryptoException("Invalid public value: 0");

            return val;
        }

        /**
        * Computes the Window NAF (non-adjacent Form) of an integer.
        * @param width The width <code>w</code> of the Window NAF. The width is
        * defined as the minimal number <code>w</code>, such that for any
        * <code>w</code> consecutive digits in the resulting representation, at
        * most one is non-zero.
        * @param k The integer of which the Window NAF is computed.
        * @return The Window NAF of the given width, such that the following holds:
        * <code>k = &#8722;<sub>i=0</sub><sup>l-1</sup> k<sub>i</sub>2<sup>i</sup>
        * </code>, where the <code>k<sub>i</sub></code> denote the elements of the
        * returned <code>sbyte[]</code>.
        */
        public sbyte[] WindowNaf(sbyte width, IBigInteger k)
        {
            // The window NAF is at most 1 element longer than the binary
            // representation of the integer k. sbyte can be used instead of short or
            // int unless the window width is larger than 8. For larger width use
            // short or int. However, a width of more than 8 is not efficient for
            // m = log2(q) smaller than 2305 Bits. Note: Values for m larger than
            // 1000 Bits are currently not used in practice.
            sbyte[] wnaf = new sbyte[k.BitLength + 1];

            // 2^width as short and BigInteger
            short pow2wB = (short)(1 << width);
            IBigInteger pow2wBI = BigInteger.ValueOf(pow2wB);

            int i = 0;

            // The actual length of the WNAF
            int length = 0;

            // while k >= 1
            while (k.SignValue > 0)
            {
                // if k is odd
                if (k.TestBit(0))
                {
                    // k Mod 2^width
                    IBigInteger remainder = k.Mod(pow2wBI);

                    // if remainder > 2^(width - 1) - 1
                    if (remainder.TestBit(width - 1))
                    {
                        wnaf[i] = (sbyte)(remainder.IntValue - pow2wB);
                    }
                    else
                    {
                        wnaf[i] = (sbyte)remainder.IntValue;
                    }
                    // wnaf[i] is now in [-2^(width-1), 2^(width-1)-1]

                    k = k.Subtract(BigInteger.ValueOf(wnaf[i]));
                    length = i;
                }
                else
                {
                    wnaf[i] = 0;
                }

                // k = k/2
                k = k.ShiftRight(1);
                i++;
            }

            length++;

            // Reduce the WNAF array to its actual length
            sbyte[] wnafShort = new sbyte[length];
            Array.Copy(wnaf, 0, wnafShort, 0, length);
            return wnafShort;
        }