public static class SHA    //256
        {
            static void DBL_INT_ADD(ref uint a, ref uint b, uint c)
            {
                if (a > 0xffffffff - c) ++b; a += c;
            }

            static uint ROTLEFT(uint a, byte b)
            {
                return ((a << b) | (a >> (32 - b)));
            }

            static uint ROTRIGHT(uint a, byte b)
            {
                return (((a) >> (b)) | ((a) << (32 - (b))));
            }

            static uint CH(uint x, uint y, uint z)
            {
                return (((x) & (y)) ^ (~(x) & (z)));
            }

            static uint MAJ(uint x, uint y, uint z)
            {
                return (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)));
            }

            static uint EP0(uint x)
            {
                return (ROTRIGHT(x, 2) ^ ROTRIGHT(x, 13) ^ ROTRIGHT(x, 22));
            }

            static uint EP1(uint x)
            {
                return (ROTRIGHT(x, 6) ^ ROTRIGHT(x, 11) ^ ROTRIGHT(x, 25));
            }

            static uint SIG0(uint x)
            {
                return (ROTRIGHT(x, 7) ^ ROTRIGHT(x, 18) ^ ((x) >> 3));
            }

            static uint SIG1(uint x)
            {
                return (ROTRIGHT(x, 17) ^ ROTRIGHT(x, 19) ^ ((x) >> 10));
            }

            struct SHA256_CTX
            {
                public byte[] data;
                public uint datalen;
                public uint[] bitlen;
                public uint[] state;
            }

            static uint[] k = {
    0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
    0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
    0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
    0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
    0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
    0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
    0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
    0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
};

            static void SHA256Transform(ref SHA256_CTX ctx, byte[] data)
            {
                uint a, b, c, d, e, f, g, h, i, j, t1, t2;
                uint[] m = new uint[64];

                for (i = 0, j = 0; i < 16; ++i, j += 4)
                    m[i] = (uint)((data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]));

                for (; i < 64; ++i)
                    m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];

                a = ctx.state[0];
                b = ctx.state[1];
                c = ctx.state[2];
                d = ctx.state[3];
                e = ctx.state[4];
                f = ctx.state[5];
                g = ctx.state[6];
                h = ctx.state[7];

                for (i = 0; i < 64; ++i)
                {
                    t1 = h + EP1(e) + CH(e, f, g) + k[i] + m[i];
                    t2 = EP0(a) + MAJ(a, b, c);
                    h = g;
                    g = f;
                    f = e;
                    e = d + t1;
                    d = c;
                    c = b;
                    b = a;
                    a = t1 + t2;
                }

                ctx.state[0] += a;
                ctx.state[1] += b;
                ctx.state[2] += c;
                ctx.state[3] += d;
                ctx.state[4] += e;
                ctx.state[5] += f;
                ctx.state[6] += g;
                ctx.state[7] += h;
            }

            static void SHA256Init(ref SHA256_CTX ctx)
            {
                ctx.datalen = 0;
                ctx.bitlen[0] = 0;
                ctx.bitlen[1] = 0;
                ctx.state[0] = 0x6a09e667;
                ctx.state[1] = 0xbb67ae85;
                ctx.state[2] = 0x3c6ef372;
                ctx.state[3] = 0xa54ff53a;
                ctx.state[4] = 0x510e527f;
                ctx.state[5] = 0x9b05688c;
                ctx.state[6] = 0x1f83d9ab;
                ctx.state[7] = 0x5be0cd19;
            }

            static void SHA256Update(ref SHA256_CTX ctx, byte[] data, uint len)
            {
                for (uint i = 0; i < len; ++i)
                {
                    ctx.data[ctx.datalen] = data[i];
                    ctx.datalen++;

                    if (ctx.datalen == 64)
                    {
                        SHA256Transform(ref ctx, ctx.data);
                        DBL_INT_ADD(ref ctx.bitlen[0], ref ctx.bitlen[1], 512);
                        ctx.datalen = 0;
                    }
                }
            }

            static void SHA256Final(ref SHA256_CTX ctx, byte[] hash)
            {
                uint i = ctx.datalen;

                if (ctx.datalen < 56)
                {
                    ctx.data[i++] = 0x80;

                    while (i < 56)
                        ctx.data[i++] = 0x00;
                }
                else
                {
                    ctx.data[i++] = 0x80;

                    while (i < 64)
                        ctx.data[i++] = 0x00;

                    SHA256Transform(ref ctx, ctx.data);
                }

                DBL_INT_ADD(ref ctx.bitlen[0], ref ctx.bitlen[1], ctx.datalen * 8);
                ctx.data[63] = (byte)(ctx.bitlen[0]);
                ctx.data[62] = (byte)(ctx.bitlen[0] >> 8);
                ctx.data[61] = (byte)(ctx.bitlen[0] >> 16);
                ctx.data[60] = (byte)(ctx.bitlen[0] >> 24);
                ctx.data[59] = (byte)(ctx.bitlen[1]);
                ctx.data[58] = (byte)(ctx.bitlen[1] >> 8);
                ctx.data[57] = (byte)(ctx.bitlen[1] >> 16);
                ctx.data[56] = (byte)(ctx.bitlen[1] >> 24);
                SHA256Transform(ref ctx, ctx.data);

                for (i = 0; i < 4; ++i)
                {
                    hash[i] = (byte)(((ctx.state[0]) >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 4] = (byte)(((ctx.state[1]) >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 8] = (byte)(((ctx.state[2]) >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 12] = (byte)((ctx.state[3] >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 16] = (byte)((ctx.state[4] >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 20] = (byte)((ctx.state[5] >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 24] = (byte)((ctx.state[6] >> (int)(24 - i * 8)) & 0x000000ff);
                    hash[i + 28] = (byte)((ctx.state[7] >> (int)(24 - i * 8)) & 0x000000ff);
                }
            }