Tables64kGcmMultiplier.cs :  » PDF » iTextSharp » Org » BouncyCastle » Crypto » Modes » Gcm » C# / CSharp Open Source

using System;

using Org.BouncyCastle.Crypto.Utilities;

namespace Org.BouncyCastle.Crypto.Modes.Gcm{
  public class Tables64kGcmMultiplier
    : IGcmMultiplier
  {
    private readonly uint[][][] M = new uint[16][][];

    public void Init(byte[] H)
    {
      M[0] = new uint[256][];
      M[0][0] = new uint[4];
      M[0][128] = GcmUtilities.AsUints(H);
      for (int j = 64; j >= 1; j >>= 1)
      {
        uint[] tmp = (uint[])M[0][j + j].Clone();
        GcmUtilities.MultiplyP(tmp);
        M[0][j] = tmp;
      }
      for (int i = 0;;)
      {
        for (int j = 2; j < 256; j += j)
        {
          for (int k = 1; k < j; ++k)
          {
            uint[] tmp = (uint[])M[i][j].Clone();
            GcmUtilities.Xor(tmp, M[i][k]);
            M[i][j + k] = tmp;
          }
        }

        if (++i == 16) return;

        M[i] = new uint[256][];
        M[i][0] = new uint[4];
        for (int j = 128; j > 0; j >>= 1)
        {
          uint[] tmp = (uint[])M[i - 1][j].Clone();
          GcmUtilities.MultiplyP8(tmp);
          M[i][j] = tmp;
        }
      }
    }

    public void MultiplyH(byte[] x)
    {
      uint[] z = new uint[4];
      for (int i = 0; i != 16; ++i)
      {
        //GcmUtilities.Xor(z, M[i][x[i]]);
        uint[] m = M[i][x[i]];
        z[0] ^= m[0];
        z[1] ^= m[1];
        z[2] ^= m[2];
        z[3] ^= m[3];
      }

      Pack.UInt32_To_BE(z[0], x, 0);
      Pack.UInt32_To_BE(z[1], x, 4);
      Pack.UInt32_To_BE(z[2], x, 8);
      Pack.UInt32_To_BE(z[3], x, 12);
    }
  }
}