Tables8kGcmMultiplier.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 Tables8kGcmMultiplier
    : IGcmMultiplier
  {
    private readonly uint[][][] M = new uint[32][][];
    
    public void Init(byte[] H)
    {
      M[0] = new uint[16][];
      M[1] = new uint[16][];
      M[0][0] = new uint[4];
      M[1][0] = new uint[4];
      M[1][8] = GcmUtilities.AsUints(H);

      for (int j = 4; j >= 1; j >>= 1)
      {
        uint[] tmp = (uint[])M[1][j + j].Clone();
        GcmUtilities.MultiplyP(tmp);
        M[1][j] = tmp;
      }

      {
        uint[] tmp = (uint[])M[1][1].Clone();
        GcmUtilities.MultiplyP(tmp);
        M[0][8] = tmp;
      }

      for (int j = 4; 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 < 16; 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 == 32) return;

        if (i > 1)
        {
          M[i] = new uint[16][];
          M[i][0] = new uint[4];
          for(int j = 8; j > 0; j >>= 1)
          {
            uint[] tmp = (uint[])M[i - 2][j].Clone();
            GcmUtilities.MultiplyP8(tmp);
            M[i][j] = tmp;
          }
        }
      }
    }

    public void MultiplyH(byte[] x)
    {
      uint[] z = new uint[4];
      for (int i = 15; i >= 0; --i)
      {
        //GcmUtilities.Xor(z, M[i + i][x[i] & 0x0f]);
        uint[] m = M[i + i][x[i] & 0x0f];
        z[0] ^= m[0];
        z[1] ^= m[1];
        z[2] ^= m[2];
        z[3] ^= m[3];
        //GcmUtilities.Xor(z, M[i + i + 1][(x[i] & 0xf0) >> 4]);
        m = M[i + i + 1][(x[i] & 0xf0) >> 4];
        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);
    }
  }
}