HC128Engine.cs :  » PDF » iTextSharp » Org » BouncyCastle » Crypto » Engines » C# / CSharp Open Source

using System;

using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto.Utilities;

namespace Org.BouncyCastle.Crypto.Engines{
  /**
  * HC-128 is a software-efficient stream cipher created by Hongjun Wu. It
  * generates keystream from a 128-bit secret key and a 128-bit initialization
  * vector.
  * <p>
  * http://www.ecrypt.eu.org/stream/p3ciphers/hc/hc128_p3.pdf
  * </p><p>
  * It is a third phase candidate in the eStream contest, and is patent-free.
  * No attacks are known as of today (April 2007). See
  *
  * http://www.ecrypt.eu.org/stream/hcp3.html
  * </p>
  */
  public class HC128Engine
    : IStreamCipher
  {
    private uint[] p = new uint[512];
    private uint[] q = new uint[512];
    private uint cnt = 0;

    private static uint F1(uint x)
    {
      return RotateRight(x, 7) ^ RotateRight(x, 18) ^ (x >> 3);
    }

    private static uint F2(uint x)
    {
      return RotateRight(x, 17) ^ RotateRight(x, 19) ^ (x >> 10);
    }

    private uint G1(uint x, uint y, uint z)
    {
      return (RotateRight(x, 10) ^ RotateRight(z, 23)) + RotateRight(y, 8);
    }

    private uint G2(uint x, uint y, uint z)
    {
      return (RotateLeft(x, 10) ^ RotateLeft(z, 23)) + RotateLeft(y, 8);
    }

    private static uint RotateLeft(uint  x, int bits)
    {
      return (x << bits) | (x >> -bits);
    }

    private static uint RotateRight(uint x, int bits)
    {
      return (x >> bits) | (x << -bits);
    }

    private uint H1(uint x)
    {
      return q[x & 0xFF] + q[((x >> 16) & 0xFF) + 256];
    }

    private uint H2(uint x)
    {
      return p[x & 0xFF] + p[((x >> 16) & 0xFF) + 256];
    }

    private static uint Mod1024(uint x)
    {
      return x & 0x3FF;
    }

    private static uint Mod512(uint x)
    {
      return x & 0x1FF;
    }

    private static uint Dim(uint x, uint y)
    {
      return Mod512(x - y);
    }

    private uint Step()
    {
      uint j = Mod512(cnt);
      uint ret;
      if (cnt < 512)
      {
        p[j] += G1(p[Dim(j, 3)], p[Dim(j, 10)], p[Dim(j, 511)]);
        ret = H1(p[Dim(j, 12)]) ^ p[j];
      }
      else
      {
        q[j] += G2(q[Dim(j, 3)], q[Dim(j, 10)], q[Dim(j, 511)]);
        ret = H2(q[Dim(j, 12)]) ^ q[j];
      }
      cnt = Mod1024(cnt + 1);
      return ret;
    }

    private byte[] key, iv;
    private bool initialised;

    private void Init()
    {
      if (key.Length != 16)
        throw new ArgumentException("The key must be 128 bits long");

      cnt = 0;

      uint[] w = new uint[1280];

      for (int i = 0; i < 16; i++)
      {
        w[i >> 2] |= ((uint)key[i] << (8 * (i & 0x3)));
      }
      Array.Copy(w, 0, w, 4, 4);

      for (int i = 0; i < iv.Length && i < 16; i++)
      {
        w[(i >> 2) + 8] |= ((uint)iv[i] << (8 * (i & 0x3)));
      }
      Array.Copy(w, 8, w, 12, 4);

      for (uint i = 16; i < 1280; i++)
      {
        w[i] = F2(w[i - 2]) + w[i - 7] + F1(w[i - 15]) + w[i - 16] + i;
      }

      Array.Copy(w, 256, p, 0, 512);
      Array.Copy(w, 768, q, 0, 512);

      for (int i = 0; i < 512; i++)
      {
        p[i] = Step();
      }
      for (int i = 0; i < 512; i++)
      {
        q[i] = Step();
      }

      cnt = 0;
    }

    public string AlgorithmName
    {
      get { return "HC-128"; }
    }

    /**
    * Initialise a HC-128 cipher.
    *
    * @param forEncryption whether or not we are for encryption. Irrelevant, as
    *                      encryption and decryption are the same.
    * @param params        the parameters required to set up the cipher.
    * @throws ArgumentException if the params argument is
    *                                  inappropriate (ie. the key is not 128 bit long).
    */
    public void Init(
      bool        forEncryption,
      ICipherParameters  parameters)
    {
      ICipherParameters keyParam = parameters;

      if (parameters is ParametersWithIV)
      {
        iv = ((ParametersWithIV)parameters).GetIV();
        keyParam = ((ParametersWithIV)parameters).Parameters;
      }
      else
      {
        iv = new byte[0];
      }

      if (keyParam is KeyParameter)
      {
        key = ((KeyParameter)keyParam).GetKey();
        Init();
      }
      else
      {
        throw new ArgumentException(
          "Invalid parameter passed to HC128 init - " + parameters.GetType().Name,
          "parameters");
      }

      initialised = true;
    }

    private byte[] buf = new byte[4];
    private int idx = 0;

    private byte GetByte()
    {
      if (idx == 0)
      {
        Pack.UInt32_To_LE(Step(), buf);        
      }
      byte ret = buf[idx];
      idx = idx + 1 & 0x3;
      return ret;
    }

    public void ProcessBytes(
      byte[]  input,
      int    inOff,
      int    len,
      byte[]  output,
      int    outOff)
    {
      if (!initialised)
        throw new InvalidOperationException(AlgorithmName + " not initialised");
      if ((inOff + len) > input.Length)
        throw new DataLengthException("input buffer too short");
      if ((outOff + len) > output.Length)
        throw new DataLengthException("output buffer too short");

      for (int i = 0; i < len; i++)
      {
        output[outOff + i] = (byte)(input[inOff + i] ^ GetByte());
      }
    }

    public void Reset()
    {
      idx = 0;
      Init();
    }

    public byte ReturnByte(byte input)
    {
      return (byte)(input ^ GetByte());
    }
  }
}