context: using System;
  
  using Nequeo.Cryptography.Key.Crypto.Parameters;
  using Nequeo.Cryptography.Key.Crypto.Utilities;
  
  namespace Nequeo.Cryptography.Key.Crypto.Engines
  {
  	/// <remarks>A class that provides a basic DES engine.</remarks>
      public class DesEngine
  		: IBlockCipher
      {
          internal const int BLOCK_SIZE = 8;
  
  		private int[] workingKey;
  
          public virtual int[] GetWorkingKey()
  		{
  			return workingKey;
  		}
  
  		/**
          * initialise a DES cipher.
          *
          * @param forEncryption whether or not we are for encryption.
          * @param parameters the parameters required to set up the cipher.
          * @exception ArgumentException if the parameters argument is
          * inappropriate.
          */
          public virtual void Init(
              bool				forEncryption,
              ICipherParameters	parameters)
          {
              if (!(parameters is KeyParameter))
  				throw new ArgumentException("invalid parameter passed to DES init - " + parameters.GetType().ToString());
  
  			workingKey = GenerateWorkingKey(forEncryption, ((KeyParameter)parameters).GetKey());
          }
  
  		public virtual string AlgorithmName
          {
              get { return "DES"; }
          }
  
  		public bool IsPartialBlockOkay
  		{
  			get { return false; }
  		}
  
  		public virtual int GetBlockSize()
          {
              return BLOCK_SIZE;
          }
  
          public virtual int ProcessBlock(
              byte[]	input,
              int		inOff,
              byte[]	output,
              int		outOff)
          {
              if (workingKey == null)
                  throw new InvalidOperationException("DES engine not initialised");
  			if ((inOff + BLOCK_SIZE) > input.Length)
                  throw new DataLengthException("input buffer too short");
              if ((outOff + BLOCK_SIZE) > output.Length)
                  throw new DataLengthException("output buffer too short");
  
  			DesFunc(workingKey, input, inOff, output, outOff);
  
  			return BLOCK_SIZE;
          }
  
          public virtual void Reset()
          {
          }
  
          /**
          * what follows is mainly taken from "Applied Cryptography", by
          * Bruce Schneier, however it also bears great resemblance to Richard
          * Outerbridge's D3DES...
          */
  
  //        private static readonly short[] Df_Key =
  //        {
  //            0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef,
  //            0xfe,0xdc,0xba,0x98,0x76,0x54,0x32,0x10,
  //            0x89,0xab,0xcd,0xef,0x01,0x23,0x45,0x67
  //        };
  
  		private static readonly short[] bytebit =
          {
              128, 64, 32, 16, 8, 4, 2, 1
          };
  
  		private static readonly int[] bigbyte =
          {
              0x800000,	0x400000,	0x200000,	0x100000,
              0x80000,	0x40000,	0x20000,	0x10000,
              0x8000,		0x4000,		0x2000,		0x1000,
              0x800,		0x400,		0x200,		0x100,
              0x80,		0x40,		0x20,		0x10,
              0x8,		0x4,		0x2,		0x1
          };
  
  		/*
          * Use the key schedule specified in the Standard (ANSI X3.92-1981).
          */
          private static readonly byte[] pc1 =
          {
              56, 48, 40, 32, 24, 16,  8,   0, 57, 49, 41, 33, 25, 17,
              9,  1, 58, 50, 42, 34, 26,  18, 10,  2, 59, 51, 43, 35,
              62, 54, 46, 38, 30, 22, 14,   6, 61, 53, 45, 37, 29, 21,
              13,  5, 60, 52, 44, 36, 28,  20, 12,  4, 27, 19, 11,  3
          };
  
          private static readonly byte[] totrot =
          {
              1, 2, 4, 6, 8, 10, 12, 14,
              15, 17, 19, 21, 23, 25, 27, 28
          };
  
  		private static readonly byte[] pc2 =
          {
              13, 16, 10, 23,  0,  4,  2, 27, 14,  5, 20,  9,
              22, 18, 11,  3, 25,  7, 15,  6, 26, 19, 12,  1,
              40, 51, 30, 36, 46, 54, 29, 39, 50, 44, 32, 47,
              43, 48, 38, 55, 33, 52, 45, 41, 49, 35, 28, 31
          };
  
  		private static readonly uint[] SP1 =
  		{
              0x01010400, 0x00000000, 0x00010000, 0x01010404,
              0x01010004, 0x00010404, 0x00000004, 0x00010000,
              0x00000400, 0x01010400, 0x01010404, 0x00000400,
              0x01000404, 0x01010004, 0x01000000, 0x00000004,
              0x00000404, 0x01000400, 0x01000400, 0x00010400,
              0x00010400, 0x01010000, 0x01010000, 0x01000404,
              0x00010004, 0x01000004, 0x01000004, 0x00010004,
              0x00000000, 0x00000404, 0x00010404, 0x01000000,
              0x00010000, 0x01010404, 0x00000004, 0x01010000,
              0x01010400, 0x01000000, 0x01000000, 0x00000400,
              0x01010004, 0x00010000, 0x00010400, 0x01000004,
              0x00000400, 0x00000004, 0x01000404, 0x00010404,
              0x01010404, 0x00010004, 0x01010000, 0x01000404,
              0x01000004, 0x00000404, 0x00010404, 0x01010400,
              0x00000404, 0x01000400, 0x01000400, 0x00000000,
              0x00010004, 0x00010400, 0x00000000, 0x01010004
          };
  
  		private static readonly uint[] SP2 =
  		{
              0x80108020, 0x80008000, 0x00008000, 0x00108020,
              0x00100000, 0x00000020, 0x80100020, 0x80008020,
              0x80000020, 0x80108020, 0x80108000, 0x80000000,
              0x80008000, 0x00100000, 0x00000020, 0x80100020,
              0x00108000, 0x00100020, 0x80008020, 0x00000000,
              0x80000000, 0x00008000, 0x00108020, 0x80100000,
              0x00100020, 0x80000020, 0x00000000, 0x00108000,
              0x00008020, 0x80108000, 0x80100000, 0x00008020,
              0x00000000, 0x00108020, 0x80100020, 0x00100000,
              0x80008020, 0x80100000, 0x80108000, 0x00008000,
              0x80100000, 0x80008000, 0x00000020, 0x80108020,
              0x00108020, 0x00000020, 0x00008000, 0x80000000,
              0x00008020, 0x80108000, 0x00100000, 0x80000020,
              0x00100020, 0x80008020, 0x80000020, 0x00100020,
              0x00108000, 0x00000000, 0x80008000, 0x00008020,
              0x80000000, 0x80100020, 0x80108020, 0x00108000
          };
  
  		private static readonly uint[] SP3 =
  		{
              0x00000208, 0x08020200, 0x00000000, 0x08020008,
              0x08000200, 0x00000000, 0x00020208, 0x08000200,
              0x00020008, 0x08000008, 0x08000008, 0x00020000,
              0x08020208, 0x00020008, 0x08020000, 0x00000208,
              0x08000000, 0x00000008, 0x08020200, 0x00000200,
              0x00020200, 0x08020000, 0x08020008, 0x00020208,
              0x08000208, 0x00020200, 0x00020000, 0x08000208,
              0x00000008, 0x08020208, 0x00000200, 0x08000000,
              0x08020200, 0x08000000, 0x00020008, 0x00000208,
              0x00020000, 0x08020200, 0x08000200, 0x00000000,
              0x00000200, 0x00020008, 0x08020208, 0x08000200,
              0x08000008, 0x00000200, 0x00000000, 0x08020008,
              0x08000208, 0x00020000, 0x08000000, 0x08020208,
              0x00000008, 0x00020208, 0x00020200, 0x08000008,
              0x08020000, 0x08000208, 0x00000208, 0x08020000,
              0x00020208, 0x00000008, 0x08020008, 0x00020200
          };
  
  		private static readonly uint[] SP4 =
  		{
              0x00802001, 0x00002081, 0x00002081, 0x00000080,
              0x00802080, 0x00800081, 0x00800001, 0x00002001,
              0x00000000, 0x00802000, 0x00802000, 0x00802081,
              0x00000081, 0x00000000, 0x00800080, 0x00800001,
              0x00000001, 0x00002000, 0x00800000, 0x00802001,
              0x00000080, 0x00800000, 0x00002001, 0x00002080,
              0x00800081, 0x00000001, 0x00002080, 0x00800080,
              0x00002000, 0x00802080, 0x00802081, 0x00000081,
              0x00800080, 0x00800001, 0x00802000, 0x00802081,
              0x00000081, 0x00000000, 0x00000000, 0x00802000,
              0x00002080, 0x00800080, 0x00800081, 0x00000001,
              0x00802001, 0x00002081, 0x00002081, 0x00000080,
              0x00802081, 0x00000081, 0x00000001, 0x00002000,
              0x00800001, 0x00002001, 0x00802080, 0x00800081,
              0x00002001, 0x00002080, 0x00800000, 0x00802001,
              0x00000080, 0x00800000, 0x00002000, 0x00802080
          };
  
  		private static readonly uint[] SP5 =
  		{
              0x00000100, 0x02080100, 0x02080000, 0x42000100,
              0x00080000, 0x00000100, 0x40000000, 0x02080000,
              0x40080100, 0x00080000, 0x02000100, 0x40080100,
              0x42000100, 0x42080000, 0x00080100, 0x40000000,
              0x02000000, 0x40080000, 0x40080000, 0x00000000,
              0x40000100, 0x42080100, 0x42080100, 0x02000100,
              0x42080000, 0x40000100, 0x00000000, 0x42000000,
              0x02080100, 0x02000000, 0x42000000, 0x00080100,
              0x00080000, 0x42000100, 0x00000100, 0x02000000,
              0x40000000, 0x02080000, 0x42000100, 0x40080100,
              0x02000100, 0x40000000, 0x42080000, 0x02080100,
              0x40080100, 0x00000100, 0x02000000, 0x42080000,
              0x42080100, 0x00080100, 0x42000000, 0x42080100,
              0x02080000, 0x00000000, 0x40080000, 0x42000000,
              0x00080100, 0x02000100, 0x40000100, 0x00080000,
              0x00000000, 0x40080000, 0x02080100, 0x40000100
          };
  
  		private static readonly uint[] SP6 =
  		{
              0x20000010, 0x20400000, 0x00004000, 0x20404010,
              0x20400000, 0x00000010, 0x20404010, 0x00400000,
              0x20004000, 0x00404010, 0x00400000, 0x20000010,
              0x00400010, 0x20004000, 0x20000000, 0x00004010,
              0x00000000, 0x00400010, 0x20004010, 0x00004000,
              0x00404000, 0x20004010, 0x00000010, 0x20400010,
              0x20400010, 0x00000000, 0x00404010, 0x20404000,
              0x00004010, 0x00404000, 0x20404000, 0x20000000,
              0x20004000, 0x00000010, 0x20400010, 0x00404000,
              0x20404010, 0x00400000, 0x00004010, 0x20000010,
              0x00400000, 0x20004000, 0x20000000, 0x00004010,
              0x20000010, 0x20404010, 0x00404000, 0x20400000,
              0x00404010, 0x20404000, 0x00000000, 0x20400010,
              0x00000010, 0x00004000, 0x20400000, 0x00404010,
              0x00004000, 0x00400010, 0x20004010, 0x00000000,
              0x20404000, 0x20000000, 0x00400010, 0x20004010
          };
  
  		private static readonly uint[] SP7 =
  		{
              0x00200000, 0x04200002, 0x04000802, 0x00000000,
              0x00000800, 0x04000802, 0x00200802, 0x04200800,
              0x04200802, 0x00200000, 0x00000000, 0x04000002,
              0x00000002, 0x04000000, 0x04200002, 0x00000802,
              0x04000800, 0x00200802, 0x00200002, 0x04000800,
              0x04000002, 0x04200000, 0x04200800, 0x00200002,
              0x04200000, 0x00000800, 0x00000802, 0x04200802,
              0x00200800, 0x00000002, 0x04000000, 0x00200800,
              0x04000000, 0x00200800, 0x00200000, 0x04000802,
              0x04000802, 0x04200002, 0x04200002, 0x00000002,
              0x00200002, 0x04000000, 0x04000800, 0x00200000,
              0x04200800, 0x00000802, 0x00200802, 0x04200800,
              0x00000802, 0x04000002, 0x04200802, 0x04200000,
              0x00200800, 0x00000000, 0x00000002, 0x04200802,
              0x00000000, 0x00200802, 0x04200000, 0x00000800,
              0x04000002, 0x04000800, 0x00000800, 0x00200002
          };
  
  		private static readonly uint[] SP8 =
  		{
              0x10001040, 0x00001000, 0x00040000, 0x10041040,
              0x10000000, 0x10001040, 0x00000040, 0x10000000,
              0x00040040, 0x10040000, 0x10041040, 0x00041000,
              0x10041000, 0x00041040, 0x00001000, 0x00000040,
              0x10040000, 0x10000040, 0x10001000, 0x00001040,
              0x00041000, 0x00040040, 0x10040040, 0x10041000,
              0x00001040, 0x00000000, 0x00000000, 0x10040040,
              0x10000040, 0x10001000, 0x00041040, 0x00040000,
              0x00041040, 0x00040000, 0x10041000, 0x00001000,
              0x00000040, 0x10040040, 0x00001000, 0x00041040,
              0x10001000, 0x00000040, 0x10000040, 0x10040000,
              0x10040040, 0x10000000, 0x00040000, 0x10001040,
              0x00000000, 0x10041040, 0x00040040, 0x10000040,
              0x10040000, 0x10001000, 0x10001040, 0x00000000,
              0x10041040, 0x00041000, 0x00041000, 0x00001040,
              0x00001040, 0x00040040, 0x10000000, 0x10041000
          };
  
  		/**
          * Generate an integer based working key based on our secret key
          * and what we processing we are planning to do.
          *
          * Acknowledgements for this routine go to James Gillogly and Phil Karn.
          *         (whoever, and wherever they are!).
          */
          protected static int[] GenerateWorkingKey(
              bool	encrypting,
              byte[]	key)
          {
              int[] newKey = new int[32];
              bool[] pc1m = new bool[56];
  			bool[] pcr = new bool[56];
  
  			for (int j = 0; j < 56; j++ )
              {
                  int l = pc1[j];
  
  				pc1m[j] = ((key[(uint) l >> 3] & bytebit[l & 07]) != 0);
              }
  
              for (int i = 0; i < 16; i++)
              {
                  int l, m, n;
  
                  if (encrypting)
                  {
                      m = i << 1;
                  }
                  else
                  {
                      m = (15 - i) << 1;
                  }
  
                  n = m + 1;
                  newKey[m] = newKey[n] = 0;
  
                  for (int j = 0; j < 28; j++)
                  {
                      l = j + totrot[i];
                      if ( l < 28 )
                      {
                          pcr[j] = pc1m[l];
                      }
                      else
                      {
                          pcr[j] = pc1m[l - 28];
                      }
                  }
  
                  for (int j = 28; j < 56; j++)
                  {
                      l = j + totrot[i];
                      if (l < 56 )
                      {
                          pcr[j] = pc1m[l];
                      }
                      else
                      {
                          pcr[j] = pc1m[l - 28];
                      }
                  }
  
                  for (int j = 0; j < 24; j++)
                  {
                      if (pcr[pc2[j]])
                      {
                          newKey[m] |= bigbyte[j];
                      }
  
                      if (pcr[pc2[j + 24]])
                      {
                          newKey[n] |= bigbyte[j];
                      }
                  }
              }
  
              //
              // store the processed key
              //
              for (int i = 0; i != 32; i += 2)
              {
                  int i1, i2;
  
                  i1 = newKey[i];
                  i2 = newKey[i + 1];
  
                  newKey[i] = (int) ( (uint) ((i1 & 0x00fc0000) << 6)  |
                                      (uint) ((i1 & 0x00000fc0) << 10) |
                                      ((uint) (i2 & 0x00fc0000) >> 10) |
                                      ((uint) (i2 & 0x00000fc0) >> 6));
  
                  newKey[i + 1] = (int) ( (uint) ((i1 & 0x0003f000) << 12) |
                                          (uint) ((i1 & 0x0000003f) << 16) |
                                          ((uint) (i2 & 0x0003f000) >> 4) |
                                          (uint) (i2 & 0x0000003f));
              }
  
              return newKey;
          }
  
          /**
          * the DES engine.
          */
          internal static void DesFunc(
              int[]	wKey,
              byte[]	input,
              int		inOff,
              byte[]	outBytes,
              int		outOff)
          {
  			uint left = Pack.BE_To_UInt32(input, inOff);
  			uint right = Pack.BE_To_UInt32(input, inOff + 4);
  			uint work;
  
              work = ((left >> 4) ^ right) & 0x0f0f0f0f;
              right ^= work;
              left ^= (work << 4);
              work = ((left >> 16) ^ right) & 0x0000ffff;
              right ^= work;
              left ^= (work << 16);
              work = ((right >> 2) ^ left) & 0x33333333;
              left ^= work;
              right ^= (work << 2);
              work = ((right >> 8) ^ left) & 0x00ff00ff;
              left ^= work;
              right ^= (work << 8);
              right = (right << 1) | (right >> 31);
              work = (left ^ right) & 0xaaaaaaaa;
              left ^= work;
              right ^= work;
              left = (left << 1) | (left >> 31);
  
              for (int round = 0; round < 8; round++)
              {
                  uint fval;
  
                  work  = (right << 28) | (right >> 4);
                  work ^= (uint)wKey[round * 4 + 0];
                  fval  = SP7[work         & 0x3f];
                  fval |= SP5[(work >>  8) & 0x3f];
                  fval |= SP3[(work >> 16) & 0x3f];
                  fval |= SP1[(work >> 24) & 0x3f];
                  work  = right ^ (uint)wKey[round * 4 + 1];
                  fval |= SP8[ work        & 0x3f];
                  fval |= SP6[(work >>  8) & 0x3f];
                  fval |= SP4[(work >> 16) & 0x3f];
                  fval |= SP2[(work >> 24) & 0x3f];
                  left ^= fval;
                  work  = (left << 28) | (left >> 4);
                  work ^= (uint)wKey[round * 4 + 2];
                  fval  = SP7[ work        & 0x3f];
                  fval |= SP5[(work >>  8) & 0x3f];
                  fval |= SP3[(work >> 16) & 0x3f];
                  fval |= SP1[(work >> 24) & 0x3f];
  
gt:                 work  = left ^ (uint)wKey[round * 4 + 3];