context: //
  // MD4Managed.cs - Message Digest 4 Managed Implementation
  //
  // Author:
  //	Sebastien Pouliot (sebastien@ximian.com)
  //
  // (C) 2003 Motus Technologies Inc. (http://www.motus.com)
  // Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
  //
  // Permission is hereby granted, free of charge, to any person obtaining
  // a copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to
  // permit persons to whom the Software is furnished to do so, subject to
  // the following conditions:
  // 
  // The above copyright notice and this permission notice shall be
  // included in all copies or substantial portions of the Software.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  //
  
  using System;
  
  namespace CryptoNet.Security.Cryptography { 
  
  	// References:
  	// a.     RFC1320: The MD4 Message-Digest Algorithm
  	//        http://www.ietf.org/rfc/rfc1320.txt
  
  	internal class MD4Managed : MD4 {
  
  		private uint[] state;
  		private byte[] buffer;
  		private uint[] count;
  		private uint[] x;
  
  		private const int S11 = 3;
  		private const int S12 = 7;
  		private const int S13 = 11;
  		private const int S14 = 19;
  		private const int S21 = 3;
  		private const int S22 = 5;
  		private const int S23 = 9;
  		private const int S24 = 13;
  		private const int S31 = 3;
  		private const int S32 = 9;
  		private const int S33 = 11;
  		private const int S34 = 15;
  
  		private byte[] digest;
  
  		//--- constructor -----------------------------------------------------------
                  
  		public MD4Managed ()
  		{
  			// we allocate the context memory
  			state = new uint [4];
  			count = new uint [2];
  			buffer = new byte [64];
  			digest = new byte [16];
  			// temporary buffer in MD4Transform that we don't want to keep allocate on each iteration
  			x = new uint [16];
  			// the initialize our context
  			Initialize ();
  		}
  
  		public override void Initialize ()
  		{
  			count [0] = 0;
  			count [1] = 0;
  			state [0] = 0x67452301;
  			state [1] = 0xefcdab89;
  			state [2] = 0x98badcfe;
  			state [3] = 0x10325476;
  			// Zeroize sensitive information
  			Array.Clear (buffer, 0, 64);
  			Array.Clear (x, 0, 16);
  		}
  
  		protected override void HashCore (byte[] array, int ibStart, int cbSize)
  		{
  			/* Compute number of bytes mod 64 */
  			int index = (int) ((count [0] >> 3) & 0x3F);
  			/* Update number of bits */
  			count [0] += (uint) (cbSize << 3);
  			if (count [0] < (cbSize << 3))
  				count [1]++;
  			count [1] += (uint) (cbSize >> 29);
  
  			int partLen = 64 - index;
  			int i = 0;
  			/* Transform as many times as possible. */
  			if (cbSize >= partLen) {
  				//MD4_memcpy((POINTER)&context->buffer[index], (POINTER)input, partLen);
  				Buffer.BlockCopy (array, ibStart, buffer, index, partLen);
  				MD4Transform (state, buffer, 0);
  
  				for (i = partLen; i + 63 < cbSize; i += 64) {
  					// MD4Transform (context->state, &input[i]);
  					MD4Transform (state, array, i);
  				}
  
  				index = 0;
  			}
  
  			/* Buffer remaining input */
  			//MD4_memcpy ((POINTER)&context->buffer[index], (POINTER)&input[i], inputLen-i);
  			Buffer.BlockCopy (array, ibStart + i, buffer, index, (cbSize-i));
  		}
  
  		protected override byte[] HashFinal ()
  		{
  			/* Save number of bits */
  			byte[] bits = new byte [8];
  			Encode (bits, count);
  
  			/* Pad out to 56 mod 64. */
  			uint index = ((count [0] >> 3) & 0x3f);
  			int padLen = (int) ((index < 56) ? (56 - index) : (120 - index));
  			HashCore (Padding (padLen), 0, padLen);
  
  			/* Append length (before padding) */
  			HashCore (bits, 0, 8);
  
  			/* Store state in digest */
  			Encode (digest, state);
  
  			// Zeroize sensitive information.
  			Initialize ();
  
  			return digest;
  		}
  
  		//--- private methods ---------------------------------------------------
  
  		private byte[] Padding (int nLength) 
  		{
  			if (nLength > 0) {
  				byte[] padding = new byte [nLength];
  				padding [0] = 0x80;
  				return padding;
  			}
  			return null;
  		}
  
  		/* F, G and H are basic MD4 functions. */
  		private uint F (uint x, uint y, uint z) 
  		{
  			return (uint) (((x) & (y)) | ((~x) & (z)));
  		}
  
  		private uint G (uint x, uint y, uint z) 
  		{
  			return (uint) (((x) & (y)) | ((x) & (z)) | ((y) & (z)));
  		}
  
  		private uint H (uint x, uint y, uint z) 
  		{
  			return (uint) ((x) ^ (y) ^ (z));
  		}
  
  		/* ROTATE_LEFT rotates x left n bits. */
  		private uint ROL (uint x, byte n) 
  		{
  			return (uint) (((x) << (n)) | ((x) >> (32-(n))));
  		}
  
  		/* FF, GG and HH are transformations for rounds 1, 2 and 3 */
  		/* Rotation is separate from addition to prevent recomputation */
  		private void FF (ref uint a, uint b, uint c, uint d, uint x, byte s) 
  		{
  			a += F (b, c, d) + x;
  			a = ROL (a, s);
  		}
  
  		private void GG (ref uint a, uint b, uint c, uint d, uint x, byte s) 
  		{
  			a += G (b, c, d) + x + 0x5a827999;
  			a = ROL (a, s);
  		}
  
  		private void HH (ref uint a, uint b, uint c, uint d, uint x, byte s) 
  		{
  			a += H (b, c, d) + x + 0x6ed9eba1;
  			a = ROL (a, s);
  		}
  
  		private void Encode (byte[] output, uint[] input)
  		{
  			for (int i = 0, j = 0; j < output.Length; i++, j += 4) {
  				output [j]   = (byte)(input [i]);
  				output [j+1] = (byte)(input [i] >> 8);
  				output [j+2] = (byte)(input [i] >> 16);
  				output [j+3] = (byte)(input [i] >> 24);
  			}
  		}
  
  		private void Decode (uint[] output, byte[] input, int index) 
  		{
  			for (int i = 0, j = index; i < output.Length; i++, j += 4) {
  				output [i] = (uint) ((input [j]) | (input [j+1] << 8) | (input [j+2] << 16) | (input [j+3] << 24));
  			}
  		}
  
  		private void MD4Transform (uint[] state, byte[] block, int index)
  		{
  			uint a = state [0];
  			uint b = state [1];
  			uint c = state [2];
  			uint d = state [3];
  
  			Decode (x, block, index);
  
  			/* Round 1 */
  			FF (ref a, b, c, d, x[ 0], S11); /* 1 */
  			FF (ref d, a, b, c, x[ 1], S12); /* 2 */
  			FF (ref c, d, a, b, x[ 2], S13); /* 3 */
  			FF (ref b, c, d, a, x[ 3], S14); /* 4 */
  			FF (ref a, b, c, d, x[ 4], S11); /* 5 */
  			FF (ref d, a, b, c, x[ 5], S12); /* 6 */
  			FF (ref c, d, a, b, x[ 6], S13); /* 7 */
  			FF (ref b, c, d, a, x[ 7], S14); /* 8 */
  			FF (ref a, b, c, d, x[ 8], S11); /* 9 */
  			FF (ref d, a, b, c, x[ 9], S12); /* 10 */
  			FF (ref c, d, a, b, x[10], S13); /* 11 */
  			FF (ref b, c, d, a, x[11], S14); /* 12 */
  			FF (ref a, b, c, d, x[12], S11); /* 13 */
  			FF (ref d, a, b, c, x[13], S12); /* 14 */
  			FF (ref c, d, a, b, x[14], S13); /* 15 */
  			FF (ref b, c, d, a, x[15], S14); /* 16 */
  
  			/* Round 2 */
  			GG (ref a, b, c, d, x[ 0], S21); /* 17 */
  			GG (ref d, a, b, c, x[ 4], S22); /* 18 */
  			GG (ref c, d, a, b, x[ 8], S23); /* 19 */
  			GG (ref b, c, d, a, x[12], S24); /* 20 */
  			GG (ref a, b, c, d, x[ 1], S21); /* 21 */
  			GG (ref d, a, b, c, x[ 5], S22); /* 22 */
  			GG (ref c, d, a, b, x[ 9], S23); /* 23 */
  			GG (ref b, c, d, a, x[13], S24); /* 24 */
  			GG (ref a, b, c, d, x[ 2], S21); /* 25 */
  			GG (ref d, a, b, c, x[ 6], S22); /* 26 */
  			GG (ref c, d, a, b, x[10], S23); /* 27 */
  			GG (ref b, c, d, a, x[14], S24); /* 28 */
  			GG (ref a, b, c, d, x[ 3], S21); /* 29 */
  			GG (ref d, a, b, c, x[ 7], S22); /* 30 */
  			GG (ref c, d, a, b, x[11], S23); /* 31 */
  			GG (ref b, c, d, a, x[15], S24); /* 32 */
  
  			HH (ref a, b, c, d, x[ 0], S31); /* 33 */
  			HH (ref d, a, b, c, x[ 8], S32); /* 34 */
  			HH (ref c, d, a, b, x[ 4], S33); /* 35 */
  			HH (ref b, c, d, a, x[12], S34); /* 36 */
  			HH (ref a, b, c, d, x[ 2], S31); /* 37 */
  			HH (ref d, a, b, c, x[10], S32); /* 38 */
  			HH (ref c, d, a, b, x[ 6], S33); /* 39 */
  
gt: 			HH (ref b, c, d, a, x[14], S34); /* 40 */