SSH.NET/Renci.SshClient/Renci.SshNet/Security/Cryptography/Ciphers/TwofishCipher.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Renci.SshNet.Security.Cryptography.Ciphers
{
	/// <summary>
	/// Implements Twofish cipher algorithm
	/// </summary>
	public class TwofishCipher : BlockCipher
	{
		/// <summary>
		/// Initializes a new instance of the <see cref="TwofishCipher"/> class.
		/// </summary>
		/// <param name="key">The key.</param>
		/// <param name="mode">The mode.</param>
		/// <param name="padding">The padding.</param>
		/// <exception cref="ArgumentNullException"><paramref name="key"/> is null.</exception>
		/// <exception cref="ArgumentException">Keysize is not valid for this algorithm.</exception>
		public TwofishCipher(byte[] key, CipherMode mode, CipherPadding padding)
			: base(key, 16, mode, padding)
		{
			var keySize = key.Length * 8;

			if (!(keySize == 128 || keySize == 192 || keySize == 256))
				throw new ArgumentException(string.Format("KeySize '{0}' is not valid for this algorithm.", keySize));

			//  TODO:   Refactor this algorithm

			// calculate the MDS matrix
			int[] m1 = new int[2];
			int[] mX = new int[2];
			int[] mY = new int[2];
			int j;

			for (int i = 0; i < MAX_KEY_BITS; i++)
			{
				j = P[0, i] & 0xff;
				m1[0] = j;
				mX[0] = Mx_X(j) & 0xff;
				mY[0] = Mx_Y(j) & 0xff;

				j = P[1, i] & 0xff;
				m1[1] = j;
				mX[1] = Mx_X(j) & 0xff;
				mY[1] = Mx_Y(j) & 0xff;

				gMDS0[i] = m1[P_00] | mX[P_00] << 8 | mY[P_00] << 16 | mY[P_00] << 24;

				gMDS1[i] = mY[P_10] | mY[P_10] << 8 | mX[P_10] << 16 | m1[P_10] << 24;

				gMDS2[i] = mX[P_20] | mY[P_20] << 8 | m1[P_20] << 16 | mY[P_20] << 24;

				gMDS3[i] = mX[P_30] | m1[P_30] << 8 | mY[P_30] << 16 | mX[P_30] << 24;
			}

			this.k64Cnt = key.Length / 8; // pre-padded ?
			this.SetKey(key);
		}

		/// <summary>
		/// Encrypts the specified region of the input byte array and copies the encrypted data to the specified region of the output byte array.
		/// </summary>
		/// <param name="inputBuffer">The input data to encrypt.</param>
		/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
		/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
		/// <param name="outputBuffer">The output to which to write encrypted data.</param>
		/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
		/// <returns>
		/// The number of bytes encrypted.
		/// </returns>
		public override int EncryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
		{
			int x0 = BytesTo32Bits(inputBuffer, inputOffset) ^ gSubKeys[INPUT_WHITEN];
			int x1 = BytesTo32Bits(inputBuffer, inputOffset + 4) ^ gSubKeys[INPUT_WHITEN + 1];
			int x2 = BytesTo32Bits(inputBuffer, inputOffset + 8) ^ gSubKeys[INPUT_WHITEN + 2];
			int x3 = BytesTo32Bits(inputBuffer, inputOffset + 12) ^ gSubKeys[INPUT_WHITEN + 3];

			int k = ROUND_SUBKEYS;
			int t0, t1;
			for (int r = 0; r < ROUNDS; r += 2)
			{
				t0 = Fe32_0(x0);
				t1 = Fe32_3(x1);
				x2 ^= t0 + t1 + gSubKeys[k++];
				x2 = (int)((uint)x2 >> 1) | x2 << 31;
				x3 = (x3 << 1 | (int)((uint)x3 >> 31)) ^ (t0 + 2 * t1 + gSubKeys[k++]);

				t0 = Fe32_0(x2);
				t1 = Fe32_3(x3);
				x0 ^= t0 + t1 + gSubKeys[k++];
				x0 = (int)((uint)x0 >> 1) | x0 << 31;
				x1 = (x1 << 1 | (int)((uint)x1 >> 31)) ^ (t0 + 2 * t1 + gSubKeys[k++]);
			}

			Bits32ToBytes(x2 ^ gSubKeys[OUTPUT_WHITEN], outputBuffer, outputOffset);
			Bits32ToBytes(x3 ^ gSubKeys[OUTPUT_WHITEN + 1], outputBuffer, outputOffset + 4);
			Bits32ToBytes(x0 ^ gSubKeys[OUTPUT_WHITEN + 2], outputBuffer, outputOffset + 8);
			Bits32ToBytes(x1 ^ gSubKeys[OUTPUT_WHITEN + 3], outputBuffer, outputOffset + 12);

			return this.BlockSize;
		}

		/// <summary>
		/// Decrypts the specified region of the input byte array and copies the decrypted data to the specified region of the output byte array.
		/// </summary>
		/// <param name="inputBuffer">The input data to decrypt.</param>
		/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
		/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
		/// <param name="outputBuffer">The output to which to write decrypted data.</param>
		/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
		/// <returns>
		/// The number of bytes decrypted.
		/// </returns>
		public override int DecryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
		{
			int x2 = BytesTo32Bits(inputBuffer, inputOffset) ^ gSubKeys[OUTPUT_WHITEN];
			int x3 = BytesTo32Bits(inputBuffer, inputOffset + 4) ^ gSubKeys[OUTPUT_WHITEN + 1];
			int x0 = BytesTo32Bits(inputBuffer, inputOffset + 8) ^ gSubKeys[OUTPUT_WHITEN + 2];
			int x1 = BytesTo32Bits(inputBuffer, inputOffset + 12) ^ gSubKeys[OUTPUT_WHITEN + 3];

			int k = ROUND_SUBKEYS + 2 * ROUNDS - 1;
			int t0, t1;
			for (int r = 0; r < ROUNDS; r += 2)
			{
				t0 = Fe32_0(x2);
				t1 = Fe32_3(x3);
				x1 ^= t0 + 2 * t1 + gSubKeys[k--];
				x0 = (x0 << 1 | (int)((uint)x0 >> 31)) ^ (t0 + t1 + gSubKeys[k--]);
				x1 = (int)((uint)x1 >> 1) | x1 << 31;

				t0 = Fe32_0(x0);
				t1 = Fe32_3(x1);
				x3 ^= t0 + 2 * t1 + gSubKeys[k--];
				x2 = (x2 << 1 | (int)((uint)x2 >> 31)) ^ (t0 + t1 + gSubKeys[k--]);
				x3 = (int)((uint)x3 >> 1) | x3 << 31;
			}

			Bits32ToBytes(x0 ^ gSubKeys[INPUT_WHITEN], outputBuffer, outputOffset);
			Bits32ToBytes(x1 ^ gSubKeys[INPUT_WHITEN + 1], outputBuffer, outputOffset + 4);
			Bits32ToBytes(x2 ^ gSubKeys[INPUT_WHITEN + 2], outputBuffer, outputOffset + 8);
			Bits32ToBytes(x3 ^ gSubKeys[INPUT_WHITEN + 3], outputBuffer, outputOffset + 12);

			return this.BlockSize;
		}

		#region Static Definition Tables

		private static readonly byte[,] P =  {
		{  // p0
			(byte) 0xA9, (byte) 0x67, (byte) 0xB3, (byte) 0xE8,
			(byte) 0x04, (byte) 0xFD, (byte) 0xA3, (byte) 0x76,
			(byte) 0x9A, (byte) 0x92, (byte) 0x80, (byte) 0x78,
			(byte) 0xE4, (byte) 0xDD, (byte) 0xD1, (byte) 0x38,
			(byte) 0x0D, (byte) 0xC6, (byte) 0x35, (byte) 0x98,
			(byte) 0x18, (byte) 0xF7, (byte) 0xEC, (byte) 0x6C,
			(byte) 0x43, (byte) 0x75, (byte) 0x37, (byte) 0x26,
			(byte) 0xFA, (byte) 0x13, (byte) 0x94, (byte) 0x48,
			(byte) 0xF2, (byte) 0xD0, (byte) 0x8B, (byte) 0x30,
			(byte) 0x84, (byte) 0x54, (byte) 0xDF, (byte) 0x23,
			(byte) 0x19, (byte) 0x5B, (byte) 0x3D, (byte) 0x59,
			(byte) 0xF3, (byte) 0xAE, (byte) 0xA2, (byte) 0x82,
			(byte) 0x63, (byte) 0x01, (byte) 0x83, (byte) 0x2E,
			(byte) 0xD9, (byte) 0x51, (byte) 0x9B, (byte) 0x7C,
			(byte) 0xA6, (byte) 0xEB, (byte) 0xA5, (byte) 0xBE,
			(byte) 0x16, (byte) 0x0C, (byte) 0xE3, (byte) 0x61,
			(byte) 0xC0, (byte) 0x8C, (byte) 0x3A, (byte) 0xF5,
			(byte) 0x73, (byte) 0x2C, (byte) 0x25, (byte) 0x0B,
			(byte) 0xBB, (byte) 0x4E, (byte) 0x89, (byte) 0x6B,
			(byte) 0x53, (byte) 0x6A, (byte) 0xB4, (byte) 0xF1,
			(byte) 0xE1, (byte) 0xE6, (byte) 0xBD, (byte) 0x45,
			(byte) 0xE2, (byte) 0xF4, (byte) 0xB6, (byte) 0x66,
			(byte) 0xCC, (byte) 0x95, (byte) 0x03, (byte) 0x56,
			(byte) 0xD4, (byte) 0x1C, (byte) 0x1E, (byte) 0xD7,
			(byte) 0xFB, (byte) 0xC3, (byte) 0x8E, (byte) 0xB5,
			(byte) 0xE9, (byte) 0xCF, (byte) 0xBF, (byte) 0xBA,
			(byte) 0xEA, (byte) 0x77, (byte) 0x39, (byte) 0xAF,
			(byte) 0x33, (byte) 0xC9, (byte) 0x62, (byte) 0x71,
			(byte) 0x81, (byte) 0x79, (byte) 0x09, (byte) 0xAD,
			(byte) 0x24, (byte) 0xCD, (byte) 0xF9, (byte) 0xD8,
			(byte) 0xE5, (byte) 0xC5, (byte) 0xB9, (byte) 0x4D,
			(byte) 0x44, (byte) 0x08, (byte) 0x86, (byte) 0xE7,
			(byte) 0xA1, (byte) 0x1D, (byte) 0xAA, (byte) 0xED,
			(byte) 0x06, (byte) 0x70, (byte) 0xB2, (byte) 0xD2,
			(byte) 0x41, (byte) 0x7B, (byte) 0xA0, (byte) 0x11,
			(byte) 0x31, (byte) 0xC2, (byte) 0x27, (byte) 0x90,
			(byte) 0x20, (byte) 0xF6, (byte) 0x60, (byte) 0xFF,
			(byte) 0x96, (byte) 0x5C, (byte) 0xB1, (byte) 0xAB,
			(byte) 0x9E, (byte) 0x9C, (byte) 0x52, (byte) 0x1B,
			(byte) 0x5F, (byte) 0x93, (byte) 0x0A, (byte) 0xEF,
			(byte) 0x91, (byte) 0x85, (byte) 0x49, (byte) 0xEE,
			(byte) 0x2D, (byte) 0x4F, (byte) 0x8F, (byte) 0x3B,
			(byte) 0x47, (byte) 0x87, (byte) 0x6D, (byte) 0x46,
			(byte) 0xD6, (byte) 0x3E, (byte) 0x69, (byte) 0x64,
			(byte) 0x2A, (byte) 0xCE, (byte) 0xCB, (byte) 0x2F,
			(byte) 0xFC, (byte) 0x97, (byte) 0x05, (byte) 0x7A,
			(byte) 0xAC, (byte) 0x7F, (byte) 0xD5, (byte) 0x1A,
			(byte) 0x4B, (byte) 0x0E, (byte) 0xA7, (byte) 0x5A,
			(byte) 0x28, (byte) 0x14, (byte) 0x3F, (byte) 0x29,
			(byte) 0x88, (byte) 0x3C, (byte) 0x4C, (byte) 0x02,
			(byte) 0xB8, (byte) 0xDA, (byte) 0xB0, (byte) 0x17,
			(byte) 0x55, (byte) 0x1F, (byte) 0x8A, (byte) 0x7D,
			(byte) 0x57, (byte) 0xC7, (byte) 0x8D, (byte) 0x74,
			(byte) 0xB7, (byte) 0xC4, (byte) 0x9F, (byte) 0x72,
			(byte) 0x7E, (byte) 0x15, (byte) 0x22, (byte) 0x12,
			(byte) 0x58, (byte) 0x07, (byte) 0x99, (byte) 0x34,
			(byte) 0x6E, (byte) 0x50, (byte) 0xDE, (byte) 0x68,
			(byte) 0x65, (byte) 0xBC, (byte) 0xDB, (byte) 0xF8,
			(byte) 0xC8, (byte) 0xA8, (byte) 0x2B, (byte) 0x40,
			(byte) 0xDC, (byte) 0xFE, (byte) 0x32, (byte) 0xA4,
			(byte) 0xCA, (byte) 0x10, (byte) 0x21, (byte) 0xF0,
			(byte) 0xD3, (byte) 0x5D, (byte) 0x0F, (byte) 0x00,
			(byte) 0x6F, (byte) 0x9D, (byte) 0x36, (byte) 0x42,
			(byte) 0x4A, (byte) 0x5E, (byte) 0xC1, (byte) 0xE0 },
		{  // p1
			(byte) 0x75, (byte) 0xF3, (byte) 0xC6, (byte) 0xF4,
			(byte) 0xDB, (byte) 0x7B, (byte) 0xFB, (byte) 0xC8,
			(byte) 0x4A, (byte) 0xD3, (byte) 0xE6, (byte) 0x6B,
			(byte) 0x45, (byte) 0x7D, (byte) 0xE8, (byte) 0x4B,
			(byte) 0xD6, (byte) 0x32, (byte) 0xD8, (byte) 0xFD,
			(byte) 0x37, (byte) 0x71, (byte) 0xF1, (byte) 0xE1,
			(byte) 0x30, (byte) 0x0F, (byte) 0xF8, (byte) 0x1B,
			(byte) 0x87, (byte) 0xFA, (byte) 0x06, (byte) 0x3F,
			(byte) 0x5E, (byte) 0xBA, (byte) 0xAE, (byte) 0x5B,
			(byte) 0x8A, (byte) 0x00, (byte) 0xBC, (byte) 0x9D,
			(byte) 0x6D, (byte) 0xC1, (byte) 0xB1, (byte) 0x0E,
			(byte) 0x80, (byte) 0x5D, (byte) 0xD2, (byte) 0xD5,
			(byte) 0xA0, (byte) 0x84, (byte) 0x07, (byte) 0x14,
			(byte) 0xB5, (byte) 0x90, (byte) 0x2C, (byte) 0xA3,
			(byte) 0xB2, (byte) 0x73, (byte) 0x4C, (byte) 0x54,
			(byte) 0x92, (byte) 0x74, (byte) 0x36, (byte) 0x51,
			(byte) 0x38, (byte) 0xB0, (byte) 0xBD, (byte) 0x5A,
			(byte) 0xFC, (byte) 0x60, (byte) 0x62, (byte) 0x96,
			(byte) 0x6C, (byte) 0x42, (byte) 0xF7, (byte) 0x10,
			(byte) 0x7C, (byte) 0x28, (byte) 0x27, (byte) 0x8C,
			(byte) 0x13, (byte) 0x95, (byte) 0x9C, (byte) 0xC7,
			(byte) 0x24, (byte) 0x46, (byte) 0x3B, (byte) 0x70,
			(byte) 0xCA, (byte) 0xE3, (byte) 0x85, (byte) 0xCB,
			(byte) 0x11, (byte) 0xD0, (byte) 0x93, (byte) 0xB8,
			(byte) 0xA6, (byte) 0x83, (byte) 0x20, (byte) 0xFF,
			(byte) 0x9F, (byte) 0x77, (byte) 0xC3, (byte) 0xCC,
			(byte) 0x03, (byte) 0x6F, (byte) 0x08, (byte) 0xBF,
			(byte) 0x40, (byte) 0xE7, (byte) 0x2B, (byte) 0xE2,
			(byte) 0x79, (byte) 0x0C, (byte) 0xAA, (byte) 0x82,
			(byte) 0x41, (byte) 0x3A, (byte) 0xEA, (byte) 0xB9,
			(byte) 0xE4, (byte) 0x9A, (byte) 0xA4, (byte) 0x97,
			(byte) 0x7E, (byte) 0xDA, (byte) 0x7A, (byte) 0x17,
			(byte) 0x66, (byte) 0x94, (byte) 0xA1, (byte) 0x1D,
			(byte) 0x3D, (byte) 0xF0, (byte) 0xDE, (byte) 0xB3,
			(byte) 0x0B, (byte) 0x72, (byte) 0xA7, (byte) 0x1C,
			(byte) 0xEF, (byte) 0xD1, (byte) 0x53, (byte) 0x3E,
			(byte) 0x8F, (byte) 0x33, (byte) 0x26, (byte) 0x5F,
			(byte) 0xEC, (byte) 0x76, (byte) 0x2A, (byte) 0x49,
			(byte) 0x81, (byte) 0x88, (byte) 0xEE, (byte) 0x21,
			(byte) 0xC4, (byte) 0x1A, (byte) 0xEB, (byte) 0xD9,
			(byte) 0xC5, (byte) 0x39, (byte) 0x99, (byte) 0xCD,
			(byte) 0xAD, (byte) 0x31, (byte) 0x8B, (byte) 0x01,
			(byte) 0x18, (byte) 0x23, (byte) 0xDD, (byte) 0x1F,
			(byte) 0x4E, (byte) 0x2D, (byte) 0xF9, (byte) 0x48,
			(byte) 0x4F, (byte) 0xF2, (byte) 0x65, (byte) 0x8E,
			(byte) 0x78, (byte) 0x5C, (byte) 0x58, (byte) 0x19,
			(byte) 0x8D, (byte) 0xE5, (byte) 0x98, (byte) 0x57,
			(byte) 0x67, (byte) 0x7F, (byte) 0x05, (byte) 0x64,
			(byte) 0xAF, (byte) 0x63, (byte) 0xB6, (byte) 0xFE,
			(byte) 0xF5, (byte) 0xB7, (byte) 0x3C, (byte) 0xA5,
			(byte) 0xCE, (byte) 0xE9, (byte) 0x68, (byte) 0x44,
			(byte) 0xE0, (byte) 0x4D, (byte) 0x43, (byte) 0x69,
			(byte) 0x29, (byte) 0x2E, (byte) 0xAC, (byte) 0x15,
			(byte) 0x59, (byte) 0xA8, (byte) 0x0A, (byte) 0x9E,
			(byte) 0x6E, (byte) 0x47, (byte) 0xDF, (byte) 0x34,
			(byte) 0x35, (byte) 0x6A, (byte) 0xCF, (byte) 0xDC,
			(byte) 0x22, (byte) 0xC9, (byte) 0xC0, (byte) 0x9B,
			(byte) 0x89, (byte) 0xD4, (byte) 0xED, (byte) 0xAB,
			(byte) 0x12, (byte) 0xA2, (byte) 0x0D, (byte) 0x52,
			(byte) 0xBB, (byte) 0x02, (byte) 0x2F, (byte) 0xA9,
			(byte) 0xD7, (byte) 0x61, (byte) 0x1E, (byte) 0xB4,
			(byte) 0x50, (byte) 0x04, (byte) 0xF6, (byte) 0xC2,
			(byte) 0x16, (byte) 0x25, (byte) 0x86, (byte) 0x56,
			(byte) 0x55, (byte) 0x09, (byte) 0xBE, (byte) 0x91  }
		};

		#endregion

		/**
		* Define the fixed p0/p1 permutations used in keyed S-box lookup.
		* By changing the following constant definitions, the S-boxes will
		* automatically Get changed in the Twofish engine.
		*/
		private const int P_00 = 1;
		private const int P_01 = 0;
		private const int P_02 = 0;
		private const int P_03 = P_01 ^ 1;
		private const int P_04 = 1;

		private const int P_10 = 0;
		private const int P_11 = 0;
		private const int P_12 = 1;
		private const int P_13 = P_11 ^ 1;
		private const int P_14 = 0;

		private const int P_20 = 1;
		private const int P_21 = 1;
		private const int P_22 = 0;
		private const int P_23 = P_21 ^ 1;
		private const int P_24 = 0;

		private const int P_30 = 0;
		private const int P_31 = 1;
		private const int P_32 = 1;
		private const int P_33 = P_31 ^ 1;
		private const int P_34 = 1;

		/* Primitive polynomial for GF(256) */
		private const int GF256_FDBK = 0x169;
		private const int GF256_FDBK_2 = GF256_FDBK / 2;
		private const int GF256_FDBK_4 = GF256_FDBK / 4;

		private const int RS_GF_FDBK = 0x14D; // field generator

		//====================================
		// Useful constants
		//====================================

		private const int ROUNDS = 16;
		private const int MAX_ROUNDS = 16;  // bytes = 128 bits
		private const int MAX_KEY_BITS = 256;

		private const int INPUT_WHITEN = 0;
		private const int OUTPUT_WHITEN = INPUT_WHITEN + 16 / 4; // 4
		private const int ROUND_SUBKEYS = OUTPUT_WHITEN + 16 / 4;// 8

		private const int TOTAL_SUBKEYS = ROUND_SUBKEYS + 2 * MAX_ROUNDS;// 40

		private const int SK_STEP = 0x02020202;
		private const int SK_BUMP = 0x01010101;
		private const int SK_ROTL = 9;

		private int[] gMDS0 = new int[MAX_KEY_BITS];
		private int[] gMDS1 = new int[MAX_KEY_BITS];
		private int[] gMDS2 = new int[MAX_KEY_BITS];
		private int[] gMDS3 = new int[MAX_KEY_BITS];

		/**
		* gSubKeys[] and gSBox[] are eventually used in the
		* encryption and decryption methods.
		*/
		private int[] gSubKeys;
		private int[] gSBox;

		private int k64Cnt;

		private void SetKey(byte[] key)
		{
			int[] k32e = new int[MAX_KEY_BITS / 64]; // 4
			int[] k32o = new int[MAX_KEY_BITS / 64]; // 4

			int[] sBoxKeys = new int[MAX_KEY_BITS / 64]; // 4
			gSubKeys = new int[TOTAL_SUBKEYS];

			if (k64Cnt < 1)
			{
				throw new ArgumentException("Key size less than 64 bits");
			}

			if (k64Cnt > 4)
			{
				throw new ArgumentException("Key size larger than 256 bits");
			}

			/*
			* k64Cnt is the number of 8 byte blocks (64 chunks)
			* that are in the input key.  The input key is a
			* maximum of 32 bytes ( 256 bits ), so the range
			* for k64Cnt is 1..4
			*/
			for (int i = 0, p = 0; i < k64Cnt; i++)
			{
				p = i * 8;

				k32e[i] = BytesTo32Bits(key, p);
				k32o[i] = BytesTo32Bits(key, p + 4);

				sBoxKeys[k64Cnt - 1 - i] = RS_MDS_Encode(k32e[i], k32o[i]);
			}

			int q, A, B;
			for (int i = 0; i < TOTAL_SUBKEYS / 2; i++)
			{
				q = i * SK_STEP;
				A = F32(q, k32e);
				B = F32(q + SK_BUMP, k32o);
				B = B << 8 | (int)((uint)B >> 24);
				A += B;
				gSubKeys[i * 2] = A;
				A += B;
				gSubKeys[i * 2 + 1] = A << SK_ROTL | (int)((uint)A >> (32 - SK_ROTL));
			}

			/*
			* fully expand the table for speed
			*/
			int k0 = sBoxKeys[0];
			int k1 = sBoxKeys[1];
			int k2 = sBoxKeys[2];
			int k3 = sBoxKeys[3];
			int b0, b1, b2, b3;
			gSBox = new int[4 * MAX_KEY_BITS];
			for (int i = 0; i < MAX_KEY_BITS; i++)
			{
				b0 = b1 = b2 = b3 = i;
				switch (k64Cnt & 3)
				{
					case 1:
						gSBox[i * 2] = gMDS0[(P[P_01, b0] & 0xff) ^ M_b0(k0)];
						gSBox[i * 2 + 1] = gMDS1[(P[P_11, b1] & 0xff) ^ M_b1(k0)];
						gSBox[i * 2 + 0x200] = gMDS2[(P[P_21, b2] & 0xff) ^ M_b2(k0)];
						gSBox[i * 2 + 0x201] = gMDS3[(P[P_31, b3] & 0xff) ^ M_b3(k0)];
						break;
					case 0: /* 256 bits of key */
						b0 = (P[P_04, b0] & 0xff) ^ M_b0(k3);
						b1 = (P[P_14, b1] & 0xff) ^ M_b1(k3);
						b2 = (P[P_24, b2] & 0xff) ^ M_b2(k3);
						b3 = (P[P_34, b3] & 0xff) ^ M_b3(k3);
						goto case 3;
					case 3:
						b0 = (P[P_03, b0] & 0xff) ^ M_b0(k2);
						b1 = (P[P_13, b1] & 0xff) ^ M_b1(k2);
						b2 = (P[P_23, b2] & 0xff) ^ M_b2(k2);
						b3 = (P[P_33, b3] & 0xff) ^ M_b3(k2);
						goto case 2;
					case 2:
						gSBox[i * 2] = gMDS0[(P[P_01, (P[P_02, b0] & 0xff) ^ M_b0(k1)] & 0xff) ^ M_b0(k0)];
						gSBox[i * 2 + 1] = gMDS1[(P[P_11, (P[P_12, b1] & 0xff) ^ M_b1(k1)] & 0xff) ^ M_b1(k0)];
						gSBox[i * 2 + 0x200] = gMDS2[(P[P_21, (P[P_22, b2] & 0xff) ^ M_b2(k1)] & 0xff) ^ M_b2(k0)];
						gSBox[i * 2 + 0x201] = gMDS3[(P[P_31, (P[P_32, b3] & 0xff) ^ M_b3(k1)] & 0xff) ^ M_b3(k0)];
						break;
				}
			}

			/*
			* the function exits having setup the gSBox with the
			* input key material.
			*/
		}

		/*
		* TODO:  This can be optimised and made cleaner by combining
		* the functionality in this function and applying it appropriately
		* to the creation of the subkeys during key setup.
		*/
		private int F32(int x, int[] k32)
		{
			int b0 = M_b0(x);
			int b1 = M_b1(x);
			int b2 = M_b2(x);
			int b3 = M_b3(x);
			int k0 = k32[0];
			int k1 = k32[1];
			int k2 = k32[2];
			int k3 = k32[3];

			int result = 0;
			switch (k64Cnt & 3)
			{
				case 1:
					result = gMDS0[(P[P_01, b0] & 0xff) ^ M_b0(k0)] ^
							 gMDS1[(P[P_11, b1] & 0xff) ^ M_b1(k0)] ^
							 gMDS2[(P[P_21, b2] & 0xff) ^ M_b2(k0)] ^
							 gMDS3[(P[P_31, b3] & 0xff) ^ M_b3(k0)];
					break;
				case 0: /* 256 bits of key */
					b0 = (P[P_04, b0] & 0xff) ^ M_b0(k3);
					b1 = (P[P_14, b1] & 0xff) ^ M_b1(k3);
					b2 = (P[P_24, b2] & 0xff) ^ M_b2(k3);
					b3 = (P[P_34, b3] & 0xff) ^ M_b3(k3);
					goto case 3;
				case 3:
					b0 = (P[P_03, b0] & 0xff) ^ M_b0(k2);
					b1 = (P[P_13, b1] & 0xff) ^ M_b1(k2);
					b2 = (P[P_23, b2] & 0xff) ^ M_b2(k2);
					b3 = (P[P_33, b3] & 0xff) ^ M_b3(k2);
					goto case 2;
				case 2:
					result =
					gMDS0[(P[P_01, (P[P_02, b0] & 0xff) ^ M_b0(k1)] & 0xff) ^ M_b0(k0)] ^
					gMDS1[(P[P_11, (P[P_12, b1] & 0xff) ^ M_b1(k1)] & 0xff) ^ M_b1(k0)] ^
					gMDS2[(P[P_21, (P[P_22, b2] & 0xff) ^ M_b2(k1)] & 0xff) ^ M_b2(k0)] ^
					gMDS3[(P[P_31, (P[P_32, b3] & 0xff) ^ M_b3(k1)] & 0xff) ^ M_b3(k0)];
					break;
			}
			return result;
		}

		/**
		* Use (12, 8) Reed-Solomon code over GF(256) to produce
		* a key S-box 32-bit entity from 2 key material 32-bit
		* entities.
		*
		* @param    k0 first 32-bit entity
		* @param    k1 second 32-bit entity
		* @return     Remainder polynomial Generated using RS code
		*/
		private int RS_MDS_Encode(int k0, int k1)
		{
			int r = k1;
			for (int i = 0; i < 4; i++) // shift 1 byte at a time
			{
				r = RS_rem(r);
			}
			r ^= k0;
			for (int i = 0; i < 4; i++)
			{
				r = RS_rem(r);
			}

			return r;
		}

		/**
		* Reed-Solomon code parameters: (12,8) reversible code:
		* <p>
		* <pre>
		* G(x) = x^4 + (a+1/a)x^3 + ax^2 + (a+1/a)x + 1
		* </pre>
		* where a = primitive root of field generator 0x14D
		* </p>
		*/
		private int RS_rem(int x)
		{
			int b = (int)(((uint)x >> 24) & 0xff);
			int g2 = ((b << 1) ^
					((b & 0x80) != 0 ? RS_GF_FDBK : 0)) & 0xff;
			int g3 = ((int)((uint)b >> 1) ^
					((b & 0x01) != 0 ? (int)((uint)RS_GF_FDBK >> 1) : 0)) ^ g2;
			return ((x << 8) ^ (g3 << 24) ^ (g2 << 16) ^ (g3 << 8) ^ b);
		}

		private int LFSR1(int x)
		{
			return (x >> 1) ^
					(((x & 0x01) != 0) ? GF256_FDBK_2 : 0);
		}

		private int LFSR2(int x)
		{
			return (x >> 2) ^
					(((x & 0x02) != 0) ? GF256_FDBK_2 : 0) ^
					(((x & 0x01) != 0) ? GF256_FDBK_4 : 0);
		}

		private int Mx_X(int x)
		{
			return x ^ LFSR2(x);
		} // 5B

		private int Mx_Y(int x)
		{
			return x ^ LFSR1(x) ^ LFSR2(x);
		} // EF

		private int M_b0(int x)
		{
			return x & 0xff;
		}

		private int M_b1(int x)
		{
			return (int)((uint)x >> 8) & 0xff;
		}

		private int M_b2(int x)
		{
			return (int)((uint)x >> 16) & 0xff;
		}

		private int M_b3(int x)
		{
			return (int)((uint)x >> 24) & 0xff;
		}

		private int Fe32_0(int x)
		{
			return gSBox[0x000 + 2 * (x & 0xff)] ^
				gSBox[0x001 + 2 * ((int)((uint)x >> 8) & 0xff)] ^
				gSBox[0x200 + 2 * ((int)((uint)x >> 16) & 0xff)] ^
				gSBox[0x201 + 2 * ((int)((uint)x >> 24) & 0xff)];
		}

		private int Fe32_3(int x)
		{
			return gSBox[0x000 + 2 * ((int)((uint)x >> 24) & 0xff)] ^
				gSBox[0x001 + 2 * (x & 0xff)] ^
				gSBox[0x200 + 2 * ((int)((uint)x >> 8) & 0xff)] ^
				gSBox[0x201 + 2 * ((int)((uint)x >> 16) & 0xff)];
		}

		private int BytesTo32Bits(byte[] b, int p)
		{
			return ((b[p] & 0xff)) |
				((b[p + 1] & 0xff) << 8) |
				((b[p + 2] & 0xff) << 16) |
				((b[p + 3] & 0xff) << 24);
		}

		private void Bits32ToBytes(int inData, byte[] b, int offset)
		{
			b[offset] = (byte)inData;
			b[offset + 1] = (byte)(inData >> 8);
			b[offset + 2] = (byte)(inData >> 16);
			b[offset + 3] = (byte)(inData >> 24);
		}
	}
}