<?php
//+------------------------------------------------------------------+
//|                                             MetaTrader 5 Web API |
//|                   Copyright 2000-2021, MetaQuotes Software Corp. |
//|                                        http://www.metaquotes.net |
//+------------------------------------------------------------------+
/**
 * Crypt aes 256
 */
class MT5CryptAes256
  {
  //--- The number of 32-bit words comprising the plaintext and columns comrising the state matrix of an AES cipher.
  private static $m_nb = 4;
  // The number of 32-bit words comprising the cipher key in this AES cipher.
  private $m_nk;
  //--- The number of rounds in this AES cipher.
  private $m_nr;
  //--- The S-Box substitution table.
  private static $m_sbox = array(0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16);
  //--- The inverse S-Box substitution table.
  private static $m_inv_sbox = array(0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d);
  // Log table based on 0xe5
  private static $m_ltable = array(0x00, 0xff, 0xc8, 0x08, 0x91, 0x10, 0xd0, 0x36, 0x5a, 0x3e, 0xd8, 0x43, 0x99, 0x77, 0xfe, 0x18, 0x23, 0x20, 0x07, 0x70, 0xa1, 0x6c, 0x0c, 0x7f, 0x62, 0x8b, 0x40, 0x46, 0xc7, 0x4b, 0xe0, 0x0e, 0xeb, 0x16, 0xe8, 0xad, 0xcf, 0xcd, 0x39, 0x53, 0x6a, 0x27, 0x35, 0x93, 0xd4, 0x4e, 0x48, 0xc3, 0x2b, 0x79, 0x54, 0x28, 0x09, 0x78, 0x0f, 0x21, 0x90, 0x87, 0x14, 0x2a, 0xa9, 0x9c, 0xd6, 0x74, 0xb4, 0x7c, 0xde, 0xed, 0xb1, 0x86, 0x76, 0xa4, 0x98, 0xe2, 0x96, 0x8f, 0x02, 0x32, 0x1c, 0xc1, 0x33, 0xee, 0xef, 0x81, 0xfd, 0x30, 0x5c, 0x13, 0x9d, 0x29, 0x17, 0xc4, 0x11, 0x44, 0x8c, 0x80, 0xf3, 0x73, 0x42, 0x1e, 0x1d, 0xb5, 0xf0, 0x12, 0xd1, 0x5b, 0x41, 0xa2, 0xd7, 0x2c, 0xe9, 0xd5, 0x59, 0xcb, 0x50, 0xa8, 0xdc, 0xfc, 0xf2, 0x56, 0x72, 0xa6, 0x65, 0x2f, 0x9f, 0x9b, 0x3d, 0xba, 0x7d, 0xc2, 0x45, 0x82, 0xa7, 0x57, 0xb6, 0xa3, 0x7a, 0x75, 0x4f, 0xae, 0x3f, 0x37, 0x6d, 0x47, 0x61, 0xbe, 0xab, 0xd3, 0x5f, 0xb0, 0x58, 0xaf, 0xca, 0x5e, 0xfa, 0x85, 0xe4, 0x4d, 0x8a, 0x05, 0xfb, 0x60, 0xb7, 0x7b, 0xb8, 0x26, 0x4a, 0x67, 0xc6, 0x1a, 0xf8, 0x69, 0x25, 0xb3, 0xdb, 0xbd, 0x66, 0xdd, 0xf1, 0xd2, 0xdf, 0x03, 0x8d, 0x34, 0xd9, 0x92, 0x0d, 0x63, 0x55, 0xaa, 0x49, 0xec, 0xbc, 0x95, 0x3c, 0x84, 0x0b, 0xf5, 0xe6, 0xe7, 0xe5, 0xac, 0x7e, 0x6e, 0xb9, 0xf9, 0xda, 0x8e, 0x9a, 0xc9, 0x24, 0xe1, 0x0a, 0x15, 0x6b, 0x3a, 0xa0, 0x51, 0xf4, 0xea, 0xb2, 0x97, 0x9e, 0x5d, 0x22, 0x88, 0x94, 0xce, 0x19, 0x01, 0x71, 0x4c, 0xa5, 0xe3, 0xc5, 0x31, 0xbb, 0xcc, 0x1f, 0x2d, 0x3b, 0x52, 0x6f, 0xf6, 0x2e, 0x89, 0xf7, 0xc0, 0x68, 0x1b, 0x64, 0x04, 0x06, 0xbf, 0x83, 0x38);
  //--- Inverse log table
  private static $m_atable = array(0x01, 0xe5, 0x4c, 0xb5, 0xfb, 0x9f, 0xfc, 0x12, 0x03, 0x34, 0xd4, 0xc4, 0x16, 0xba, 0x1f, 0x36, 0x05, 0x5c, 0x67, 0x57, 0x3a, 0xd5, 0x21, 0x5a, 0x0f, 0xe4, 0xa9, 0xf9, 0x4e, 0x64, 0x63, 0xee, 0x11, 0x37, 0xe0, 0x10, 0xd2, 0xac, 0xa5, 0x29, 0x33, 0x59, 0x3b, 0x30, 0x6d, 0xef, 0xf4, 0x7b, 0x55, 0xeb, 0x4d, 0x50, 0xb7, 0x2a, 0x07, 0x8d, 0xff, 0x26, 0xd7, 0xf0, 0xc2, 0x7e, 0x09, 0x8c, 0x1a, 0x6a, 0x62, 0x0b, 0x5d, 0x82, 0x1b, 0x8f, 0x2e, 0xbe, 0xa6, 0x1d, 0xe7, 0x9d, 0x2d, 0x8a, 0x72, 0xd9, 0xf1, 0x27, 0x32, 0xbc, 0x77, 0x85, 0x96, 0x70, 0x08, 0x69, 0x56, 0xdf, 0x99, 0x94, 0xa1, 0x90, 0x18, 0xbb, 0xfa, 0x7a, 0xb0, 0xa7, 0xf8, 0xab, 0x28, 0xd6, 0x15, 0x8e, 0xcb, 0xf2, 0x13, 0xe6, 0x78, 0x61, 0x3f, 0x89, 0x46, 0x0d, 0x35, 0x31, 0x88, 0xa3, 0x41, 0x80, 0xca, 0x17, 0x5f, 0x53, 0x83, 0xfe, 0xc3, 0x9b, 0x45, 0x39, 0xe1, 0xf5, 0x9e, 0x19, 0x5e, 0xb6, 0xcf, 0x4b, 0x38, 0x04, 0xb9, 0x2b, 0xe2, 0xc1, 0x4a, 0xdd, 0x48, 0x0c, 0xd0, 0x7d, 0x3d, 0x58, 0xde, 0x7c, 0xd8, 0x14, 0x6b, 0x87, 0x47, 0xe8, 0x79, 0x84, 0x73, 0x3c, 0xbd, 0x92, 0xc9, 0x23, 0x8b, 0x97, 0x95, 0x44, 0xdc, 0xad, 0x40, 0x65, 0x86, 0xa2, 0xa4, 0xcc, 0x7f, 0xec, 0xc0, 0xaf, 0x91, 0xfd, 0xf7, 0x4f, 0x81, 0x2f, 0x5b, 0xea, 0xa8, 0x1c, 0x02, 0xd1, 0x98, 0x71, 0xed, 0x25, 0xe3, 0x24, 0x06, 0x68, 0xb3, 0x93, 0x2c, 0x6f, 0x3e, 0x6c, 0x0a, 0xb8, 0xce, 0xae, 0x74, 0xb1, 0x42, 0xb4, 0x1e, 0xd3, 0x49, 0xe9, 0x9c, 0xc8, 0xc6, 0xc7, 0x22, 0x6e, 0xdb, 0x20, 0xbf, 0x43, 0x51, 0x52, 0x66, 0xb2, 0x76, 0x60, 0xda, 0xc5, 0xf3, 0xf6, 0xaa, 0xcd, 0x9a, 0xa0, 0x75, 0x54, 0x0e, 0x01);
  //--- The key schedule in this AES cipher.
  private $m_cipher;
  //--- The state matrix in this AES cipher with Nb columns and 4 rows
  private $m_cipher_table;
  //--- Determines the lenght of key z
  private $keyLength;

  /**
   * Constructs an AES cipher using a specific key.
   *
   * @param $key
   */
  public function __construct($key,$len=32)
    {
    $this->Init($key,$len);
    }

  /**
   * initialization key
   *
   * @param $aes_key
   *
   * @return void
   */
  public function Init($aes_key,$len=32)
    {
    $this->m_nk = $len / 4;
    $this->m_nr = $this->m_nk + self::$m_nb + 2;
    if($this->m_nk != 4 && $this->m_nk != 6 && $this->m_nk != 8) return ''; //("Key is " . ($this->m_nk * 32) . " bits long. *not* 128, 192, or 256.");
    $this->m_nr           = $this->m_nk + self::$m_nb + 2;
    $this->m_cipher       = array(); // Nb*(Nr+1) 32-bit words
    $this->m_cipher_table = array(array()); // 2-D array of Nb colums and 4 rows
    $this->KeyExpansion($aes_key); // places expanded key in w
    }

  /** Encrypts the 16-byte plain text.
   *
   * @params   string $key
   *
   * @returns  $x 16-byte ciphertext
   * @return string
   */
  public function encryptBlock($x)
    {
    $y = ''; // 16-byte string
    // place input x into the initial state matrix in column order
    for($i = 0; $i < 4 * self::$m_nb; $i++)
      {
      // we want integerger division for the second index
      $this->m_cipher_table[$i % 4][($i - $i % self::$m_nb) / self::$m_nb] = ord($x[$i]);
      }
    //--- add round key
    $this->addRoundKey(0);
    //---
    for($i = 1; $i < $this->m_nr; $i++)
      {
      //--- substitute bytes
      $this->subBytes();

      //--- shift rows
      $this->shiftRows();

      //--- mix columns
      $this->mixColumns();
      //--- add round key
      $this->addRoundKey($i);

      }

    //--- substitute bytes
    $this->subBytes();
    //--- shift rows
    $this->shiftRows();
    //--- add round key
    $this->addRoundKey($i);
    //--- place state matrix s into y in column order
    for($i = 0; $i < 4 * self::$m_nb; $i++)
      {
       $y .= chr($this->m_cipher_table[$i % 4][($i - $i % self::$m_nb) / self::$m_nb]);
      }
    return $y;
    }

  public function __destruct()
    {
    unset($this->m_cipher);
    unset($this->m_cipher_table);
    }

  /** makes a big key out of a small one
   * @returns void
   **/
  private function KeyExpansion($key)
    {
    // Rcon is the round constant
    static $rcon = array(0x00000000, 0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000, 0x20000000, 0x40000000, 0x80000000, 0x1b000000, 0x36000000, 0x6c000000, 0xd8000000, 0xab000000, 0x4d000000, 0x9a000000, 0x2f000000);
    // the first Nk words of w are the cipher key z
    for($i = 0; $i < $this->m_nk; $i++)
      {
      $this->m_cipher[$i] = 0;
      // fill an entire word of expanded key m_cipher
      // by pushing 4 bytes into the m_cipher[i] word
      $this->m_cipher[$i] = ord($key[4 * $i]); // add a byte in
      $this->m_cipher[$i] <<= 8; // make room for the next byte
      $this->m_cipher[$i] += ord($key[4 * $i + 1]);
      $this->m_cipher[$i] <<= 8;
      $this->m_cipher[$i] += ord($key[4 * $i + 2]);
      $this->m_cipher[$i] <<= 8;
      $this->m_cipher[$i] += ord($key[4 * $i + 3]);
      }
    //---
    for(; $i < self::$m_nb * ($this->m_nr + 1); $i++)
      {
      $temp = $this->m_cipher[$i - 1];
      //---
      if($i % $this->m_nk == 0) $temp = $this->subWord($this->rotWord($temp)) ^ $rcon[$i / $this->m_nk];
      else if($this->m_nk > 6 && $i % $this->m_nk == 4) $temp = $this->subWord($temp);
      //---
      $this->m_cipher[$i] = $this->m_cipher[$i - $this->m_nk] ^ $temp;
      //---
      self::make32BitWord($this->m_cipher[$i]);
      }
    }

  /**
   * adds the key schedule for a round to a state matrix.
   * @returns void
   *
   * @param $round
   */
  private function addRoundKey($round)
    {
    for($i = 0; $i < 4; $i++)
      {
      for($j = 0; $j < self::$m_nb; $j++)
        {
        //--- place the i-th byte of the j-th word from expanded key w into temp
        $temp = $this->m_cipher[$round * self::$m_nb + $j] >> (3 - $i) * 8;
        //--- Cast temp from a 32-bit word into an 8-bit byte.
        $temp %= 256;
        //-- Can't do unsigned shifts, so we need to make this temp positive
        $temp = ($temp < 0 ? (256 + $temp) : $temp);
        //---
        $this->m_cipher_table[$i][$j] ^= $temp; // xor temp with the byte at location (i,j) of the state
        }
      }
    }

  /**
   * unmixes each column of a state matrix.
   * @returns void
   **/
  private function invMixColumns()
    {
    //--- There are m_nb columns
    for($i = 0; $i < self::$m_nb; $i++)
      {
      $s0 = $this->m_cipher_table[0][$i];
      $s1 = $this->m_cipher_table[1][$i];
      $s2 = $this->m_cipher_table[2][$i];
      $s3 = $this->m_cipher_table[3][$i];
      //---
      $this->m_cipher_table[0][$i] = $this->mult(0x0e, $s0) ^ $this->mult(0x0b, $s1) ^ $this->mult(0x0d, $s2) ^ $this->mult(0x09, $s3);
      $this->m_cipher_table[1][$i] = $this->mult(0x09, $s0) ^ $this->mult(0x0e, $s1) ^ $this->mult(0x0b, $s2) ^ $this->mult(0x0d, $s3);
      $this->m_cipher_table[2][$i] = $this->mult(0x0d, $s0) ^ $this->mult(0x09, $s1) ^ $this->mult(0x0e, $s2) ^ $this->mult(0x0b, $s3);
      $this->m_cipher_table[3][$i] = $this->mult(0x0b, $s0) ^ $this->mult(0x0d, $s1) ^ $this->mult(0x09, $s2) ^ $this->mult(0x0e, $s3);
      }
    }

  /**
   * applies an inverse cyclic shift to the last 3 rows of a state matrix.
   * @returns void
   **/
  private function invShiftRows()
    {
    $temp = "";
    for($i = 1; $i < 4; $i++)
      {
      for($j = 0; $j < self::$m_nb; $j++) $temp[($i + $j) % self::$m_nb] = $this->m_cipher_table[$i][$j];
      for($j = 0; $j < self::$m_nb; $j++) $this->m_cipher_table[$i][$j] = $temp[$j];
      }
    }

  /**
   * applies inverse S-Box substitution to each byte of a state matrix.
   * @returns void
   **/
  private function invSubBytes()
    {
    for($i = 0; $i < 4; $i++) for($j = 0; $j < self::$m_nb; $j++) $this->m_cipher_table[$i][$j] = self::$m_inv_sbox[$this->m_cipher_table[$i][$j]];
    }

  /**
   * mixes each column of a state matrix.
   * @returns void
   **/
  private function mixColumns()
    {
    //--- There are m_nb columns
    for($i = 0; $i < self::$m_nb; $i++)
      {
      $s0 = $this->m_cipher_table[0][$i];
      $s1 = $this->m_cipher_table[1][$i];
      $s2 = $this->m_cipher_table[2][$i];
      $s3 = $this->m_cipher_table[3][$i];
      //---
      $this->m_cipher_table[0][$i] = $this->mult(0x02, $s0) ^ $this->mult(0x03, $s1) ^ $this->mult(0x01, $s2) ^ $this->mult(0x01, $s3);
      $this->m_cipher_table[1][$i] = $this->mult(0x01, $s0) ^ $this->mult(0x02, $s1) ^ $this->mult(0x03, $s2) ^ $this->mult(0x01, $s3);
      $this->m_cipher_table[2][$i] = $this->mult(0x01, $s0) ^ $this->mult(0x01, $s1) ^ $this->mult(0x02, $s2) ^ $this->mult(0x03, $s3);
      $this->m_cipher_table[3][$i] = $this->mult(0x03, $s0) ^ $this->mult(0x01, $s1) ^ $this->mult(0x01, $s2) ^ $this->mult(0x02, $s3);
      }
    }

  /**
   * applies a cyclic shift to the last 3 rows of a state matrix.
   * @returns void
   **/
  private function shiftRows()
    {
    $temp = array();
    for($i = 1; $i < 4; $i++)
      {
      for($j = 0; $j < self::$m_nb; $j++)
        {
        $temp[$j] = $this->m_cipher_table[$i][($j + $i) % self::$m_nb];
        }
      for($j = 0; $j < self::$m_nb; $j++) $this->m_cipher_table[$i][$j] = $temp[$j];
      }
    }

  /**
   * applies S-Box substitution to each byte of a state matrix.
   * @returns void
   **/
  private function subBytes()
    {
    for($i = 0; $i < 4; $i++)
      {
      for($j = 0; $j < self::$m_nb; $j++) $this->m_cipher_table[$i][$j] = self::$m_sbox[$this->m_cipher_table[$i][$j]];
      }
    }

  /**
   * multiplies two polynomials a(x), b(x) in GF(2^8) modulo the irreducible polynomial m(x) = x^8+x^4+x^3+x+1
   *
   * @param $a
   * @param $b
   *
   * @return int 8-bit value
   */
  private static function mult($a, $b)
    {
    $sum = self::$m_ltable[$a] + self::$m_ltable[$b];
    $sum %= 255;
    //--- Get the antilog
    $sum = self::$m_atable[$sum];
    return ($a == 0 ? 0 : ($b == 0 ? 0 : $sum));
    }

  /**
   * applies a cyclic permutation to a 4-byte word.
   *
   * @param string $w
   *
   * @return int
   */
  private static function rotWord($w)
    {
    $temp = $w >> 24; // put the first 8-bits into temp
    $w <<= 8; // make room for temp to fill the lower end of the word
    self::make32BitWord($w);
    //--- Can't do unsigned shifts, so we need to make this temp positive
    $temp = ($temp < 0 ? (256 + $temp) : $temp);
    $w += $temp;
    //---
    return $w;
    }

  /**
   * applies S-box substitution to each byte of a 4-byte word.
   *
   * @param string $w
   *
   * @return int
   */
  private static function subWord($w)
    {
    //--- loop through 4 bytes of a word
    for($i = 0; $i < 4; $i++)
      {
      $temp = $w >> 24; // put the first 8-bits into temp
      //--- Can't do unsigned shifts, so we need to make this temp positive
      $temp = ($temp < 0 ? (256 + $temp) : $temp);
      $w <<= 8; // make room for the substituted byte in w;
      self::make32BitWord($w);
      $w += self::$m_sbox[$temp]; // add the substituted byte back
      }
    //---
    self::make32BitWord($w);
    //---
    return $w;
    }

  /**
   * @returns void
   **/
  /**
   * reduces a 64-bit word to a 32-bit word
   *
   * @param int $w
   *
   * @return float
   */
  private static function make32BitWord(&$w)
    {
    // Reduce this 64-bit word to 32-bits on 64-bit machines
    $w &= 0x00000000FFFFFFFF;
    }
  }

?>