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   1  <?php
   2  
   3  /**
   4   * PHPExcel_Reader_Excel5_RC4
   5   *
   6   * Copyright (c) 2006 - 2015 PHPExcel
   7   *
   8   * This library is free software; you can redistribute it and/or
   9   * modify it under the terms of the GNU Lesser General Public
  10   * License as published by the Free Software Foundation; either
  11   * version 2.1 of the License, or (at your option) any later version.
  12   *
  13   * This library is distributed in the hope that it will be useful,
  14   * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16   * Lesser General Public License for more details.
  17   *
  18   * You should have received a copy of the GNU Lesser General Public
  19   * License along with this library; if not, write to the Free Software
  20   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  21   *
  22   * @category   PHPExcel
  23   * @package    PHPExcel_Reader_Excel5
  24   * @copyright  Copyright (c) 2006 - 2015 PHPExcel (http://www.codeplex.com/PHPExcel)
  25   * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
  26   * @version    ##VERSION##, ##DATE##
  27   */
  28  class PHPExcel_Reader_Excel5_RC4
  29  {
  30      // Context
  31      protected $s = array();
  32      protected $i = 0;
  33      protected $j = 0;
  34  
  35      /**
  36       * RC4 stream decryption/encryption constrcutor
  37       *
  38       * @param string $key Encryption key/passphrase
  39       */
  40      public function __construct($key)
  41      {
  42          $len = strlen($key);
  43  
  44          for ($this->i = 0; $this->i < 256; $this->i++) {
  45              $this->s[$this->i] = $this->i;
  46          }
  47  
  48          $this->j = 0;
  49          for ($this->i = 0; $this->i < 256; $this->i++) {
  50              $this->j = ($this->j + $this->s[$this->i] + ord($key[$this->i % $len])) % 256;
  51              $t = $this->s[$this->i];
  52              $this->s[$this->i] = $this->s[$this->j];
  53              $this->s[$this->j] = $t;
  54          }
  55          $this->i = $this->j = 0;
  56      }
  57  
  58      /**
  59       * Symmetric decryption/encryption function
  60       *
  61       * @param string $data Data to encrypt/decrypt
  62       *
  63       * @return string
  64       */
  65      public function RC4($data)
  66      {
  67          $len = strlen($data);
  68          for ($c = 0; $c < $len; $c++) {
  69              $this->i = ($this->i + 1) % 256;
  70              $this->j = ($this->j + $this->s[$this->i]) % 256;
  71              $t = $this->s[$this->i];
  72              $this->s[$this->i] = $this->s[$this->j];
  73              $this->s[$this->j] = $t;
  74  
  75              $t = ($this->s[$this->i] + $this->s[$this->j]) % 256;
  76  
  77              $data[$c] = chr(ord($data[$c]) ^ $this->s[$t]);
  78          }
  79          return $data;
  80      }
  81  }