vendor/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Reader/Xls/RC4.php

   1 <?php
   2
   3 namespace PhpOffice\PhpSpreadsheet\Reader\Xls;
   4
   5 class RC4
   6 {
   7     // Context
   8     protected $s = [];
   9
  10     protected $i = 0;
  11
  12     protected $j = 0;
  13
  14     /**
  15      * RC4 stream decryption/encryption constrcutor.
  16      *
  17      * @param string $key Encryption key/passphrase
  18      */
  19     public function __construct($key)
  20     {
  21         $len = strlen($key);
  22
  23         for ($this->i = 0; $this->i < 256; ++$this->i) {
  24             $this->s[$this->i] = $this->i;
  25         }
  26
  27         $this->j = 0;
  28         for ($this->i = 0; $this->i < 256; ++$this->i) {
  29             $this->j = ($this->j + $this->s[$this->i] + ord($key[$this->i % $len])) % 256;
  30             $t = $this->s[$this->i];
  31             $this->s[$this->i] = $this->s[$this->j];
  32             $this->s[$this->j] = $t;
  33         }
  34         $this->i = $this->j = 0;
  35     }
  36
  37     /**
  38      * Symmetric decryption/encryption function.
  39      *
  40      * @param string $data Data to encrypt/decrypt
  41      *
  42      * @return string
  43      */
  44     public function RC4($data)
  45     {
  46         $len = strlen($data);
  47         for ($c = 0; $c < $len; ++$c) {
  48             $this->i = ($this->i + 1) % 256;
  49             $this->j = ($this->j + $this->s[$this->i]) % 256;
  50             $t = $this->s[$this->i];
  51             $this->s[$this->i] = $this->s[$this->j];
  52             $this->s[$this->j] = $t;
  53
  54             $t = ($this->s[$this->i] + $this->s[$this->j]) % 256;
  55
  56             $data[$c] = chr(ord($data[$c]) ^ $this->s[$t]);
  57         }
  58
  59         return $data;
  60     }
  61 }