RC4.php
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<?php
namespace PhpOffice\PhpSpreadsheet\Reader\Xls;
class RC4
{
// Context
protected $s = [];
protected $i = 0;
protected $j = 0;
/**
* RC4 stream decryption/encryption constrcutor.
*
* @param string $key Encryption key/passphrase
*/
public function __construct($key)
{
$len = strlen($key);
for ($this->i = 0; $this->i < 256; ++$this->i) {
$this->s[$this->i] = $this->i;
}
$this->j = 0;
for ($this->i = 0; $this->i < 256; ++$this->i) {
$this->j = ($this->j + $this->s[$this->i] + ord($key[$this->i % $len])) % 256;
$t = $this->s[$this->i];
$this->s[$this->i] = $this->s[$this->j];
$this->s[$this->j] = $t;
}
$this->i = $this->j = 0;
}
/**
* Symmetric decryption/encryption function.
*
* @param string $data Data to encrypt/decrypt
*
* @return string
*/
public function RC4($data)
{
$len = strlen($data);
for ($c = 0; $c < $len; ++$c) {
$this->i = ($this->i + 1) % 256;
$this->j = ($this->j + $this->s[$this->i]) % 256;
$t = $this->s[$this->i];
$this->s[$this->i] = $this->s[$this->j];
$this->s[$this->j] = $t;
$t = ($this->s[$this->i] + $this->s[$this->j]) % 256;
$data[$c] = chr(ord($data[$c]) ^ $this->s[$t]);
}
return $data;
}
}