Criptografia em php

Para quem estiver precisando de um código de criptografia bom, que utiliza objeto, e que gente grande utiliza, veja abaixo o que eu achei no CodeIgner:

class CI_Encrypt {

var $CI;
var $encryption_key = '';
var $_hash_type = 'sha1';
var $_mcrypt_exists = FALSE;
var $_mcrypt_cipher;
var $_mcrypt_mode;

/**
* Constructor
*
* Simply determines whether the mcrypt library exists.
*
*/
function CI_Encrypt()
{
$this->CI =& get_instance();
$this->_mcrypt_exists = ( ! function_exists('mcrypt_encrypt')) ? FALSE : TRUE;
log_message('debug', "Encrypt Class Initialized");
}

// --------------------------------------------------------------------

/**
* Fetch the encryption key
*
* Returns it as MD5 in order to have an exact-length 128 bit key.
* Mcrypt is sensitive to keys that are not the correct length
*
* @access public
* @param string
* @return string
*/
function get_key($key = '')
{
if ($key == '')
{
if ($this->encryption_key != '')
{
return $this->encryption_key;
}

$CI =& get_instance();
$key = $CI->config->item('encryption_key');

if ($key === FALSE)
{
show_error('In order to use the encryption class requires that you set an encryption key in your config file.');
}
}

return md5($key);
}

// --------------------------------------------------------------------

/**
* Set the encryption key
*
* @access public
* @param string
* @return void
*/
function set_key($key = '')
{
$this->encryption_key = $key;
}

// --------------------------------------------------------------------

/**
* Encode
*
* Encodes the message string using bitwise XOR encoding.
* The key is combined with a random hash, and then it
* too gets converted using XOR. The whole thing is then run
* through mcrypt (if supported) using the randomized key.
* The end result is a double-encrypted message string
* that is randomized with each call to this function,
* even if the supplied message and key are the same.
*
* @access public
* @param string the string to encode
* @param string the key
* @return string
*/
function encode($string, $key = '')
{
$key = $this->get_key($key);
$enc = $this->_xor_encode($string, $key);

if ($this->_mcrypt_exists === TRUE)
{
$enc = $this->mcrypt_encode($enc, $key);
}
return base64_encode($enc);
}

// --------------------------------------------------------------------

/**
* Decode
*
* Reverses the above process
*
* @access public
* @param string
* @param string
* @return string
*/
function decode($string, $key = '')
{
$key = $this->get_key($key);

if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string))
{
return FALSE;
}

$dec = base64_decode($string);

if ($this->_mcrypt_exists === TRUE)
{
if (($dec = $this->mcrypt_decode($dec, $key)) === FALSE)
{
return FALSE;
}
}

return $this->_xor_decode($dec, $key);
}

// --------------------------------------------------------------------

/**
* XOR Encode
*
* Takes a plain-text string and key as input and generates an
* encoded bit-string using XOR
*
* @access private
* @param string
* @param string
* @return string
*/
function _xor_encode($string, $key)
{
$rand = '';
while (strlen($rand) < 32)
{
$rand .= mt_rand(0, mt_getrandmax());
}

$rand = $this->hash($rand);

$enc = '';
for ($i = 0; $i < strlen($string); $i++)
{
$enc .= substr($rand, ($i % strlen($rand)), 1).(substr($rand, ($i % strlen($rand)), 1) ^ substr($string, $i, 1));
}

return $this->_xor_merge($enc, $key);
}

// --------------------------------------------------------------------

/**
* XOR Decode
*
* Takes an encoded string and key as input and generates the
* plain-text original message
*
* @access private
* @param string
* @param string
* @return string
*/
function _xor_decode($string, $key)
{
$string = $this->_xor_merge($string, $key);

$dec = '';
for ($i = 0; $i < strlen($string); $i++)
{
$dec .= (substr($string, $i++, 1) ^ substr($string, $i, 1));
}

return $dec;
}

// --------------------------------------------------------------------

/**
* XOR key + string Combiner
*
* Takes a string and key as input and computes the difference using XOR
*
* @access private
* @param string
* @param string
* @return string
*/
function _xor_merge($string, $key)
{
$hash = $this->hash($key);
$str = '';
for ($i = 0; $i < strlen($string); $i++)
{
$str .= substr($string, $i, 1) ^ substr($hash, ($i % strlen($hash)), 1);
}

return $str;
}

// --------------------------------------------------------------------

/**
* Encrypt using Mcrypt
*
* @access public
* @param string
* @param string
* @return string
*/
function mcrypt_encode($data, $key)
{
$init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode());
$init_vect = mcrypt_create_iv($init_size, MCRYPT_RAND);
return $this->_add_cipher_noise($init_vect.mcrypt_encrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), $key);
}

// --------------------------------------------------------------------

/**
* Decrypt using Mcrypt
*
* @access public
* @param string
* @param string
* @return string
*/
function mcrypt_decode($data, $key)
{
$data = $this->_remove_cipher_noise($data, $key);
$init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode());

if ($init_size > strlen($data))
{
return FALSE;
}

$init_vect = substr($data, 0, $init_size);
$data = substr($data, $init_size);
return rtrim(mcrypt_decrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), "\0");
}

// --------------------------------------------------------------------

/**
* Adds permuted noise to the IV + encrypted data to protect
* against Man-in-the-middle attacks on CBC mode ciphers
* http://www.ciphersbyritter.com/GLOSSARY.HTM#IV
*
* Function description
*
* @access private
* @param string
* @param string
* @return string
*/
function _add_cipher_noise($data, $key)
{
$keyhash = $this->hash($key);
$keylen = strlen($keyhash);
$str = '';

for ($i = 0, $j = 0, $len = strlen($data); $i < $len; ++$i, ++$j)
{
if ($j >= $keylen)
{
$j = 0;
}

$str .= chr((ord($data[$i]) + ord($keyhash[$j])) % 256);
}

return $str;
}

// --------------------------------------------------------------------

/**
* Removes permuted noise from the IV + encrypted data, reversing
* _add_cipher_noise()
*
* Function description
*
* @access public
* @param type
* @return type
*/
function _remove_cipher_noise($data, $key)
{
$keyhash = $this->hash($key);
$keylen = strlen($keyhash);
$str = '';

for ($i = 0, $j = 0, $len = strlen($data); $i < $len; ++$i, ++$j)
{
if ($j >= $keylen)
{
$j = 0;
}

$temp = ord($data[$i]) - ord($keyhash[$j]);

if ($temp < 0)
{
$temp = $temp + 256;
}

$str .= chr($temp);
}

return $str;
}

// --------------------------------------------------------------------

/**
* Set the Mcrypt Cipher
*
* @access public
* @param constant
* @return string
*/
function set_cipher($cipher)
{
$this->_mcrypt_cipher = $cipher;
}

// --------------------------------------------------------------------

/**
* Set the Mcrypt Mode
*
* @access public
* @param constant
* @return string
*/
function set_mode($mode)
{
$this->_mcrypt_mode = $mode;
}

// --------------------------------------------------------------------

/**
* Get Mcrypt cipher Value
*
* @access private
* @return string
*/
function _get_cipher()
{
if ($this->_mcrypt_cipher == '')
{
$this->_mcrypt_cipher = MCRYPT_RIJNDAEL_256;
}

return $this->_mcrypt_cipher;
}

// --------------------------------------------------------------------

/**
* Get Mcrypt Mode Value
*
* @access private
* @return string
*/
function _get_mode()
{
if ($this->_mcrypt_mode == '')
{
$this->_mcrypt_mode = MCRYPT_MODE_ECB;
}

return $this->_mcrypt_mode;
}

// --------------------------------------------------------------------

/**
* Set the Hash type
*
* @access public
* @param string
* @return string
*/
function set_hash($type = 'sha1')
{
$this->_hash_type = ($type != 'sha1' AND $type != 'md5') ? 'sha1' : $type;
}

// --------------------------------------------------------------------

/**
* Hash encode a string
*
* @access public
* @param string
* @return string
*/
function hash($str)
{
return ($this->_hash_type == 'sha1') ? $this->sha1($str) : md5($str);
}

// --------------------------------------------------------------------

/**
* Generate an SHA1 Hash
*
* @access public
* @param string
* @return string
*/
function sha1($str)
{
if ( ! function_exists('sha1'))
{
if ( ! function_exists('mhash'))
{
require_once(BASEPATH.'libraries/Sha1'.EXT);
$SH = new CI_SHA;
return $SH->generate($str);
}
else
{
return bin2hex(mhash(MHASH_SHA1, $str));
}
}
else
{
return sha1($str);
}
}

}

// END CI_Encrypt class

/* End of file Encrypt.php */
/* Location: ./system/libraries/Encrypt.php */