<?php
 

    /**
     * Cipher
     *
     * Simple mcrypt interface.
     *
     * Cipher is a simple class for working with mcrypt.
     *
     * @package     Cipher
     * @author      Nathan Lucas <nathan@gimpstraw.com>
     * @link        http://www.gimpstraw.com/
     * @copyright   Copyright (c) 2008, Nathan Lucas

 * @version     2.0.0
 *
 * Added $iv to both encrypt() and decrypt() allowing you to use preset IVs
 * while encrypting/decrypting data.
 *
 * Also added getIV(), which returns the instance's current IV in base64
 * allowing you to store this IV for use on other instances of Cipher.
 */
class Cipher {

    /**
     * Algorithm to use.
     *
     * @access  private
     * @var     string
     */
    private $algo;

    /**
     * Encryption mode.
     *
     * @access  private
     * @var     string
     */
    private $mode;

    /**
     * Randomization source.
     *
     * @access  private
     * @var     integer
     */
    private $source;

    /**
     * Initialization vector.
     *
     * @access  private
     * @var     string
     */
    private $iv = null;

    /**
     * Encryption key.
     *
     * @access  private
     * @var     string
     */
    private $key = null;

    /**
     * Cipher($algo, $mode, $source)
     *
     * Cipher constructor. Sets the algorithm being used, the encryption
     * mode, and the IV.
     *
     * @param   string $algo
     * @param   string $mode
     * @param   integer $source (randomization source)
     * @access  public
     * @return  void
     */
    public function __construct($algo = MCRYPT_3DES, $mode = MCRYPT_MODE_CBC, $source = MCRYPT_RAND) {
        $this->algo = $algo;
        $this->mode = $mode;
        $this->source = $source;

        if (is_null($this->algo) || (strlen($this->algo) == 0)) {
            $this->algo = MCRYPT_3DES;
        }
        if (is_null($this->mode) || (strlen($this->mode) == 0)) {
            $this->mode = MCRYPT_MODE_CBC;
        }
    }

    /**
     * encrypt($data, $key, $iv)
     *
     * Returns encrpyted $data, base64 encoded. $key must be specified at
     * least once, it can be changed at any point.
     *
     * @param   string $data
     * @param   mixed $key
     * @param   string $iv
     * @access  public
     * @return  string
     */
    public function encrypt($data, $key = null, $iv = null) {
        $key = (strlen($key) == 0) ? $key = null : $key;

        $this->setKey($key);
        $this->setIV($iv);

        $out = mcrypt_encrypt($this->algo, $this->key, $data, $this->mode, $this->iv);
        return base64_encode($out);
    }

    /**
     * decrypt($data, $key, $iv)
     *
     * Returns decrypted $data. $key must be specified at least once, it can
     * be changed at any point.
     *
     * @param   mixed $data
     * @param   mixed $key
     * @param   string $iv
     * @access  public
     * @return  string
     */
    public function decrypt($data, $key = null, $iv = null) {
        $key = (strlen($key) == 0) ? $key = null : $key;

        $this->setKey($key);
        $this->setIV($iv);

        $data = base64_decode($data);
        $out = mcrypt_decrypt($this->algo, $this->key, $data, $this->mode, $this->iv);
        return trim($out);
    }

    /**
     * getIV()
     *
     * Returns the IV used for encryption so you can use it again in another
     * Cipher instance to decrypt data.
     *
     * @access  public
     * @return  string
     */
    public function getIV() {
        return base64_encode($this->iv);
    }

    /**
     * setIV($iv)
     *
     * Sets IV. If $iv is specified, the instance IV will be set to this. If not,
     * the instance will generate an IV.
     *
     * @param   string $iv
     * @access  private
     * @return  void
     */
    private function setIV($iv) {
        if (!is_null($iv)) {
            $this->iv = base64_decode($iv);
        }
        if (is_null($this->iv)) {
            $iv_size = mcrypt_get_iv_size($this->algo, $this->mode);
            $this->iv = mcrypt_create_iv($iv_size, $this->source);
        }
    }

    /**
     * setKey($data, $key)
     *
     * Sets Cipher::key. This will be the key used for the encrypt and decrypt
     * methods until another $key is specified. This will trigger an error if
     * no initial key is set.
     *
     * @param   mixed $key
     * @access  private
     * @return  void
     */
    private function setKey($key) {
        if (!is_null($key)) {
            $key_size = mcrypt_get_key_size($this->algo, $this->mode);
            $this->key = hash("sha256", $key, true);
            $this->key = substr($this->key, 0, $key_size);
        }
        if (is_null($this->key)) {
            trigger_error("You must specify a key at least once in either Cipher::encrpyt() or Cipher::decrypt().", E_USER_ERROR);
        }
    }
}
?>

