<?php
/**
 * php AES加解密类
 * 如果要与java共用，则密钥长度应该为16位长度
 * 因为java只支持128位加密，所以php也用128位加密，可以与java互转。
 * 同时AES的标准也是128位。只是RIJNDAEL算法可以支持128，192和256位加密。
 * java 要使用AES/CBC/NoPadding标准来加解密
 * 
 * @author Terry
 *
 */
class PhpAes
{
 /**
  * This was AES-128 / CBC / NoPadding encrypted.
  * return base64_encode string
  * @author Terry
  * @param string $plaintext
  * @param string $key
  */
 public static function AesEncrypt($plaintext,$key = null)
 {
  $plaintext = trim($plaintext);
  if ($plaintext == '') return '';
  if(!extension_loaded('mcrypt'))
   throw new CException(Yii::t('yii','AesEncrypt requires PHP mcrypt extension to be loaded in order to use data encryption feature.'));
  $size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
  $module = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
  $key=self::substr($key===null ? Yii::app()->params['encryptKey'] : $key, 0, mcrypt_enc_get_key_size($module));
  /* Create the IV and determine the keysize length, use MCRYPT_RAND
   * on Windows instead */
  $iv = substr(md5($key),0,mcrypt_enc_get_iv_size($module));
  /* Intialize encryption */
  mcrypt_generic_init($module, $key, $iv);

  /* Encrypt data */
  $encrypted = mcrypt_generic($module, $plaintext);

  /* Terminate encryption handler */
  mcrypt_generic_deinit($module);
  mcrypt_module_close($module);
  return base64_encode($encrypted);
 }

 /**
  * This was AES-128 / CBC / NoPadding decrypted.
  * @author Terry
  * @param string $encrypted  base64_encode encrypted string
  * @param string $key
  * @throws CException
  * @return string
  */
 public static function AesDecrypt($encrypted, $key = null)
 {
  if ($encrypted == '') return '';
  if(!extension_loaded('mcrypt'))
   throw new CException(Yii::t('yii','AesDecrypt requires PHP mcrypt extension to be loaded in order to use data encryption feature.'));

  $ciphertext_dec = base64_decode($encrypted);
  $module = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
  $key=self::substr($key===null ? Yii::app()->params['encryptKey'] : $key, 0, mcrypt_enc_get_key_size($module));

  $iv = substr(md5($key),0,mcrypt_enc_get_iv_size($module));

  /* Initialize encryption module for decryption */
  mcrypt_generic_init($module, $key, $iv);

  /* Decrypt encrypted string */
  $decrypted = mdecrypt_generic($module, $ciphertext_dec);

  /* Terminate decryption handle and close module */
  mcrypt_generic_deinit($module);
  mcrypt_module_close($module);
  return rtrim($decrypted,"\0");
 }

 /**
  * Returns the length of the given string.
  * If available uses the multibyte string function mb_strlen.
  * @param string $string the string being measured for length
  * @return integer the length of the string
  */
 private static function strlen($string)
 {
  return extension_loaded('mbstring') ? mb_strlen($string,'8bit') : strlen($string);
 }

 /**
  * Returns the portion of string specified by the start and length parameters.
  * If available uses the multibyte string function mb_substr
  * @param string $string the input string. Must be one character or longer.
  * @param integer $start the starting position
  * @param integer $length the desired portion length
  * @return string the extracted part of string, or FALSE on failure or an empty string.
  */
 private static function substr($string,$start,$length)
 {
  return extension_loaded('mbstring') ? mb_substr($string,$start,$length,'8bit') : substr($string,$start,$length);
 }
}