php写的AES加密解密类分享

今天写了一个php的AES加密类。适用于Yii的扩展。
如果不用在Yii框架中，把代码中Yii::app()->params['encryptKey'] 换成你对应的默认key就可以了。
类代码:

    <?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);
        }
    }