AES-256 加密 PHP实现

class aes {
 
    static public $mode = MCRYPT_MODE_NOFB;
     
    static public function generateKey($length=32) {
        if (!in_array($length,array(16,24,32)))
            return False;
 
        $str = '';
        for ($i=0;$i<$length;$i++) {
            $str .= chr(rand(33,126));
        }
 
        return $str;
    }
 
    static public function encrypt($data, $key) {
 
        if (strlen($key) > 32 || !$key)
            return trigger_error('key too large or key is empty.', E_USER_WARNING) && False;
 
        $ivSize = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, self::$mode);
        $iv = mcrypt_create_iv($ivSize, (substr(PHP_OS,0,1) == 'W' ? MCRYPT_RAND : MCRYPT_DEV_URANDOM ));
        $encryptedData = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $data, self::$mode, $iv);
        $encryptedData = $iv . $encryptedData;
 
        return base64_encode($encryptedData);
    }
 
    static public function decrypt($data, $key) {
 
        if (strlen($key) > 32 || !$key)
            return trigger_error('key too large or key is empty.', E_USER_WARNING) && False;
 
        $data = base64_decode($data);
        if (!$data)
            return False;
 
        $ivSize = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, self::$mode);
        $iv = substr($data, 0, $ivSize);
 
        $data = substr($data, $ivSize);
 
        $decryptData = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $data, self::$mode, $iv);
 
        return $decryptData;
    }}