RFID is a key technology that can be used to create the pervasive society. The tag is an important part of the RFID system and most popular tags are some low-cost passive tags. These tags have limited computing and storing resources, and no more attentions are paid to their security and privacy. So the application of these tags is not secure. Lightweight authentication protocols are considered as an effective method to solve the security and privacy of low-cost RFID tags. The authors propose a novel lightweight authentication protocol by means of some functions provided by EPC-global Class-1 Gen-2 tags.