Abstract: In the development of the Internet of Things, RFID technology with its lightweight advantage plays an important role in the Internet of Things (IoT) system. At the same time, RFID authentication protocols are also subject to security threats due to physical limitations. By sorting out the current mainstream RFID authentication protocols, they are divided into ultra-lightweight, lightweight, middleweight, and heavyweight security authentication protocols according to the magnitude of the encryption algorithm. The security problems of typical security authentication protocols are analyzed, and the security performance and performance indicators of the improved protocols proposed in recent years are discussed and compared according to the magnitude. Finally, the possible development direction of RFID authentication protocols is discussed. 

Key words: Internet of Things(IoT), RFID, authentication, security authentication protocol