Abstract: In application of RFID (Radio Frequency IDentification), security threats are on the rise. The demand for the privacy protection of tag is becoming more and more urgent. In RFID system, the privacy protection is against not only the outside attacker, but also the readers. In many exists the representative researches, the tags are only anonymous and untraceable for the outside attackers. In this paper, the list of protocol and the the key updated of protocol are proposed, which allow RFID tags to authenticate to readers without revealing the tag identity or any other information that allows tags to be traced. Compared with the scheme proposed by Armknecht et al., two schemes achieves anonymousness and untraceability authentication of RFID tags without the help of anonymizer. Furthermore, the key updated of scheme make sure that the revocatory tags will not be still tracked by updating key .