Radio Frequency Identification (RFID) is a technology designed to automatically identify a myriad of everyday objects and people. Due to widely spread of the RFID applications, some useful message can be attacked by adversaries. Thus, to eliminate the security problem, the security requirements for privacy-preserving RFID authentication protocols are evident. In this paper, we discuss unique manin-the-middle attacks on extending RFID authentication protocols. In particular, we show that the revised protocols which rely on the use of elliptic curve cryptography (ECC), grouping proof and RFID localization algorithms. Furthermore, we demonstrate that the proposed protocols can resist unique man-in-the-middle attacks and replay attacks.