A method for authenticating an RFID tag with the aid of an RFID reader via a radio interface, wherein a user-specific key is stored in the RFID reader and a tag-specific identifier and a password generated from the identifier and the key in accordance with a known derivative function are stored in the RFID tag, comprising the following steps performed in the RFID reader: receiving via the radio interface the identifier of an RFID tag to be authenticated, generating the correct password from the received identifier and the stored key according to the known derivative function, and generating at least one incorrect password differing from the correct password, sending a series of at least two passwords, at least one being correct and at least one being incorrect, via the radio interface to the RFID tag, and authenticating the RFID tag if no confirmation response is received to any incorrect password.