A Radio-Frequency Identification (RFID) tag is a small and cheap device which combined IC tip and an antenna for radio communications, and it emits an ID in response to query from a reader which is a radio communication device. For this reason, a RFID tag is used for management of goods and its circulation, and it is used as a substitute of a bar code in the future. However, RFID tags are too limited in their capabilities to implement complex authentication and cryptosystem. Thus, since the information on a tag is simply drawn out by the reader, RFID tags may infringe on a possessor's privacy. And RFID tags leak its possessor's location called "location privacy" by attackers extracting data from RFID tags. Therefore we research the privacy protection in low-cost RFID tags.
