1. 1 Security problems on RFID tags (short introduction) Sakurai Lab., Kyushu Univ. Junichiro SAITO saito@itslab.csce.kyushu-u.ac.jp

2. 2 What is a Radio Frequency Identification （ RFID ） tag? A small and inexpensive microchip that emits an ID in response to query from a reader Used as a substitute for a bar code  management of goods and its circulation, theft detection Little computational power Easily readable by a reader Be monitored communication between a RFID tag and a reader →Infringement of privacy

3. 3 Privacy problems ID leakage –An adversary can eavesdrop ID information –She can read by using a reader leakage of information about belongings ID tracing –If ID information on an RFID tag is fixed, an adversary can trace tag owner's activity Infringement on location privacy price of the suit ○○ yen in wallet shoe size

4. 4 Our research themes Location privacy –We can use re-encryption scheme to change ID information Yoking proof and grouping proof –We showed a replay attack against Juels's yoking proof Owner changing –After changing owner, new owner doesn't want that old owner can read the RFID tag We proposed Re-encryption scheme with a check We proposed secure yoking proof by using a time stamp We proposed a key change scheme for changing owner