Abstract: The secure mutual authentication or secure communication between the low-cost RFID tags and the card readers depends on a secret key shared by the two parties, which can be gained directly by apower attacker by means of physical attacks.Taking advantage of the physical unclonable feature of PUF circuits, two secure key exchange protocols are presented in this paper, such that the two parties can generate a same random key which can be used to secure the following authentication or communication. Security analysis shows that these two protocols can resist physical attack, reply attack, counterfeit attack, man-in-the-middle-attack, offline guessing attack and online guessing attack, and also can provide forward security and backward security.