【摘要】Radio Frequency IDentification (RFID) systems have been studied as an emerging technology for automatic identification of objects and assets in various applications ranging from inventory tracking to point of sale applications and from healthcare applications to e-passport. The expansion of RFID technology, however, gives rise to severe security and privacy concerns. To ensure the widespread deployment of this technology, the security and privacy threats must be addressed. However, providing solutions to the security and privacy threats has been a challenge due to extremely inadequate resources of typical RFID tags. Authentication protocols can be a possible solution to secure RFID communications.;In this thesis, we consider RFID authentication protocols based on symmetric key cryptography. We identify the security and privacy requirements for an RFID system. We present four protocols in this thesis. First, we propose a lightweight authentication protocol for typical tags that can perform symmetric key operations. This protocol makes use of pseudo random number generators (PRNG) and one way hash functions to ensure the security and privacy requirements of RFID systems. Second, we define the desynchronizing attack and describe the vulnerabilities of this attack in RFID systems. We propose a robust authentication protocol that can prevent the desynchronizing attack. This protocol can recover the disabled tags that are desynchronized with the reader because of this attack. Third, we introduce a novel authentication protocol based on elliptic curve cryptography (ECC) to avoid the counterfeiting problem of RFID systems. This protocol is appropriate for the RFID tags that can perform the operations of ECC. Finally, to address the tradeoff between scalability and privacy of RFID systems, we propose an efficient anonymous authentication protocol. We characterize the privacy of RFID systems and prove that our protocol preserves the privacy of RFID tags and achieves better scalability as well.