Radio Frequency Identification (RFID) is a common technology for identifying objects, animals, or people. The main form of barcode-type RFID device is known as an Electronic Product Code (EPC) and the most popular standard for passive RFID tags is Class-1 Generation-2. In this technology, the information transmitted between devices is through the air, therefore adversaries can eavesdrop these messages passed on the insecure radio channel and finally, the security of the system can be compromised. In this chapter, the authors analyze the security of EPC Class-1 Generation-2 standard, showing its security weaknesses and presenting some possible countermeasures. © 2013, IGI Global.