The privacy problem of many RFID systems has been extensively studied. Yet integrity in RFID has notreceived much attention as regular computer systems. When we evaluate an identification protocol for an RFID system foranti-counterfeiting, it is important to consider integrity issues. Moreover, many RFID systems are accessed by multiple leveltrust parties, which makes comprehensive integrity protection even harder. In this paper, we first propose an integrity modelfor RFID protocols. Then we use the model to analyze the integrity problems in Squealing Euros protocol. Squealing Euroswas proposed by Juels and Pappu for RFID enabled banknotes that will support anti-forgery and lawful tracing yet preserveindividual’s privacy. We analyze its integrity, we then discuss the problems that arise and propose some solutions to theseproblems. Then an improved protocol with integrity protection for the law enforcement is constructed, which includes anunforgeable binding between the banknote serial number and the RF ciphertext only readable to law enforcement. This sameprotocol can be applied in many other applications which require a privacy protecting anti-counterfeiting mechanism.