In Radio Frequency Identification (RFID) systems very small RF tags communicate wirelessly with tag readers as soon as they are close enough to each other. The data transmitted by the tag can provide identification or location information, or specifics about the product tagged. RFID systems have great potential for further automating warehousing, tracking & tracing, and can help prevent fraud or counterfeiting. Widespread use of RFID tags would raise enormous privacy concerns. RFID tags embedded in clothes - for inventory management or to prevent shoplifting - could be exploited (after the purchase) to track your movements. Moreover, warehousing based on RFID technology increases the risk of corporate espionage. Classical security measures or privacy enhancing technologies cannot be applied to RFID systems due to their pervasiveness and limited computing power. The goal of this project is to develop tools and methodologies as well as their theoretical foundations for using RFID systems while preserving the user's privacy. We will formally model the relevant privacy and security properties, develop new privacy enhancing protocols for the extremely resource constrained RFID environment, shape a context in which the user can check the privacy policies enforced by the RFID-based application, and develop methods to secure the integration of RFID tags and the backoffice applications that will support them.