Supporting Privacy in RFID Systems

To improve on its supply chain management (SCM) one of US's largest chain of supermarkets, Wal-Mart, on June 11, 2003, announced that from January 2005 its top 100 suppliers are required to put radio frequency (RFID) tags on their cases and pallets. This goal seems to be achieved as all of the a#ected suppliers have announced they will be ready. Other companies monitor the situation closely, and due to the apparent success they are expected to follow Wal-Mart's example soon. Basically RFID consists of two devices: A chip, called a transponder or tag, and a device which reads the contents of the chip, referred to as a reader. A tag/reader pair does not have to be in physical contact to communicate, as this is done through air using radio waves. This means that communication can be performed even if the reader cannot see the transponder i.e. no lineof -sight between them. To even further improve on SCM and the handling of inventory inside stores, placing a tag on individual items is presently discussed. The flipside is that this will bring RFID out to the individual consumer, where it can be used to invade his privacy. Anyone with a scanner (which does not have to be stationary!) will now be able to trace him and know what is in his bags. To prevent this "Big Brother"-like scenario, di#erent solutions have been suggested. Some of these are based on encryption, which is the objective of this report. At present the main problem regarding encryption in RFID systems is not the strength of the algorithms, but due to constraints whether it is possible (and feasible). The constraints are that tags need to be small, and that only a limited supply of power is available to a tag. Besides these limits tags are not allowed to cost much either! In this report several encryption algori..