Radio-frequency identification

Radio-frequency identification (RFID) is used in tags attached to objects which are "read" by sending radio waves to them. Some are passively detected by such waves (echoing back the energy arriving in radio waves and not requiring an additional power source) and others take a more active role in responding to them. Contactless smart cards are a related, and more actively "intelligent", technology. RFID tags are used to identify and track various sorts of objects, including in industrial production and in tracking animals.

Links

 * Wikipedia article
 * iClass cipher reconstruction, reconstructing for experimental use the cipher used in one RFID implementation (which received this legal threat)