Airport dating protocol
An active tag has an on-board battery and periodically transmits its ID signal.
A battery-assisted passive (BAP) has a small battery on board and is activated when in the presence of an RFID reader.
Transponders are still used by most powered aircraft.
Another early work exploring RFID is the landmark 1948 paper by Harry Stockman, who predicted that "...
RFID tags contain at least three parts: an integrated circuit that stores and processes information and that modulates and demodulates radio-frequency (RF) signals; a means of collecting DC power from the incident reader signal; and an antenna for receiving and transmitting the signal.That makes a difference in interference and in exposure to radiation.Tags may either be read-only, having a factory-assigned serial number that is used as a key into a database, or may be read/write, where object-specific data can be written into the tag by the system user.These concerns resulted in standard specifications development addressing privacy and security issues.ISO/IEC 18000 and ISO/IEC 29167 use on-chip cryptography methods for untraceability, tag and reader authentication, and over-the-air privacy.