ADS-B Authentication

The Automatic Dependent Surveillance – Broadcast (ADS-B) is a surveillance technology mandated in many airspaces. It is now widely deployed but suffers a lack of security and privacy. From a security point of view, it is relatively easy to spoof the ADS-B messages. With the appropriate readily available hardware and software. From a privacy point of view, all the messages contain the aircraft’s assigned 24-bit ICAO address, which makes it easy to link to data about the aircraft, in particular to know when a particular aircraft has flown and where to. In addition, the main transmission medium utilized for ADS-B, i.e. the 1090 MHz frequency used by Extended Squitter (1090ES), is approaching saturation in some parts of the world, resulting in packet loss in certain areas [RF_Usage]. This paper presents how to use the IETF TESLA protocol along with X.509 certificates issued by ICAO member states for each aircraft to authenticate all ADS-B messaging. It leverages the 8PSK phase overlay (PO) scheme proposed in the Minimum Operational Performance Standards (MOPS) for ADS-B (RTCA [DO-260C]), which enables 1090ES ADS-B transmissions to convey three times more information, to support the transmission of the extra security information required by the authentication scheme. By doing so, the impact of authentication on channel usage is negligible. Beyond message authentication, this scheme proposed has two important additional benefits: 1) the possibility to implement a Flight Authorization scheme, allowing ATC and intercepting aircraft to not only authenticate an aircraft but to verify that it is authorizes to conduct that flight and 2) a methodology for adequately protecting the privacy by assigning rotating 24-bit identifiers to designated aircraft, while maintaining the possibility to (blindly) authenticate their ADS-B transmissions.