Interoperable ADS-B Confidentiality

The worldwide air traffic infrastructure is in the late stages of transition from legacy transponder systems to Automatic Dependent Surveillance - Broadcast ADS-B based systems. ADS-B relies on position information from GNSS and requires aircraft to transmit their identification, state, and position. ADS-B promises the availability of high-fidelity air traffic information however, position and identification data are not secured via authentication or encryption. This lack of security for ADS-B allows non-participants to observe and collect data on both government and private flight activity. This is a proposal for a lightweight, interoperable ADS-B confidentiality protocol which uses existing format preserving encryption and an innovative unidirectional key handoff to ensure backward compatibility. Anonymity and data confidentiality are achieved selectively on a per-session basis. This research also investigates the effect of false replies unsynchronized in time FRUIT on the packet error ratio PER for Mode S transmissions. High PERs result in range and time limits being imposed on the key handoff mechanism of this proposal. Overall, this confidentiality protocol is ready for implementation, however further research is required to validate a revised key handoff mechanism.