A Combined Link Layer Security Solution for FCI Datalink Technologies

With the surge in global air travel demand, the aviation industry is facing significant challenges. The saturation of frequencies in Air Traffic Management (ATM) results in communication issues, necessitating the replacement of traditional analogue systems with digital alternatives. For that purpose several new datalinks are introduced as the Future Communications Infrastructure (FCI). This multilink system aims to ease communications, by allowing data to be routed via any datalink in the FCI, the aircraft is currently connected to. While some FCI datalinks, such as AeroMACS, LDACS, and partially SatCOM, have dedicated security concepts, others like VDLm2 lack such measures. This raises the question of how to securely and efficiently route traffic over any FCI datalink while ensuring the multilink itself remains secure at the link layer.The objective of this work is to propose an overall multilink security concept for FCI datalinks. We introduce an initial authentication and key establishment scheme, discuss various security concepts for aircraft authentication to ground endpoints, and propose multiple handover protocols for secure transitions between radios within the multilink. The proposed protocols are evaluated using the Tamarin symbolic model checker, considering their impact on the datalink and ground access network performance. Ultimately, we recommend two suitable concepts for ensuring multilink security at the link layer.