Efficient Control-Channel Security for the Aeronautical Communications System LDACS

Since Air Traffic Management (ATM) is still conducted largely via analogue voice communications, the digitization of data transmission is crucial to automate and secure ATM in civil aviation. For that purpose, several new digital data links are developed. The continental, terrestrial long-range candidate is the L-band Digital Aeronautical Communications System (LDACS), which is a cellular, ground-based digital communications system for flight guidance and communications related to the safety and regularity of flight. The security of LDACS has been the focus of recent works, however, the problem to secure data on its small control-channels remains unsolved. The objective of this work is to propose slim and efficient security measures to protect data on the LDACS control-channels and evaluate their security and performance impact. First, via a 3-pass adaptation of the ISO/IEC 11770-3:2021 ``Key agreement mechanism 7'' protocol, keys to secure LDACS control-channels are established between air and ground radios. Second, via these point-to-point keys and point-to-multipoint group keys, the control-channels are secured. Thereby the limitations set by the limited bandwidth are respected and cryptographic overhead optimized. Finally, the security of our proposal is validated using a symbolic model with the Tamarin proof system. Also, via computer simulations, the LDACS performance impact of the control-channel security solutions is evaluated