As of 2022, Air Traffic Management (ATM) is in the process of becoming gradually digitized, which is crucial to automate and secure data transmission in civil aviation. For that purpose, new digital data links, such as the L-band Digital Aeronautical Communications System (LDACS) are introduced. LDACS is a cellular, ground-based digital communications system for flight guidance and communications related to the safety and regularity of flight. Unfortunately, many datalinks in the aeronautical communications ecosystem lack link layer security measures. Among them is LDACS. In this doctoral thesis, we introduce a cybersecurity architecture for LDACS. The chosen modular security approach allows for seamless integration of various pre- and post-quantum security algorithms, thus ensuring longevity of the security solution. The LDACS cybersecurity architecture thereby pays attention to the various aspects of LDACS use cases. Due to the multitude of applications and services, a variety of security measures to protect LDACS user-data and control-data is developed. Among them are two new authentication and key establishment protocols and a novel approach to secure control-data of resource constraint wireless communications system. Evaluations in an aeronautical communications simulation framework show an added latency of 570 to 620 milliseconds when an aircraft attaches securely to a cell, and an added data overhead of 5% to 10%. Experiments in flight trials show a 99% secured GBAS over LDACS availability, which represents an important milestone since both, secure GBAS, and GBAS over LDACS, have never been demonstrated before. The presented security solutions enable future aeronautical applications, such as 4D-Trajectories and thus pave a way into a digitized, automatized future of civil aviation.weiterlesen