Satellite Based Augmentation Systems (SBAS) are primarily designed to provide Safety of Life (SoL) services to aviation users as defined in ICAO SARPs  (Standards And Recommended Practices). SBAS’ augment Global Navigation Satellite Systems (GNSS), broadcasting corrections and integrity information to aviation users via geostationary satellites. This not only improves the accuracy of the navigation solution, it also allows aeronautic receivers to compute a protection level, bounding the residual position error with the required level of confidence. The European Geostationary Navigation Overlay Service (EGNOS) provides service levels up to LPV200 (Localizer Performance with Vertical guidance), which enables aircraft approaches that are operationally equivalent to Category I (CAT-I) Instrument Landing System (ILS) using GNSS. In recent years, there have been increasing cases of radio frequency interference (RFI) and cyberattacks (spoofing) targeting navigation systems. The message stream broadcast by SBAS is currently not protected from message level cyber-attacks, providing a potentially hazardous backdoor for adversaries to affect navigation solutions. The European Commission (EC) is exploring the possibility of improving the security of SBAS, considering SBAS authentication as a possible barrier against this type of attack. The SPARC (Simulation Platform for Authentication Reliable Concept) project was financed by the EC with the objective of identifying viable solutions for SBAS authentication. This paper focuses on the investigation of various SBAS authentication paradigms from the perspective of receiver processing, providing an overview of assumptions and a discussion on design considerations that impact the definition of an SBAS authentication capability.