Integral to any authentication system is the design of its public key infrastructure (PKI), allowing the system to divide and allocate the responsibility of security between different entities. Moreover, any PKI is closely tied to its associated key management (KM) architecture that is responsible for the distribution, maintenance, and revocation of cryptographic keys. This paper develops two candidate authentication schemes: one each for an L5 I-channel and L5 Q-channel implementation. A PKI is then proposed along with its associated KM architecture. A simulator, introduced as MCOS, is developed to enable large scale Monte Carlo tests of these different PKI and KM designs. The schemes are tested using MCOS producing results concerning key performance metrics of these authentication schemes and their associated PKI. This work concludes that a strictly over-the-air method of delivering PKI information is feasible for SBAS data authentication systems using the proposed PKI and KM architecture.