This paper analyzes candidate schemes for PPP/PPP-RTK (precise point positioning/real-time kinematic) data authentication. Asymmetric schemes are proposed based on existing standards and compatible with GNSS messages. Post-quantum cryptographic signatures are also reviewed and discussed. Two schemes are selected for analysis: digital signature (DS) based on ECDSA, and delayed disclosure (DD) based on a hybrid scheme using the TESLA protocol. Each of them is described in detail for both Galileo high-accuracy service and QZSS centimeter-level accuracy service. The performance of the schemes in terms of time to receive the corrections message and increase in the age of data (?AOD) is analyzed. The analysis is complemented by a review of the CPU consumption at receiver level.