During the recent years GNSS robustness and resilience against malicious attacks is becoming a major priority for the GNSS system developers and the community. The addition of cryptographic protection in the navigation message is one of the techniques that have been proposed to provide data-level authentication. This technique, known as Navigation Message Authentication or NMA, generally refers to the authentication of the navigation messages broadcast by a GNSS.
Galileo is designing and testing a navigation message authentication for the Open Service (OS-NMA) through the E1-B. E1-B broadcasts the I/NAV Galileo navigation message at a carrier frequency of 1575.45 MHz with a bitrate of 125 bps, encoded with a ½ coding rate into 250 sps through forward error correction and interleaved. Every 30 seconds, a full I/NAV subframe is transmitted, which contains a full set of ephemeris and other information allowing to compute a PVT solution. Every 2 seconds, a Galileo I/NAV page is transmitted, including a CRC.
The aim of the future Galileo OS-NMA service is to allow Galileo users to calculate an authenticated positioning and timing solution with minimum latency and similar performance than the obtained with standard services.