Enhanced GNSS Authentication Based on the Joint CHIMERA/OSNMA Scheme

The authentication of the navigation signals can be considered as the contribution of the system to the robustness against spoofing attacks and it is becoming an important requirement for a growing number of user communities. GPS and Galileo systems are proposing evolutions of their civil signals to embed features of authentication. For Galileo, the Open Service Navigation Message Authentication (OSNMA) is integrated in the Galileo E1 OS signal. For the GPS, the Chips-Message Robust Authentication (Chimera) solution, designed for the GPS L1C signal, is foreseen to be tested soon. On the other hand, suitable signal processing techniques can be implemented inside the receiver to monitor the quality of the received signals and protect against spoofing attacks. Such techniques shall work as a complement to the authentication strategies, to further increase the signals' robustness. Within this context, the paper presents the Joint Chimera/OSNMA scheme, designed to be adopted by a multi-constellation receiver that already exploits both OSNMA and Chimera enhancements. The idea is to further strengthen the robustness with respect to the individual use of the two solutions, to tackle sophisticated spoofing attacks, which are able to avoid detection from navigation message authentication (NMA) techniques. The manuscript proves the high performance of the joint scheme, presenting the results of a wide bench of tests, under different scenarios of spoofing, and user conditions.