In order to combat the spoofing of global navigation satellite system (GNSS)
signals we propose a novel approach for satellite signal authentication based
on information-theoretic security. In particular we superimpose to the
navigation signal an authentication signal containing a secret message
corrupted by artificial noise (AN), still transmitted by the satellite. We
impose the following properties: a) the authentication signal is synchronous
with the navigation signal, b) the authentication signal is orthogonal to the
navigation signal and c) the secret message is undecodable by the attacker due
to the presence of the AN. The legitimate receiver synchronizes with the
navigation signal and stores the samples of the authentication signal with the
same synchronization. After the transmission of the authentication signal,
through a separate public asynchronous authenticated channel (e.g., a secure
Internet connection) additional information is made public allowing the
receiver to a) decode the secret message, thus overcoming the effects of AN,
and b) verify the secret message. We assess the performance of the proposed
scheme by the analysis of both the secrecy capacity of the authentication
message and the attack success probability, under various attack scenarios. A
comparison with existing approaches shows the effectiveness of the proposed
scheme
