Enhancing Spreading Code Signal Authentication in GNSS: a GLRT-based Approach

The threat of signal spoofing against global navigation satellite systems (GNSS) has grown in recent years and has motivated the study of anti-spoofing techniques. This paper addresses the challenge of verifying the authenticity of signals protected by spreading code authentication (SCA). Conventional methods rely on either the correlation or cross-energy checks between the received signal and a local replica of the transmitted signal generated by the verifier using the authentic code. However, these methods are vulnerable to specific attacks. In particular, we show how to forge an effective spoofing signal just by using publicly available information. We introduce a novel and more effective generalized likelihood ratio test (GLRT)-based authentication mechanism. Its robustness will be proved by testing it against a wide class of attacks. Among others, this class includes the attack successful against the cross-energy check and a specific attack, which we prove to be statistically optimal against the proposed check. Finally, we provide a comparative performance evaluation against state-of-the-art attacks, showcasing the effectiveness of our proposed approach.