Range Authentication of Galileo E1 / E5a Signals Using the ACAS Method on a GNSS Hardware Receiver

Benedikt Schreiber, Fabio Garzia, Rocío Parra, Himanshu Gupta, Matthias Overbeck, and Alexander Rügamer

Peer Reviewed

Abstract:	This paper addresses the growing need for resilient Global Navigation Satellite System (GNSS) receivers against jamming and spoofing threats. We present the implementation of an Assisted Commercial Authentication Service (ACAS) method for range authentication of Galileo signals using the GOOSE v2 receiver. The ACAS service ensures signal integrity by publishing encrypted Pseudo Random Noise (PRN) code snippets, enabling signal authentication through post processing. Our implementation captures snapshots of incoming signals and computes their pseudoranges, allowing for real-time comparison with GNSS system data. Through a series of experiments, including dynamic spoofing scenarios and a 24-hour open-sky test, we demonstrate that the ACAS method can effectively authenticate E1 and E5a signals, achieving a success rate of approximately 99.99%. The results indicate that the first authenticated fix can be achieved within 50 seconds from a cold start and within 5 seconds from a hot start. This is 3 times faster than an authenticated PVT based on message authentication, e.g. OSNMA. These findings underscore the effectiveness of ACAS in enhancing GNSS receiver security and reliability. Index Terms—spoofing, authentication, range authentication, navigation message authentication, ACAS, Galileo
Published in:	2025 IEEE/ION Position, Location and Navigation Symposium (PLANS) April 28 - 1, 2025 Salt Lake Marriott Downtown at City Creek Salt Lake City, UT
Pages:	391 - 397
Cite this article:	Schreiber, Benedikt, Garzia, Fabio, Parra, Rocío, Gupta, Himanshu, Overbeck, Matthias, Rügamer, Alexander, "Range Authentication of Galileo E1 / E5a Signals Using the ACAS Method on a GNSS Hardware Receiver," 2025 IEEE/ION Position, Location and Navigation Symposium (PLANS), Salt Lake City, UT, April 2025, pp. 391-397.
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