Jason Anderson

This work derives the authentication security of pseudorandom function (PRF) GNSS ranging under multiple GNSS spoofing models, including the Security Code Estimation and Replay (SCER) spoofer. When GNSS ranging codes derive from a PRF utilizing a secret known only to the broadcaster, the spoofer cannot predict the ranging code before broadcast. Therefore, PRF ranging can be used to establish trust in the GNSS pseudoranges and the resulting receiver position, navigation, and timing (PNT) solution. I apply the methods herein to Galileo’s Signal Authentication Service (SAS) utilizing the encrypted Galileo E6-C signal to compute that, at most, 400 ms of Galileo E6-C data to assert 128-bit authentication security under non-SCER models. For the SCER adversary, I predict the adversary’s needed receiving radio equipment to break authentication security. One can use this work to design a PRF GNSS ranging protocol to meet useful authentication security requirements by computing the probability of missed detection.

Cryptographic Ranging Authentication is here! We present initial results on the Pulsar authenticated ranging service broadcast from space with Pulsar-0 utilizing a recording taken at Xona headquarters in Burlingame, CA. No assumptions pertaining to the ownership or leakage of encryption keys are required. This work discusses the Pulsar watermark design and security analysis. We derive the Pulsar watermark’s probabilities of missed detection and false alarm, and we discuss the required receiver processing needed to utilize the Pulsar watermark. We present validation results of the Pulsar watermark utilizing the transmissions from orbit. Lastly, we provide results that demonstrate the spoofing detection efficacy with a spoofing scenario that incorporates the authentic transmissions from orbit. Because we make no assumption about the leakage of symmetric encryption keys, this work provides mathematical justification of the watermark’s security, and our July 2025 transmissions from orbit, we claim the world’s first authenticated satellite pseudorange from orbit.

As timed efficient stream loss-tolerant authentication (TESLA)-enabled global navigation satellite systems (GNSS) for authenticated positioning reaches ubiquity, receivers must use an onboard, GNSS-independent clock (GIC) and carefully constructed time synchronization algorithms to assert the authenticity afforded. This work provides the necessary checks and synchronization protocols needed in the broadcast-only GNSS context. We provide proof of security for each of our algorithms under a delay-capable adversary. The algorithms included herein enable a GNSS receiver to use its GIC to determine whether a message arrived at the correct time, to determine whether its GIC is safe to use and when the clock will no longer be safe in the future due to predicted clock drift, and to resynchronize its GIC. Each algorithm is safe to use even when an adversary induces delays within the protocol. Moreover, we discuss the implications of GNSS authentication schemes that use two simultaneous TESLA instances of different authentication cadences. To a receiver implementer or standards author, this work provides the necessary implementation algorithms to assert security and provides a comprehensive guide on why these methods are required. We discuss and address a vulnerability related to the standard synchronization protocols in the context of broadcast-only TESLA.