A practical technique is proposed to authenticate civil GPS signals. The technique combines cryptographic authentication of the GPS navigation message with signal timing authentication based on statistical hypothesis tests to secure civil GPS receivers against spoofing attacks. The notion of GNSS signal authentication is defined in probabilistic terms. Candidate GPS signal authentication schemes are evaluated in terms of effectiveness and practicality leading to a proposal for incorporating digital signatures into the extensible GPS civil navigation (CNAV) message. The proposal is sufficiently detailed to facilitate near‐term implementation of security‐hardened civil GPS. Copyright © 2012 Institute of Navigation.

Abstract-We propose a simple low-cost technique that enables civil Global Positioning System (GPS) receivers and other civil global navigation satellite system (GNSS) receivers to reliably detect carry-off spoofing and jamming. The technique, which we call the Power-Distortion detector, classifies received signals as interference-free, multipath-afflicted, spoofed, or jammed according to observations of received power and correlation function distortion. It does not depend on external hardware or a network connection and can be readily implemented on many receivers via a firmware update. Crucially, the detector can with high probability distinguish low-power spoofing from ordinary multipath. In testing against over 25 high-quality empirical data sets yielding over 900,000 separate detection tests, the detector correctly alarms on all malicious spoofing or jamming attacks while maintaining a <0.6% single-channel false alarm rate.

Abstract-A proposal for civil GPS navigation message authentication (NMA) is presented with sufficient specificity to enable near-term implementation. Although previous work established the practicality and efficacy of NMA for civil GPS signal authentication, there remains a need for a detailed proposal that addresses several outstanding considerations regarding implementation. In particular, this paper (1) provides a definitive evaluation of the tradeoffs involved in the choice of cryptographic protocol, and (2) optimizes the placement of digital signature bits in the GPS CNAV message stream. By offering GPS engineers and policymakers a detailed blueprint for civil NMA, this work advances the possibility of NMA implementation on modernized civil GPS signals.

Civil Global Navigation Satellite System (GNSS) signals are vulnerable to spoofing attacks that deceive a victim receiver into reporting counterfeit position or time information. The primary contribution of this paper is a non-cryptographic GNSS anti-spoofing technique that "sandwiches" a spoofer between a correlation function distortion monitor and a total in-band power monitor. The defense exploits the difficulty of mounting an effective spoofing attack that simultaneously maintains a low-enough counterfeit signal power to avoid power monitoring alarms while minimizing distortions of the received crosscorrelation profile that are indicative of a spoofing attack. Results presented in this paper demonstrate the defense's effectiveness against a sophisticated spoofing attack.

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