Almost every aspect of American life today relies on some aspect of positioning, navigation, and timing (PNT) data provided by the Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS).
Along those lines, the Department of Homeland Security’s Science & Technology Directorate in coordination with the Office of Infrastructure Protection and the National Coordination Office for Space-Based Positioning, Navigation and Timing (PNT) created a Best Practices Guide to improve the operations and development of Global Positioning System (GPS) equipment used by critical infrastructure.
The goal of the paper is to provide owners, operators, researchers, designers, and manufacturers with information to improve the security and resilience of PNT equipment across the spectrum of equipment development, deployment, and use.
Specifically, recommendations should consider:
• Installation and operation strategies that can be implemented for current equipment
• Strategies that can result in more resilient new and/or improved products based on existing technology and knowledge
Implementing these recommendations will lead to increased “competence” — that is, equipment better able to accommodate imperfections in their inputs, regardless of whether these imperfections are intentional or not.
The appendices include observations and interactions with critical infrastructure owners and operators whose insights on their use of PNT information provided significant background for this document; details on the operational benefits of blocking antennas; and research topics where additional information could add to the knowledge of relevant communities and capabilities of equipment using GNSS-provided data for PNT operations.
A. Interference and jamming: Interference arises from unintentionally produced RF waveforms that raise the effective noise floor in the receiver processing, thus degrading or denying a receiver’s ability to operate. Jamming is intentionally produced RF waveforms that have the same effect as interference; the only difference is the intent to degrade or deny a target receiver’s operation.
B. Spoofing: Spoofing is caused by RF waveforms that mimic true signals in some ways, but deny, degrade, disrupt, or deceive a receiver’s operation when they are processed. Spoofing may be unintentional, such as effects from the signals of a GPS repeater, or they may be intentional and even malicious. There are two classes of spoofing:
• Measurement spoofing introduces RF waveforms that cause the target receiver to produce incorrect measurements of time of arrival or frequency of arrival or their rates of change.
• Data spoofing introduces incorrect digital data to the target receiver for its use in processing of signals and the calculation of PNT.
Either type of spoofing can cause a range of effects, from incorrect outputs of PNT to receiver malfunction. The onset of these effects can be instantaneous or delayed and it is possible for effects to continue even after the spoofing has ended.
This guidance document identifies 22 specific recommendations for receivers and equipment today and existing techniques that can be inserted into new products. These installation and operation strategies and development opportunities described herein can significantly enhance the ability of GNSS receivers and associated equipment to defend against a range of interference, jamming, and spoofing attacks.
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