SemperFi

Abstract

With the advent of autonomous cyber-physical systems such as self-driving cars and unmanned aerial vehicles, the use of Global Positioning System (GPS) for positioning and navigation has become ubiquitous. It is well-known that GPS is vulnerable to signal spoofing attacks. There is a need to design and develop a standalone GPS receiver capable of autonomous recovery during a spoofing attack. In this work, we present SemperFi, a single antenna, standalone, GPS receiver that is capable of tracking legitimate GPS satellite signals and estimating the true location even during a spoofing attack. Unlike majority of wireless systems where data contained in the wireless signals is important, GPS relies on the time of arrival of satellite signals. This presents a unique challenge and to address this challenge, SemperFi consists of specially designed algorithms and modules based on successive interference cancellation that are capable of recovering legitimate GPS signals that are overshadowed completely by a powerful adversary. We implement our design using Soft-GNSS and evaluate its performance against a variety of GPS datasets. Our evaluations show that SemperFi can recover from a seamless takeover attack with an accuracy of 100 m and power advantage of an attacker up to 15 dB. SemperFi can also be incorporated as a pluggable module capable of generating a spoofer free GPS signal for processing on any COTS GPS receiver available today. Finally, we release the implementation of our receiver design to the community for further development.