A Low-Cost Approach to Securing Commercial GPS Receivers Against Spoofing Attacks

Abstract

AbstractThe Global Positioning System (GPS) has been used ubiquitously for navigation and time synchronization. Nowadays, numerous telecommunication, transportation, finance, and aviation systems rely heavily on GPS for routine operations. However, due to the unencrypted nature of civilian GPS signals, commercial off-the-shelf GPS receivers are susceptible to spoofing attacks, which has been confirmed in a number of reported events. Although plenty of approaches to GPS spoofing defense have been proposed, most of these approaches require access to raw GPS signals (which are not accessible from commercial GPS receivers) or additional navigation sensors (which increase cost or engineering time), making them inappropriate for mass-market applications to secure commercial GPS receivers. We propose a low-cost spoofing detection approach for vehicular GPS receivers by purposely perturbing and then examining changes in the Doppler shift that are directly reported by most commercial GPS receivers. More specifically, by purposely enforcing vehicle velocity variations that are unpredictable to potential spoofers, we can enforce unpredictable variations to the actual Doppler shift on a GPS receiver. Then, through cross-checking if the Doppler shift value reported by a GPS receiver is consistent with the variation in velocity, we can tell if the GPS receiver is receiving genuine GPS signals or not. The variation in vehicle velocity is directly accessed from the vehicle On-Board Diagnostics (OBD) system available on all cars manufactured after 1996, which avoids using extra navigation sensors. The proposed approach requires neither dedicated radios to acquire raw GPS signals nor extra navigation sensors and is directly applicable to commercial off-the-shelf receivers, making it promising for mass-market applications to protect commercial GPS receivers. Extensive field experiments were conducted to systematically evaluate the performance as well as potential limitations of the proposed approach.