Tire Pressure Monitoring System encryption to improve vehicular security

Vehicles are increasingly wirelessly connected and each wireless connection is a potential cyber threat surface. Many of these wireless communications are related to the infotainment systems and are optional, some are not. Since 2008, when the U.S. government mandated the need for real-time tire pressure diagnostics, automotive manufacturers have inserted Tire Pressure Monitoring System (TPMS)-based devices in all vehicles sold domestically. These sensors are divided into “direct” and “indirect” TPMS based on the mechanisms used to observe the tire pressure, temperature, and other characteristics; while marginally more expensive, most such systems are directly embedded in the tire to achieve the diagnostics requirements stated in National Highway Traffic Safety Administration [1], [2], necessitating a wireless communications link back to a car's Controller Area Network (CAN) bus and engine control unit (ECU). In this paper, we seek to evaluate the cyber-security of that TPMS wireless communications interface, proposing and evaluating the viability of incorporating a more secure TPMS protocol that takes advantage of simple linear feedback shift register (LFSR)-based message encryption. The proposed models were designed and implemented in both a Universal Serial Radio Peripheral (USRP) N210 software defined radio (SDR) testbed that replicates each side of the TPMS link; the resulting capabilities were also simulated on an inexpensive Arduino platform to demonstrate cost realism in the threat to the TPMS system.