Tire pressure monitor systems could reveal driver location

Researchers from Rutgers University and University of South Carolina have found that wireless communications between new cars and their tires can be intercepted or even forged.

While the potential for misuse may be minimal, this vulnerability points to a troubling lack of rigor with secure software development for new automobiles, said Wenyuan Xu, a computer science assistant professor at the University of South Carolina, who was a co-lead on the study.

"If no one mentions [such flaws], then they won't bother with security," Xu said.

The researchers will present their findings at the Usenix Security Symposium, being held this week in Washington D.C.

The system that the researchers tested monitors the air pressure of each tire on an automobile. The U.S. has required such systems in new automobiles since 2008, thanks to legislation passed after controversy erupted over possible defective Firestone tires in 2000. The European Union will require new automobiles to have similar monitoring systems in place by 2012.

As computerized systems are being increasingly used in automobiles, critics such as Xu are asking what safeguards system makers are putting in place to prevent vulnerabilities in such systems, knowing that bugs and security holes invariably sneak into all software.

Toyota came under the scrutiny of U.S. law makers earlier this year, who asked the car maker if software bugs could be a reason for the unattended acceleration of its vehicles, a charge Toyota officials denied.

With such systems, "people just try to make things work first, and they don't care about the security or privacy during the first run of design," Xu said.

The tire pressure monitoring systems (TPMS) consist of battery-powered radio frequency identification (RFID) tags on each tire, which can respond with the air pressure readings of the tire when wirelessly queried by an electronic control unit (ECU).

The researchers had found that each sensor has a unique 32-bit ID and that communication between the tag and the control unit was unencrypted, meaning it could be intercepted by third parties from as far away as 130 feet.

"If the sensor IDs were captured at roadside tracking points and stored in databases, third parties could infer or prove that the driver has visited potentially sensitive locations such as medical clinics, political meetings, or nightclubs," the researchers write, in a paper that accompanies the presentation.

Such messages could also be forged. An attacker could flood the control unit with low pressure readings that would repeatedly set off the warning light, causing the driver to lose confidence in the sensor readings, the researchers contend. An attacker could also send nonsensical messages to the control unit, confusing or possibly even breaking the unit.

"We have observed that it was possible to convince the TPMS control unit to display readings that were clearly impossible," the researchers write. In one case, the researchers had confounded the control unit so badly that it could no longer operate properly, even after rebooting, and had to be replaced by the dealer.

Xu said that while it is possible to track someone by their tire IDs, the feasibility of doing so would be quite low. "Someone would have to invest money at putting receivers at different locations," she said. Also multiple tire manufacturers have different types of sensors, requiring different receivers. Each receiver in this test cost $1,500.

Nonetheless, component manufacturers could take some easy steps to strengthen the security of these systems, the researchers conclude. Communications could be encrypted. Also the ECU should filter incoming messages so that any with unexpected payloads should be discarded, so they do not corrupt the system.

"The consumer may be willing to pay few dollars to make their autos secure," Xu said.

Joab Jackson covers enterprise software and general technology breaking news for The IDG News Service. Follow Joab on Twitter at @Joab_Jackson. Joab's e-mail address is Joab_Jackson@idg.com

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