Just like flat-screen televisions, cell phones, and computers, Global Positioning System (GPS) technology is becoming something people can't imagine living without. So if such a ubiquitous system were to come under attack, would we be ready?

It’s an uncomfortable question, but one that a group of Virginia Tech and Cornell University researchers have considered with their research into spoofing GPS receivers.

GPS is a United States navigation system of more than 30 satellites circling Earth twice a day in specific orbits, transmitting signals to receivers on land, sea, and in air to calculate their exact locations. Spoofing, a not-quite-technical term first coined in the radar community, is the transmission of fake GPS signals that receivers accept as authentic ones.

The Virginia Tech and Cornell University researchers, after more than a year of building equipment and experimenting, presented a paper on their findings at a meeting of the Institute of Navigation GNSS, Sept. 19 in Savannah, Ga.

Brent Ledvina, an assistant professor of electrical and computer engineering in Virginia Tech’s College of Engineering, said the joint project with Cornell was the result of professional friendships he developed when he was at the Ithaca, N.Y. university. He and the first author of the paper, Todd Humphreys, had met as doctoral candidates. Ledvina’s former advisers were Cornell professors Paul Kintner and Mark Psiaki.

Ledvina joined the Virginia Tech faculty in 2006. When Humphreys looked for collaborators to help him research his idea, he turned to Ledvina, Kintner, and Psiaki.

Kintner and Psiaki started by demonstrating how a navigation device can be fooled. They programmed a briefcase-size GPS receiver used in ionospheric research to send out fake signals. Paper co-authors Ledvina and first author Todd Humphreys, described how the phony receiver was placed in the proximity of a navigation device, where it anticipated the signal being transmitted from the GPS satellite. Almost instantly, the reprogrammed receiver sent out a false signal that the navigation device took for the real thing.

Handheld GPS receivers are popular for their usefulness in navigating unfamiliar highways or backpacking into wilderness areas. But GPS is also embedded in the world’s technological fabric. Such large commercial enterprises as utility companies and financial institutions have made GPS an essential part of their operations.

“GPS is woven into our technology infrastructure, just like the power grid or the water system,” said Kintner, electrical and computer engineering professor and director of the Cornell GPS Laboratory. “If it were attacked, there would be a serious impact.”

By demonstrating the vulnerability of receivers to spoofing, the researchers believe that they can help devise methods to guard against such attacks.

“Our goal is to inspire people who design GPS hardware to think about ways to make it so the kinds of things we’re showing can be overcome,” said Psiaki, Cornell professor of mechanical and aerospace engineering.

At Virginia Tech, Ledvina developed the enabling software technology that allowed the signal to be sent out in real time. The researchers have filed a provisional patent application on this technology through Virginia Tech Intellectual Properties.

The idea of GPS receiver spoofing isn’t new; in fact, the U.S. government addressed the issue in a December 2003 report detailing seven countermeasures against such an attack.

But, according to the researchers, such countermeasures would not have successfully guarded against the signals produced by their reprogrammed receiver.

“We’re fairly certain we could spoof all of these, and that’s the value of our work,” Humphreys said.

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