Smartphone sensors leave trackable fingerprints

Smartphone sensors – not just the ones meant to track your location – can leave real-time fingerprints unique to each individual device, a new study by Indian-origin researchers has found. Researchers from the University of Illinois College of Engineering have demonstrated that these fingerprints exist within smartphone sensors, mainly because of imperfections during the hardware manufacturing process.

Research by Associate Professor Romit Roy Choudhury and graduate students Sanorita Dey and Nirupam Roy has demonstrated that these fingerprints exist within smartphone sensors, mainly because of imperfections during the hardware manufacturing process.

In some ways, it's like cutting out sugar cookies. Even using the same dinosaur-shaped cutter, each cookie will come out slightly different: a blemish here, a pock there. For smartphone sensors, these imperfections simply occur at the micro- or nanoscale.

Their findings were published at the Network and Distributed System Security Symposium (NDSS). The research also won the best poster award at the HotMobile international workshop in 2013.

The researchers focused specifically on the accelerometer, a sensor that tracks three-dimensional movements of the phone—essential for countless applications, including pedometers, sleep monitoring, mobile gaming—but their findings suggest that other sensors could leave equally unique fingerprints.

"When you manufacture the hardware, the factory cannot produce the identical thing in millions," Roy said. "So these imperfections create fingerprints."

Of course, these fingerprints are only visible when accelerometer data signals are analyzed in detail. Most applications do not require this level of analysis, yet the data shared with all applications—your favorite game, your pedometer—bear the mark. Should someone want to perform this analysis, they could do so. The researchers tested more than 100 devices over the course of nine months: 80 standalone accelerometer chips used in popular smartphones, 25 Android phones and two tablets.