Tim Pierson’s dissertation work resulted in an innovative method for single-antenna Wi-Fi devices (like many mHealth devices, medical devices, or those in the IoT) to determine with strong confidence whether a Wi-Fi transmitter is close by (within a few centimeters).  This proximity detector can be the basis for trustworthy relationships between devices.   A poster paper about this idea just won the best-poster award at MobiCom 2018, and the full paper was just accepted for presentation at MobiCom 2019. See below for the abstract, or check out the corresponding three-page paper.

Abstract:

Close physical proximity among wireless devices that have never shared a secret key is sometimes used as a basis of trust.  In these cases, devices in close proximity are deemed trustworthy while more distant devices are viewed as potential adversaries.

Because radio waves are invisible, however, a user may believe a wireless device is communicating with a nearby device when in fact the user’s device is communicating with a distant adversary.  Researchers have previously proposed methods for multi-antenna devices to ascertain physical proximity with other devices, but devices with a single antenna, such as those commonly used in the Internet of Things, cannot take advantage of these techniques.

We investigate a method for a single-antenna Wi-Fi device to quickly determine proximity with another Wi-Fi device.  Our approach leverages the repeating nature Wi-Fi’s preamble and the characteristics of a transmitting antenna’s near field to detect proximity with high probability.  Our method never falsely declares proximity at ranges longer than 14 cm.