Abstract: Wearables, including fitness bracelets, smart watches, and smart jewelry, are increasingly popular to help users monitor their physical activities and receive notifications. However, wearables are small and have limited user interfaces, hence they often wirelessly interface with a personal smartphone or a personal computer to relay information from the wearable for display or other interactions. In this paper, we envision a new method by which a wearable can establish a secure connection to an ambient display, such as a television or computer monitor, based on the user's intention to connect to the display. The user can access and display the bracelet's information without having to carry personal display devices. Such connections must only be made intentionally, must be secure to prevent impersonation attacks, must work with unmodified display hardware, and must be easy to establish even when a new display is encountered. We propose a secure wearable/display connection solution, named LightTouch. LightTouch uses standard RF methods (like Bluetooth) for communicating the data to display, securely bootstrapped with a key shared via a brightness channel between the low cost, low power, ambient light sensor of a wearable and the screen of the display. A screen touch gesture is adopted by users to ensure the modulation of screen brightness can be accurately and securely captured by the ambient light sensor. Wireless coordination with the processor driving the display establishes a shared secret based on the brightness channel information. We further propose novel on-screen localization and correlation algorithms to improve security and reliability. Through experiments we demonstrate that LightTouch is compatible with current display and wearable designs, easy-to-use (5-6 seconds), reliable for connecting multiple displays in various ambient light conditions (98% success connection ratio), and secure against impersonation attacks. Our solution should also work with many other mobile electronic devices.
Copyright © 2018 by the authors.