Listening Watch: Wearable Two-Factor Authentication using Speech Signals Resilient to Near-Far Attacks

Reducing the level of user effort involved in traditional two-factor authentication (TFA) constitutes an important research topic. A recent effort in this direction leverages ambient sounds to detect the proximity between the second factor device (phone) and the login terminal (browser), and eliminates the need for the user to transfer PIN codes. This approach is highly usable, but is completely vulnerable against far-near attackers, i.e., ones who are remotely located and can guess the victim's audio environment or make the phone create predictable sounds (e.g., ringers), and those who are in physical proximity of the user. In this paper, we propose Listening-Watch, a new TFA mechanism based on a wearable device (watch/bracelet) and active browser-generated random speech sounds. As the user attempts to login, the browser populates a short random code encoded into speech, and the login succeeds if the watch's audio recording contains this code (decoded using speech recognition), and is similar enough to the browser's audio recording. The remote attacker, who has guessed the user's environment or created predictable phone/watch sounds, will be defeated since authentication success relies upon the presence of the random code in watch's recordings. The proximity attacker will also be defeated unless it is extremely close to the watch, since the wearable microphones are usually designed to be only capable of picking up nearby sounds (e.g., voice commands). Furthermore, due to the use of a wearable second factor device, Listening-Watch naturally enables two-factor security even when logging in from a mobile phone. Our contributions are three-fold. First, we introduce the idea of strong and low-effort TFA based on wearable devices, active speech sounds and speech recognition, giving rise to the Listening-Watch system that is secure against both remote and proximity attackers. Second, we design and implement Listening-Watch for an Android smartwatch (and companion smartphone) and the Chrome browser, without the need for any browser plugins. Third, we evaluate Listening-Watch for authentication errors in both benign and adversarial settings. Our results show that Listening-Watch can result in minimal errors in both settings based on appropriate thresholdization and speaker volume levels.