A 2-FA for home voice assistants using inaudible acoustic signal

Abstract

Voice assistants have been shown to be vulnerable to replay attacks, impersonation attacks and inaudible voice commands. Existing defenses do not provide a practical solution as they either rely on external hardware or work under very constrained settings. We introduce a hand gesture-based authentication system for smart home voice assistants called HandLock, which uses built-in microphones and speakers to generate and sense inaudible acoustic signals to detect the presence of a known hand gesture. Our proposed approach can act as a second-factor authentication (2-FA) for performing specific sensitive operations like confirming online purchases through voice assistants. The experiments involving 45 participants show that HandLock can achieve on average 96.51% true-positive-rate at the expense of 0.82% false-acceptance-rate.