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

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.