  Earables (ear wearables) is rapidly emerging as a new platform encompassing a
diverse range of personal applications. The traditional authentication methods
hence become less applicable and inconvenient for earables due to their limited
input interface. Nevertheless, earables often feature rich around-the-head
sensing capability that can be leveraged to capture new types of biometrics. In
this work, we proposeToothSonic which leverages the toothprint-induced sonic
effect produced by users performing teeth gestures for earable authentication.
In particular, we design representative teeth gestures that can produce
effective sonic waves carrying the information of the toothprint. To reliably
capture the acoustic toothprint, it leverages the occlusion effect of the ear
canal and the inward-facing microphone of the earables. It then extracts
multi-level acoustic features to reflect the intrinsic toothprint information
for authentication. The key advantages of ToothSonic are that it is suitable
for earables and is resistant to various spoofing attacks as the acoustic
toothprint is captured via the user's private teeth-ear channel that modulates
and encrypts the sonic waves. Our experiment studies with 25 participants show
that ToothSonic achieves up to 95% accuracy with only one of the users' tooth
gestures.
