  Making contactless payments using a smartwatch is increasingly popular, but
this payment medium lacks traditional biometric security measures such as
facial or fingerprint recognition. In 2022, Sturgess et al. proposed WatchAuth,
a system for authenticating smartwatch payments using the physical gesture of
reaching towards a payment terminal. While effective, the system requires the
user to undergo a burdensome enrolment period to achieve acceptable error
levels. In this dissertation, we explore whether applications of deep learning
can reduce the number of gestures a user must provide to enrol into an
authentication system for smartwatch payment. We firstly construct a
deep-learned authentication system that outperforms the current
state-of-the-art, including in a scenario where the target user has provided a
limited number of gestures. We then develop a regularised autoencoder model for
generating synthetic user-specific gestures. We show that using these gestures
in training improves classification ability for an authentication system.
Through this technique we can reduce the number of gestures required to enrol a
user into a WatchAuth-like system without negatively impacting its error rates.
