  In recent years, biometric authentication technology for smartphones has
become widespread, with the mainstream methods being fingerprint authentication
and face recognition. However, fingerprint authentication cannot be used when
hands are wet, and face recognition cannot be used when a person is wearing a
mask. Therefore, we examine a personal authentication system using the pinna as
a new approach for biometric authentication on smartphones. Authentication
systems based on the acoustic transfer function of the pinna (PRTF: Pinna
Related Transfer Function) have been investigated. However, the authentication
accuracy decreases due to the positional fluctuation across each measurement.
In this paper, we propose multimodal personal authentication on smartphones
using PRTF. The pinna image and positional sensor information are used with the
PRTF, and the effectiveness of the authentication method is examined. We
demonstrate that the proposed authentication system can compensate for the
positional changes in each measurement and improve robustness.
