Tangible 2FA - An In-the-Wild Investigation of User-Defined Tangibles for Two-Factor Authentication.

Although two-factor authentication (2FA) mechanisms can be usable, they poorly integrate into users' daily routines, especially during mobile use. Using tangibles for 2FA is a promising alternative that beneficially combines customisable authentication routines and object geometries, personalisable to each user. Yet, it remains unclear how they integrate into daily routines. In this paper, we first let 226 participants design 2FA tangibles to understand user preferences. Second, we prototyped the most common shapes and performed a one-week long in-the-wild study (N=15) to investigate how 2FA tangibles perform in different environments. We show that most users prefer objects that a) fit in wallets, b) connect to daily items or c) are standalone. Users enjoyed interacting with 2FA tangibles and considered them a viable and more secure alternative. Yet, they voiced concerns on portability. We conclude by an outlook for a real world implementation and distribution of 2FA tangibles addressing user concerns.