SnapApp is a novel unlock concept for mobile devices that reduces authentication overhead with a time-constrained quick-access option. SnapApp provides two unlock methods at once: While PIN entry enables full access to the device, users can also bypass authentication with a short sliding gesture (Snap). This grants access for a limited amount of time (e.g. 30 seconds). The device then automatically locks itself upon expiration. Our concept further explores limiting the possible number of Snaps in a row, and configuring blacklists for app use during short access (e.g. to exclude banking apps). We discuss opportunities and challenges of this concept based on a 30-day field study with 18 participants, including data logging and experience sampling methods. Snaps significantly reduced unlock times, and our app was perceived to offer a good tradeoff. Conceptual challenges include, for example, supporting users in configuring their blacklists.
D. Buschek, F. Hartmann, E. von Zezschwitz, A. De Luca, and F. Alt, “SnapApp: Reducing Authentication Overhead with a Time-Constrained Fast Unlock Option,” in Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, New York, NY, USA, 2016.
The core concept of SnapApp is to provide two unlock methods at once to reduce authentication overhead for short usage sessions. In contrast to current unlock methods, our concept thus provides users with two trade-offs regarding authentication time versus actual use: either spending more time on authentication for full access, or quickly bypassing authentication for limited access. In particular, users decide how to unlock based on their expected interaction time:
- PIN entry gives full access to the device, as usual.
- A fast sliding gesture grants time-constrained access to a user-defined subset of applications.
Short access via slide (i.e. Snap) limits access to a user-specified amount of time (Snap time). The device locks itself after this time has passed. Expiration is announced via short vibration, issued at five seconds prior to the session’s end. The system allows ten Snaps in a row without entering the PIN. The current number of Snaps is displayed on the Snap bar – see Figure 1 (“10 Snaps left”). When all Snaps have been used, unlock by sliding cannot be used any more. Successful PIN entry sets the number of Snaps back to ten.