The Anatomy of Smartphone Unlocking: A Field Study of Android Lock Screens
Venue
Proceedings of the 34th Annual ACM Conference on Human Factors in Computing Systems (CHI'16), ACM, New York, NY, USA (2016) (to appear)
Publication Year
2016
Authors
Marian Harbach, Alexander De Luca, Serge Egelman
BibTeX
Abstract
To prevent unauthorized parties from accessing data stored on their smartphones,
users have the option of enabling a "lock screen" that requires a secret code
(e.g., PIN, drawing a pattern, or biometric) to gain access to their devices. We
present a detailed analysis of the smartphone locking mechanisms currently
available to billions of smartphone users worldwide. Through a month-long field
study, we logged events from a panel of users with instrumented smartphones
(N=134). We are able to show how existing lock screen mechanisms provide users with
distinct tradeoffs between usability (unlocking speed vs. unlocking frequency) and
security. We find that PIN users take longer to enter their codes, but commit fewer
errors than pattern users, who unlock more frequently and are very prone to errors.
Overall, PIN and pattern users spent the same amount of time unlocking their
devices on average. Additionally, unlock performance seemed unaffected for users
enabling the stealth mode for patterns. Based on our results, we identify areas
where device locking mechanisms can be improved to result in fewer human errors -
increasing usability - while also maintaining security.
