The Anatomy of Smartphone Unlocking: A Field Study of Android Lock Screens

TitleThe Anatomy of Smartphone Unlocking: A Field Study of Android Lock Screens
Publication TypeConference Paper
Year of Publication2016
AuthorsHarbach, M., De Luca A., & Egelman S.
Published inProceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI ’16)
Place PublishedNew York, NY, USA

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.


We would like to thank the PhoneLab team at University of Buffalo for their support in gathering the data. This work was partly supported by a fellowship within the FITweltweit program of the German Academic Exchange Service (DAAD), as well as by the U.S. National Science Foundation under award CNS-1318680.

ICSI Research Group

Usable Security and Privacy