Common user authentication methods on smartphones, such as lock patterns, PINs, or passwords, impose a trade-off between security and password memorability. Image-based passwords were proposed as a secure and usable alternative. As of today, however, it remains unclear how such schemes are used in the wild. We present the first study to investigate how image-based passwords are used over long periods of time in the real world. Our analyses are based on data from 2318 unique devices collected over more than one year using a custom application released in the Android Play store. We present an in-depth analysis of what kind of images users select, how they define their passwords, and how secure these passwords are. Our findings provide valuable insights into real-world use of image-based passwords and inform the design of future graphical authentication schemes.

@inproceedings{alt15_mobilehci,
  title = {Graphical Passwords in the Wild -- Understanding How Users Choose Pictures and Passwords in Image-based Authentication Schemes},
  author = {Florian Alt and Stefan Schneegass and Alireza Sahami and Mariam Hassib and Andreas Bulling},
  year = {2015},
  booktitle = {Proc. ACM International Conference on Human-Computer Interaction with Mobile Devices and Services (MobileHCI)},
  pages = {316-322},
  doi = {10.1145/2785830.2785882},
}