The Android pattern lock screen (or graphical password) is a popular user authentication method that relies on the advantages provided by the visual representation of a password, which enhance its memorability. Graphical passwords are vulnerable to attacks (e.g. shoulder surfing); thus, the need for more complex passwords becomes apparent. This paper aims to focus on the features that constitute a usable and secure pattern and investigate the existence of heuristic and physical rules that possibly dictate the formation of a pattern.
Andriotis, P., Oikonomou, G., Mylonas, A., & Tryfonas, T. (2016). A Study on Usability and Security Features of the Android Pattern Lock Screen. Information and Computer Security, 24(1), 53-72. https://doi.org/10.1108/ICS-01-2015-0001