Diversify to Survive: Making Passwords Stronger with Adaptive Policies


Sean Segreti, William Melicher, Saranga Komanduri, Darya Melicher, and Richard Shay, Carnegie Mellon University; Blase Ur, University of Chicago; Lujo Bauer, Nicolas Christin, and Lorrie Cranor, Carnegie Mellon University; Michelle Mazurek, University of Maryland


Password-composition policies are intended to increase resistance to guessing attacks by requiring certain features (e.g., a minimum length and the inclusion of a digit). Sadly, they often result in users' passwords exhibiting new, yet still predictable, patterns. In this paper, we investigate the usability and security of adaptive password-composition policies, which dynamically change password requirements over time as users create new passwords. We conduct a 2,619- participant between-subjects online experiment to evaluate the strength and usability of passwords created with two adaptive password policies. We also design and test a feedback system that guides users to successfully create a password conforming to these policies. We find that a well-configured, structure-based adaptive password policy can significantly increase password strength with little to no decrease in usability. We discuss how system administrators can use these results to improve password diversity.

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@inproceedings {205158,
author = {Sean M. Segreti and William Melicher and Saranga Komanduri and Darya Melicher and Richard Shay and Blase Ur and Lujo Bauer and Nicolas Christin and Lorrie Faith Cranor and Michelle L. Mazurek},
title = {Diversify to Survive: Making Passwords Stronger with Adaptive Policies},
booktitle = {Thirteenth Symposium on Usable Privacy and Security (SOUPS 2017)},
year = {2017},
isbn = {978-1-931971-39-3},
address = {Santa Clara, CA},
pages = {1--12},
url = {https://www.usenix.org/conference/soups2017/technical-sessions/presentation/segreti},
publisher = {USENIX Association},
month = jul

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