Minimal-Feedback Hints for Remembering Passwords
http://www.uigarden.net/english/minimal-feedback-hints-for-remembering-passwords

Hertzum, Morten
uiGarden
2006

Abstract:

Passwords are a widely used mechanism for user authentication and are thus critical to the security of many systems. Strong passwords (e.g., b5j#Kv!8N) are less vulnerable to attack but at the same time more difficult to remember. Minimal-feedback hints are introduced to support users in remembering their passwords and thereby enabling them to choose stronger passwords.