Applying Psychometrics to Measure User Comfort when Constructing a Strong Password

As mobile devices become increasingly common for accessing services online, the security of these services in turn depends more on password entry on these devices. Unfortunately, users are not comfortable with existing textual password entry mechanisms on mobile phone handsets. In this study, we investigate this issue of user comfort from the viewpoint of psychometrics. By applying standard techniques of psychometrics, we develop a questionnaire (known as a scale in psychometrics) that measures the comfort of constructing a strong password when using a particular interface. We establish the essential psychometric properties (reliability and validity) of this scale and demonstrate how the scale can be used to profile password construction interfaces of popular smartphone handsets. We also theoretically conceptualize user comfort across different dimensions and use confirmatory factor analysis to verify our theory. Finally, we highlight several issues related to scale development and discuss how psychometric approaches may be useful in general for measuring various subjective concepts that are related to usable security.