Between easy-to-counterfeit physical IDs, the poor adoption of some digital alternatives, and the weak security of others, the need for better identity solutions becomes apparent. As such, this thesis explores how digital identity services can be designed in a usable, secure, and privacy-preserving manner.

Our first user study examines the discoverability of participants' personally identifiable information (PII) to determine what information is suitable for identity proofing. We found that many different types of PII could be obtained by an imposter and that individuals significantly underestimate the risk of said information being available.

Our second user study explores the usability of a prototype digital identity service for smartphone users. We identify and categorize users' perceptions, opinions, and concerns over using this type of service. Our findings highlight the need to support users in developing accurate mental models to avoid usability issues.