Learning from Authoritative Security Experiment Results
Dead on Arrival: Recovering from Fatal Flaws in Email Encryption Tools
Juan Ramon Ponce Mauries, Kat Krol, Simon Parkin, Ruba Abu-Salma, and M. Angela Sasse
University College London and University of Cambridge
Background. Since Whitten and Tygar’s seminal study of PGP 5.0 in 1999, there have been continuing efforts to produce email encryption tools for adoption by a wider user base, where these efforts vary in how well they consider the usability and utility needs of prospective users.
Aim. We conducted a study aiming to assess the user experience of two open-source encryption software tools – Enigmail and Mailvelope. The study combined labbased sessions with remote tasks.
Method. We conducted a three-part user study (installation, home use, and debrief) with two groups of users using either Enigmail or Mailvelope. Users had access to help during installation (installation guide and experimenter with domain-specific knowledge), and were set a primary task of organising a mock flash mob through encrypted emails in the course of a week.
Results. Participants struggled to install the tools – they would not have been able to complete installation without help. Even with help, setup time was around 40 minutes. Participants using Mailvelope failed to encrypt their initial emails, due to usability problems. Participants said they were unlikely to continue using the tools after the study, indicating that their creators must also consider utility.
Conclusions. Through our mixed study approach, we conclude that Mailvelope and Enigmail had too many software quality and usability issues to be adopted by mainstream users. Methodologically, the study made us rethink the role of the experimenter as that of a helper assisting novice users with setting up a demanding technology.