Balancing Security and Usability in Encrypted Email.

End-to-end encryption is the best way to protect digital messages. Historically, end-to-end encryption has been extremely difficult for people to use, but recent tools have made it more broadly accessible, largely by employing key-directory services. These services sacrifice some security properties for convenience. The authors wanted to understand how average users think about these tradeoffs. They conducted a 52-person user study and found that participants could learn to understand properties of different encryption models. Users also made coherent assessments about when different tradeoffs might be appropriate. Participants recognized that the less-convenient exchange model was more secure overall, but considered the registration model's security sufficient for most everyday purposes.