Secure email is increasingly being touted as usable by novice users, with a push for adoption based on recent concerns about government surveillance. To determine whether secure email is ready for grassroots adoption, we employ a laboratory user study that recruits pairs of novice users to install and use several of the latest systems to exchange secure messages. We present both quantitative and qualitative results from 28 pairs of novices as they use Private WebMail (Pwm), Tutanota, and Virtru and 10 pairs of novices as they use Mailvelope. Participants report being more at ease with this type of study and better able to cope with mistakes since both participants are "on the same page." We find that users prefer integrated solutions over depot-based solutions and that tutorials are important in helping first-time users. Finally, our results demonstrate that Pretty Good Privacy using manual key management is still unusable for novice users, with 9 of 10 participant pairs failing to complete the study. CCS Concepts: • Security and privacy → Domain-specific security and privacy architectures; Usability in security and privacy; • Human-centered computing → User studies; Empirical studies in HCI; Laboratory experiments;

Messaging applications like SnapChat illustrate that users are concerned about the permanence of information. We find that this concern extends to email. In this paper we present a usability study of an end-to-end secure email tool with the option to securely delete messages. This tool uses ephemeral keys, one per message thread, and default expiration times, with a user prompt to renew or delete keys. Deleting keys causes the messages in the thread to be unreadable for that user. We compare the usability of this tool to a nearly identical tool that uses long term keys and lacks a feature to expire keys. We also interview participants about their email use patterns and attitudes towards information permanence. We find that participants are especially interested in the ability to control the lifetime of an email message. Participants also report trusting the tool that allowed them to make their email messages ephemeral more than the tool that just encrypted their email.

This paper describes MessageGuard, a browser-based platform for research into usable content-based encryption. MessageGuard is designed to enable collaboration between security and usability researchers on long-standing research questions in this area. It significantly simplifies the effort required to work in this space and provides a place for research results to be shared, replicated, and compared with minimal confounding factors. MessageGuard provides ubiquitous encryption and secure cryptographic operations, enabling research on any existing web application, with realistic usability studies on a secure platform. We validate MessageGuard's compatibility and performance, and we illustrate its utility with case studies for Gmail and Facebook Chat. 1. Substantial modifications are needed because existing open source content-based encryption tools are unusable [16]. 2. A diff-based patch of MessageGuard's code base.