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.
T. Monson, J. Reynolds, T. Smith, S. Ruoti, D. Zappala, and K. Seamons. A Usability Study of Secure Email Deletion, European Workshop on Usable Security (EuroUSEC), April 2018.
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