Secure Email Using Key Continuity Management

Simson Garfinkel & Robert Miller

Abstract
Secure email has struggled with significant obstacles to adoption, among them the low usability of encryption software and the cost and overhead of obtaining public key certificates. Key continuity management (KCM) has been proposed as a way to lower these barriers to adoption, by making key generation, key management, and message signing essentially automatic. We present the first user study of KCM-secured email, conducted on naive users who had no previous experience with secure email. Our secure email prototype, CoPilot, color-codes messages depending on whether they were signed and whether the signer was previously known or unknown. This interface makes users significantly less susceptible to social engineering attacks overall, but new-identity attacks (from email addresses never seen before) are still effective. Also, naive users do use the Sign and Encrypt button on the Outlook Express toolbar when the situation seems to warrant it, even without explicit instruction, although some falsely hoped that Encrypt would protect a secret message even when sent directly to an attacker. We conclude that KCM is a workable model for improving email security today, but work is needed to alert users to "phishing" attacks.

Signed email message with key continuity management

References:

[1] Simson L. Garfinkel and Robert C. Miller. "Johnny 2: A User Test of Key Continuity Management with S/MIME and Outlook Express." Proceedings of the Symposium on Usable Privacy and Security (SOUPS '05), Pittsburgh, PA, July 2005.

[2]Simson L. Garfinkel, Erik Nordlander, Robert C. Miller, David Margrave, Jeffrey I. Schiller. "How to Make Secure Email Easier to Use." Conference on Human Factors in Computing Systems (CHI 2005), April 2005.

[3]Simson L. Garfinkel, Jeffrey I. Schiller, Erik Nordlander, David Margrave, and Robert C. Miller. "Views, Reactions, and Impact of Digitally-Signed Mail in e-Commerce." Proceedings of the Ninth International Conference on Financial Cryptography and Data Security (FC 2005), February 2005.