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.
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.
