Security and usability engineering with particular attention to electronic mail

Abstract

Support for strong electronic mail security is widely available yet only few communicants appear to make use of these features. Apparently, the operational overhead of security outweighs its perceived benefits. Towards increasing the benefits versus overhead ratio we follow an approach that considers security and usability tradeoffs from the outset. We separate key exchange from binding keys to identities. The best effort key exchange and key maintenance scheme that we devise operates transparently for the user. We also describe complementary visualization and interaction techniques that communicate the security state of sent and received mail to users in a non-intrusive fashion. Structured interviews were conducted with 19 users to assess the usability of the metaphors and the complementary visualizations of the security state. Towards a practical assessment of the overheads of binding keys to identities, we conducted a quantitative analysis of 17 users' anonymized mailbox extracts to determine which security mechanisms would be most appropriate for their communication patterns. We argue that for individual non-commercial users, out-of-band verification of keys could be more economical than building trust in public key certificates issued by third parties

Metaphors considered harmful? An exploratory study of the effectiveness of functional metaphors for end-to-end encryption

“…Roth et al [19] suggested mail envelopes and postcards. Tong et al [20] proposed metaphors arguably couched in the jargon of domain experts, such as key, lock, seal and imprint.…”

Usable secure mailing lists with untrusted servers

“…We adopted the first approach for Study I because we assumed that understanding the GnuPG key trust assignment model would be very complex for users. This assumption was based in part on the complexity of this model as it allows for transitive trust establishment and in part on previous usability studies with secure email [12,28,32]. However, it turns out that the key signing approach is not appropriate based on our usability observations.…”

“…GnuPG allows two ways of achieving trust: signing keys or using the GnuPG trust model. We decided to study both ways of achieving trust with the initial assumption and default implementation that the first approach will work because prior usability studies in secure email indicated that users find it very challenging to deal with the GnuPG trust model [12,28,32]. For managing and using multiple keys we proposed a simple approach, namely, recommend that users use the same passphrase to protect all private keys and use the passphrase caching tools to manage that passphrase.…”

Unpopuläre E-Mail-Verschlüsselung – Auflösung des Henne-Ei-Problems

“…Diverse Autoren schlugen daher vor, auf Zertifizierungsstellen (CAs) zu verzichten und auf alternative Modelle wie bspw. selbst-signierte Zertifikate und Key Continuity Management (KCM) zurückzugreifen [3,10,11,12]. Die Nutzer müssten sich bei einem solchen System jedoch selbst darum kümmern, die Authentizität der initial verwendeten Schlüssel zu verifizieren, bspw.…”

“…Ein automatisierter Ansatz ohne diese Nachteile stammt von Google. 10 Generell hat sich unter Experten noch kein klarer Konsens gebildet, ob Nutzer dabei unterstützt werden sollen, die Funktionsweise von Public-Key-Systemen sowie entsprechende Risiken zu verstehen [13,14] bzw. hilfreiche mentale Modelle zu bilden [15], oder ob Benutzungsschnittstellen möglichst transparent gestaltet und die internen Prozesse vor den Nutzern verborgen werden sollten [4,16].…”