@article{1090416,
 author = {Volker Roth and Tobias Straub and Kai Richter},
 title = {Security and usability engineering with particular attention to electronic mail},
 journal = {Int. J. Hum.-Comput. Stud.},
 volume = {63},
 number = {1-2},
 year = {2005},
 issn = {1071-5819},
 pages = {51--73},
 doi = {http://dx.doi.org/10.1016/j.ijhcs.2005.04.015},
 publisher = {Academic Press, Inc.},
 address = {Duluth, MN, USA},
 }

doi:10.1016/j.ijhcs.2005.04.015       
Copyright © 2005 Elsevier Ltd All rights reserved. 
Security and usability engineering with particular attention to electronic mail 

Volker Roth, Tobias Straub and Kai Richter 
OGM Laboratory LLC, Omaha, NE 68106, USA
Technische Universität Darmstadt, Hochschulstr. 10, 64289 Darmstadt, Germany
Zentrum für Graphische Datenverarbeitung e.V., Fraunhoferstr. 5, 64283
Darmstadt, Germany 

Available online 31 May 2005. 

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. 

Keywords: Security engineering; Usability and security; Secure electronic mail;
Human–computer interaction; Transparent encryption; Transparent digital
signatures