Usable Secure Email Communications - Criteria and Evaluation of Existing Approaches

Email communication has been used for many years and replaces more and more traditional letters. Compared to postal service the mail service is easier, faster and free of charge. However, the standard email is from a security point of view comparable to post cards and not to letters. While end-to-end secure email communication is possible with PGP and S/MIME, only few people use it due to a lack of awareness, low usability, and lacking an understanding of PKIs. Recently, some new approaches for secure email communication have been proposed. In order to enable a comparison of all these different email services we define security, usability, and interoperability criteria and apply them to existing approaches. Based on the result, we propose future directives for usable secure email communication.