User-visible cryptography in email and web scenarios

This paper aims to classify different types of “user-visible cryptography” and evaluate the value of user-visible cryptographic mechanisms in typical email and web scenarios for non-expert IT users.

The authors review the existing literature, and then identify user stories typical to their users of interest. They analyse the risks, mitigations of risks and the limits of those mitigations in the user stories.

The scenarios identified suggest that background, opportunistic encryption has value, but more explicit, user-visible cryptographic mechanisms do not provide any further mitigation. Other mechanisms beyond technological mitigations provide the required mitigation for the users.

Further work should be carried out on the trust issues with trusted third parties, as they are intrinsic to global, automated cryptographic mechanisms. The authors suggest that deployed systems should rely on automation rather than explicit user involvement; further work on how best to involve users effectively remains valuable.

Deployed systems should rely on automation rather than explicit user dialogues. This follows from recognised aspects of user behaviour, such as ignoring dialogues and unconsciously making a holistic assessment of risk that is mostly mitigated by social factors.

The user populations concerned rely significantly on the existing legal and social infrastructure to mitigate some risks, such as those associated with e-commerce. Guarantees from third parties and the existence of fallback procedures improve user confidence.

This work uses user stories as a basis for a holistic review of the issues surrounding the use of cryptography. The authors concentrate on a relatively large population (non-expert IT users) carrying out typical tasks (web and email).