Digital Dotted Lines: Design and Evaluation of a Prototype for Digitally Signing Documents Using Identity Wallets

TL;DR

This paper presents a prototype for digitally signing documents using identity wallets, aiming to improve usability and security, but highlights challenges in user trust and interpretation of signature information.

Contribution

The paper introduces a novel prototype for digital signatures with identity wallets and evaluates its usability through user testing, revealing trust issues and interpretation challenges.

Findings

Participants generally satisfied with the prototype.

Users misunderstood signature information, leading to unwarranted trust.

Trust issues pose security challenges for digital signatures.

Abstract

Documents are largely stored and shared digitally. Yet, digital documents are still commonly signed using (copies of) handwritten signatures, which are sensitive to fraud. Though secure, cryptography-based signature solutions exist, they are hardly used due to usability issues. This paper proposes to use digital identity wallets for securely and intuitively signing digital documents with verified personal data. Using expert feedback, we implemented this vision in an interactive prototype. The prototype was assessed in a moderated usability test (N = 15) and a subsequent unmoderated remote usability test (N = 99). While participants generally expressed satisfaction with the system, they also misunderstood how to interpret the signature information displayed by the prototype. Specifically, signed documents were also trusted when the document was signed with irrelevant personal data of the signer. We conclude that such unwarranted trust forms a threat to usable digital signatures and requires attention by the usable security community.