  In this paper, we introduce a data capsule model, a self-contained and
self-enforcing data container based on emerging self-sovereign identity
standards, blockchain, and attribute-based encryption. A data capsule allows
for a transparent, privacy-respecting, and secure exchange of personal data,
enabling a progressive trust scheme in a semi-trusted environment. Each data
capsule is bundled with its own access policy structure and verifiable data,
drastically reducing the number of interactions needed among the user, the
service providers, and data custodians. Moreover, by relying on the
decentralized nature of blockchain and attribute-based encryption our proposed
model ensures the access policies published by service providers are public,
transparent, and strictly followed.
