David Bauer, Douglas M. Blough, Apurva Mohan,
Redactable Signatures on Data with Dependencies
Storage of personal information by service providers risks privacy
loss from data breaches. Our prior work on minimal disclosure credentials
presented a mechanism to limit the amount of personal
information provided. In that work, personal data was broken into
individual claims, which can be released in arbitrary subsets while still being
cryptographically verifiable. In applying that work, we encountered the
problem of connections between claims, which manifest as release dependencies.
In this work, we provide an efficient way to provide
minimal disclosure, but with cryptographic enforcement of dependencies between
claims, as specified by the claims certifier. This provides a mechanism for
redactable signatures on data with release dependencies. We show that an
implementation of our scheme can verify thousands of dependent claims in tens
of milliseconds. We also describe ongoing work in which the approach is being
used within a larger system for dispensing personal health records.