  Trust management systems often use registries to authenticate data, or form
trust decisions. Examples are revocation registries and trust status lists. By
introducing distributed ledgers (DLs), it is also possible to create
decentralized registries. A verifier then queries a node of the respective
ledger, e.g., to retrieve trust status information during the verification of a
credential. While this ensures trustworthy information, the process requires
the verifier to be online and the ledger node available. Additionally, the
connection from the verifier to the registry poses a privacy issue, as it leaks
information about the user's behavior.
  In this paper, we resolve these issues by extending existing ledger APIs to
support results that are trustworthy even in an offline setting. We do this by
introducing attestations of the ledger's state, issued by ledger nodes,
aggregatable into a collective attestation by all nodes. This attestation
enables a user to prove the provenance of DL-based data to an offline verifier.
Our approach is generic. So once deployed it serves as a basis for any use case
with an offline verifier. We also provide an implementation for the Ethereum
stack and evaluate it, demonstrating the practicability of our approach.
