Anchoring and resolution: overview

These guides explain how an application publishes data with its operator, how the published data can reference other data, and how everything is turned back into a single, verifiable result.

The running example is an assignment of receivable between three parties: the assignor (cédant), the assignee (cessionnaire) and the debtor.

The big picture

1. Your application anchors data. Each anchoring produces a microblock in a virtual blockchain.
2. A microblock can contain special keys that point to other data: another microblock, off-chain data, a signed payload or a verifiable presentation.
3. Later, the resolver reads a microblock, follows every special key, and returns a resolutionProof: the fully resolved data, together with the proofs that back each part of it.
4. Anyone holding that resolutionProof can submit it to the proof checker, which verifies every proof and its consistency with the data.

Special keys

A special key is an object field whose name starts and ends with a double underscore. The operator and the resolver give them a meaning.

Key	You put it in anchored data to…	Resolution result	Guide
__resolution_link__	Reference another microblock.	The referenced data replaces the link.	Reference microblocks
__digest__	Anchor only the hash of data stored off-chain.	The plaintext replaces the digest, once checked.	Off-chain data
__digest_data__	Anchor the plaintext of off-chain data next to its link (re-anchoring).	The plaintext is checked against the referenced digest.	Off-chain data
__signature__	Anchor a payload signed by another operator.	The payload replaces the signature, once checked.	Signed data
__vp__	Anchor a verifiable presentation.	The credential claims replace the presentation.	Verifiable credentials

Where to start

1. Anchor data on-chain: the simplest method, and the basis of the others.
2. Pick the guides that match your needs (references, off-chain data, signatures, credentials).
3. Resolve and check proofs to give your users something verifiable.