Fidacy Artifact Anchoring, existence and integrity proof by hash

AI can forge a convincing document in seconds, which makes "is this file the original?" the question every contract, invoice and claim now faces. This skill answers it by hash: the file never leaves your machine, only its SHA-256 travels, and that digest lands on a tamper-evident chain checkpointed to the Bitcoin blockchain. Later, anyone holding the file recomputes the hash and checks it publicly, with zero trust in Fidacy or in you.

When to use this skill

The moment an artifact becomes final: a signed contract, an invoice you are about to pay, a claim document you received, a report you generated, a prescription, an image used as evidence. Anchor first, act second.

How to use it

1. You need the Fidacy MCP server (npx -y @fidacy/mcp) with an engine API key (free at https://app.fidacy.com/signup, scope assess:write).

2. Anchor: call the anchor_artifact tool with the file path and a kind (contract, invoice, prescription, claim, document, image, audio, video). The tool streams the SHA-256 locally and registers only the digest. You get back a signed receipt (JWS) and the anchor status.

3. Verify, any time, three ways, none needing an account:

   • Call the check_artifact tool with the file path or digest.
   • Drop the file at https://fidacy.com/verify (hashed in the browser, never uploaded).
   • Query the public API: GET https://api.fidacy.com/v1/verify/artifact?sha256=<hex>.

A freshly anchored digest is on the tamper-evident chain immediately and shows "pending Bitcoin confirmation" until the next checkpoint confirms (about one to two hours). One changed byte in the file produces a completely different hash; that mismatch is the forgery signal.

What this is not

Not storage (Fidacy never holds the file), not a signature on the content's truth (it proves integrity since anchoring, not that the contract is fair), and not custody of anything.