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A receipt is only useful if you don’t have to trust QED Proof to believe it. The reference checker in the open-source qed-proof-core repository verifies a receipt entirely offline (plus one optional RPC call for the anchor), against nothing but the receipt itself and the issuer’s published keys.

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What it checks

  1. Parses the receipt and rejects an unsupported spec version.
  2. Resolves issuer.key_id against the issuer’s published key set, checks the key’s validity window, and verifies the Ed25519 signature over the receipt body.
  3. Recomputes the claim digest and confirms it matches.
  4. If a proof is present, verifies the Merkle inclusion proof — and, if you pass an RPC URL, verifies the on-chain anchor too (see anchoring).
  5. Reports the achieved trust level and the verdict.

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Running it

From a checkout of the qed-proof-core repository:
Leave off --rpc to check everything except the anchor (signature, schema, and Merkle inclusion), which reports the anchor as "not_checked_offline" rather than skipping it silently. The tool prints a JSON report, for example:
valid is only true if every applicable check passes. achieved_trust_level is what the checker could actually confirm — 2 requires both a verified inclusion proof and a verified on-chain anchor; without --rpc, the ceiling is 1.

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Change entries and policy

The log holds a second kind of entry besides receipts: a change entry, recorded when something changed at a destination that no claim explained. It has no claim and no verdict, and it is signed under its own domain so it can never pass as a receipt. The same checker handles it; the report adds "entry_kind": "change" and has no claim_digest check. A receipt or change entry made by a pipeline carries a policy: the pipeline’s id, version and digest. Give the checker the pipeline document and it confirms the digest, id and version match:
The report then has "policy": true (or false, which makes the entry invalid). Without the document it reports "policy": "not_checked" and the entry stays valid on its other checks.

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In the browser

Until then, use the command-line checker above, or point any RFC 6962-compatible Merkle verifier and an Ed25519 signature check at the receipt’s body, signature, and proof per the receipt spec.