Prove which offers you authorized.
Give buyers a way to distinguish inventory you authorized from an offer that merely claims your name. Six short chapters, one fixed catalog, and every proof checkable in this browser.
Publish and sign
A fictional publisher, The Meridian Ledger, signs an article at publication. The signature names the property and the signing key, so anyone holding the article can confirm what was published and by whom.
The Meridian Ledger
Harbor District Approves the Port Expansion
- Content identity
- meridian-ledger/port-expansion-2026-07
- Property
- article_inventory
- Signer
- listing-2026-07
- Verified state
- Signed at publication. Verification passes.
Authorize the offer
The article backs a publisher-authorized ad-space listing. The offer terms below, six fields exactly, are canonicalized, hashed, and bound into the publisher listing signature. Change any field and the signed digest no longer matches.
The six signed terms behind the publisher listing proof.
- currency
- USD
- price
- 10
- pricing_model
- cpm
- pricing_option_id
- po-verified-encypher
- product_id
- verified-encypher
- property_id
- article_inventory
A counterfeit appears
Another seller re-uses the publisher listing signature for a different offer, syndicated inventory the publisher never authorized.
The counterfeit signature is cryptographically valid. What fails is the binding: the digest inside the signature covers the terms the publisher authorized, and the substituted terms hash to a different value. Signatures do not stop copying. Digest binding makes the substitution detectable by any buyer who checks.
The buyer checks, automatically
A buyer sets a policy once and the check runs on every offer. The table below is already computed under the strictest policy, Require proof. Prefer and Ignore are one tap away for comparison.
The buyer requires publisher-authorized provenance. Both authorized offers stay eligible and the buyer selects among them, in this run the compatibly signed offer. The substituted offer and the unproven rows are excluded, each with a reason a person can read.
| Offer | Provenance | Eligibility | Why |
|---|---|---|---|
Northfield Sports Daily Sports section ad space, signed with a compatible provenance key. verified-compatible / sports_inventory | Verified | EligibleSelected | Publisher listing proof verified. The terms are the ones the publisher signed. |
The Meridian Ledger Article backed ad space, signed by the publisher at publication. verified-encypher / article_inventory | Verified | Eligible | Publisher listing proof verified. The terms are the ones the publisher signed. |
Harbor Weather Report Ad space whose listing proof carries a signature that does not verify. invalid-proof / weather_inventory | Unverified | Excluded | The listing proof failed signature verification. |
Culture Notes Weekly Ad space offered without any listing proof. ordinary-unsigned / culture_inventory | Unverified | Excluded | No listing proof was presented for this offer. |
Syndicated Reseller Offer An offer that reuses a valid listing signature for different terms. counterfeit-listing / syndicated_inventory | Unverified | Excluded | Valid signature, substituted terms. The signed digest does not match this offer. |
The publisher win is eligibility and demand access: authorized offers stay in the running with buyers who check, and an offer that borrowed the publisher name is excluded with a stated reason.
The Require outcome, translated for your team
Commercial lead
Authorized offers stay eligible with buyers who require proof, and a substituted offer that uses your name is excluded with a stated reason.
Ad operations
Every row carries a reason you can read and forward. Exclusions come from failed checks on signed terms, not from a vendor score.
Editorial and product
The article is signed at publication. The listing proof extends that discipline to the ad-space offer the article backs.
Technical evaluator
Every artifact is one disclosure away: compact JWS, public JWK, key thumbprint, and two checks that run in this browser against committed sample vectors.
The signed receipt
The run ends with a receipt you can keep and forward. Four things were proved, and the evidence for each sits one disclosure away.
- Content proof: the article was signed at publication and verifies.
- Listing proof: the offer terms were bound into the publisher listing signature.
- Policy decision: every offer carries its eligibility and a stated reason under the buyer policy.
- Run-key receipt: the run record is signed with the sandbox run key.
Receipt fields, sanitized sample values.
- sandbox_run_key
- 1f6a2c3e-8d4b-4f0a-9c2d-5e7b1a3c9d40
- signature_verified
- true
- proof_scope
- schema_digest_and_run_key_signature
- record_key_thumbprint
- uM9xpCqvv29Z6IC-gh17R_AmwM_3YFOFdH6Po0a9760
Run a pilot
Test one property, ten URLs, and one buyer policy. Your team reads the outcomes in a table like the one above, with every proof attached.
More demos: try it yourself, no accountfor AI teamsfor publishersper-sentence signing liveprivate team walkthrough