# WAI Extension: Transparency Emission > Status: Draft. Adds an **external encoding** for WAI receipts so a party with > no WAI tooling can check them, and a registration profile so a receipt's > existence is independently witnessed. Strictly **additive**: the JWP receipt > chain is unchanged, and nothing here replaces it. > Keywords **MUST**, **MUST NOT**, **SHOULD**, **MAY** are RFC 2119/8174. ## 1. What is actually missing Not verifiability. An Ed25519 signature over a group Merkle root is checkable by anyone holding the publisher key, and [`jwp-receipts`](jwp-receipts.md) §3 specifies exactly how. Three properties are missing, and none of them is a signature property: - **Non-equivocation.** Nothing prevents a publisher showing one receipt chain to one party and a different chain to another. Both verify. - **Independent timestamping.** A receipt says when the publisher says it was made. - **Detectability of suppression.** A receipt that was never shown to anyone leaves no trace of its absence. These are log properties, not envelope properties, and they are why this extension exists. ## 2. The move, and its shape The family already owns both halves: a transparency log with consistency proofs exists, and JCR-1 (deterministic CBOR + COSE_Sign1, RFC 9052) is already the canonical receipt envelope across sibling standards. What nothing in the family has is a **standardised external encoding** that an outside auditor's off-the-shelf tooling can verify with no bespoke verifier. So the sequence is: bring WAI's receipts onto JCR-1 as its siblings already are, then emit in the standardised encodings on top. - A WAI receipt **SHOULD** be expressible as a JCR-1 envelope. This is alignment with the family, not a new format. - An implementation **MAY** additionally emit an RFC 9942 (COSE Receipts) encoding of a group receipt, and **MAY** use the RFC 9995 COSE Hash Envelope form where the payload is carried by hash rather than by value. - These emissions are **additional encodings of the same facts**. An implementation **MUST NOT** let the JWP chain and an emitted encoding disagree, and where they do, the JWP chain is authoritative and the emission is in error. ## 3. What is registered, and what is not SCITT registers per-artifact Signed Statements over an HTTP API. WAI emits per-object receipts at media-group cadence. These cadences do not match, and forcing them together would put a registration round-trip in the per-object path. - An implementation **MUST NOT** register per-object receipts individually. - An implementation **SHOULD** register the **group** receipt, or periodic checkpoints over the receipt chain, leaving the per-object receipt exactly where it is. - Registration **MUST NOT** be a precondition for a receipt being valid. An unregistered receipt is a receipt whose existence is unwitnessed, not a receipt that is wrong. - A registration **MAY** be recorded on the receipt chain as a `log-inclusion` claim ([`jwp-receipts`](jwp-receipts.md) §2.4.7): its subject is the registered receipt's link hash, and its body carries the Transparency Service's receipt verbatim with the profile it was registered against. Accepting that claim is not verifying the inclusion (§6). - An origin that publishes a key log ([`jwp-receipts`](jwp-receipts.md) §7) **SHOULD** register each revision as it registers group receipts. A fork in the log is then visible to every Relying Party that checks the log, not only to one that happened to hold both branches. The registration witnesses a revision; it does not anchor the origin (§6). The checking party is the **Relying Party** in the terminology of the SCITT architecture; this extension uses that term rather than coining another. ## 4. The hash-algorithm constraint RFC 9995's `payload_hash_alg` takes an identifier from the COSE Algorithms registry. **BLAKE3 — which `jwp-receipts` §2.1 uses throughout — does not appear in that registry.** This is a real constraint, not a detail to be waved through: - An implementation **MUST NOT** emit a COSE Hash Envelope naming BLAKE3 by an unregistered or invented identifier. An identifier a Relying Party cannot resolve defeats the entire purpose of emitting in a standard encoding. - Until a registration exists, an implementation **MUST** either omit the hash envelope form, or carry a **second digest** under a registered algorithm alongside the BLAKE3 commitment, stating plainly that the two cover the same bytes. - A dual-hash carry **MUST NOT** be presented as evidence that BLAKE3 is registered. Registering BLAKE3 in the COSE Algorithms registry is a separate action with its own process, and this extension does not assume its outcome. ## 5. Stage discipline The referenced work is at mixed maturity, and an implementation **MUST NOT** present any of it as more settled than it is: | document | status | |---|---| | SCITT architecture (RFC 9943) | Standards Track, published | | COSE Receipts (RFC 9942) | Standards Track, published | | COSE Hash Envelope (RFC 9995) | published | | SCRAPI (registration/resolution API) | approved, in the RFC Editor queue | | a concrete log profile | Working Group Last Call — **not ratified** | An implementation **MUST NOT** describe the log profile as ratified, and **SHOULD** state which profile it registered against, since a Relying Party cannot check a proof without knowing the log's rules. ## 6. What this does not do - It does **not** replace the JWP receipt chain, and it does **not** move the per-object commitment anywhere. - It does **not** make registration a trust anchor. A Transparency Service witnesses that a receipt existed at a time; it does not attest that the receipt is true, and an implementation **MUST NOT** report registration as verification. - It does **not** solve key discovery. [`jwp-receipts`](jwp-receipts.md) §7 does, for a signer that names its web origin and publishes its keys there. A log entry naming a key the Relying Party cannot confirm under that section is still unconfirmed, and registering a key-log revision witnesses it without anchoring the origin.