ee44f1871c
The reach receipt workloads verified a receipt copied from the site, written by wai_prov before its signer id became a label: it named a domain under did:web, which signer_ids_are_labels refuses (jwp-receipts §7.1, §7.8). wai_prov gains --carry <receipt.json>: it measures nothing, carries each step's figure and label from an earlier receipt for the same lineage, and signs them with its published test seed (0x70 x 32) under its label did:example:wai-prov. It refuses a receipt that does not verify or whose steps are not this run's (operations, input and output hashes, work), and writes no report. The vector is regenerated with it: the envelope is unchanged, the figures are the ones wai_prov first measured for these bytes, and carrying the receipt onto itself writes both files again byte for byte. The vector's README states how it is made and the command. Co-Authored-By: Claude Opus 5.5 <[email protected]>
5.2 KiB
WAI Extension: Asset Provenance
Status: Draft. Lever 4 — content-addressing + receipts + measured energy for content that cannot be reduced to instructions. WAI does not reconstruct the asset; it carries the opaque bytes and a signed, energy-accounted lineage. Conformance is content-hash-equivalence (recompute, compare) + signature validity. Reference impl: the
provenancefeature ofwai-rs; tooling:wai_prov; live sink: wai.transaction.science/provenance. Keywords MUST, MUST NOT, SHOULD, MAY are RFC 2119/8174.
1. Scope and model
A wai.asset.provenance object is not a content capability — it is a
JWP receipt profile about a carried asset, the way jwp-receipts is.
The asset itself declares an ordinary capability (wai.image.jpeg,
wai.audio.flac, …) and WAI carries it unchanged; the provenance receipt
adds three things the carried bytes do not have on their own:
- Tamper-evidence — the asset is content-addressed
(
asset_content_hash, BLAKE3 over the complete WAI envelope); a verifier recomputes it and compares. - Lineage — an ordered chain of processing steps, each binding its input and output content hashes, signed as one group.
- Energy accounting — each step carries its measured/declared microjoules; the receipt totals them.
This is the "verifies whatever it carries" half of the thesis, for the content the reconstruct half cannot touch. WAI never decodes the asset — a sink hands the bytes to whatever native element renders that media.
In scope: the step model, the AssetReceipt group, the verification
obligations. Out of scope: a transport; a capture device; the asset's own
codec (it is opaque here).
2. The step
A ProvStep is one transformation in the asset's lineage:
| field | meaning |
|---|---|
op |
operation, e.g. "origin.synthesize", "encode.jpeg", "derive.thumbnail" |
input_hash |
content hash of the input (all-zero for an originating step) |
output_hash |
content hash of the output |
work |
exact deterministic work (pixels, samples) |
joules_micro |
measured/carried microjoules; 0 is the unmetered marker, never 0 J (energy-measurement §2) |
Step content hash:
BLAKE3("wai:prov-step\x01" || op_len | op | input | output | work | joules).
3. The receipt (AssetReceipt)
A JWP group: the asset's content hash is the identity, the per-step
hashes are the Merkle leaves (JWP's exact moq-jwp:merkle-{leaf,node}
domains), and one Ed25519 signature covers a profile payload carrying the
asset hash, the declared media + capability, the Merkle root, the
step chain, and the total joules. It chains across edits via
parent_receipt_hash, like the worlds / audio / haptic / splat receipts.
4. Conformance
A conforming verifier MUST: (a) recompute the asset's content hash and require it equal the receipt's
asset_hash; (b) require the step chain be linked — each step'sinput_hashequals the previous step'soutput_hash, and the finaloutput_hashequalsasset_hash; (c) recompute the Merkle root from the step hashes; (d) verify the Ed25519 signature as SPEC §7 Signatures requires. A failure at any point is a failure — the asset is reported unverified, never "probably fine".
There is no tolerance parameter: the content hash matches or it does not.
5. Energy is measured, never invented
joules_micro per step is carried from a meter, exactly as the other
receipts carry it: wai_prov measures the real CPU energy of each encode
(IOReport via macmon, no sudo) and signs the figure. An unmetered step
carries the unmetered marker 0, which a reader presents as unmetered and never
totals as zero joules. The receipt never derives energy it did not measure.
Each step's figure carries its acquisition class as an optional label
(energy-measurement §2.8), because the steps of one
lineage can be metered by different parties in different ways. A labelled step
binds its class into its leaf hash; a step with no label keeps its legacy leaf
and its figure is unlabelled. wai_prov labels each encode it measures
OnChipCounter, with its declared uncertainty, and records an encode whose
measurement fails the §4 ratio or the power reader's liveness (§3.1) as
unmetered, and writes a measurement report for each step it measured
(energy-measurement §6). With --carry it measures nothing: it carries each
figure, and its label, from an earlier receipt for the same lineage, which must
verify and whose steps must have the same operations, hashes and work, and writes
no report. total_joules_micro carries no class of its own, and a
total over steps that include an unmetered one covers only the measured steps
(Partial).
Appendix
The reconstruct classes prove WAI can ship a world, a sound, a body, a volume as instructions and have every sink rebuild them identically. Provenance proves the complement: for the photograph that is just a photograph, WAI still adds something a bare file cannot — a tamper-evident identity, a signed lineage, and an honest energy ledger — without ever pretending to understand the pixels. Carries whatever it can reconstruct; verifies whatever it carries.