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Every Ed25519 signature WAI defines is verified strictly, in order: a canonical key, a key not of small order, S < L, R not of small order, and the cofactorless equation with R compared byte for byte. OER/2's chain signature keeps the rule oer-receipts §5 settles. jwp-receipts §3.1 step 3, http-delivery's playlist receipt and packaging's receipt cite it instead of restating it; the worlds, avatars, feeds, spatial-audio, haptics, volumetric, score, film, provenance, ternary and quantum receipt texts cite it where they name their signature. CHANGELOG records the sweep. Co-Authored-By: Claude Opus 5.5 <[email protected]>
102 lines
5 KiB
Markdown
102 lines
5 KiB
Markdown
# WAI Extension: Asset Provenance
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> Status: Draft. Lever 4 — content-addressing + receipts + measured
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> energy for content that cannot be reduced to instructions. WAI does not
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> reconstruct the asset; it carries the opaque bytes and a signed,
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> energy-accounted lineage. Conformance is **content-hash-equivalence**
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> (recompute, compare) + signature validity. Reference impl: the
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> `provenance` feature of `wai-rs`; tooling: `wai_prov`; live sink:
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> wai.transaction.science/provenance.
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Keywords **MUST**, **MUST NOT**, **SHOULD**, **MAY** are RFC 2119/8174.
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## 1. Scope and model
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A `wai.asset.provenance` object is **not a content capability** — it is a
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JWP receipt profile *about* a carried asset, the way `jwp-receipts` is.
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The asset itself declares an ordinary capability (`wai.image.jpeg`,
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`wai.audio.flac`, …) and WAI carries it unchanged; the provenance receipt
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adds three things the carried bytes do not have on their own:
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1. **Tamper-evidence** — the asset is content-addressed
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([`asset_content_hash`], BLAKE3 over the complete WAI envelope); a
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verifier recomputes it and compares.
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2. **Lineage** — an ordered chain of processing **steps**, each binding
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its input and output content hashes, signed as one group.
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3. **Energy accounting** — each step carries its measured/declared
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microjoules; the receipt totals them.
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This is the "verifies whatever it carries" half of the thesis, for the
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content the reconstruct half cannot touch. WAI never decodes the asset —
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a sink hands the bytes to whatever native element renders that media.
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In scope: the step model, the `AssetReceipt` group, the verification
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obligations. Out of scope: a transport; a capture device; the asset's own
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codec (it is opaque here).
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## 2. The step
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A `ProvStep` is one transformation in the asset's lineage:
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| field | meaning |
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|---|---|
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| `op` | operation, e.g. `"origin.synthesize"`, `"encode.jpeg"`, `"derive.thumbnail"` |
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| `input_hash` | content hash of the input (all-zero for an originating step) |
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| `output_hash` | content hash of the output |
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| `work` | exact deterministic work (pixels, samples) |
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| `joules_micro` | measured/carried microjoules; `0` is the unmetered marker, never 0 J ([energy-measurement](energy-measurement.md) §2) |
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Step content hash:
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`BLAKE3("wai:prov-step\x01" || op_len | op | input | output | work | joules)`.
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## 3. The receipt (`AssetReceipt`)
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A JWP group: the asset's content hash is the identity, the per-step
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hashes are the Merkle leaves (JWP's exact `moq-jwp:merkle-{leaf,node}`
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domains), and one Ed25519 signature covers a profile payload carrying the
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asset hash, the declared `media` + `capability`, the Merkle root, the
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step chain, and the total joules. It chains across edits via
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`parent_receipt_hash`, like the worlds / audio / haptic / splat receipts.
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## 4. Conformance
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> A conforming verifier MUST: (a) recompute the asset's content hash and
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> require it equal the receipt's `asset_hash`; (b) require the step chain
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> be linked — each step's `input_hash` equals the previous step's
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> `output_hash`, and the final `output_hash` equals `asset_hash`; (c)
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> recompute the Merkle root from the step hashes; (d) verify the Ed25519
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> signature as SPEC §7 *Signatures* requires. A failure at any point is a failure — the asset is reported
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> unverified, never "probably fine".
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There is no tolerance parameter: the content hash matches or it does not.
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## 5. Energy is measured, never invented
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`joules_micro` per step is **carried** from a meter, exactly as the other
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receipts carry it: `wai_prov` measures the real CPU energy of each encode
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(IOReport via macmon, no sudo) and signs the figure. An unmetered step
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carries the unmetered marker `0`, which a reader presents as unmetered and never
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totals as zero joules. The receipt never derives energy it did not measure.
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Each step's figure carries its acquisition class as an optional label
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([energy-measurement](energy-measurement.md) §2.8), because the steps of one
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lineage can be metered by different parties in different ways. A labelled step
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binds its class into its leaf hash; a step with no label keeps its legacy leaf
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and its figure is unlabelled. `wai_prov` labels each encode it measures
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`OnChipCounter`, with its declared uncertainty, and records an encode whose
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measurement fails the §4 ratio or the power reader's liveness (§3.1) as
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unmetered, and writes a measurement report for each step it measured
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(energy-measurement §6). `total_joules_micro` carries no class of its own, and a
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total over steps that include an unmetered one covers only the measured steps
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(`Partial`).
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## Appendix
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The reconstruct classes prove WAI can ship a world, a sound, a body, a
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volume as instructions and have every sink rebuild them identically.
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Provenance proves the complement: for the photograph that is just a
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photograph, WAI still adds something a bare file cannot — a tamper-evident
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identity, a signed lineage, and an honest energy ledger — without ever
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pretending to understand the pixels. Carries whatever it can reconstruct;
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verifies whatever it carries.
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[`asset_content_hash`]: ../wai-rs/src/world/mod.rs
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