The byte-exact decoder's payoff: a provenance binding neural-coded media normally
cannot carry. A hard binding hashes asset bytes; over the decoded image it was
impossible, because a neural decode isn't reproducible — JPEG AI's own normative
conformance point is the entropy-decoder output (not pixels), and its multi-branch
design lets one codestream reconstruct three ways, so a decoded-pixel hash isn't
portable. Provenance over the rendered result has had to fall back to fuzzy soft
bindings.
WAI decodes to RGB deterministically, which restores a stable, portable decoded-pixel
hash — pinning one reconstruction is a determinism guarantee beyond what the base
standard requires. This adds:
- reconstruction_binding (feature provenance): ReconstructionBinding::bind hashes the
canonical RGB8 buffer (row-major, no padding) under a descriptor that pins the
reproducible decode (synthesis branch / profile / level / layout / color space);
verify re-decodes-and-compares. SHA-256 — the C2PA default — so the digest is
reproducible by any validator. bind/verify/tamper/JSON tests pass.
- extensions/reconstruction-binding.md: the standard. Decode-equivalence conformance;
carriage as a custom C2PA/JPEG-Trust assertion (science.transaction.wai.hash.
reconstruction, CBOR, beside the standard byte-binding); and a note that a signed
binding over reconstructed content is a substrate for machine-readable AI-content
marking (e.g. EU AI Act Article 50, from 2 Aug 2026) — stated as a capability, not a
legal claim.
It is the reconstruct-side analogue of the provenance extension: that binds the opaque
carried bytes; this binds the reconstructed pixels.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
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