An open, onchain C2PA manifest repository with a soft-binding resolver. Find who made an image from the image itself — after screenshots, crops and re-encoding.
Status: in build. Monad Metropolis, Track 04. Build window 1 Sep – 13 Oct 2026. This README is a placeholder; the one written for judges lands in Milestone 4 with measured numbers in it. Nothing below is a claim about working software yet.
C2PA already solved the format of content provenance. A Content Credential is a signed manifest describing where a piece of media came from — and it gets stripped by every screenshot, re-encode and platform that doesn't support the standard.
C2PA's answer is the durable Content Credential: a soft binding — an invisible watermark or a content fingerprint — that survives the copy, plus a Soft Binding Resolution API for looking the manifest back up inside a Manifest Repository.
The spec defines the API. It does not say who runs the repository. Today that is Adobe, Digimarc or Truepic: the lookup table deciding who made a piece of media is proprietary, per-vendor and deletable.
Grain is that manifest repository, onchain, permissionless, on Monad.
Not an NFT. Records are looked up by the content itself, not by a token id; ten thousand copies of an image resolve to one manifest; nothing is minted, traded or scarce. There is no ERC-721 anywhere in this project, including in licensing.
Grain is C2PA-compatible, not C2PA-certified. We implement the Soft Binding
Resolution API shape and the soft binding assertion structure. We do not run the
c2pa-rs signing stack with X.509 certificates from the C2PA trust list.
| Document | What it is |
|---|---|
| SPEC.md | Single source of truth for the build |
| UX_SPEC.md | The product surface, expanded from SPEC §8 |
| docs/ROBUSTNESS.md | Milestone 0 measurements — the constants everything depends on |
| docs/DEMO.md | The demo script |
| contracts/ | Interface definitions, with the design decisions in the comments |
| schemas/ | Manifest and resolution-result schemas |
MIT © 2026 Jerry Musaga, Musaga Technology