@gsengai/c2pa

C2PA Content Credentials signing for AI-generated images (PNG/JPEG): signed manifests declaring AI generation, pre-existing manifests preserved as chained ingredients (never overwritten), one evidence record per signing. Supports compliance with EU AI Act Article 50 and California SB 942.

Part of gsengai, open-source transparency and provenance tooling for AI product teams.

Install

pnpm add @gsengai/c2pa @gsengai/core

Requires Node ≥ 22.

Platform support: works out of the box on macOS (Apple Silicon). On Linux, Windows, and Intel macs, install c2patool once (prebuilt binaries or cargo install c2patool) and have it on PATH — the fallback backend is auto-detected and produces equivalent manifests. GSENGAI_C2PATOOL_PATH or the c2patoolPath option point at a specific binary; GSENGAI_C2PA_BACKEND=native|c2patool forces a backend. Details in docs/production.md.

Usage

import { createEvidenceStore } from "@gsengai/core";
import { createImageSigner, readManifest } from "@gsengai/c2pa";

const store = createEvidenceStore({ path: "./evidence.db" });
const signer = createImageSigner({ store, systemId: "my-image-feature" });
// ⚠ no certPath/keyPath given → bundled DEV certificates + a one-time warning

const { record, manifestLabel } = await signer.signImage({
  input: "./generated.png",
  output: "./generated.signed.png",
  model: "gpt-image-1",
});
console.log(record); // evidence record: modality 'image', marking ['c2pa']

// Verify locally: manifest label, ingredient chain, exact validation codes
console.log(await readManifest("./generated.signed.png"));

The manifest carries a c2pa.created action with digitalSourceType: trainedAlgorithmicMedia, the model identifier, and a timestamp. If the input already carries a C2PA manifest, signImage never overwrites it — the existing manifest is chained as the parent ingredient and stays resolvable. Signing and reading are fully offline: no OCSP, no remote manifest fetches, no TSA.

The bundled development certificates are untrusted by public validators by design — for integration testing only. For production, pass your own certPath / keyPath; see docs/CERTIFICATES.md.

Manifests can be removed downstream by re-encoding, screenshots, or platform uploads — that is exactly why the evidence log exists.

Positioning

This package supports compliance with EU AI Act Article 50 and California SB 942. It does not make you compliant — compliance depends on your system, your deployment context, and your processes. It is not legal advice.

License

Apache-2.0