@apertrue/trust-list

Merkle tree operations for C2PA signer verification. Manages a trust list of intermediate CA certificates and generates inclusion proofs for ZK circuits.

Installation

npm install @apertrue/trust-list

How It Works

The trust list is a Merkle tree of intermediate CA certificate public keys. When a user uploads a C2PA-signed image, the ZK circuit proves that the signing certificate's issuer is in this tree — without revealing which specific certificate was used.

Hash Schemes

Different certificate algorithm families use different hash schemes to fit within the BN254 scalar field:

| Algorithm | Key Representation | Hash Scheme | |-----------|-------------------|-------------| | RSA-2048 | 18 BN254-field limbs | Two-level tree: pedersen([hash_lo, hash_hi]) | | RSA-4096 | 8 BN254-field limbs | Flat: pedersen(limbs[0..8]) | | ECDSA P-256 | (x, y) coordinates | pedersen([x, y]) | | ECDSA P-384 | (x, y) mod BN254 | pedersen([x % BN254, y % BN254]) | | ProofMode (2-cert) | DN bytes | hashIssuerDN() — packs DN into 31-byte field chunks |

Oracle Bundle

The trust list is distributed as a signed oracle bundle (bundle.json) with multi-signature governance. New intermediate CAs are added through an append-only promotion process.

Usage

import { TrustList } from '@apertrue/trust-list';

const trustList = await TrustList.fromBundle(bundleJson);

// Generate Merkle inclusion proof for a certificate
const proof = trustList.generateProof(certificateLeafHash);
// Returns: { root, pathElements, pathIndices }

Building

npm run build    # Compile TypeScript

License

Apache 2.0 — see LICENSE.