ORIGINPROOF

Cryptographic file provenance using Ed25519 + SHA-256. Sign any file to create a .oproof sidecar that proves who created it and that it hasn't been tampered with. Verification is offline — no server, no blockchain, no account needed.

A companion Chrome extension lets anyone verify .oproof files without installing the CLI.

Install

npm install
npm run build

Requires Node.js >= 22.

CLI

Initialize a signing identity

npx originproof init

Generates an Ed25519 keypair at ~/.originproof/keys/ and prints your key ID. Idempotent — running it again reuses existing keys.

Sign a file

npx originproof sign photo.jpg

Creates photo.jpg.oproof alongside the original file.

Verify a file

npx originproof verify photo.jpg

Checks photo.jpg against photo.jpg.oproof. Prints one of four results:

Result	Meaning	Exit code
VERIFIED	File is authentic and unmodified	0
HASH_MISMATCH	File has been modified since signing	2
INVALID_SIGNATURE	Signature doesn't match the embedded public key	3
MALFORMED_PROOF	Proof file is missing, corrupt, or has an unsupported version	4

Exit code 1 is reserved for operational errors (missing file, uninitialized keystore, etc.). Distinct codes let scripts distinguish failure types.

To verify with a proof at a different path:

npx originproof verify photo.jpg /path/to/photo.jpg.oproof

Web UI

npm start

Opens a local server at http://localhost:3000 with Sign and Verify tabs.

Env var	Default	Purpose
PORT	3000	Server port
CORS_ORIGIN	(none)	Set to allow cross-origin API access (e.g. http://localhost:5173)

API routes are rate-limited to 100 requests per 15 minutes per IP.

.oproof format

A .oproof file is JSON:

{
  "version": "1.0.0",
  "file": {
    "name": "photo.jpg",
    "size": 2048576,
    "algorithm": "sha256",
    "hash": "b94d27b..."
  },
  "signer": {
    "keyId": "082788...",
    "publicKey": "-----BEGIN PUBLIC KEY-----\n..."
  },
  "createdAt": "2026-04-09T14:30:00.000Z",
  "signature": "7qu1Y1c3..."
}

The signature is an Ed25519 signature over the canonical (key-sorted, compact) JSON of everything except the signature field itself. The public key is embedded, so verification is self-contained.

API

All endpoints return JSON. Verification results always return HTTP 200 — the status code reflects whether the operation succeeded, not whether the file is authentic.

Method	Path	Request	Response
POST	/api/sign	multipart/form-data with field file	ProofRecord JSON
POST	/api/verify	multipart/form-data with fields file and proof	{ status, message, proof? }
GET	/api/identity	—	{ keyId, algorithm, createdAt }
GET	/api/health	—	{ status: "ok", version }

Upload limit: 100 MB.

Tests

npm test

Runs 37 tests covering hash, proof serialization, keystore, signing, and verification (including tamper detection, key substitution, and insertion-order invariance).