@smartledger/notaryhash

Client SDK for NotaryHash — anchor a signed hash to the BSV blockchain and verify the resulting certificate, in any Node.js app.

• Privacy-preserving — you hash and sign locally; only the hash, signature, and public key are ever sent. Your document and private key never leave your process.
• Post-quantum — ECDSA plus ML-DSA (FIPS 204) and SLH-DSA (FIPS 205).
• Trustless verification — verify a certificate against Bitcoin block headers alone, with no dependency on the issuing service.
• Tiny — depends only on @noble crypto. No server code.

npm install @smartledger/notaryhash

Notarize (sign locally, anchor via a service)

import { generateKey, notarizeBytes } from '@smartledger/notaryhash';
import { readFileSync } from 'node:fs';

const key = generateKey('ECDSA-secp256k1'); // keep key.privateKey secret — it never leaves you

const { certificate } = await notarizeBytes(readFileSync('contract.pdf'), key.privateKey, {
  url: 'https://notaryhash.com',
  apiKey: process.env.NOTARYHASH_API_KEY, // write endpoint requires a key
});

console.log('anchored:', certificate.anchor.txid);

Swap generateKey('ML-DSA-65') (or any of the 16 algorithms) for post-quantum signatures — pass the same algorithm to notarizeBytes via the options.

Verify (offline, against block headers — no trust in the service)

import { verifyCertificateStandalone, MultiSourceHeaderProvider, WocHeaderProvider } from '@smartledger/notaryhash';

const headers = new MultiSourceHeaderProvider([
  new WocHeaderProvider('https://api.whatsonchain.com/v1/bsv/main'),
  // add more independent sources for a real cross-check
]);

const verdict = await verifyCertificateStandalone(certificate, headers);
// { ok, signatureValid, proofHashValid, anchorValid, verificationMethod: 'spv', blockHeight, reasons }

verifyCertificateOffline(certificate) checks the signature and proof hash with no network at all (the anchor check needs a block header).

CLI

This package also installs a notaryhash CLI:

notaryhash keygen   --algorithm ECDSA-secp256k1 --out key.json
notaryhash notarize contract.pdf --algorithm ECDSA-secp256k1 \
  --key "$(node -e "console.log(require('./key.json').privateKey)")" \
  --url https://notaryhash.com --api-key "$NOTARYHASH_API_KEY"
notaryhash verify cert.json --offline

What this SDK does and does not do

It produces and verifies proofs. It does not run the notarization service (anchoring, fee-paying wallet, key issuance) — that is operated by a NotaryHash provider such as notaryhash.com. Verification is free and open; anchoring goes through a provider's authenticated API.

See the protocol specification (BRC-141).

License

MIT © SmartLedger.Technology