verify-proof (Node.js)

Verify blockchain-anchored timestamp proofs offline. Zero dependencies — only node:crypto and node:fs.

This is the Node.js port of the verify-proof Python package. Both share the same JSON proof format and the same verification semantics, tested against the same fixtures, so a proof verified by one is verified by the other.

Works with proofs from ProofLedger and compatible blockchain timestamping services.

Install

npm install -g verify-proof     # CLI
npm install verify-proof        # library

Or run without installing:

npx verify-proof hash document.pdf

CLI

# Compute a file's SHA-256 (the file never leaves your machine)
verify-proof hash document.pdf

# Verify a file against a blockchain proof
verify-proof verify document.pdf --proof proof.json
# VERIFIED: Proof verified. File hash matches blockchain anchor on polygon. ...

Exit code 0 on verified, 1 on any failure — safe to gate a CI job on.

Library

import { hashFile, verifyProof, loadProof } from "verify-proof";

const digest = await hashFile("document.pdf");           // streaming, any size
const result = verifyProof(digest, loadProof("proof.json"));

if (result.verified) {
  console.log(result.message);        // includes chain, tx id, anchored-at
} else {
  console.error(result.error);        // hash mismatch, missing anchor, ...
}

What verification checks

1. The file's SHA-256, computed locally, matches the proof's recorded hash
2. The Merkle path (when present) recomputes to its root
3. The proof references a blockchain transaction, whose timestamp is the evidence

What it does not prove

A proof establishes that a digest existed no later than the block it was anchored in. It does not prove who created the file, that it is original, or that its contents are true.

License

MIT © Fulcrum Enterprises LLC