proofledger

n8n community node for ProofLedger: anchor a file's SHA-256 hash on the Polygon blockchain, read proofs back, and start workflows when a proof is anchored. The file never leaves n8n.

Package Information

Released: this month
Downloads: 0 weekly / 0 monthly
Latest Version: 0.1.0
Author: Craig Solomon

Available Nodes

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ProofLedger icon
ProofLedger
Anchor a file’s SHA-256 hash on the Polygon blockchain and read proofs back. Only the hash is sent; the file never leaves n8n.
ProofLedger Trigger icon
ProofLedger Trigger
Starts the workflow when ProofLedger anchors a proof on Polygon. Registers the webhook for you and checks every delivery’s signature.

Documentation

n8n-nodes-proofledger

An n8n community node for ProofLedger: anchor a file's SHA-256 hash on the Polygon blockchain from any workflow, read proofs back, and start workflows the moment a proof is anchored.

Only the hash is sent. The file never leaves n8n.

Install

In n8n: Settings → Community Nodes → Install, enter n8n-nodes-proofledger.

Self-hosted without the UI installer: npm install n8n-nodes-proofledger in your n8n user folder (~/.n8n/nodes), then restart n8n. The n8n docs cover both paths.

Credentials

One credential, ProofLedger API:

Field Value
API Key Issued from Account → API Keys on any ProofLedger plan, including Free. Starts with sk_ and is shown once.
Base URL https://proofledger.io. Leave it.

The credential test calls GET /api/v1/branding, which costs nothing and proves the key.

ProofLedger node

Resource Operation What it does
Proof Create From File Hashes a binary field locally with SHA-256 and submits the hash. Filename defaults to the binary's file name.
Proof Create From Hash Submits a 64-character SHA-256 hex digest you already have.
Proof Create Many Every incoming item's hash, in batches of 100, one request per batch. Output is one item per input (result: created, exists or invalid, plus the proof).
Proof Get Status, Polygon transaction and certificate links by proof ID.
Proof Get by External ID Look a proof up by the external_id you sent.
Proof Get Bundle Everything needed to verify the proof without ProofLedger, in the verify-proof file format.
Proof Get Many Newest first; filter by Anchored Since; Return All pages through the cursor.
Proof Verify The public verify endpoint: does this hash have a proof?
Webhook Create / Get Many / Delete / Test Manage webhook endpoints by hand. The trigger node below does this for you.
Account Get Branding Whether partner branding is approved and the exact line shown on certificates.

External ID. Send your own record ID on create (Additional Fields → External ID). Sending the same one again returns the existing proof instead of creating another, so retries are safe.

Errors. Turn on Continue On Fail to get { "error": "..." } items instead of a stopped workflow. A 429 means the key's 120 requests per minute or the plan's monthly proof allowance (Free 25, Professional 500, Business 5,000) is used up; the message says which.

Trigger

ProofLedger Trigger starts the workflow when a proof on your account is anchored on Polygon.

  • On activation it registers a webhook endpoint at your n8n webhook URL (POST /api/v1/webhooks) and stores the signing secret in the workflow's static data. Deactivating removes the endpoint.
  • Every delivery is checked against ProofLedger-Signature (t=<unix seconds>,v1=<hex HMAC-SHA256 of "t.body">, 5-minute tolerance). Anything that fails is answered 401 and never starts the workflow.
  • The item is the event body: type, created_at, and data.proof (status, chain_tx, certificate and verification URLs) plus data.bundle (the verify-proof bundle), so you can store the bundle next to the file without another call.
  • Include Test Events also runs the workflow for the signed webhook.test event, which you can send from the ProofLedger account page or POST /api/v1/webhooks/:id/test.

Your n8n webhook URL must be reachable from the internet over https. ProofLedger refuses private, loopback and plain-http addresses.

Templates

Two importable workflows in templates/:

  • anchor-file-and-save-bundle.json: read a file from disk → Create From File → wait for the anchor → Get Bundle → write <file>.proof.json next to it. Swap the first node for any node that produces a binary field (a form upload, Google Drive, S3, HTTP Request).
  • when-proof-anchored.json: ProofLedger Trigger → one flat item per anchored proof (ID, hash, transaction, certificate link, bundle), ready for a database, an email or storage.

Facts worth knowing

  • One chain: every proof is one transaction on Polygon, usually confirmed within a minute. Nothing to pay per proof.
  • A proof shows that a file with this fingerprint existed by a date. It does not prove who made it and is not a copyright registration.
  • Anyone can verify a proof without an account: the public verify page, the public verify endpoint, or the verify-proof package offline from the bundle.
  • API reference: https://proofledger.io/api.html. Changelog: https://proofledger.io/changelog. Terms for API use: https://proofledger.io/api-terms.

Development

npm install
npm run build      # compiles to dist/
npm run lint       # n8n's community-node rules
npm test           # signature verification unit tests (needs a build)

Releases after the first go through GitHub Actions with npm provenance, as n8n requires for verified nodes since May 2026: npm run release lints, builds, bumps the version, tags and pushes, and .github/workflows/publish.yml publishes the tag. One-time setup on npmjs.com: package settings → Trusted Publishers → GitHub Actions, owner Fulcrum-Enterprises, repo n8n-nodes-proofledger, workflow publish.yml.

The package was proven against a real n8n 2.43 and a scratch ProofLedger instance: every operation above, trigger registration on activation, a forged and an unsigned delivery refused with 401, and a signed test event and a real anchored-proof event each starting an execution. The harness lives in e2e/ and depends on a local ProofLedger checkout, so it is not part of npm test.

License

MIT. ProofLedger is a product of ProofLedger LLC; this node is maintained by the same people.

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