Blockchain notarization: tamper-proof proof that a document existed.
Blockchain notarization records a document’s fingerprint on a public blockchain, turning the network’s own permanent, timestamped ledger into independent evidence that your file existed at a moment in time — and has not been altered since. No trusted middleman, and nothing anyone can quietly change later.
What blockchain notarization actually is
Traditional notarization asks you to trust an authority: a notary’s stamp says “this existed and I witnessed it.” Blockchain notarization removes the need to trust anyone. You compute a SHA-256 fingerprint of your document — a 64-character value that only that exact file can produce — and write that fingerprint into a public blockchain. The block that includes it is timestamped by the network and is effectively impossible to alter after the fact. From then on, the fingerprint on-chain is independent, tamper-evident evidence that your document existed no later than that block, and (because any change to the file changes the fingerprint) that it has not been modified since.
Crucially, your document is never revealed. A fingerprint cannot be reversed into the original, so you get a public, permanent proof while the file itself stays private.
How notaros does it — five steps
Client-side fingerprint
Your browser hashes the file with SHA-256. The file never leaves your device; only the 32-byte fingerprint is transmitted.
Anchor on Base
notaros writes the fingerprint to a smart contract on Base (an Ethereum layer-2). The block timestamp is the authoritative proof-of-existence instant. We front the gas — you need no wallet.
Commit to Bitcoin via OpenTimestamps
In parallel, the fingerprint is committed to Bitcoin through OpenTimestamps for maximum long-term permanence, at negligible cost via aggregation.
Self-contained certificate
You receive a compact JSON certificate plus a signed PDF — everything a third party needs to check the proof.
Independent verification
Anyone re-hashes the file and reads the chain to confirm the proof. Full walkthrough →
Why anchor to both Base and Bitcoin?
They are complementary. Bitcoin offers the strongest, most widely recognized long-term permanence — the gold standard for “this cannot be rewritten.” Base offers fast, low-cost confirmation and a queryable smart-contract record you can read with a single call. Full-service notarization gives you both, so your proof is both immediately checkable and durable for the long haul.
Blockchain notarization vs. the alternatives
| notaros | Traditional notary | Bare OpenTimestamps | |
|---|---|---|---|
| Proves a file existed at a time | Yes | Only when notarized in person | Yes (Bitcoin) |
| Verifiable without the issuer | Yes — public chain | No — relies on the notary’s records | Yes |
| Document kept private | Yes — hashed locally | No — shown to the notary | Yes |
| Base anchor + signed PDF certificate | Yes | Paper certificate | No |
| Identity notarization / RON | No (by design) | Yes | No |
See the detailed comparisons: blockchain vs. traditional notary and notaros vs. OpenTimestamps.
What people notarize
Anything whose date and integrity matter: intellectual property and trade secrets, legal evidence, contracts and agreements, source code releases, journalism and media, and research data.
A note on legal weight
Be precise about what this is. A blockchain notarization is strong, independent evidence that a document existed at a point in time and has not changed since. It is not a notary public’s act, an identity verification, or Remote Online Notarization, and how a court or counterparty weighs it varies by jurisdiction. Treat it as robust proof of existence and integrity, and consult a qualified professional for a specific matter.