How it works

How your file gets a timestamp no one can fake.

CardanoWall turns any file into a permanent, public proof that it existed at a given moment. Your device fingerprints the file, that fingerprint is timestamped on Cardano, and anyone can verify the date forever. Optionally, seal the file so only your chosen recipient can open it.

What actually happens, in one paragraph.

When you publish a record, your device fingerprints the file — that fingerprint is the proof, and it is filed on the Cardano network with a date attached. From then on, anyone can check the date. The file itself stays with you by default. If you also choose to keep an encrypted copy with us — for yourself or for chosen recipients — your device locks it so only those keyholders can open it, and the locked bytes are parked on Arweave. The contents stay private; only the date is public.

The three phases.

There is no server in the middle. Each step happens on your device, on the public Cardano network, or in any verifier — ours, your own, or a recipient's. Sealing a record for someone is optional; only the people you choose can open what you sealed.

01
Prepare — on your device
We compute a cryptographic fingerprint (a hash) of your file in the browser. That fingerprint is the proof — and by default it is all that gets published. You can also opt to keep an encrypted copy of the file itself — for yourself (so a future local edit can't break the proof), or for chosen recipients — using modern, well-audited primitives (Ed25519, X25519, ChaCha20-Poly1305, the same family that protects Signal, WireGuard, and Apple's iMessage). Your plain file is never sent anywhere; anything that leaves your device leaves encrypted.
02
Publish — on Cardano
A short anchor — the fingerprint of your file, plus an Arweave pointer if you chose to upload an encrypted copy — is committed to the Cardano mainnet. It costs a few cents. Once it is in a block, it cannot be changed, removed, or backdated by anyone, including us. Any encrypted file goes to Arweave, a permanent decentralised storage network; the plain file never leaves your device.
03
Verify — anyone, forever
Anyone holding the transaction reference can confirm the date straight from the public Cardano chain, forever, with no account and no trust in us — our open-source command-line tool lets you check it against any explorer yourself. If the record was sealed for a recipient, only they can open its contents; everyone else still sees the proof, just not what it protects.

What lands on the chain

What is actually on Cardano (and what is not).

On chain

A cryptographic fingerprint of your file: a hash, not the file itself. A record can carry one or two hash types.
If you chose to encrypt and store the file — a content-addressed pointer to where the ciphertext lives (an Arweave transaction ID). Otherwise, only the fingerprint.
Only if you choose to sign: a public key. Records can also be published anonymously, with no signer key on chain at all.

Off chain

Your file. By default it stays with you and only its fingerprint is published. You can also encrypt it (for yourself, or for chosen recipients) and have us store the ciphertext on Arweave — a permanent decentralised storage network — so the original bytes survive even if your local copy is later modified or lost.
The recipient's identity. The chain never sees who they are — only the encrypted envelope they alone can open.
Any personal data. We never ask for names, addresses, or identity documents — there is nothing to leak.

The standard

Label 309 — the standard we wrote and gave away.

We authored Label 309 — a Cardano Improvement Proposal that defines exactly how a proof-of-existence record looks on the chain — and are bringing it through the official CIP process. Anyone, including direct competitors, can write a wallet, viewer, or auditor that speaks the same language. CardanoWall is one implementation; the spec belongs to the community.

Read Label 309