Straight answers, no jargon.

It is a way of producing a tiny receipt that says: this exact file existed at this exact moment. Anyone can check the receipt later. Nobody — not even us — can change the date once it is filed.

A regular server is owned by someone. That someone can change the date, delete the record, or quietly disappear. Cardano is a public network run by thousands of independent computers; no single party can rewrite history. That is what makes the receipt trustworthy without trusting us.

No. The Cardano blockchain only stores a compact fingerprint (a hash) of your file — a number that uniquely identifies the file but reveals nothing about it. That fingerprint alone is enough to prove the file existed at that moment, and many users stop there: the file stays with them. Optionally — and this is one of the most useful features — you can encrypt the file (by default, just for yourself; or for chosen recipients) and have us store the ciphertext on Arweave, a permanent decentralised storage network. This solves a real problem: if you kept the file only locally and later modified, lost, or restored an older version, the hash would no longer match and the proof would be unverifiable. With the encrypted file preserved on Arweave alongside the proof, the original bytes are tied to the timestamp forever — and only the chosen keyholders can ever decrypt them.

No. By default the file never leaves your device at all — only its fingerprint goes on chain. All the cryptography happens on your side: in your browser, our open-source SDKs, or the command-line tool (with a desktop app on the way). If you do choose to upload an encrypted copy (for backup, or to share with a recipient), the file is encrypted on your device first with industry-standard ChaCha20-Poly1305 under a key derived from the recipient's X25519 public key — and that recipient can be you yourself. Our service only ever receives data that is already prepared and encrypted, ready to publish: it never sees your plaintext, and only a holder of the matching private key can ever decrypt the contents.

Every receipt on the Cardano network keeps working without us. CardanoWall is just the first service that implements the open Label 309 standard, not the standard itself: anyone can verify a record with the open spec and any Cardano explorer, with no help from us. We are also preparing an open-source release so you can run your own instance locally or build a competing service against the same standard. The proof never depended on the company, and it never will.

Partly — and the parts that matter for trust are. The Label 309 standard, our TypeScript, Python, and Rust SDKs, the command-line tool, and the cryptography library are all open source on GitHub: Apache-2.0 for the code, CC-BY-4.0 for the standard text. Anyone can read the code, run it, fork it, or build a competing service against the same standard. The cardanowall.com web app itself is our proprietary product, but because it sits on top of the open spec and the open SDKs, you are never locked into us: any record we publish can be verified without our involvement, by anyone, forever.

Two ways. Open the public viewer link to see the file's fingerprint, the moment it was sealed, and a link to the matching block on a Cardano explorer. Or — if you do not want to trust our viewer — install our open-source command-line verifier and check the record yourself against any public Cardano explorer (Koios, Blockfrost, or your own node). Either way, the proof stands without cardanowall.com.

A small per-record fee covering the Cardano network fee plus a service margin, a few cents at typical network conditions. If you also store an encrypted copy on Arweave, permanent storage adds a one-time cost that scales with the file size. There is no monthly subscription; you only pay when you publish.

Confidentiality already is. When you seal a record, it's encrypted by default with a post-quantum hybrid — X-Wing (ML-KEM-768 + X25519) — so a future quantum computer can't decrypt content harvested today. Sealing is optional, and even when you seal, classical X25519 stays available as an opt-out for more recipients or files per transaction. Signing keys (Ed25519) and hashes are still classical for now, like almost everything on the public internet. CardanoWall was designed with algorithm-agility from day one: the wire format references every algorithm by name from an extensible registry, so as the NIST post-quantum signature standards (ML-DSA, SLH-DSA) land, they slot in additively — and every record sealed beforehand keeps verifying.

By default, a sealed record reveals very little. Because Cardano is public, the fact of the record — its block time and its fingerprint — is public too. But unless you choose to sign the record, your identity is not on the chain at all: no name, no email, no signer key. The contents stay private — nobody, including us, can tell what file the fingerprint belongs to unless they already have it. If you want a public, attributable record (a press release, an authored document), you can opt in to sign it; otherwise sealed records are anonymous at the protocol layer.

Not directly. To seal a record, you need the recipient's public key first — but, crucially, that key does NOT have to come from CardanoWall. The recipient can use any Label 309-compatible tool — another implementation of the standard, a command-line client, their own software — generate their key there, and simply share it with you. You paste or pick the key in the composer, and the sealed record is fully standards-compliant: the recipient decrypts it with whichever tool they prefer. This is the point of the open standard — no lock-in to us. (If a timestamp is all you need, you can also publish a hash-only proof and share the file through any other channel.)

Label 309 is the Cardano Improvement Proposal we authored that defines the exact byte format for a proof-of-existence record on Cardano. We are bringing it through the official CIP process so that any independent tool — wallet, viewer, auditor — can read and write the same records. CardanoWall is one implementation; the spec belongs to the community.

As long as the Cardano network exists. The receipt is part of the public ledger; it does not expire and there is no renewal fee. If you also kept the sealed envelope, the recipient can unseal it at any time.

No. You can sign in with email, Google, or Apple and use everything — publish records, run an inbox, manage identities — without a Cardano wallet. We handle the infrastructure on your behalf: Cardano network fees and Arweave storage fees are paid by us and billed to your prepaid USD balance at the live price quoted at submission time. A Cardano wallet is only relevant if you want to attach a wallet-bound signature to a record, so that the record is publicly attributed to your Cardano stake address.

You can't, and that is by design. A record is anchored on the Cardano network, which is immutable: no one, including us, can remove or change it once it is filed. That permanence is exactly what makes the proof worth anything. There is also nothing personal to remove: only a hash of your file ever goes on chain, never the file itself or your identity, unless you deliberately signed it. If you uploaded an encrypted copy to Arweave, it stays there permanently too, but without the decryption key its contents are unreadable to everyone, including us.