Anchor a document on the Bitcoin blockchain
Give any file a provable date: you will be able to prove that it existed on that date and has not been changed since. Free, no account, your file stays with you.
Anchor my document1 minute, 3 steps
Your file
PDF, photo, quote, invoice, letter, plan… up to 9 files at once, 100 MB in total.
The fingerprint
Calculated on your device: the file is never sent, neither to OSCAR nor anywhere else.
The dated proof
The fingerprint is anchored on the Bitcoin blockchain: it cannot be backdated or changed.
You download a folder: your files, their proofs, one PDF certificate per document and a guide.
What for?
Contracts and agreements
The contract, agreement or deal signed between you, big or small.
Works and quotes
The accepted quote, the invoice, the before/after photos.
Damage claims
Photos of water damage, to show your insurer.
Letters
The formal notice, the termination notice, the complaint you sent.
Creations
A logo, a text, a plan: proof that it existed on that date.
Professionals: your privately signed contracts
Partnership agreement, service contract, non-disclosure agreement, settlement, amendment, purchase order… Big or small, anchor the PDF once it is signed: the dating is done and provable. Anyone can check that this document, with these signatures, existed on that date and has not been changed since, without going through OSCAR.
Useful if there is ever a disagreement about the signed version or the date of the agreement. Good to know: a legally "certain date" that is binding on third parties follows each country's own rules (in France, registering the deed with the tax office or a notarial deed); the anchoring is a piece of evidence of the date, assessed by the judge.
Why the blockchain?
A file's date can be changed in two clicks. Its digital fingerprint, recorded on the Bitcoin blockchain, the most recognised and most secure in the world, proves that it already existed on that date: the slightest change to the file changes the fingerprint. Anyone can check it for free, without going through OSCAR.
Your file stays with you
The fingerprint is calculated on your phone or computer. Only this string of numbers and letters, which cannot be used to recover the content, is sent to be timestamped. OSCAR neither sees nor keeps your document, unless you then choose to store it in your OSCAR vault (free account, 10 MB, 6 months): keep the downloaded folder safe.
Landlord? OSCAR does it for all your documents
In an OSCAR account, rent receipts, leases, check-in reports and every document in your vault are anchored automatically, with nothing to do, and can be checked at any time.
Good to know
Anchoring proves that a file existed on a date and has not changed since. It does not prove who wrote it or that its content is accurate, and it is not an eIDAS qualified timestamp: it is a dated piece of evidence, freely assessed by whoever receives it. More on the legal value of signatures.
Frequently asked questions
What is anchoring a document on the blockchain for?
To prove that a file already existed on a given date and has not been changed since. Useful for an invoice for works, an accepted quote, a letter you sent, photos of damage, house rules, a plan, a creation you want to date (logo, text, mock-up)…
I am a professional: can I anchor a signed contract or agreement?
Yes. Anchor the PDF once it is signed, whether it is a partnership agreement, a service contract, a non-disclosure agreement or a simple purchase order. The dating is done and provable: anyone can check that this document, with these signatures, existed on that date and has not been changed since. Note: in French law, a "certain date" binding on third parties (article 1377 of the Civil Code) is only obtained by registering the deed, a notarial deed or the death of a signatory, and other countries have their own rules; the anchoring is a piece of evidence of the date, assessed by the judge.
Is the service really free?
Yes, with no account and no subscription. Everything happens on your device, and the timestamp uses the Bitcoin blockchain, the most recognised and most secure in the world.
Is my document sent to OSCAR?
No. The file's digital fingerprint is calculated on your phone or computer. Only this fingerprint (a string of numbers and letters that cannot be used to recover the content) is sent to be timestamped. OSCAR neither sees nor keeps your document, unless you then choose to store it in your OSCAR vault (free account, 10 MB, 6 months): keep the downloaded folder safe.
What is in the downloaded folder?
Your file as it is, its anchoring proof (.ots file), a PDF certificate to show (fingerprint, date, how to verify) and a guide. Do not modify the file: the slightest change, even simply saving it again, changes the fingerprint.
Can I anchor several documents at once?
Yes, up to 9 files at once (100 MB in total), for example a contract and its appendices. Each document gets its own fingerprint, its own proof and its certificate, all in a single ZIP folder. To verify, drop that folder: the verification page lets you choose the document.
How long does confirmation take?
The fingerprint is sent straight away; its confirmation in a Bitcoin block comes a few hours later. Then come back to the verification page with the folder: it shows the confirmed date and gives you the complete proof to keep.
How can someone check my proof?
For free, with no account, by dropping the file and its .ots proof (or the ZIP folder) on OSCAR's "Verify a blockchain anchoring" page, or with a standard blockchain verification tool, without going through OSCAR.
Does this proof have legal value?
It is a dated piece of evidence: it shows that a file existed on a date and has not changed since. It does not prove who wrote it or that its content is accurate, and it is not an eIDAS qualified timestamp. The person, insurer or judge who receives it assesses it freely.
I am a landlord: can OSCAR do it automatically?
Yes. In an OSCAR account, rent receipts, leases, check-in reports and every document in your vault are anchored on the blockchain automatically and stored with their proof, with nothing to do.