PROXAE

How Proxae proves what you knew.

No magic. No blind trust. Mathematics and time.

Fingerprint β†’ Global registry β†’ Permanent proof

Interactive demo

Certify in 30 seconds

See how Proxae anchors your proof in the Bitcoin blockchain.

9:41
Proxae

Drop

Drop your file here

File ready to certify

Hash

SHA-256

Fingerprint computed locally

Your file never leaves your device.

Certify now

Anchor

ID a7f3…c912
Status Pending
Hash e3b0c442…7852b855

proof-a7f3c912.ots

OpenTimestamps receipt

Bitcoin anchoring in progress…

Confirmed

Status Confirmed
Block #896,412
Date 2026-05-05 14:32 UTC
Tx 3a1b…f8e2 β†—

βœ“ Immutable proof

Anchored in the Bitcoin blockchain forever.

Try for free

No sign-up required β€” free and unlimited.

Interactive demo

The essential idea in 30 seconds

πŸ“„

Your file

Stays with you

β—ˆ

Proxae

SHA-256 hash

β›“

Global registry

Forever

Imagine you slip a document into an envelope, seal it, and deposit it in a Swiss bank that nobody controls β€” not even us.

Proxae does exactly that, digitally.

Your document never leaves your computer. Proxae computes its "digital fingerprint" β€” a unique sequence of characters that exclusively represents your file. If your file changes by a single character, the fingerprint changes completely.

This fingerprint β€” and only it β€” is sent and engraved into a public registry maintained and verified around the clock by thousands of computers worldwide.

✦ Result: it becomes mathematically very difficult to contest that your document existed on that date.

How it works in detail

Write your idea, contract, or creation in any format. Our recommendation: export it as a PDF. It's the most stable format β€” it doesn't change when you copy or share it.

✦ Word β†’ File β†’ Export as PDF

✦ Google Docs β†’ File β†’ Download β†’ PDF

✦ Pages β†’ File β†’ Export β†’ PDF

✦ Any app β†’ Print β†’ Save as PDF

Technical detail
Any file type is accepted. The SHA-256 fingerprint is computed on the raw bytes of the file β€” regardless of format or filename. A renamed file produces the same hash. A file modified by even a single bit produces a completely different hash.

When you upload your file to Proxae, your browser immediately computes its fingerprint β€” a 64-character string that uniquely identifies your file anywhere in the universe.

This computation happens entirely on your computer. Your file never leaves your browser. Only the fingerprint is sent to Proxae.

Input Mon contrat de startup.pdf
Fingerprint a3f9b2c1d4e5f6a7b8c9d0e1f2a3b4c5…

This fingerprint is like a thumbprint: unique, impossible to forge, and it changes completely if the file changes.

Technical detail
Proxae uses the SHA-256 algorithm via the browser's SubtleCrypto API β€” the same cryptography used by banks and governments. The computation is performed in native JavaScript, no plugin or extension required. The source code is public and auditable.
JavaScript
const hashBuffer = await crypto.subtle.digest('SHA-256', fileBuffer);

Proxae sends your fingerprint to several independent servers that aggregate it with other fingerprints from the same moment β€” like thousands of letters slipped into the same envelope. This collective envelope is then sealed into the Bitcoin network β€” a ledger maintained by thousands of computers in over 100 countries, owned by no one and modifiable by no one.

⚑ Bitcoin here is not money. It's an unforgeable public ledger β€” the network's most precious property. We use its trust infrastructure, not its currency.

This operation takes between 1 and 2 hours β€” the time it takes for the Bitcoin network to confirm the block containing your fingerprint.

Technical detail
Proxae uses the OpenTimestamps (OTS) protocol, open-source and auditable. Your fingerprints are aggregated into a Merkle tree β€” a mathematical structure that proves membership in a set via a single blockchain anchor. Result: 1,000,000 fingerprints = 1 single Bitcoin transaction. The .ots file contains the mathematical path (Merkle path) proving that your specific fingerprint was included in that precise Bitcoin block.

As a Pro option, your proof is also timestamped by Sectigo β€” a qualified trust service provider recognised under the European eIDAS regulation. An official PDF certificate is generated, summarising all evidence: fingerprint, Bitcoin anchor, Sectigo timestamp, and verified identity if you completed KYC.

Proxae holds one half: the fingerprint certified in the global registry. You hold the other half: your original file. Together they form a verifiable proof of prior existence. Apart, they prove nothing.

This is why preserving your original file is just as important as the certification itself.

☐ Save the file to your personal cloud (Google Drive, iCloud, Dropbox)
☐ Keep a local copy on your computer
☐ Download your .ots certificate from Proxae
☐ Never modify the original file β€” even renaming is risky
☐ Note your Proxae proof URL
Technical detail
The .ots file is a standardized binary file containing the complete Merkle path. It can be verified by anyone, forever, without Proxae, without internet (with a local full Bitcoin node) or online at opentimestamps.org. Format: binary, ~500 bytes, .ots extension.

How to verify a Proxae proof

Three methods, from simplest to most technical

Recommended Β· No installation

  1. 1. Go to proxae.com/p/[your-proof-id]
  2. 2. Drop your original file into the verification zone
  3. 3. Proxae recomputes the fingerprint locally
  4. 4. βœ… "Match confirmed"
    ❌ "This file doesn't match this proof β€” it may have been modified"

Proxae-independent Β· No installation

This method proves that Proxae is not needed to verify your proof. You can verify independently, now and 50 years from now.

  1. 1. Download your .ots file from your Proxae proof page
  2. 2. Go to opentimestamps.org
  3. 3. Drop your .ots file AND your original file
Success! Bitcoin block 892341
attests existence as of 2026-04-21 14:32 UTC

If your proof is still 'Pending', come back after 2 hours β€” the Bitcoin network must first confirm the block.

For developers Β· Fully local verification

The most sovereign method. Zero trust in anyone β€” not even opentimestamps.org.

macOS

brew install python3
pip3 install opentimestamps-client

Linux (Debian/Ubuntu)

sudo apt install python3-pip
pip3 install opentimestamps-client

Windows

# Install Python from python.org
pip install opentimestamps-client

Place your original file and the .ots in the same folder

ots verify myFile.pdf.ots

With a local Bitcoin node (100% offline verification):

ots --bitcoin-node http://user:[email protected]:8332/ verify myFile.pdf.ots

Our trust model β€” let's be transparent

What Proxae sees What Proxae doesn't see
● The SHA-256 fingerprint of your file
β—‹ The content of your file
● The date and time of certification
β—‹ What the hash represents
● Your email address (if account created)
β—‹ Your original file
● Your hashed IP address (not raw)
β—‹ Your identity if anonymous

Even if Proxae disappeared tomorrow, your proofs would remain verifiable forever.

The Bitcoin registry is decentralized and belongs to no one. Your .ots file contains everything needed to verify your proof independently. We are not a single point of failure.

Legal value β€” let's be honest

Basic proof

Free Serious evidence

Bitcoin anchoring constitutes serious, technically robust evidence of prior existence. Recognized as evidence in many civil disputes in France and Europe, particularly in intellectual property and unfair competition matters. Not enforceable alone before a court, but highly effective combined with other evidence.

Equivalent

Comparable to a registered email with delivery confirmation.

Enhanced proof

Pro Strong evidential value RFC 3161

The Pro certificate adds RFC 3161 anchoring via a Qualified Trust Service Provider (QTSP) recognized by the European eIDAS regulation. This Bitcoin + RFC 3161 combination constitutes admissible evidence before most European courts.

Equivalent

Comparable to a private deed with a certified date.

Sample PDF certificate β†’

Maximum proof

Pro + Identity Maximum value

Add identity verification to cryptographically link your proof to your certified identity. The PDF certificate mentions your verified identity, the verification date, and the method used.

Equivalent

Close to a notarized affidavit for non-notarial use cases.

Sample PDF certificate β†’

Proxae is not a legal service. Evidential value depends on context, jurisdiction, and litigation strategy. Consult a lawyer for any actual dispute. Proxae does not confer exclusive rights (patent, trademark) and does not replace a notarial act.

Frequently asked questions

Not only. Bitcoin is first and foremost a large, unforgeable global ledger, shared by thousands of independent computers. Proxae records the fingerprint of your document in it β€” no financial value, no transaction. It is the same technology, used for proof rather than exchange.

No. Technically impossible. Once inscribed in a Bitcoin block, no actor β€” not even Proxae, not even Bitcoin miners β€” can modify the timestamp without invalidating the entire chain that follows, which would require controlling 51% of global computing power.

Your fingerprint remains in the global registry, but you can no longer match it to your content. The proof exists β€” you just can't present it. That's why we insist so strongly on keeping your original file in multiple locations.

Yes. PDF, Word, image, video, audio, source code, ZIP archive, text β€” any file up to 50 MB is accepted. We recommend PDF for its stability: a PDF copy is always identical to the original, unlike some formats that can subtly change.

Between 1 and 3 hours in general. The Bitcoin network produces a new block approximately every 10 minutes. Proxae automatically checks and updates your status upon confirmation.

That's a legitimate question. Proxae's impact on Bitcoin is infinitesimal: millions of fingerprints are grouped into a single transaction thanks to the OpenTimestamps protocol. Proxae adds virtually no additional transactions to the Bitcoin network.

Yes, but with an important caveat: any difference in spaces or characters during future verification will produce a different hash. For legal or important use, always create a PDF. For a simple prediction, plain text is sufficient.

Proxae certifies the existence of a hash at a date β€” not the identity of the submitter. To link the proof to your identity, create a Pro account and enable identity verification. Your certified identity will appear in the PDF certificate.

Yes. We don't store your content β€” only its fingerprint. If you have an account, you can request deletion of your data at any time. Fingerprints in Bitcoin cannot be deleted, but they contain no personal data.

It's your proof certificate. A binary file of approximately 500 bytes containing the mathematical path linking your fingerprint to a specific Bitcoin block. Standardized, open-source, verifiable by anyone via OpenTimestamps CLI or at opentimestamps.org.

A .tsr (Time-Stamp Response) file is the raw response issued by the Sectigo certification authority under the RFC 3161 protocol. It contains the timestamp cryptographically signed by Sectigo, proving that at the exact moment of issuance, your fingerprint already existed. This is the file you can independently verify with openssl.

The sectigo-chain.pem file contains Sectigo's certificate chain β€” the public keys used to verify that the .tsr was indeed signed by Sectigo and not by anyone else. Without this file, openssl cannot validate the authenticity of the timestamp. It is included in the download bundle.

It summarises all information about your proof in a machine-readable format: identifier, SHA-256 fingerprint, creation date, confirmed Bitcoin block, and verified identity if applicable. It is the entry point for any integration or automated verification, without having to parse binary files.

Your proofs are permanent. The Bitcoin registry is decentralized β€” no company, no government can remove it. Your .ots file is enough to verify your proof forever, without Proxae, on opentimestamps.org or via CLI.

No. The .ots file, the .tsr, or the PDF certificate are public on your proof page β€” but they are worthless without your original file. A timestamp certificate proves that a fingerprint existed at a given date, not that you own the corresponding content. To constitute valid proof, both are required: the certificate and the original file you certified. Without that file, it is impossible to recompute the fingerprint and therefore to prove anything. You hold the half that matters.

Try it now

Compute the fingerprint of any text

"Bonjour"

β†’ 60303ae…

"bonjour"

β†’ 2f05477…

Change just one character and observe the result

Certify this text on Proxae β†’

This computation happens entirely in your browser. Nothing is sent to Proxae.

Now you understand how it works.

Timestamp something that matters.

Proxae establishes prior existence with cryptographic strength at least equivalent to an official prior art deposit. It does not confer exclusive rights and does not replace a notarial act or legal advice.