The second anchor · When?

The Bitcoin blockchain.
A proof built to last.

One clarification to begin with: DfinA Vault uses neither the cryptocurrency nor speculation. It uses the Bitcoin blockchain as a public ledger of proof. Your file stays private: only its anonymous fingerprint serves to establish that it already existed on a given date.

✓No file published on the Bitcoin blockchain✓No wallet to create✓Payment in your usual currency
Your document stays with youThe content is never published on the Bitcoin blockchain.
DfinA Vault · PremiumPublic ledger
Block# A81
Block# A82
Block# A83
Anonymous fingerprint linked to the proof71a8b20fd4d8e9c37e64a10bfb896b6d…
Public: a mathematical proof
Private: your file, its content and your identity
A proof verifiable without DfinAThe certificate rests on a public ledger and open standards.
The essential idea

An independent technological infrastructure.

DfinA Vault uses this infrastructure as a large public ledger of proof, maintained collectively and designed to make rewriting the past extremely difficult.

Your file

It stays on your phone or your computer. Its content is never published on the Bitcoin blockchain.

Private · With you

Its fingerprint

A string of characters computed from the file represents its exact state without making it possible to reconstruct the content.

Anonymous · Non-reversible

The public ledger

Anchoring ties the proof to a block that existed at a given moment. The fingerprint can no longer be backdated.

Public · Verifiable
In one sentence

We use the permanence of the Bitcoin blockchain, not a market price.

The value sought is technological: a public, global and durable ledger whose history no single actor can freely alter.

0
No digital asset to buyDfinA Vault handles the technical layer. You pay a fixed price with a usual payment method.
∅
No personal data publishedThe anchoring protocol receives neither your name, nor your file, nor its description.
✓
An independent proofVerification does not need to take DfinA's word for it.
Privacy by design

What stays private. What becomes public.

The separation is fundamental: DfinA Vault protects the content by circulating only its cryptographic fingerprint.

On your device

The original file

Contract, photograph, video, artwork, archive or personal document: it stays under your control.

PDFcontract-final-version.pdf
Content readable only by you and your recipients
Local computation → SHA-256: 71a8b20fd4d8…
✓The content is never published on the Bitcoin blockchain.
✓The file cannot be reconstructed from its fingerprint.
✓You choose for yourself where to keep the original.
→
In the public proof

An anonymous fingerprint

A mathematical value ties your certificate to the anchoring. It tells nothing about the nature of the document.

Abbreviated example71a8b20fd4d8e9c37e64a10bfb896b6d…
✓It makes it possible to recognize exactly the same file.
✓It contains no name, no title, no readable metadata.
✓A tiny change produces a different fingerprint.

A fingerprint is not an encryption of the file: it is a one-way mathematical identifier, designed for comparison.

From file to ledger

The proof's journey, step by step.

The process is automatic for the user. This view simply helps you understand what happens behind the Premium button.

Step 1

The file becomes a fingerprint.

The browser reads the file on your device and computes a unique value. The content itself never leaves the device.

Your filePrivate
→
Local computationHash function
→
FingerprintString of characters
Why it works: the same file yields the same fingerprint; the slightest change produces a different one.
Step 2

Fingerprints can be aggregated.

Several proofs are grouped in a mathematical structure. Each document then keeps a path that lets it prove it belongs to the common root.

Fingerprint A
Fingerprint B
Fingerprint C
Fingerprint D
Branch AB
Branch CD
Common root to anchor
This aggregation avoids recording each document separately and makes it possible to efficiently share the technical cost of anchoring.
Step 3

The root is tied to a transaction recorded on the Bitcoin blockchain.

Once included in a block, the proof benefits from the cumulative security of the chain. Each subsequent block progressively reinforces the depth of this anchoring.

Block# A81
Anchoring# A82
Block# A83
The block's time gives a public reference point: the proven data existed no later than the moment of this anchoring.
Step 4

The certificate gathers the verification path.

You keep the original document and its proof. A later verification recomputes the fingerprint, follows the aggregation path and checks the public anchoring.

DfinA Vault certificateAnchored
Fingerprint71a8b20fd4d8…
InfrastructureBitcoin blockchain
ProofVerifiable inclusion path
FileKept by the user
The proof stays useful only if you also keep the file whose existence and integrity you want to demonstrate.
The choice of infrastructure

Why the Bitcoin blockchain specifically?

It is today the most battle-tested reference for durable public anchoring: seniority, decentralization, cumulative security, open standards and verification independent of the provider.

No proprietary company

The Bitcoin blockchain belongs to no company. It is maintained by a global network of independent actors, and DfinA has no button that could rewrite a past date.

Cumulative security

Each new block adds a new layer of protection to the history already recorded, which makes a retrospective change increasingly unrealistic.

Open standards

The proof format and the verification tools can be checked publicly, without depending on an opaque private database.

Global reach

The same ledger is accessible from different countries and is not limited to the infrastructure of a single national operator.

Built to last

The proof stays verifiable from public standards, even if the site or the company that generated it is no longer available.

Discreet

The ledger receives only a mathematical value. It does not need to know the document, its author or its subject.

A history that thickens

The more blocks are added, the more the anchoring becomes practically tamper-proof.

Changing an old piece of data would require rebuilding the protection of the block concerned and then of all the following blocks, while outpacing the rest of the network. It is this cumulative resistance that makes the Bitcoin blockchain the most solidly proven public anchoring infrastructure.

Block 1
Block 2
Block 3
Block 4
Anchoring
A self-contained proof

Verify without trusting DfinA.

The principle of a good technical proof is that it can be checked by a third party with the file, the certificate and compatible public tools.

The complete check

Three matches to verify.

Each link answers a specific question.

1Does the file match the fingerprint?Verification recomputes the value of the received document locally.
2Does the fingerprint belong to the aggregated proof?The mathematical path ties the document to the common root.
3Is this root actually anchored on the Bitcoin blockchain?The public ledger confirms it already appeared in a dated block.
Why it matters

The proof does not rest on our memory.

A private database can be modified, lost or become inaccessible. An open proof limits this dependency.

✓No internal ledger to trustThe date does not come only from a line stored at DfinA.
✓No mandatory account for the recipientThe verification logic is attached to the proof itself.
✓No publication of the fileThe check can be public without making the document public.
✓No absolute dependence on DfinAThe Bitcoin blockchain and open standards remain consultable separately.
In all rigor

What anchoring proves. And what it does not prove.

Precision strengthens the value of the proof: a technical timestamp answers a temporal question, but does not replace all other forms of proof.

What anchoring provides

  • The technical proof that a fingerprint existed no later than a public instant
  • The ability to detect any modification of the original file
  • An independent verification based on an open ledger
  • A proof that does not require publishing the document's content
  • A second temporal assurance in the Premium plan

What it does not establish on its own

  • Who created the file or who is its legal owner
  • The truthfulness, legality or quality of the content
  • That the document did not exist before the anchoring
  • A civil identity or a qualified electronic signature
  • The automatic outcome of a dispute: a proof is still assessed according to its context

And the quantum threat?

In the long run it concerns the whole of modern cryptography, including the mechanisms used by the Bitcoin blockchain. A serious presentation must neither ignore it nor promise eternal invulnerability. The choice of the Bitcoin blockchain rests on its depth of use, its technical ecosystem and the strong collective incentive to evolve its protections should quantum capabilities become genuinely threatening.

Premium adds a double temporal assurance.

Integrity already works without public anchoring. Anchoring on the Bitcoin blockchain is intended for files for which an independent proof of date brings additional value.

Compare the plans