Proof of Priority: 8 Methods Compared (Cost, Delays, Evidentiary Value)

When a dispute arises, the question isn't "who had the idea first?", but often: can you demonstrate that content existed at a given date, and that it hasn't been modified since.

The good news: there are several methods, with very different levels of formality (and cost). The not-so-good news: most are either too expensive, too slow, or too complex for everyday use.

This is exactly the problem we created LegalStamp to solve: a solution that combines the best of modern technologies (cryptographic hash + blockchain anchoring) with maximum ease of use.

In this article, we compare 8 proof of priority methods to help you make the right choice.

A proof of priority serves to demonstrate that a document existed at a given date, ideally also guaranteeing its integrity (non-modification).

Simple Definition

Proof of priority aims to establish a fact: at such date, such content already existed. In practice, a solid proof combines 2 building blocks:

1. The hash: a cryptographic fingerprint of your file (if the file changes, the hash changes).
2. The timestamp: a mechanism that associates this hash with a date/time, via a third party or a verifiable system.

Hash = integrity, Timestamp = date, Together = credible proof of priority.

How It Works

The goal is to build a proof that is verifiable, reproducible, and difficult to contest.

1. 1
   Freeze the content (hash)

   Calculate the cryptographic fingerprint of the file (e.g., SHA-256). This is your reference: if the file changes, the fingerprint changes.
2. 2
   Timestamp the fingerprint

   Associate this hash with a date via a third party (INPI, notary, bailiff, eIDAS provider...) or a publicly verifiable mechanism (e.g., blockchain).
3. 3
   Archive the proof elements

   Keep the original file, the hash, the receipt/certificate, and the context (emails, versioning, exchanges, logs). Ideally, duplicate storage locally + cloud/digital vault.
4. 4
   Be able to verify later

   When you need to prove it: you recalculate the file's hash and compare it to the timestamped hash (and verify the authenticity of the receipt/certificate).

Why LegalStamp Is the Ideal Solution

Unlike traditional methods (notary, e-Soleau, bailiff), LegalStamp offers:

• Instant: your proof is created in seconds, not days
• Controlled cost: much cheaper than a notary or bailiff
• Simplicity: drag and drop your file, that's it
• Confidentiality: only the hash is anchored, never your document
• Public verifiability: thanks to Bitcoin blockchain anchoring, anyone can verify authenticity
• Unlimited validity: the Bitcoin blockchain is immutable and decentralized

Comparison Table: 8 Methods

Quick read: "evidentiary value" always depends on context, the judge, and the quality of the file. The table below gives a practical trend.

When to Choose What?

1) Daily and regular use → LegalStamp

For the vast majority of professional needs:

• Contract versions, terms of service, specifications
• Client deliverables, exports, reports
• Mockups, designs, creations
• Source code, technical documentation
• Construction site photos, condition reports

LegalStamp is the ideal solution: fast, economical, and the proof is anchored on the Bitcoin blockchain for unlimited validity.

Create my first proof for free →

2) Major legal stakes → Complement with a professional

For potentially significant disputes or highly regulated contexts:

• Use LegalStamp as a first layer of proof (immediate and economical)
• Complement if necessary with a bailiff's affidavit or a notarized deed

This "belt and suspenders" approach gives you the best of both worlds.

3) Prove a transmission → Registered mail + LegalStamp

If you need to prove who sent what and when:

• Use a qualified electronic registered mail (eIDAS) for transmission
• Timestamp attachments with LegalStamp to guarantee their integrity

4) Very tight budget → LegalStamp rather than nothing

Many businesses and creators don't protect their work "because it's too expensive or complicated". With LegalStamp, you have no more excuses: creating a proof takes a few seconds and costs a fraction of traditional methods.

What It Proves / Doesn't Prove

What LegalStamp Proves

• ✅ Existence at a date: "this document already existed at this precise date"
• ✅ Integrity: "this document has not been modified since timestamping"
• ✅ Verifiability: anyone can independently verify via the blockchain

What No Method Proves on Its Own

• ❌ That you are the original author (but priority is a strong indication)
• ❌ An automatic exclusive right (patents, trademarks require specific procedures)
• ❌ The truthfulness of the content (it proves existence, not that it's "true")

Best Practices with LegalStamp

• [ ] Systematically timestamp your important documents as soon as they are finalized
• [ ] Keep the original file exactly as it was timestamped
• [ ] Document the context: what this file corresponds to, for which project, which recipients
• [ ] Version: a new version = a new timestamp
• [ ] Keep your certificates in a dedicated folder (or use your LegalStamp space)
• [ ] Test verification to be ready when you need it

FAQ

Is LegalStamp legally recognized?

Yes. Blockchain timestamping relies on recognized cryptographic standards (SHA-256, OpenTimestamps). The proof is independently verifiable by any expert, which gives it strong evidentiary value. The LegalStamp certificate clearly explains the technical process to facilitate understanding by a judge or lawyer.

Why blockchain rather than a traditional trusted third party?

The Bitcoin blockchain offers unique guarantees:

• Immutability: impossible to modify or delete a record
• Decentralization: no single point of failure
• Durability: the Bitcoin network has existed since 2009 and has never been compromised
• Public verifiability: no need to trust us, you can verify yourself

Does my document remain confidential?

Absolutely. Only the hash (the cryptographic fingerprint) is anchored on the blockchain. Your document never leaves your device if you wish. It is mathematically impossible to reconstruct your document from the hash.

What's the difference with e-Soleau?

| Criterion | LegalStamp | e-Soleau (INPI) | | --------------- | ------------------------ | --------------------------------- | | Cost | More accessible | €15 + renewal every 5 years | | Speed | Instant | A few minutes | | Validity | Unlimited (blockchain) | 5 years (renewable) | | Confidentiality | Hash only | Document stored by INPI | | Verification | Public and independent | Via INPI only |

Can I use LegalStamp in addition to other methods?

Yes, it's even recommended for important stakes. LegalStamp provides immediate and economical proof. You can complement it with a bailiff's affidavit or notarized deed if the stakes justify it.

How long is my proof valid?

For life. The anchoring on the Bitcoin blockchain is permanent and immutable. As long as the Bitcoin network exists (and there's no reason it would disappear), your proof remains verifiable.

Conclusion

There are many methods to prove the priority of a document, but most are too expensive, too slow, or too complex for everyday use.

LegalStamp changes the game: by combining the cryptographic power of SHA-256 hash with the immutability of the Bitcoin blockchain, we offer a solution that is:

• Instant: your proof in seconds
• Economical: a fraction of a notary or bailiff's cost
• Confidential: only the hash is published, never your document
• Verifiable: by anyone, independently, forever

Don't leave your creations, contracts, and important documents unprotected anymore.

Create my free account →

Disclaimer: This article is informative and general. It does not constitute legal advice. For a sensitive situation (dispute, IP strategy, procedure), have your approach validated by a legal professional.

References

• eIDAS Regulation (910/2014) - EUR-Lex
• EU Trusted List Browser
• OpenTimestamps - Open Standard