Understanding ETcH
How a simple digital fingerprint becomes an imperishable proof.
How it works
What you will do with ETcH
Select your document
Drop your file(s). Nothing leaves your browser.
Hash computation
The SHA-256 algorithm generates a unique 64-character fingerprint.
Secure payment
Pay EUR 2 by credit card via Stripe. No cryptocurrency needed.
Etched on Ethereum
The fingerprint is recorded on the blockchain with an unfalsifiable timestamp.
Why You Receive a ZIP
After anchoring, ETcH delivers a ZIP archive — your self-contained, court-ready proof. This archive is the single source of truth: it can be verified independently by anyone, without recourse to ETcH.
What the ZIP contains
- Your original file(s) — the exact document(s) whose hash was anchored.
- manifest.json — all metadata: hash, email, timestamp, network, transaction details.
- confirmation_log.json — the identity chain: IP address, user-agent and timestamp recorded when you clicked the confirmation link.
- transaction.json — Ethereum transaction hash, block number, network and explorer URL.
- certificate.pdf — a human-readable summary of the proof, suitable for printing or sharing.
Treat this ZIP archive as you would treat your original manuscript. If you lose it, the blockchain record remains — but you lose the file that corresponds to the hash. Store it on a reliable medium (cloud drive, external disk) alongside your original file.
How can I verify my proof?
ETcH provides a built-in verification tool: just drop your file or paste its hash on the Verify page — the result appears in seconds.
What if ETcH no longer existed?
Your proof remains valid. No ETcH account or software needed — the ZIP contains everything required to verify independently, using only public tools and the Ethereum blockchain.
How to verify a proof →What legal value?
A blockchain anchor constitutes admissible evidence before courts — in France, the European Union, Japan, Australia and beyond. The exact weight depends on the legal framework of each country.
- It is not an intellectual property title.
- It is not a guarantee of winning a dispute.
- It does not replace a filing with an official body (INPI, bailiff).
How it works in practice
ETcH creates an immutable, timestamped record on the Ethereum blockchain. If a dispute ever arises, a bailiff (commissaire de justice) can verify and certify the anchoring at that point — using only public tools and the Ethereum blockchain.
This is exactly what happened in the AZ Factory case (TJ Marseille, March 2025): the blockchain anchors were made in May and September 2021. The bailiff's verification report was dated October 2022 — over a year later. The court accepted both as valid proof of prior authorship.
You only need that extra step if a dispute actually occurs. For the vast majority of users, the ETcH anchoring alone serves as a permanent, verifiable record — and a strong deterrent.
Legal Recognition
Blockchain timestamping is gaining recognition from courts and legislators worldwide. The weight it carries depends on your jurisdiction — but the trend is consistently in one direction.
| Year | Jurisdiction | Development |
|---|---|---|
| 2018 | China | Hangzhou Internet Court — first court worldwide to admit blockchain as evidence in a copyright dispute. China's Supreme Court formalised this for all internet courts in September 2018. |
| 2019 | Italy | Law No. 12/19, Art. 8 ter — first country to legislate that blockchain storage produces the same legal effect as a qualified electronic timestamp under eIDAS. |
| 2016–2020 | USA | Vermont, Arizona, Nevada, Delaware, Illinois, Ohio: state laws explicitly recognising blockchain records as admissible evidence in legal proceedings. |
| 2024 | European Union | eIDAS 2 (Regulation 2024/1183) — formal recognition of electronic ledgers including blockchains as a qualified trust service, with legal presumption of integrity. |
| 2025 | France | Tribunal judiciaire de Marseille (RG 23/00046) — first European court ruling recognising blockchain timestamping as proof of copyright ownership in an IP dispute. |
| 2025 | Australia | Poulton v Conrad (Tasmania, Full Court) — blockchain records recognised as possessable property, signalling growing receptiveness to blockchain evidence. |
Legal guides by country
Detailed legal frameworks for blockchain timestamping — France, Europe, Italy, Japan, Australia, Canada, United States.
How anchoring works
What is blockchain?
The Ethereum blockchain is a digital ledger distributed across thousands of computers worldwide. Once information is recorded, it can never be altered or deleted.
- No central authority controls the ledger.
- Recorded data cannot be modified or deleted.
- Anyone can verify the recorded information.
What is a hash?
A hash is like a digital fingerprint for your data. The SHA-256 algorithm transforms any content into a 64-character string, always the same length.
- The same input always produces the same hash.
- Two different contents never produce the same hash.
- It is impossible to recover the original content from the hash.
- The slightest change completely alters the hash.
Try it yourself below
Try hashing
Change even a single character and see how the hash changes completely.
How to proceed
Step-by-step walkthrough
Drop your file(s)
Drag your file(s) into the drop zone or click to browse. All formats are accepted.
Prepare Your File(s)
Before anchoring, create a read-only copy of your file(s). Keep both the original file (for its intrinsic value) and the proof ZIP that ETcH delivers (as the authoritative proof record).
The proof ZIP delivered by ETcH is your primary record — it contains your original file, the PDF certificate, the JSON proof and the transaction metadata. If you modify the original file after anchoring — even by a single space — the hash changes and the proof becomes unusable. Read-only protects you against accidental modifications.
Windows
- Right-click the file → Properties
- Check 'Read-only' at the bottom
- Click OK
Mac
- Select the file
- File → Get Info (or ⌘+I)
- Check 'Locked'
Linux
chmod 444 my-file.pdfFile format stability
The hash changes if the file changes — even by a single bit. Always anchor the final version, in a format that does not modify itself when opened.
| Format | Stability | Reason |
|---|---|---|
| ✅ | Stable when opened, universal, does not modify its metadata. | |
| Plain text(.txt, .md) | ✅ | Binary stable, no hidden metadata. |
| Source code | ✅ | Plain text, fully stable. |
| Video / Audio | ✅ | Stable if not re-encoded. |
| PNG / JPEG / WebP | ⚠️ | EXIF metadata may change when re-opened or re-shared. |
| SVG / AI / EPS | ⚠️ | Stable if not re-saved in an editor. |
| PSD / Clip Studio | ⚠️ | Stable if not re-saved. |
| Word(.docx / .pages) | ❌ | Modifies its internal metadata on every open — export to PDF before anchoring. |
| Excel / Numbers | ❌ | Same issue as Word. |
Naming tip
Name your files clearly so you know which file corresponds to which proof:
MyNovel_v1_ANCHORED_2026-02-13.pdfMyNovel_v1_etch_2026-02-13.zipDevelopers: Anchor your codebase
Prove the exact state of your project at any moment — every file, every line.
Method 1 — Git archive (full source snapshot)
git archive --format=zip HEAD > project-v1.0.zipBest for: small to medium repositories under 50 MB.
Method 2 — Gitingest (text digest)
Export your entire codebase as a single text file via . Lightweight and readable — ideal for AI code reviews and documentation snapshots.
Requires the repo to be public during ingestion (under 2 minutes). You can switch it back to private immediately after downloading the text file.
Use cases
Note: ETcH supports files up to 50 MB. For larger repositories, use gitingest or archive specific folders:
git archive HEAD --format=zip -o code.zip -- src/ lib/How verification works
A real proof kit
Here is the exact content of an ETcH proof kit — not a mock example, but the very first anchoring ever made on Ethereum mainnet.
The original file is not included here — it is a private manuscript. In your own kit, your file will be present. This is precisely why the ZIP must be kept safe.
ZIP contents
{
"version": "1.0",
"type": "complete",
"generatedAt": "2026-02-17T05:28:35.000Z",
"service": "Etch",
"documentHash": "0xa95bbb3b9944620cbb2fee10ca2fa65f8f2da424cbe5057b7e5b1c6f135e8cb4",
"fileName": "L'Or des felures.pdf",
"fileSizeBytes": null,
"contents": [
"L'Or des felures.pdf",
"manifest.json",
"transaction.json",
"certificate.pdf",
"confirmation_log.json"
]
}Try it yourself
Copy the hash below and paste it on the Verify page to see the result in real time:
How to verify a proof
ETcH produces two levels of verifiable proof. Understanding both helps you present the strongest possible evidence.
Use the tabs below to understand each verification method — then go to etchproof.eu/verify to verify your proof.
Prove that a specific file existed at a given date
- Go to etchproof.eu/verify and drop the file.
- ETcH computes its SHA-256 hash directly in your browser.
- The hash is compared against the blockchain record. If it matches, the file existed — in that exact form — at the anchored date.
This works even if ETcH no longer exists — the Ethereum record is permanent.
The specific case of bundles
When you anchor multiple files, ETcH does not anchor each file individually on Ethereum — it anchors a single session hash that covers all of them. The individual hash of each file, referenced by its filename, is stored in bundle_manifest.json — included in your proof kit.
Your proof kit is self-contained: it holds everything needed to verify your proof independently, without ETcH, forever.
Each file has its own hash, stored in bundle_manifest.json. The session hash — anchored on Ethereum — is the SHA-256 of that manifest. The chain runs in both directions.
Why this certifies every individual file
The Ethereum blockchain records the session hash at a specific date and time. This record is permanent — no one can alter it.
The session hash is the SHA-256 of bundle_manifest.json, which lists every anchored file by name, size, and individual hash. If the session hash is certified, the manifest is certified too.
Each file's individual hash appears in that certified manifest. If the manifest is certified, every hash it contains is certified.
Each individual hash is the SHA-256 of its file — a unique mathematical fingerprint. If the hash matches your file, the file is certified.
The session hash is not a signature or a declaration — it is a mathematical fingerprint of the manifest itself. Change a single byte in any file, and the chain breaks: the manifest changes, the session hash changes, and it no longer matches what Ethereum recorded. That is what makes it unfalsifiable.