How to use and verify a blockchain timestamp
Think of BlockchainSign as a digital notary that proves when you created a document. Just as a notary stamps papers to show they are genuine, we use the blockchain to create a permanent, unchangeable record of your file.
Your file stays with you
We never receive the file itself — only a SHA-256 fingerprint computed in your browser.
Recorded on Ethereum
The fingerprint is written into a public transaction that nobody can edit or erase.
Verifiable by anyone
Your certificate contains everything a third party needs to check the record themselves.
What BlockchainSign is
Say you write a story or make a design and you want proof it was yours on a certain date. Your file stays private with you — we never keep it. Instead we take a "fingerprint" of it (a short code unique to your file) and lock that fingerprint into the blockchain: a giant public logbook shared across thousands of computers, so nobody can edit or erase it. That record is stamped with the exact date and time.
Later, if anyone claims they made it first, you can show your file matches the fingerprint and prove you had it earlier. That is all we do: give your file a tamper-proof timestamp anyone can check, without ever seeing the file itself.
How it works
- You send us your file — a document, image, or any digital file.
- We create a fingerprint — SHA-256 turns your file's information into a unique code called a hash.
- We save it to the blockchain — the fingerprint is stored permanently on Ethereum.
- You get a certificate — a file that proves all of the above.
What is a SHA-256 fingerprint?
The fingerprint is a SHA-256 hash of your payload data — the information section of your certificate. SHA-256 is a mathematical formula that turns any text into a unique 64-character code. Changing a single letter produces a completely different hash.
What you receive
You get a certificate file (cert.yml) containing:
- Your file's information — email, file details and any notes you added.
- The blockchain transaction ID — the permanent record number.
- A link to view it online — so anyone can check that it is real.
How to verify your certificate
Step 1: Open the blockchain link
In your certificate, find the line marked tx_url — for example https://etherscan.io/tx/0x1833eb71…. Opening it takes you to Etherscan, which works rather like a search engine for blockchain transactions.
Step 2: Find the stored data
On the Etherscan page:
- Look for the section called More Details.
- Find Input Data.
- Click View as UTF-8 to make the stored bytes readable.
Step 3: Check the fingerprint matches
In the readable data you will see a hash. Compare it with the payload_hash in your certificate — they should match exactly.
How to verify the SHA-256 hash yourself
You can double-check our work with any SHA-256 calculator.
Step 1 — copy your payload data. From your certificate, copy everything under the payload: section:
Email: info@exampletech.com
File SHA-256: a0566e5c4d077424a7be39d95d1308488c81b7b49274588bf9f5b2eb13554ac4
Meta: Example Tech Solutions LLC
Step 2 — remove the leading spaces. The certificate is YAML, so each line is indented. The text you hash must not be:
Email: info@exampletech.com
File SHA-256: a0566e5c4d077424a7be39d95d1308488c81b7b49274588bf9f5b2eb13554ac4
Meta: Example Tech Solutions LLC
Step 3 — generate the hash. Paste the cleaned text into any online SHA-256 generator, generate the hash, and compare it with the payload_hash in your certificate. A match proves the data in your certificate is exactly what was timestamped on the blockchain.
Why this proves your file is real
- The blockchain is permanent — once written, a record can never be changed or deleted.
- It is timestamped — the chain shows exactly when the fingerprint was saved.
- It is publicly verifiable — anyone in the world can check it on Etherscan.
Need help?
If you are having trouble verifying your certificate, email info@blockchainsign.io.