Verifiable certificates · ZERTI
Certificates anyone can verify. Forever.
The certificates you issue with ZERTI carry two independent verification seals: one anchors them on the Bitcoin chain and the other turns them into a signed digital credential (Open Badge 3.0). Neither depends on ZERTI to be checked.
The concept in 30 seconds
Two questions, two seals
A real certificate has to answer two different things. ZERTI uses one technology for each, and both are checked without calling us.
“When did it exist, and is it still intact?”
When the certificate is issued, we compute its mathematical fingerprint (a unique number) and record it permanently on the Bitcoin chain. That proves that exact certificate already existed on that date. If someone later modifies it, its fingerprint stops matching and validation marks it as “Altered”: it doesn't prevent the change, it makes it impossible to hide.
“Who issued it, and to whom?”
The certificate is also a signed digital credential under the global Open Badges 3.0 standard (the same one used by universities and leading platforms). It carries your organization's cryptographic signature, so any verifier can confirm you issued it and not an imitation.
Privacy first. No personal data travels in the clear in either seal. Only a mathematical fingerprint goes to the Bitcoin chain; in the credential, the email is hashed. The name, the PDF and the data live only in ZERTI. It's the same model MIT uses for its diplomas.
Bitcoin seal · how it works
Proof of existence, sealed on the world's most solid chain
Bitcoin is a public record that nobody controls and that has never gone down. Anchoring a certificate's fingerprint there gives it a date that cannot be faked.
The fingerprint is generated
On issuance, ZERTI computes a unique number (SHA-256) from the certificate's content. Changing a single letter would produce a completely different number.
It is sealed with OpenTimestamps
That fingerprint is recorded for free via OpenTimestamps, the same open method used by universities such as MIT. No accounts, no keys, no cost.
Bitcoin confirms it
Within hours, the fingerprint is permanently anchored in a Bitcoin block. From that moment, the certificate's existence on that date is public and irreversible.
This is how it looks on the validation page
- Bitcoin block
- #958.627 The exact block where it was anchored. Anyone can see it in a public explorer.
- Seal date
- 18/07/2026 The moment from which the certificate is demonstrably earlier.
- Fingerprint (SHA-256)
- 6e84deb4…ec55 The certificate's mathematical fingerprint. If the document changes, it stops matching.
Open Badge 3.0 · how it works
A digital credential that verifies itself
Open Badges 3.0 is the international standard for digital credentials (1EdTech / W3C). The certificate travels as a signed document that any verifier in the world recognizes.
Signed with your organization's key
ZERTI signs the credential with a cryptographic key (ES256). The public key is published at zerti.co, so anyone can check the signature.
The participant receives their credential
In addition to the PDF, they get a verifiable credential they can keep, share or present as proof of their achievement.
Anyone verifies it independently
An employer, another institution or an official verifier checks the signature and confirms who issued it and to whom — without contacting you or ZERTI.
- Issuer
- ACZOA Your organization appears as the official issuer of the credential.
- Issuer identity
- did:web:zerti.co Verifiable digital identity, published on ZERTI's domain.
- Signature
- ES256 · ✓ Cryptographic signature checked against the issuer's public key.
Verified conformance. ZERTI's credential passes the official Open Badges 3.0 validator by 1EdTech with no errors — the international standard's own conformance seal. It's not “marketing blockchain”: it's genuinely interoperable.
Practical guide
How to read a validation
When someone scans the QR or opens a certificate's validation link, this is what they'll see and what each thing means.
The certificate has not been altered
The current fingerprint matches the one sealed on Bitcoin. The document is exactly the one issued.
The credential is authentic
The digital signature is valid and belongs to your organization. The credential is not an imitation.
Something is off
The fingerprint no longer matches: the document was modified after issuance. It's the alert that makes forgery pointless.
The credential was annulled
Your organization revoked that credential. The record still exists, but marked as invalid.
Independent check
The buttons lead to external services (a Bitcoin explorer, the 1EdTech validator, CertLister). There anyone confirms the proof without depending on ZERTI.
Why it matters
What your organization gains
It's not technology for show. Each seal solves a real problem of reputation and trust.
Any forgery gives itself away
An edited diploma is detected instantly: the fingerprint stops matching. You protect the value of your certifications.
Prestige and international standard
Open Badges 3.0 is the common credential language of universities and major platforms. Your certificates play in that league.
Trust without intermediaries
An employer verifies your graduate's credential on their own, in seconds. Fewer “is this real?” calls.
Valid even if everything changes
The Bitcoin proof is permanent. The certificate stays verifiable years from now, whether or not the platform exists.
Privacy-compliant
No personal data in the clear goes to the chain or the public credential. Compatible with data protection.
A differentiator that sells
“Certificates verified on blockchain and with the Open Badges standard” is a sales argument your competition probably doesn't have.
With transparency
What it is, and what it isn't
Trust is built by being clear. This is exactly what each seal guarantees — no more, no less.
| Claim | Bitcoin seal | Open Badge 3.0 |
|---|---|---|
| Proves when the certificate existed | Yes | — |
| Detects if the document was altered | Yes | Yes |
| Proves who issued it (authenticity) | — | Yes |
| Third-party verifiable without ZERTI | Yes | Yes |
| No personal data in the clear | Yes | Yes |
| Can be revoked | No* | Yes |
* The Bitcoin seal is permanent by design: it proves something existed, it can't be “erased”. Revocation is managed from ZERTI and shown on the validation page. We never say “impossible to forge” as an absolute: we say “tamper-evident” and “independently verifiable”, which is what's correct.
Issue certificates people can trust
Bitcoin seal and Open Badges 3.0 credentials, included in ZERTI. Start free.
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