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Glossary

What Is Blockchain Certificate?

A blockchain certificate is a digital certificate whose proof of existence is written to a public blockchain, so anyone can confirm it was issued at a given moment and hasn't been altered since.

Also called: Blockchain Verifiable Certificate, Blockchain Verifiable Web3 Certificate, blockchain credential, NFT certificate

What it's for

The problem a blockchain certificate sets out to solve is a narrow one: proving that a certificate existed, unchanged, at a particular moment, without anyone having to trust the issuer's records. Write a fingerprint of the certificate to a public chain, and the timestamp is beyond the issuer's power to edit later.

That is worth having when a timestamp must outlive the issuer — a national registry, a regulated qualification, a document someone may need to defend years from now. It is not a substitute for a signature, and it is not the same thing as "tamper-proof".

How it works

The certificate itself almost never goes on the blockchain — it would be public forever, which is the last thing you want for a document carrying someone's name and email. What gets written is a hash: a short fingerprint computed from the certificate's contents.

Verifying means recomputing the hash from the certificate in front of you and checking it against the chain. Match, and this is the exact document that was anchored. Mismatch, and something has changed.

What that buys you is timestamping and immutability. What it does not buy you:

  • Authenticity. The chain proves a hash was published, not that the publisher is who they claim. That still comes from a signature and a known key.
  • Truth. A blockchain will faithfully preserve a false claim forever.
  • Revocation. Immutability actively works against you here — withdrawing an anchored credential needs a second mechanism anyway.

An ordinary digital signature already gives you authenticity and tamper-evidence. Anchoring adds an independent, public timestamp on top — useful, and a different property.

Where you'll see it

MIT's Blockcerts work made the pattern well known in education, and it's standard in some national qualification registries. It also appears heavily in marketing, where "blockchain-verified" is often doing rhetorical rather than technical work — a certificate can be tamper-evident and independently checkable with no blockchain anywhere near it. So it's worth asking exactly what is anchored, where, and who can verify it.

In Verifycate

Our version of this is the Blockchain Verifiable Web3 Certificate, available on Pro — a Web3-verifiable credential you can also present in an NFT marketplace.

When an eligible certificate is issued, we compute a fingerprint of the signed credential, batch it into a Merkle tree, and commit the batch root to two independent public ledgers:

  • Ethereum (Base L2) — an EAS attestation carries the batch root, batch sequence, and tree size on-chain.
  • Bitcoin — the same root is timestamped with OpenTimestamps, which needs no account, no key, and no fee.

The anchored bytes don't depend on us staying online either: the encrypted credential and a name-masked presentation image are also written to Arweave, so the content survives as well as the timestamp.

Each anchored certificate also carries an ERC-721 record on Base — a name-masked NFT of the certificate. OpenSea and other marketplaces can show it, and anyone can open its token page to confirm the record exists and matches the certificate. Because the image is masked (J*** D***), no recipient name is written on-chain.

Verification stays signature-first. The Open Badge 3.0 credential is signed with the workspace's own Ed25519 key, and the public page additionally reports, per channel, whether the anchor is confirmed — with links to OpenSea and BaseScan, and the Bitcoin .ots proof downloadable so anyone can check it offline against Bitcoin.

What anchoring does not change: revocation. Nothing on a chain can be withdrawn, so our expiry model is unchanged and we still don't publish a status list. Anchoring is also not a requirement — the signature alone verifies the credential.

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Common questions

Do I need blockchain to make certificates tamper-proof?
No. A digital signature makes a certificate tamper-evident: any change breaks it. A blockchain adds a public, issuer-independent timestamp on top. Verifycate gives you the signature always, and Blockchain Verifiable Web3 Certificates anchored to Base and Bitcoin for certificates that need the timestamp.
Which blockchains does Verifycate use?
Ethereum's Base L2, where an EAS attestation commits the batch root on-chain, and Bitcoin, via OpenTimestamps. The certificate's content also lives permanently on Arweave, and each anchored certificate carries a name-masked ERC-721 record on Base that's viewable in OpenSea.
What is the certificate NFT, and can I verify it on OpenSea?
It's a name-masked ERC-721 record on Base that mirrors the anchored certificate — a collectible view, not the trust mechanism. Its image replaces the recipient's name with initials, and the metadata carries no personal data. You can open it in OpenSea to confirm the token, then cross-check the matching transaction in BaseScan and the Bitcoin timestamp with the downloadable .ots proof.
Is the certificate itself stored on the blockchain?
No. Only a Merkle root goes on-chain, because a public chain is permanent and a certificate carries personal data. The certificate itself is signed, encrypted, and stored off-chain with the issuer and the recipient.
Can a blockchain certificate be revoked?
Not by removing it — nothing on a chain can be removed. In Verifycate an expired certificate is reported as expired on its public page; we don't publish a status list, and immutability is not a revocation mechanism.

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