Blockchain attestation: Signing is not proving

A blockchain attestation proves who signed a statement, not that that statement is true. Coinbase has issued 723,690 on the Base network to certify verified accounts. This is the figure recorded on October 19, 2026 on the EASSCAN explorer. The W3C, which sets web standards, reminds us that verifying a supporting document does not amount to validating its content.

Blockchain certification: a signature on a declaration

An attestation is the declaration of an entity on another entity, such as an address, or on data. Decentralized identity makes it one of its building blocks. On Ethereum and its second-layer networks, a dedicated protocol is called Ethereum Attestation Service, or EAS. This open source protocol does not have a token, and the protocol does not charge any fees.

Its documentation gives a simple definition.

At their core, attestations are simply digital signatures on structured information.

Ethereum Attestation Service, official documentation

A blockchain certificate is therefore not an NFT. According to EAS documentation, NFTs serve poorly as credentials. They transfer from one wallet to another and lack interoperability. A resold diploma would no longer have any meaning. Our beginner’s guide to NFTs details this tradable token model. EAS finally specifies that it is not an identity provider.

Two contracts and a form for each certificate

The architecture consists of two smart contracts. The first stores schemas, i.e. declaration formats. For example, an outline might contain a course title and a completion date. The second contract issues certificates based on these diagrams.

Each certificate then includes a series of fields, public when it is registered on the blockchain. It contains a unique identifier, the scheme used, the address of the sender and, where applicable, that of the recipient. Added to this is the date of creation and a possible expiration date. If the issuer has withdrawn it, the revocation date also appears. A certificate cannot be modified. Its issuer can revoke it if the scheme allows it, and this revocation remains visible.

EAS runs on Ethereum and several second-layer networks, including Optimism and Base. On these two networks, the contract appears at the same address.

Coinbase, large-scale use on Base

Coinbase relies on EAS for its “Coinbase Verifications”. According to his developer documentationthe exchange issues these certificates on Base, from the name ENS verifications.coinbase.eth. An application can thus know if a wallet is linked to a Coinbase account authorized to trade. The account verification schema contains only one field: yes or no.

The EASSCAN explorer allows you to measure this usage. As of October 19, 2026, the Coinbase “verified account” schemecreated on October 23, 2023, had 723,690 certificates. The “verified country” diagram had 306,815. This second diagram lists the country of residence clearly, readable by everyone. Coinbase nevertheless presents its certificates as proof “without revealing private information”. Its documentation also specifies: “As the attestation can be stored on the blockchain, anyone can collect EAS attestation data”.

These two schemes weigh heavily on their network. The same day, EASSCAN identified 3,644,502 certificates on Base, including more than a million for these Coinbase schemes alone. Among the three networks compared, Optimism had 1,319,168, and Ethereum only 14,957.

Blockchain certification: public or off-chain

Not all attestations end up on the blockchain. An off-chain certificate is created by a simple signature from your wallet, without network fees. According to the EAS documentation, even the explorer server is then unaware of its existence. You then keep it in the form of a file, link or QR code.

This discretion, however, comes at a price. An off-chain attestation does not carry a timestamp provided by the network. To prove that it existed on a given date, all you have to do is register your identifier on the blockchain, for a minimal cost. To make it public, you can also publish it on IPFS, a decentralized storage network: it then becomes visible on the explorer.

For a school, choice therefore matters. An on-chain attestation by default exposes its data to everyone, such as the country of residence of Coinbase customers. An off-chain certification remains between the issuer and its holder, as long as no one publishes it.

Blockchain attestation: what the proof does not establish

A valid signature proves that an address has issued a declaration, and that it has not changed. On the other hand, it says nothing about the veracity of the content. There W3C recommendation formulates it clearly: “the verifiability of a supporting document does not imply the truth of the statements it contains”. The verifier must therefore verify these assertions according to his own rules.

An address does not prove an identity either. The protocol is open to everyone: anyone can therefore create a “diploma” scheme and issue certificates. Before relying on a certificate, ask yourself five questions.

• Who issued it? Link the issuer’s address to the announced organization, by an ENS name or by its official website.
• What does she declare? Read the schema’s fields rather than its title.
• Who does it apply to? Check the recipient’s address, when it appears.
• Is it still valid? Check its expiration date and possible revocation.
• Why believe the transmitter? Look for the method behind their claim, such as an examination or identity check.

Certification without blockchain remains possible

The W3C model is based on three main actors: the issuer, the holder and the verifier. To publish the necessary identifiers, the text cites trusted databases or government identity databases. Distributed ledgers, such as a blockchain, are only one example among others.

The EAS blockchain attestation thus constitutes one solution among others, specific to the Ethereum ecosystem. Its own documentation recognizes that a contract cannot read a W3C formatted credential directly, without a gateway. Furthermore, no certificate is worth, on its own, a diploma recognized by a State.

On October 19, 2026, EASSCAN recorded 3,644,502 certificates on Base, compared to 14,957 on Ethereum. Each is based on the two EAS contracts, the logic of which is explained in our guide to how smart contracts work.