Optimism

Base

2026

Ethereum

<p>A blockchain attestation proves who signed a statement, not that the statement is true. Coinbase issued 723,690 on the Base network to certify verified accounts. This is the number recorded on October 19, 2026 on the EASSCAN explorer. The W3C, which sets web standards, reminds that verifying a credential does not amount to validating its content.</p>
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  <h2 class="in-brief--title" id="en-bref">En bref</h2>
  <ul>
   <li>723,690: the number of “verified account” attestations Coinbase had issued on Base, according to EASSCAN as of October 19, 2026.</li>
   <li>2 smart contracts: the Ethereum Attestation Service runs on one registry for data formats and one contract that issues attestations.</li>
   <li>Zero network fees: an offchain attestation only requires a signature from your wallet.</li>
   <li>May 15, 2025: the date the W3C published version 2.0 of its Verifiable Credentials data model.</li>
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<h2 id="h-blockchain-attestation-a-signature-on-a-statement">Blockchain attestation: a signature on a statement</h2>
<p>An attestation is a declaration from one entity about another entity, such as an address, or about data. <a href="https://www.cointribune.com/identite-decentralisee-sur-ethereum-revolution-et-perspectives/" rel="noopener noreferrer nofollow">Decentralized identity</a> is one of its building blocks. On Ethereum and its layer 2 networks, a dedicated protocol is called Ethereum Attestation Service, or EAS. This open-source protocol has no token, and the protocol charges no fees.</p>
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<p>Its documentation provides a simple definition.</p>
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 <p><em>Basically, attestations are simply digital signatures on structured information.</em></p><cite>Ethereum Attestation Service, <a href="https://docs.attest.org/docs/welcome" rel="noopener noreferrer nofollow">official documentation</a></cite>
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<p>A blockchain attestation is thus not an NFT. According to the EAS documentation, NFTs serve poorly as credentials. They transfer from one wallet to another and lack interoperability. A resold diploma would indeed no longer make sense. Our <a href="https://www.cointribune.com/apprendre-les-nft-guide-complet-pour-debutants/" rel="noopener noreferrer nofollow">beginner’s guide to NFTs</a> details this model of exchangeable token. EAS finally clarifies that it is not an identity provider.</p>
<h2 id="h-two-contracts-and-a-record-for-each-attestation">Two contracts and a record for each attestation</h2>
<p>The architecture consists of two smart contracts. The first records the schemas, that is, the declaration formats. For example, a schema can contain a course title and a completion date. The second contract issues attestations based on these schemas.</p>
<p>Each attestation then contains a series of fields, public when recorded on the blockchain. These include a unique identifier, the used schema, the issuer’s address and, if applicable, that of the recipient. There are also the creation date and a possible expiration date. If the issuer revoked it, the revocation date also appears. An attestation cannot be modified. Its issuer can revoke it if the schema allows it, and this revocation remains visible.</p>
<p>EAS operates on Ethereum and on several layer 2 networks, including Optimism and Base. On these two networks, the contract is even at the same address.</p>
<h2 id="h-coinbase-a-large-scale-use-on-base">Coinbase, a large-scale use on Base</h2>
<p>Coinbase relies on EAS for its “Coinbase Verifications.” According to its <a href="https://docs.cdp.coinbase.com/verifications/introduction/attestations" rel="noopener noreferrer nofollow">developer documentation</a>, the exchange issues these attestations on Base, from the ENS name verifications.coinbase.eth. An application can then know if a wallet is linked to a Coinbase account authorized to trade. The account verification schema contains only one field: yes or no.</p>
<p>The EASSCAN explorer allows measuring this usage. On October 19, 2026, the <a href="https://base.easscan.org/schema/view/0xf8b05c79f090979bf4a80270aba232dff11a10d9ca55c4f88de95317970f0de9" rel="noopener noreferrer nofollow">Coinbase “verified account” schema</a>, created on October 23, 2023, had 723,690 attestations. The “verified country” schema had 306,815. This second schema records the country of residence in clear text, readable by all. Yet Coinbase presents its attestations as evidence <em>“without revealing private information”</em>. Its documentation also specifies: <em>“since the attestation can be stored on the blockchain, anyone can collect EAS attestation data”</em>.</p>
<p>These two schemas weigh heavily on their network. On the same day, EASSCAN counted 3,644,502 attestations on Base, including more than one million for these Coinbase-only schemas. Among the three compared networks, Optimism had 1,319,168, and Ethereum only 14,957.</p>
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<h2 id="h-blockchain-attestation-public-or-off-chain">Blockchain attestation: public or off-chain</h2>
<p>Not all attestations end up on the blockchain. An off-chain attestation is created by a simple signature from your wallet, without network fees. According to EAS documentation, even the explorer server then ignores its existence. You then keep it as a file, link, or QR code.</p>
<p>However, this discretion has a price. An off-chain attestation does not have a network-provided timestamp. To prove it existed on a given date, simply record its identifier on the blockchain, for a minimal cost. To make it public, it can also be published on IPFS, a decentralized storage network: it then becomes visible on the explorer.</p>
<p>For a school, the choice matters. An on-chain attestation by default exposes its data to everyone, like the country of residence of Coinbase clients. An off-chain attestation remains between the issuer and its holder, as long as no one publishes it.</p>
<h2 id="h-blockchain-attestation-what-the-proof-does-not-establish">Blockchain attestation: what the proof does not establish</h2>
<p>A valid signature proves that an address issued a statement, and that it has not changed. However, it says nothing about the truthfulness of the content. The <a href="https://www.w3.org/TR/2025/REC-vc-data-model-2.0-20250515/" rel="noopener noreferrer nofollow">W3C recommendation</a> clearly states: <em>“verifiability of a credential does not imply the truth of the claims it contains”</em>. The verifier must therefore check these claims according to their own rules.</p>
<p>An address also does not prove identity. The protocol is open to all: anyone can thus create a “diploma” schema and issue attestations. Before trusting an attestation, ask yourself five questions.</p>
<ul>
 <li><strong>Who issued it?</strong> Link the issuer’s address to the announced organization, by an ENS name or by its official site.</li>
 <li><strong>What does it declare?</strong> Read the schema fields rather than its title.</li>
 <li><strong>To whom does it apply?</strong> Check the recipient’s address, when present.</li>
 <li><strong>Is it still valid?</strong> Check its expiration date and any revocation.</li>
 <li><strong>Why trust the issuer?</strong> Look for the method that supports its declaration, like an exam or identity check.</li>
</ul>
<h2 id="h-certification-without-blockchain-remains-possible">Certification without blockchain remains possible</h2>
<p>The W3C model relies 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, like a blockchain, appear only as one example among others.</p>
<p>EAS’s blockchain attestation thus constitutes one solution among others, specific to the Ethereum ecosystem. Its own documentation acknowledges that a contract cannot directly read a W3C-format credential without a gateway. Moreover, no attestation alone equates to a diploma recognized by a state.</p>
<p>On October 19, 2026, EASSCAN recorded 3,644,502 attestations on Base, versus 14,957 on Ethereum. Each relies on EAS’s two contracts, whose logic is explained in our guide on <a href="https://www.cointribune.com/smart-contracts-sur-ethereum-fonctionnement-et-utilites/" rel="noopener noreferrer nofollow">how smart contracts work</a>.</p>

Blockchain Attestations: Signing Is Not Proving

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