Create an Attestation

After determining the Schema and potential Modules to use, and after the deployment and registration of your Portal, you can begin creating Attestations.

Attestation registration

Attestation registration at the Portal level takes 2 parameters, defined as follows:

Property	Description
attestationPayload	The payload to attest
validationPayload	The payloads to validate via the modules to issue the attestation

attestationPayload is defined in Solidity as follows:

struct AttestationPayload {
  bytes32 schemaId;
  uint64 expirationDate;
  bytes subject;
  bytes attestationData;
}

Property	Description
schemaId	The identifier of the schema this attestation adheres to
expirationDate	The expiration date of the attestation
subject	The ID of the attestee, EVM address, DID, URL etc
attestationData	The attestation data

Manually registering an Attestation in the AttestationRegistry contract

To register an Attestation into the AttestationRegistry contract, you need to go through the Portal you have previously deployed an registered, using the attest function:

function attest(AttestationPayload memory attestationPayload, bytes[] memory validationPayload) public payable;

When attesting, the registry performs a set of integrity checks on the new attestation:

• verifies the schemaId exists

• verifies the subject field is not blank

• verifies the attestationData field is not blank

Using a blockchain explorer

Instead of drafting the smart contract call by hand, you can benefit from a chain explorer interface. Let's use the Linea Sepolia explorer, Lineascan.

The form generated by Lineascan to interact with the Portal contract

1. Retrieve the address of the Portal contract you previously deployed

2. Access the Portal contract on Lineascan

3. Got to the "Contract" tab

4. Got to the "Write" tab

5. Connect your wallet and fill the attest form with the parameters described above

6. Send the transaction

Using the official Verax SDK

We have seen rather manual ways to create an Attestation, now let's focus on the easiest way: via the Verax SDK.

Check [this page](../using-the-sdk.md) to discover how to instantiate the Verax SDK.

Once you have an SDK instance, you can create an Attestation like this:

await veraxSdk.portal.attest(
  "0x2fafe2c217be096e09b64c49825fe46b7c3e33b2",
  {
    schemaId: "0x9ba590dd7fbd5bd1a7d06cdcb4744e20a49b3520560575cd63de17734a408738",
    expirationDate: 1693583329,
    subject: "0x828c9f04D1a07E3b0aBE12A9F8238a3Ff7E57b47",
    attestationData: [{ isBuidler: true }],
  },
  [],
);

Attestation Metadata

When creating an attestation, you simply need to specify four properties, as outlined above, however, the attestation registry itself automatically populates the other fields in the attestation metadata at the point at which it is created. The full list of attestation metadata is included below:

Property	Datatype	Description
attestationId	bytes32	The unique identifier of the attestation
schemaId	bytes32	The identifier of the schema this attestation adheres to
replacedBy	uint256	The attestation ID that replaces this attestation
attester	address	The address issuing the attestation to the subject
portal	address	The address of the portal that created the attestation
attestedDate	uint64	The date the attestation is issued
expirationDate	uint64	The expiration date of the attestation
revocationDate	uint64	The date when the attestation was revoked
version	uint16	Version of the registry when the attestation was created
revoked	bool	Whether the attestation is revoked or not
revocationDate	uint64	If revoked, the date it was revoked / replaced
subject	bytes	The ID of the attestee e.g. an EVM address, DID, URL etc.
attestationData	bytes	The raw attestation data

The attestationId is derived from an internal auto-incremented counter, converted from uint32 to byte32. This corresponds to the total attestations issued. Moreover, the ID is prefixed with a chain identifier. This way, an attestation issued on Arbitrum cannot have t he same ID as an attestation issued on Linea, which is great in terms of cross-chain discovery!

Once the attestation is successfully created in the registry, an AttestationRegistered event is emitted with the attestation ID, and subsequently picked up by indexers.