4. Onchain Integration

After deploying your contract and adding it to the dashboard, update your offchain integration to target your contract address and pass attestations onchain.

Update API requests

Replace verification_hash with to (your contract address).

Pass attestations to your contract

Include the attestation struct when calling predicated functions.

Backend Changes

Replace verification_hash with your contract address in the to field.

app.post('/api/predicate/attestation', async (req, res) => {
  const { userAddress, contractAddress } = req.body;

  const response = await fetch('https://api.predicate.io/v2/attestation', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'x-api-key': process.env.PREDICATE_API_KEY,
    },
    body: JSON.stringify({
      to: contractAddress,
      from: userAddress,
      chain: 'base',
    }),
  });

  const result = await response.json();

  if (!result.is_compliant) {
    return res.status(403).json({ error: 'Not compliant' });
  }

  res.json({ attestation: result.attestation });
});

Request Parameters

Field	Description
`to`	Your deployed contract address
`from`	The user’s wallet address
`chain`	Chain name (e.g., `base`, `ethereum`, `arbitrum`)

Frontend Changes

Fetch the attestation and pass it to your contract function.

// 1) Fetch attestation from your backend
const { attestation } = await fetch('/api/predicate/attestation', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    userAddress: account,
    contractAddress: VAULT_ADDRESS,
  }),
}).then(r => r.json());

// 2) Call your contract with the attestation
const tx = await vault.deposit(
  {
    uuid: attestation.uuid,
    expiration: attestation.expiration,
    attester: attestation.attester,
    signature: attestation.signature,
  },
  { value: depositAmount }
);

Attestation Struct

Field	Type	Description
`uuid`	`bytes16`	Unique identifier for replay protection
`expiration`	`uint256`	Unix timestamp when the attestation expires
`attester`	`address`	Address of the Predicate attester that signed
`signature`	`bytes`	ECDSA signature over the attestation

Backend Changes

Update your API calls to target your program address.

app.post('/api/predicate/attestation', async (req, res) => {
  const { userPubkey, programId, data } = req.body;

  const response = await fetch('https://api.predicate.io/v2/attestation', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'x-api-key': process.env.PREDICATE_API_KEY,
    },
    body: JSON.stringify({
      to: programId,
      from: userPubkey,
      data,
      msg_value: '0',
      chain: 'solana',
    }),
  });

  const result = await response.json();

  if (!result.is_compliant) {
    return res.status(403).json({ error: 'Not compliant' });
  }

  res.json({ attestation: result.attestation });
});

Frontend Changes

Include an Ed25519 verification instruction before your program instruction, then call your method.

const { attestation } = await fetch('/api/predicate/attestation', { /* ... */ })
  .then(r => r.json());

// 1) Verify Ed25519 signature (must precede your program instruction)
const ed25519Instruction = Ed25519Program.createInstructionWithPublicKey({
  publicKey: attesterPubkey.toBytes(),
  message: messageHash,
  signature: signatureBytes,
});

// 2) Create your program instruction
const clientInstruction = await program.methods
  .yourMethod(attestation)
  .accounts({
    // ... your accounts
    predicateRegistry: registryPda,
    attesterAccount: attesterPda,
    policyAccount: policyPda,
    usedUuidAccount: usedUuidPda,
    instructionsSysvar: SYSVAR_INSTRUCTIONS_PUBKEY,
  })
  .instruction();

// 3) Build and send (Ed25519 instruction MUST come first)
const transaction = new Transaction();
transaction.add(ed25519Instruction);
transaction.add(clientInstruction);
await provider.sendAndConfirm(transaction, [userKeypair]);

​Backend Changes

​Request Parameters

​Frontend Changes

​Attestation Struct

​Backend Changes

​Frontend Changes

Backend Changes

Request Parameters

Frontend Changes

Attestation Struct

Backend Changes

Frontend Changes