Bridge USDC Across 8 Chains — Cross-Chain Transfer Protocol Integration

You: Implement USDC transfer from Ethereum to Avalanche
using CCTP. I need the smart contract interaction and
the off-chain attestation flow.

// Approve USDC spend by TokenMessenger
const usdc = new ethers.Contract(USDC_ETH, ERC20_ABI, signer);
await usdc.approve(TOKEN_MESSENGER_ETH, amount);

// Burn USDC — initiates cross-chain transfer
const tokenMessenger = new ethers.Contract(
  TOKEN_MESSENGER_ETH, TOKEN_MESSENGER_ABI, signer
);
const tx = await tokenMessenger.depositForBurn(
  amount,                    // Amount in USDC (6 decimals)
  1,                         // Destination domain (Avalanche = 1)
  destinationAddressBytes32, // Recipient on Avalanche
  USDC_ETH                   // Token contract
);
const receipt = await tx.wait();

// Extract messageBytes and messageHash from logs
const eventTopic = ethers.id("MessageSent(bytes)");
const log = receipt.logs.find(l => l.topics[0] === eventTopic);
const messageBytes = ethers.AbiCoder.defaultAbiCoder()
  .decode(["bytes"], log.data)[0];
const messageHash = ethers.keccak256(messageBytes);

// Circle signs the burn attestation (takes ~15 minutes)
async function waitForAttestation(messageHash) {
  const url = `https://iris-api.circle.com/attestations/${messageHash}`;
  while (true) {
    const res = await fetch(url);
    const data = await res.json();
    if (data.status === 'complete') {
      return data.attestation;
    }
    await sleep(10000); // Poll every 10 seconds
  }
}
const attestation = await waitForAttestation(messageHash);

// Receive the minted USDC on destination chain
const messageTransmitter = new ethers.Contract(
  MESSAGE_TRANSMITTER_AVAX, MESSAGE_TRANSMITTER_ABI, avaxSigner
);
const mintTx = await messageTransmitter.receiveMessage(
  messageBytes,
  attestation
);
await mintTx.wait();
// ✅ Native USDC now in recipient's Avalanche wallet

skills:
  - cctp-integration
  - smart-contract-platform