Quickstart: Cross-chain USDC Transfer

Overview

This example uses web3.js to transfer USDC from an address on ETH testnet to another address on AVAX testnet.

Prerequisite

The script requires Node.js installed.

Usage

1. Install dependencies by running npm install
2. Create a .env file and add below variables to it:

   ETH_TESTNET_RPC=<ETH_TESTNET_RPC_URL>
   AVAX_TESTNET_RPC=<AVAX_TESTNET_RPC_URL>
   ETH_PRIVATE_KEY=<ADD_ORIGINATING_ADDRESS_PRIVATE_KEY>
   AVAX_PRIVATE_KEY=<ADD_RECEIPIENT_ADDRESS_PRIVATE_KEY>
   RECIPIENT_ADDRESS=<ADD_RECEIPIENT_ADDRESS_FOR_AVAX>
   AMOUNT=<ADD_AMOUNT_TO_BE_TRANSFERED>

3. Run the script by running npm run start

Script Details

The script has 5 steps:

1. First step approves ETH_TOKEN_MESSENGER_CONTRACT_ADDRESS to withdraw USDC from our eth address.

   const approveTx = await usdcEthContract.methods.approve(ETH_TOKEN_MESSENGER_CONTRACT_ADDRESS, amount).send({gas: approveTxGas})

2. Second step executes depositForBurn function on TokenMessengerContract deployed in Sepolia testnet

   const burnTx = await ethTokenMessengerContract.methods.depositForBurn(amount, AVAX_DESTINATION_DOMAIN, destinationAddressInBytes32, USDC_ETH_CONTRACT_ADDRESS).send();

3. Third step extracts messageBytes emitted by MessageSent event from depositForBurn transaction logs and hashes the retrieved messageBytes using keccak256 hashing algorithm

   const transactionReceipt = await web3.eth.getTransactionReceipt(burnTx.transactionHash);
   const eventTopic = web3.utils.keccak256('MessageSent(bytes)')
   const log = transactionReceipt.logs.find((l) => l.topics[0] === eventTopic)
   const messageBytes = web3.eth.abi.decodeParameters(['bytes'], log.data)[0]
   const messageHash = web3.utils.keccak256(messageBytes);

4. Fourth step polls the attestation service to acquire signature using the messageHash from previous step.

   let attestationResponse = {status: 'pending'};
   while(attestationResponse.status != 'complete') {
       const response = await fetch(`https://iris-api-sandbox.circle.com/attestations/${messageHash}`);
       attestationResponse = await response.json()
       await new Promise(r => setTimeout(r, 2000));
   }

5. Last step calls receiveMessage function on MessageTransmitterContract deployed in Avalanche Fuji Network to receive USDC at AVAX address.

   Note: The attestation service is rate-limited, please limit your requests to less than 1 per second.

   const receiveTx = await avaxMessageTransmitterContract.receiveMessage(receivingMessageBytes, signature);