Gasless & Automated Cross-Chain Transfer Protocol

This project demonstrates gasless & automated cross-chain token transfer using Circle's CCTP as well as Gelato Relay and Gelato Web3 Functions.

Warning

Code is not yet audited by a third party - please use at your own discretion.

What is CCTP?

Cross-Chain Transfer Protocol (CCTP) is a permissionless on-chain utility that facilitates USDC transfers between blockchains via native burning and minting.

The Cross-Chain Transfer Protocol can be considered a bridge for native USDC.

Benefits:

• No need to lock-and-mint
• Unified liquidity (no synthetic tokens)

How does CCTP work?

1. USDC is burned on the source chain
2. Circle observes the event and signs an attestation signature
3. USDC is minted on the destination chain using the attestation

Limitations (motivations for this project):

• Steps one and three both require user-initiated transactions on-chain, requiring native tokens
• Subsequent transactions on the destination chain also require native tokens
• Step two can take up to ~13 minutes and the user must be present to initiate the final transaction

Vision

With Gelato Relay and Web3 Functions we can:

• Move USDC between chains and cover the cost using USDC
• Pay for subsequent transactions on the destination chain also using USDC
• Automate the entire process reliably in the background

Eliminating the dependence on native tokens gives us infinitely more freedom.

Implications:

• USDC acts as an interoperability layer connecting multiple chains
• Eliminates the need for per-chain native tokens

Note

Gasless refers to the absence of native tokens during transaction fee payment.
Gas is still paid, but abstracted away from the user and compensated in USDC.

Gasless & Automated CCTP Flow

1. Sign two off-chain ERC-3009 transfer authorization signatures.
   These authenticate token transfers, covering the base transfer amount and relay fee on each network.
   Code Snippet
2. Sign a final ERC-2771 signature which enforces our max fee and destination domain intent.
   We avoid making any trust assumptions since all data is verified on-chain to have been signed by the user.
   Code Snippet
3. Relay a depositForBurn transaction on the source chain.
   This burns the tokens and emits events which are observed by Circle and a Web3 Function.
   Code Snippet
4. The Web3 Function indexes all events and periodically fetches attestation signatures from Circle.
   Code Snippet
5. Once an attestation is issued, the Web3 Function relays a receiveMessage transaction on the destination chain.
   This uses the attestation signature in order to mint the burnt tokens 1:1.
   Code Snippet

Intermediary GelatoCCTPSender and GelatoCCTPReceiver contracts facilitate relay fee payment. These are both deployed on each CCTP-compatible network allowing for any-any chain transfers.

Implementation

Implementation is as simple as importing the cctp-sdk and calling transfer.

await transfer(
   owner,        // owner account address
   amount,       // total amount including fees
   srcMaxFee,    // max relay fee on the source chain
   dstMaxFee,    // max relay fee on the destination chain
   srcChainId,   // source chainId
   dstChainId,   // destination chainId
   signTypedData // callback to sign typed data
);

Quick Start

1. Install dependencies

   yarn install
   

2. Edit .env

   cp .env.example .env
   

3. Transfer 10 USDC from Avalanche to Arbitrum

   yarn run scripts/transfer.ts