Cross-Chain Messaging

Introduction

Cross-chain messaging allows for developers to send messages cross-chains along with a swap. Cross-chain messaging swaps follow the same flow as regular swaps but with the addition of a message that is sent to a receiver contract on the destination chain.

As described in How Swapping Works, swaps in Chainflip can be initiated via requesting a deposit address or via a smart contract call (only in EVM chains). Both of those methods support cross-chain messaging by specifying a message parameter and a gasBudget parameter. The SDK makes it seemless to request a deposit address with CCM or execute a swap with CCM.

DCA for CCM swaps

If a CCM swap is executed with DCA parameters, only the principal amount (input amount less gas budget) will be executed in multiple chunks: if a swap for gas budget is required, it will be executed in a single chunk (i.e. ignoring DCA parameters). If a CCM swap uses DCA and slippage protection, the CCM output transaction will be broadcast as long as at least one principal chunk is successfully executed. For this reason, if a gas swap is required, it will only be executed after the first successful chunk to ensure that if no principal chunks are successful and will be refunded, the gas budget can be refunded as well.

Chains supported

The following chains are supported for cross-chain messaging as destination chains:

• EVM Chains (Ethereum, Arbitrum)
• Solana

Implementation Checklist

• The destination chain needs to be a Chainflip supported CCM-compatible chain.
• The swap must be initiated by requesting a deposit address or via a smart contract call specifying the extra specifying the message and the gasBudget parameters in both cases.
• The message should be shorter than 10k bytes.
• The gas budget needs to be paid upfront on the source chain as part of initiating the swap. In the future, Chainflip might support paying the gas budget on the destination chain.
• The gas budget provided needs to be sufficient to cover the gas costs of the receiver's logic on the destination chain.
• The receiver on the destination chain needs to be a smart contract with the interface described for the destination chain, either EVM or Solana.
• The receiver on the destination chain needs to ensure that the receiving logic won't revert.

Depending on the destination chain there are some extra considerations that need to be taken into account. Check out EVM considerations and/or Solana considerations