multichain-relayer-server

Pagoda Implementation of Multichain Relayer Server facilitating cross chain transactions enabling Chain Abstraction.

Run Multichain Relayer Server

cargo run

Run and Test all Multichain Gas Relayer Systems

See Integration Tests

Technical System Design

Below is a Design Diagram of the entire multichain relayer system.

• The gas station contract and the mpc signing service contract are in the green box which take place on NEAR.
• This multichain relayer server repo focuses on the purple/blue Multichain Relayer Core Backend Services Box in the middle and the connections to the XChain systems in the red box via RPCs.
• The XChain Settlement that's happening in the yellow box is currently manual and will be automated in the future.

Technical System Description

1. The wallet sends a NEAR transaction to the gas station contract that contains 2 actions
   1. A transfer of NEAR (or FT Transfer in the future) to cover gas on the foreign chain
   2. A create_transaction function call to the gas station contract canhazgas.testnet containing the unsigned foreign chain transaction to be signed by the MPC signing service, assuming the unsigned transaction passes validation.
2. The Gas Station Contract calls the MPC signing service to sign both a funding transaction, which ensures the user's foreign chain account has sufficient gas to execute the desired transaction, and signs the unsigned foreign chain transaction.
3. Upon receipt of both the signed transactions, the Gas Station Contract emits an event which is picked up by the indexer, which then calls the /send_funding_and_user_signed_txns with the 2 signed transactions from the indexer.
4. The multichain relayer server sends the funding transaction to the foreign chain RPC to fund the user's account with gas.
5. After the gas funding transaction is confirmed, the multichain relayer server calls the foreign chain RPC again to send the signed transaction initiated by the user in step 1.
6. The Cross Chain Settlement takes care of selling the extra NEAR being sent to the gas station contract for gas tokens on foreign chains as well as bridging the tokens to the other chains. This process is currently manual, but will be automated in partnership with market makers in the future.

Supported Chains

• BSC Testnet & Mainnet
• ETH Sepolia Testnet & Mainnet
• Arbitrum Sepolia Testnet & Mainnet
• Optimism Sepolia Testnet & Mainnet
• Base Sepolia Testnet & Mainnet
• More chains coming soon!

Multichain Relayer Description

• The main function of this server is interfacing with foreign chain RPCs sending both presigned funding transactions to cover gas and the actual presigned transaction once the funding is done.
• The Multichain relayer is meant to be deployed alongside the gas-station-event-indexer on the same server so that the gas station event indexer can call the multichain relayer server via IPC instead of having to send the request over the network introducing extra latency to the system.
• Although the multichain relayer is a server in current design of this system, the goal is to package this as a library that can be called on the client side of the wallet. This will make the system more decentralized.

Functionality

1. /send_funding_and_user_signed_txns which handles both
   1. Funding the user's xchain account with gas from the paymaster treasury account, which is provided as a raw signed transaction
   2. Sending the user's raw signed transaction (in hexadecimal in EVM case) after the funding transaction has been confirmed on the foreign chain

Total Time Expectations for the End User

It depends on the chain, but in our current estimation 50-90% of the time will be on NEAR calling and waiting for the signing to complete on the MPC service. The signing service will take 15-30 seconds. We assume that both the signing of the foreign chain transaction and the gas funding transaction happen in parallel. On BSC mainnet (not beaconchain which has 1 second finality) with 3 second blocktimes there should be 2 blocks for confirmation optimistically bringing the total to 6 seconds optimistically/transaction on BSC. We need to make 2 transactions, so that's 12-24 seconds on BSC assuming 2-4 blocks for finality. Add in some network overhead for each step in the process, especially the indexer picking up the emitted event (~5-7 seconds), and we're at 30-60 seconds/transaction on BSC. For Solana it would be closer to 20-30 seconds (0.4 second block time, 1 block confirmation). See table 1 of https://usa.visa.com/solutions/crypto/deep-dive-on-solana.html for more confirmation times.

L2 real finality times can over a day for finality unless we trust a centralized sequencer for soft confirmations, which may be as fast as a few seconds as in the case of zksync era https://era.zksync.io/docs/reference/concepts/finality.html#instant-confirmations.

The difference between optimistic or soft confirmations vs real finality is something we should consider. We may get better finalized guarantees when the Eigenlayer-Near Partnership is live https://pages.near.org/blog/near-foundation-and-eigen-labs-partner-to-enable-faster-cheaper-web3-transactions-for-ethereum-rollups-via-eigenlayer/. 3-4 second finality for all ETH L2s is much more manageable.

Future Directions

Scale:

• Moar Chainzzz
• Better Capital Efficiency with ~real-time settlement using professional Market Makers

Decentralization:

• Replace Multichain Relayer Server with Client Side Libraries
• Multiple Market Makers running Relayer Servers
• Txn Trie Inclusion Proofs

Broader Wallet Support:

• Provide Chain Abstraction Services to wallets that don’t implement MPC

Intent Relayers

• AI is able to execute appropriate transactions on behalf of the user getting them the best price across all chains.
  • This involves aggregating and indexing FT, NFT market dapps.
  • i.e. User has SWEAT they'd like to swap for BTC. From these keywords, AI calls multichain relayer services to execute this action on their behalf. The actual execution may look like the user's SWEAT is sold on Orderly on the NEAR chain and they end up receiving WBTC on SOL account.