Surrogeth

Zk Relayer is a general transaction callData that helps to broadcast tansactions to the network that uses frontrunners as relayers network. It's designed to a case where a dapp's users shouldn't be paying the gas costs for their transactions in order to improve anonymity.

The target contract does not need to know about the relayer system and just needs to have a mechanism to pay msg.sender a fee specified in the function encoded calldata.End users should also be have a way of picking a reliable way to pick a broadcaster for their transaction.

Contents

The relayer system consists of three components.

component	description
server	A node server that anyone can run to contribute to the network.
contracts	A trustless mechanism to help users discover nodes and help broadcasters forward transactions.
client	Client-side lib for integrating your app with the relayer network.

Contracts

The contracts help to provide a way for relayers to show their willingness to pay gas fees for a particular transaction for a certain reward. There are 2 main contracts that help in the relaying system. These include

component	description
Registry	This contract helps keeps track of transaction broadcasters(along with their respective locators).It also helps keeps track of all relayed transactions which helps users to pick a suitable transaction relayer based on total fees and no of transactions relayed
Forwarder	A contract that helps sends broadcast requests to the target contract address when provided with the right callData. The target contract then pays the forwarder contract a fee(who sends it to the relayer)

To run contracts test

npx hardhat tests

Server

The server component is a server that when deployed online(and its domain name is registered on a contract) can help broadcast users transactions to the blockchain for a particular specified fee. Anyone can run this server and publish their endpoint to the registry

After cloning this repo and installing dependencies. cd into this directory

cd server

Environment Variables and Config

Set up a local .env file that contains the following configuration variables

    PRIVATE_KEY ="YOUR PRIVATE KEY";
    TESTNET_RPC_URL = "https://api.s0.ps.hmny.io";
    MIN_TX_PROFIT = YOUR PROFIT IN ONE;
    FEE = YOUR BASIC FEE IN ONE;
    PORT = PORT;

Then proceed to edit the config.js file

export const PRIVATE_KEY = `${String(process.env.PRIVATE_KEY)}`;
export const TESTNET_RPC_URL = String(process.env.TESTNET_RPC_URL);
export const REGISTRY_CONTRACT = "0x4a0a5D875322De27e170f7c6E3678d47f711A50F"; //Registry Address
export const FORWARDER_CONTRACT = "0xF2E505107bbD79D9eb0C4EF475623A71BcDF6DE1"; //Forwarder Address
export const MIN_TX_PROFIT = String(process.env.MIN_TX_PROFIT);
export const FEE = String(process.env.FEE);
export const ENDPOINT = "localhost:3000"; //Your endpoint to be published on registry contract
export const MAINNET_DISALLOWED_RECIPIENTS = [""]; //Array of contract addresses not to relay to
export const PORT = parseInt(String(process.env.PORT));

Running the Server

To run the server on your machine, you compile the src files and run the server

npm start

It can also be started with the docker command.

docker compose up

Then proceed to register yourself on the registry contract after setting your endpoint in the config.js file

npx ts-node register.ts

Client

This is a light weight js module to help integrate your apps with the relayer system. This can be downloaded via npm . It provides a way for applications to provide the users relayers data.

To install module

npm i relayer-client

Get Relayer(s) Data

export async function getRelayers(n = 1) {
  const provider = await getProvider("https://api.s0.ps.hmny.io");
  const client = new RegistryClient(provider);
  const relayersAddrs = await client.getRelayers(n);
  const relayersData = Promise.all(
    relayersAddrs.map(async (relayerAddr) => {
      const { count, sum } = await client.getRelayerFee(relayerAddr);
      const locator = await client.getRelayerLocator(relayerAddr);
      return {
        addr: relayerAddr,
        count: count.toNumber(),
        sum: sum.toNumber(),
        locator: locator,
      };
    })
  );
  return relayersData;
}

To submit a transaction using a relayer locator

export async function submitTx(relayerLocator, txn) {
  const provider = await getProvider("https://api.s0.ps.hmny.io");
  const client = new RegistryClient(provider);
  const result = await client.submitTx(relayerLocator, txn);
  return result;
}