Enabling Gasless Transactions

High gas fees or the requirement to hold native rBTC are major friction points for new users. RIF Relay solves this by allowing a third party (a Paymaster) to sponsor the gas or allowing users to pay fees in ERC-20 tokens like USDRIF.

Prerequisites

• RIF Relay SDK: Installed via npm.
• Smart Wallet: Users must use a RIF Relay-compatible Smart Wallet (e.g., the RIF Wallet or a custom proxy).
• Funded Paymaster: If you are sponsoring transactions, your Paymaster contract must have a t-rBTC balance on Testnet.

Getting Started

1. Install the Relay SDK

Add the necessary libraries to your frontend project.

npm install @rsksmart/rif-relay-sdk ethers

2. Configure the Relay Client

Initialize the client to connect to a Relay Server. This server acts as the "worker" that submits the transaction to the network on the user's behalf.

import { RelayProvider } from '@rsksmart/rif-relay-sdk';

const config = {
  relayHubAddress: '0x...', // Official RelayHub address
  rpcUrl: '[https://public-node.testnet.rsk.co](https://public-node.testnet.rsk.co)'
};

const provider = new RelayProvider(window.ethereum, config);

3. Sending a Sponsored Transaction

The user signs a data structure instead of a standard Ethereum transaction. The Relay server then wraps this and submits it.

const tx = await contract.populateTransaction.myFunction(arg1, arg2);
const relayRequest = await provider.createRelayRequest(tx);

// The user signs the request (does not cost gas)
const signedRequest = await provider.signRelayRequest(relayRequest);

// Submit to the Relay Server
const metadata = await provider.submitRelayRequest(signedRequest);

Troubleshooting

• "Paymaster balance too low": Ensure your Paymaster contract is funded. If the Paymaster runs out of rBTC, it cannot "wrap" and pay for user transactions.

• Signature Mismatch: Ensure the domainSeparator in your signing logic matches the RelayHub version deployed on the network.

Related Use Cases or Resources

• RIF Relay Full Documentation

• Onboarding with Smart Wallets

• Accepting USDRIF Payments