Sponsored Paymaster
Available on ZKsync Era mainnet, ZKsync Sepolia, Cronos zkEVM Mainnet, Cronos zkEVM Tesnet, Abstract Tesnet, Abstract Mainnet.
This guide will help you get started with Zyfi API sponsored endpoint to allow custom business logic.
In addition to the standard ERC20 Paymaster flow, it allows a protocol to decide how much of the transaction it wishes to sponsor for an user with their off-chain business logic by setting the sponsorshipRatio. What is not sponsored is paid by the user with the selected feeToken
For advanced usage and detailed explanation of each parameter and feature, please explore our detailed API documentation.
The basic flow consists of the following steps:
Deposit ETH in the audited Zyfi Vault contract that will be used to sponsor transactions for your users (Use the Zyfi Dashboard to deposit on the correct address)
The deposit transaction generates a corresponding balance in the vault, associated with your wallet address. This balance covers the transaction fees for your users
Get an
API-Key
connected to the vault balance (on the Zyfi Dashboard)Collect the transaction payload (similar to the ERC20 Paymaster)
Send an API request with the sponsorship information
Receive back the quote and transaction payload for the user to sign
Step 1: Send the API request
Send the required data to the erc20_sponsored_paymaster
endpoint. Below an example implementation using Javascript fetch (natively supported in most environments)
// Define the payload
const payload = {
chainId: 324, // Optional, defaults to zkSync Era Mainnet; valid options are 324, 300 (ZkSync-Sepolia), 388 (Cronos zkEVM Mainnet), 282 (Cronos zkEVM Testnet) and 11124 (Abstract Testnet).
feeTokenAddress: // ERC20 the user desires to use as gas token
sponsorshipRatio: // [0-100] which % of the transaction is sponsored by the protocol
replayLimit: // Optional (default of 5), how many times the user can execute the transaction
txData: {
from: "0x...",
to: "0x...",
data: "0x.."
}
};
// Define the function to perform the POST request
async function postTransactionData() {
try {
const response = await fetch('https://api.zyfi.org/api/erc20_sponsored_paymaster/v1', {
method: 'POST',
headers: {
'Content-Type': 'application/json',
'X-API-Key': '<API Key>'
},
body: JSON.stringify(payload),
});
if (!response.ok) {
throw new Error(`HTTP error! status: ${response.status}`);
}
const data = await response.json();
console.log(data); // Process the response data
} catch (error) {
console.error('Error during the API call:', error);
}
}
The returned object does not change the original transaction calldata, but add the paymaster fields necessary to process the transaction.
Step 2: Show the quote to the user
The response, on top of the transaction payload, returns a series of helper values that can be used by the UI to better inform the user. In particular:
tokenAddress
: ERC20 token address used to pay for the gas fee (feeToken)tokenPrice
: the estimated cost of the feeTokenfeeTokenAmount
: Max amount of the ERC20 token that the user will pay as fee (before refunds). The user need to have this balance for the transaction to not failfeeUSD
: Equivalent value of feeTokenAmount in USDmarkup
: Markup or discount applied on the gas feeprotocolAddress
: The account in the vault being used to pay for the sponsored partsponsorshipRatio
: which % of the transaction is sponsored by the protocolexpirationTime
:block.timestamp
of the quote expiration. Currently it's one hour
Step 3: Execute the transaction
Ensure you are using zksync-ethers V5 or V6.
Below an example implementation with
import { Signer, Web3Provider } from "zksync-ethers";
import * as ethers from "ethers";
const signer = Web3Provider.getSigner
rawTx = Apiresponse.txData
//since the API returns the transaction payload in the ethers format, we can use it as is
txHash = await signer.sendTransaction(rawTx);
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