ETH Deposit and Withdraw Guide

This tutorial uses the Matic Testnet ( Mumbai ) which is mapped to the Goerli Network to demonstrate the asset transfer to and fro the two blockchains. An important thing to be noted while following this tutorial is that you should always use a Proxy address whenever it is available. For eg. The RootChainManagerProxy address has to be used for interaction instead of the RootChainManager address. The PoS contract addresses, ABI, Test Token Addresses and other deployment details of the PoS bridge contracts can be found here.

Mapping your assets is necessary to integrate the PoS bridge on your application. You can submit a mapping request here. But for the purpose of this tutorial, we have already deployed the Test tokens and Mapped then on the PoS bridge. You may need it for trying out the tutorial on your own. You can request the desired Asset from the faucet. If the test tokens are unavailable on the faucet, do reach us on discord

In the upcoming tutorial, every step will be explained in detail along with a few code snippets. However, you can always refer to this repository which will have all the example source code that can help you to integrate and understand the working of PoS bridge.

High Level Flow

Deposit ETH -

  1. Make depositEtherFor call on RootChainManager and send the required ether.

Withdraw ETH -

  1. Burn tokens on matic chain.
  2. Call exit function on RootChainManager to submit proof of burn transaction. This call can be made after checkpoint is submitted for the block containing burn transaction.

Steps

Deposit

ETH can be deposited to matic chain by calling depositEtherFor on RootChainManager contract. Matic POS client exposes depositEtherForUser method to make this call.

ETH is deposited as ERC20 token on Matic chain. For withdrawing it follow the same process as withdrawing ERC20 tokens.

await maticPOSClient.depositEtherForUser(from, amount, {
from,
gasPrice: "10000000000",
});

NOTE: Deposits from Ethereum to Matic happen using a state sync mechanism and takes about ~5-7 minutes. After waiting for this time interval, it is recommended to check the balance using web3.js/matic.js library or using Metamask. The explorer will show the balance only if at least one asset transfer has happened on the child chain. This link explains how to track the deposit events.

Burn

User can call withdraw function of MaticWETH contract. This function should burn the tokens. Since Ether is an ERC20 token on matic chain, use burnERC20 method that Matic POS client exposes to make this call.

await maticPOSClient.burnERC20(childToken, amount, { from });

Store the transaction hash for this call and use it while generating burn proof.

Exit

Once the checkpoint has been submitted for the block containing burn transaction, user should call the exit function of RootChainManager contract and submit the proof of burn. Upon submitting valid proof tokens are transferred to the user. Matic POS client exposes exitERC20 method to make this call. This function can be called only after the checkpoint is included in the main chain. The checkpoint inclusion can be tracked by following this guide.

await maticPOSClient.exitERC20(burnTxHash, { from });