Transfer ERC20s Between Layer 1 and Layer 2 ​

Introduction ​

This tutorial will guide you through the process of using the Reddio API to deposit, transfer, and withdraw ERC20 between the Ethereum layer 1 and layer 2 blockchains using typescript.

You can get the Transfer ERC20s Between Layer 1 and Layer 2 project from github. After you cloned the project in your device, you can use following prompts to install all the dependencies.

yarn install

After install all the dependencies, use following prompts to start the project:

yarn start

Now we will go over important components of our project.

Testing parameters ​

During your application implementation. There shall be a form asks for ERC20 contract address. For testing purpose only, we will use the RDD20 as an example. RDD20 is the ERC20s we use in Reddio’s demo. The RDD20’s contract address on Sepolia testnet is:

0x57F3560B6793DcC2cb274c39E8b8EBa1dd18A086

Connect to wallet ​

If you want to deposit, transfer, and withdraw tokens between the Ethereum layer 1 and layer 2 blockchains, you need to connect to your wallet first. We will use Metamask as an example to show you how to connect to the wallet and create Stark keypairs based on it. There’s one thing to note that one Metamask wallet address will generate the same Stark keypair.

async function connectToWallet() {
    if (typeof window !== 'undefined') {
      //First, get the web3 provider if window is not undefined
      const provider = new ethers.providers.Web3Provider(window.ethereum);

      //Second, we need to ask the wallet to switch to specific ETH network
      //We will use Sepolia testnet to give example.Its hexValue is 11155111.
      await provider.send("wallet_switchEthereumChain", [
        { chainId: ethers.utils.hexValue(11155111) },
      ]);

      //Third, getting the account addresses from provider
      await provider.send('eth_requestAccounts', []);
      const signer = provider.getSigner();
      const ethAddress = await signer.getAddress();

      //Finally, we can create a new reddio instance (Sepolia testnet) 
      //And assign global variable to it
      const reddio = new Reddio({
        provider,
        env: 'test',
      });
      setReddio(reddio);

      const generateKey = async () => {
        try {
          //Generate stark private key and public key 
          //Store them into array
          const { privateKey, publicKey } = await reddio.keypair.generateFromEthSignature();

          //We will set ethAddress/starkKey/privateKey on our array
          setEventValue({ ...eventValue, ethAddress, starkKey: publicKey, privateKey })
        } catch (error) {
          console.error(error);
        }
      };

      generateKey();
    }
  }

After you start the project. You will see a “Connect wallet” button in the main page, after clicking on the button. MetaMask will show up and ask you to login.

After login into your wallet, your address will be shown on the “ETH Address”. And your stark key and stark private key will be shown on the forms. If you see your wallet’s address, that means your wallet is successfully connected to the application.

Deposit: from layer 1 to layer 2 ​

If you want to trade on layer 2, you need to have assets on layer 2. So you need to deposit your assets from layer 1 to layer 2 at first. We will use RDD20 (ERC20 that published by Reddio for testing purpose) to give example. You can get your own RDD20 by going to the demo page and click on the “Get test assets” button to get some RDD20.

Now, we will show you how to implement the deposit function in your application.

async function depositERC20() {
    //Authorize the ERC20 contract address to approve the transaction
    if (reddio !== null) {
      const { starkKey, tokenAmount, contractAddress } = eventValue
      const transaction = await reddio.erc20.approve({
        //Amounts that you want to approve 
        amount: tokenAmount,
        //ERC20's contract address 
        tokenAddress: contractAddress,
      })

      //Waiting for approval
      await transaction?.wait()

      //Deposit ERC20
      await reddio.apis.depositERC20({
        //Your starkKey (public key on layer 2)
        starkKey,
        //Amounts you want to deposit
        quantizedAmount: tokenAmount,
        //ERC20's contract address 
        tokenAddress: contractAddress,
      });
    }
  }

After you write down the proper information on the forms and click on the deposit button, your MetaMask will ask you to confirm all the transactions. After that, you can check your balance.

Transfer: from layer 2 to layer 2 ​

After deposit, you have your own RDD20 tokens on layer 2. Now you want to send the RDD20 tokens to others on layer 2.

Now, we will show you how to implement the transfer function in your application.

async function transferERC20() {
    if (reddio !== null) {
      const { starkKey, privateKey, tokenAmount, contractAddress, receiver } = eventValue
      //transfer the amount to another starkKey
      const { data: res } = await reddio.apis.transfer({
        starkKey,
        privateKey,
        contractAddress,
        amount: tokenAmount,
        type: 'ERC20',
        receiver,
      });
      console.log(res);
    }
  }

After you write down the proper information on the forms and click on the transfer button. You can check a response from your console likes the picture down below:

Transfering ERC20 tokens on layer 2 is quick. You can check your balance very soon.

Withdraw: from layer 2 to layer 1 ​

You already have a lot of ERC20 tokens on layer 2. You want these tokens back to your layer 1 wallet.

Now, we will show you how to implement the withdraw function in your application. Typically, withdraw methods are composed by two steps: withdraw from layer 2 to withdraw area and then withdraw th from layer 1.

The first step at least takes about 4 hour. You can check withdraw status here.

async function withdrawERC20FromL2() {
    if (reddio !== null) {
      const { starkKey, privateKey, tokenAmount, contractAddress, receiver } = eventValue
      //Step 1: withdraw tokens from layer 2 (usually takes 4 hour)
      const { data } = await reddio.apis.withdrawalFromL2({
        starkKey,
        privateKey,
        amount: tokenAmount,
        contractAddress,
        type: "ERC20",
        receiver,
      });

      console.log(data);
    }
  }

The second step is to withdraw the assets from layer 1. You can refer to guide here