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Integrate Web3Auth with the Ethereum Blockchain in Javascript

While using the Web3Auth Web SDK, you get a EIP1193 provider, similar to the Metamask Provider. This provider can be used with libraries like web3.js, ethers.js, viem etc. to make Ethereum blockchain calls like getting the user's account, fetching balance, sign transaction, send transaction, read from and write to the smart contract, etc. We have highlighted a few here to get you started quickly on that.

Installation

To interact with the Ethereum blockchain, you can use either library with Web3Auth.

npm install --save web3

Initializing Provider

Using eip155 as chainNamespace while initializing web3auth will provide an EIP1193 compatible provider as web3auth.provider after successful authentication.

Getting the chainConfig

const chainConfig = {
chainNamespace: "eip155",
chainId: "0x1",
rpcTarget: "https://rpc.ankr.com/eth",
// Avoid using public rpcTarget in production.
// Use services like Infura, Quicknode etc
displayName: "Ethereum Mainnet",
blockExplorerUrl: "https://etherscan.io",
ticker: "ETH",
tickerName: "Ethereum",
logo: "https://cryptologos.cc/logos/ethereum-eth-logo.png",
};

Initializing and instantiating the Web3Auth SDK

import { Web3Auth } from "@web3auth/modal";
import { EthereumPrivateKeyProvider } from "@web3auth/ethereum-provider";
import { WEB3AUTH_NETWORK } from "@web3auth/base";

const privateKeyProvider = new EthereumPrivateKeyProvider({
config: { chainConfig: chainConfig }
});

const web3auth = new Web3Auth({
// Get it from Web3Auth Dashboard
clientId,
web3AuthNetwork: WEB3AUTH_NETWORK.SAPPHIRE_MAINNET,
privateKeyProvider: privateKeyProvider,
});

Get User Info

After logging in, the Web3Auth instance will provide you with information regarding the user that is logged in. This information is obtained directly from the JWT token and is not stored by Web3Auth. Therefore, this information can only be accessed through social logins after the user has logged into your application.

const user = await web3auth.getUserInfo(); // web3auth instance

Get Account and Balance

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const address = (await web3.eth.getAccounts())[0];

// Get user's balance in ether
const balance = web3.utils.fromWei(
await web3.eth.getBalance(address), // Balance is in wei
);

Send Transaction

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const fromAddress = (await web3.eth.getAccounts())[0];

const destination = "0x7aFac68875d2841dc16F1730Fba43974060b907A";
const amount = web3.utils.toWei(1); // Convert 1 ether to wei

// Submit transaction to the blockchain and wait for it to be mined
const receipt = await web3.eth.sendTransaction({
from: fromAddress,
to: destination,
value: amount,
maxPriorityFeePerGas: "5000000000", // Max priority fee per gas
maxFeePerGas: "6000000000000", // Max fee per gas
});

Sign Transaction

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const fromAddress = (await web3.eth.getAccounts())[0];

const destination = "0x7aFac68875d2841dc16F1730Fba43974060b907A";
const amount = web3.utils.toWei(1); // Convert 1 ether to wei

// Submit transaction to the blockchain and wait for it to be mined
const receipt = await web3.eth.signTransaction({
from: fromAddress,
to: destination,
value: amount,
maxPriorityFeePerGas: "5000000000", // Max priority fee per gas
maxFeePerGas: "6000000000000", // Max fee per gas
});

Sign Message

Personal Sign

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const fromAddress = (await web3.eth.getAccounts())[0];

const originalMessage = "YOUR_MESSAGE";

const signedMessage = await web3.eth.personal.sign(originalMessage, fromAddress);

Sign Typed Data v1

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const fromAddress = (await web3.eth.getAccounts())[0];

const originalMessage = [
{
type: "string",
name: "fullName",
value: "Satoshi Nakamoto",
},
{
type: "uint32",
name: "userId",
value: "1212",
},
];
const params = [originalMessage, fromAddress];
const method = "eth_signTypedData";

const signedMessage = await web3.currentProvider.sendAsync({
id: 1,
method,
params,
fromAddress,
});

Sign Typed Data v3

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const fromAddress = (await web3.eth.getAccounts())[0];

const originalMessage = {
types: {
EIP712Domain: [
{
name: "name",
type: "string",
},
{
name: "version",
type: "string",
},
{
name: "verifyingContract",
type: "address",
},
],
Greeting: [
{
name: "contents",
type: "string",
},
],
},
primaryType: "Greeting",
domain: {
name: "web3auth",
version: "1",
verifyingContract: "0xE0cef4417a772512E6C95cEf366403839b0D6D6D",
},
message: {
contents: "Hello, from Web3Auth!",
},
};
const params = [fromAddress, originalMessage];
const method = "eth_signTypedData_v3";

const signedMessage = await web3.currentProvider.sendAsync({
id: 1,
method,
params,
fromAddress,
});

Sign Typed Data v4

import { Eip712TypedData } from "web3/lib/types"
...

/*
Sign Typed Data v4 adds support for
arrays and recursive data types.

Otherwise, it works the same as Sign Typed Data v3.
*/

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

// Get user's Ethereum public address
const fromAddress = (await web3.eth.getAccounts())[0];

const originalMessage:Eip712TypedData = {
domain: {
// Defining the same active chain Id
chainId: 11155111, // 1 for mainnet
// Give a user friendly name to the specific contract you are signing for.
name: "Ether Mail",
// If name isn't enough add verifying contract to make sure you are establishing contracts with the proper entity
verifyingContract: "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC",
// Just let's you know the latest version. Definitely make sure the field name is correct.
version: "1",
},

// Defining the message signing data content.
message: {
/*
- Anything you want. Just a JSON Blob that encodes the data you want to send
- No required fields
- This is DApp Specific
- Be as explicit as possible when building out the message schema.
*/
contents: "Hello, Bob!",
attachedMoneyInEth: 4.2,
from: {
name: "Cow",
wallets: ["0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826", "0xDeaDbeefdEAdbeefdEadbEEFdeadbeEFdEaDbeeF"],
},
to: [
{
name: "Bob",
wallets: [
"0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB",
"0xB0BdaBea57B0BDABeA57b0bdABEA57b0BDabEa57",
"0xB0B0b0b0b0b0B000000000000000000000000000",
],
},
],
},
// Refers to the keys of the *types* object below.
primaryType: "Mail",
types: {
// TODO: Clarify if EIP712Domain refers to the domain the contract is hosted on
EIP712Domain: [
{ name: "name", type: "string" },
{ name: "version", type: "string" },
{ name: "chainId", type: "uint256" },
{ name: "verifyingContract", type: "address" },
],
// Not an EIP712Domain definition
Group: [
{ name: "name", type: "string" },
{ name: "members", type: "Person[]" },
],
// Refer to PrimaryType
Mail: [
{ name: "from", type: "Person" },
{ name: "to", type: "Person[]" },
{ name: "contents", type: "string" },
],
// Not an EIP712Domain definition
Person: [
{ name: "name", type: "string" },
{ name: "wallets", type: "address[]" },
],
},
};

const signedMessage = await web3.eth.signTypedData(fromAddress, originalMessage)

Smart Contract

Solidity Contract

In this example, we'll be demonstrating how to use Web3Auth with web3.js or ethers.js to interact with Solidity smart contracts. The simple Hello World contract allows anyone to read and write a message to it.

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

contract HelloWorld {

string public message;

constructor(string memory initMessage) {
message = initMessage;
}

function update(string memory newMessage) public {
message = newMessage;
}
}

Deploy Contract

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

const contractABI = [
{
inputs: [{ internalType: "string", name: "initMessage", type: "string" }],
stateMutability: "nonpayable",
type: "constructor",
},
{
inputs: [],
name: "message",
outputs: [{ internalType: "string", name: "", type: "string" }],
stateMutability: "view",
type: "function",
},
{
inputs: [{ internalType: "string", name: "newMessage", type: "string" }],
name: "update",
outputs: [],
stateMutability: "nonpayable",
type: "function",
},
];
const contractByteCode =
"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const contract = new web3.eth.Contract(JSON.parse(JSON.stringify(contractABI)));

// Deploy contract with "Hello World!" in the constructor and wait to finish
const contractInstance = await contract
.deploy({
data: contractByteCode,
arguments: ["Hello World!"],
})
.send({
from: (await web3.eth.getAccounts())[0],
});

Read From Contract

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

const contractABI = [
{
inputs: [{ internalType: "string", name: "initMessage", type: "string" }],
stateMutability: "nonpayable",
type: "constructor",
},
{
inputs: [],
name: "message",
outputs: [{ internalType: "string", name: "", type: "string" }],
stateMutability: "view",
type: "function",
},
{
inputs: [{ internalType: "string", name: "newMessage", type: "string" }],
name: "update",
outputs: [],
stateMutability: "nonpayable",
type: "function",
},
];
const contractAddress = "0x04cA407965D60C2B39d892a1DFB1d1d9C30d0334";
const contract = new web3.eth.Contract(JSON.parse(JSON.stringify(contractABI)), contractAddress);

// Read message from smart contract
const message = await contract.methods.message().call();

Write to Contract

/*
Use code from the above Initializing Provider here
*/

// web3 is const web3 = new Web3(web3Auth.provider); from above.

const contractABI = [
{
inputs: [{ internalType: "string", name: "initMessage", type: "string" }],
stateMutability: "nonpayable",
type: "constructor",
},
{
inputs: [],
name: "message",
outputs: [{ internalType: "string", name: "", type: "string" }],
stateMutability: "view",
type: "function",
},
{
inputs: [{ internalType: "string", name: "newMessage", type: "string" }],
name: "update",
outputs: [],
stateMutability: "nonpayable",
type: "function",
},
];
const contractAddress = "0x04cA407965D60C2B39d892a1DFB1d1d9C30d0334";
const contract = new web3.eth.Contract(JSON.parse(JSON.stringify(contractABI)), contractAddress);

// Write message to smart contract
const receipt = await contract.methods.update("W3A").send({
from: (await web3.eth.getAccounts())[0],
});

Fetch User's Private Key

eth_private_key is used to fetch the private key of the logged in user. It is only available for in-app adapters like openlogin.

//Assuming user is already logged in.
async getPrivateKey() {
const privateKey = await web3auth.provider.request({
method: "eth_private_key"
});
//Do something with privateKey
}