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Integrate Web3Auth with the Starknet Blockchain

While using the Web3Auth Web SDK for a non EVM chain like Starknet you get a standard provider from which you can get the private key of the user. Using this private key, you can use the corresponding libraries of the blockchain to make blockchain calls like getting user's account, fetch balance, sign transaction, send transaction, read from and write to the smart contract, etc. We have highlighted a few methods here for getting you started quickly on that.

note

This reference is for the Web, however, you can use Starknet on other Mobile and Gaming Platforms as well. Please follow our reference for EVM Blockchains, and similarly use Starknet libraries that support the platforms to use the private key and make blockchain calls accordingly.

Installation​

npm install --save web3 starknet elliptic bn.js @starkware-industries/starkware-crypto-utils

Initializing Provider​

Getting the chainConfig​

const chainConfig = {
  chainNamespace: "other",
  chainId: "0x1", //
  rpcTarget: "https://rpc.ankr.com/eth",
  // Avoid using public rpcTarget in production.
  displayName: "Starknet Mainnet",
  blockExplorerUrl: "https://explorer.immutable.com",
  ticker: "STRK",
  tickerName: "Starknet",
};

Initializing and instantiating the Web3Auth SDK​

import { Web3Auth } from "@web3auth/modal";
import { CommonPrivateKeyProvider } from "@web3auth/base-provider";
import { WEB3AUTH_NETWORK, CHAIN_NAMESPACES } from "@web3auth/base";

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

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

Getting the Web3Auth provider​

After initializing Web3Auth, the next step is to initialize the provider and use it for your operations.

// Initialize for PnP Modal SDK
await web3auth.initModal();

// Trigger the login
await web3auth.connect();

// Get the provider
const provider = web3auth.provider;

// Continue using the `provider`

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 Key​

Once a user logs in, the Web3Auth SDK returns a provider. Even though Starknet is a layer 2 on Ethereum, it is not EVM compatible. Hence to use it, one cannot use the native EIP1193 provider that Web3Auth gives for EVM blockchains. Hence we need to directly use the private key to make the calls here.

Using the function, web3auth.provider.request({method: "private_key"}) from Web3Auth provider, the application can have access to the user's private key. However, we cannot use this key with Starknet EC Curve specific signing functions, hence, we first derive the Stark Key using the getStarkKey() function.

On the underhood, it uses the starkwareCrypto.ec.keyFromPrivate() function, where we pass our Private key with the hex argument since it is hex encoded. Further, we get the public key from this using the starkwareCrypto.ec.keyFromPublic() function, and we take its X-coordinate using .pub.getX() which is our starkKey. We use this starkKey on Starknet transactions.

For the deployAccount(), we use the file ArgentAccount.json which gives us the ABI of the compiled contract. We use that contract in Starknet's defaultProvider.deployContract() function to deploy the contract.

Get ArgentAccount.json from this gist.

import starkwareCrypto from "@starkware-industries/starkware-crypto-utils";
import { ec as elliptic } from "elliptic";
/*
  Use code from the above Initializing Provider here
*/

// web3authProvider is web3auth.provider from above
const privateKey = await web3authProvider.request({ method: "private_key" });
const keyPair = starkwareCrypto.ec.keyFromPrivate(privateKey, "hex");
// get the account address from the public key
const account = starkwareCrypto.ec.keyFromPublic(keyPair.getPublic(true, "hex"), "hex");

// Use this key for the Starknet transactions
const startKey = account.pub.getX().toString("hex");

Deploy Account​

import { AddTransactionResponse, defaultProvider } from "starknet";
import starkwareCrypto from "@starkware-industries/starkware-crypto-utils";
import { ec as elliptic } from "elliptic";
import CompiledAccountContractAbi from "./ArgentAccount.json";
/*
  Use code from the above Initializing Provider here
*/

// web3authProvider is web3auth.provider from above
const privateKey = await web3authProvider.request({ method: "private_key" });
const keyPair = starkwareCrypto.ec.keyFromPrivate(privateKey, "hex");
// get the account address from the public key
const account = starkwareCrypto.ec.keyFromPublic(keyPair.getPublic(true, "hex"), "hex");

const contract = JSON.parse(JSON.stringify(CompiledAccountContractAbi));
const response = await defaultProvider.deployContract({ contract });