Social Login System for Web3 (Web3Auth, Privy)

Development of Web3 Social Login System (Web3Auth, Privy)

Classic Web3 onboarding — "install MetaMask, create seed phrase, save 24 words, never show anyone" — kills conversion. Research shows 60–80% of users abandon onboarding at wallet creation stage. Social login for Web3 solves this: user logs in via Google/Apple/Twitter, gets non-custodial wallet without seed phrase, and immediately can interact with dApp. Let's review two main platforms and implementation details.

Web3Auth: MPC Under the Hood

Web3Auth uses Threshold Key Infrastructure (tKey) — MPC-protocol where private key is split into shares, never assembled together on one device.

How It Works Technically

On first login via Google:

1. OAuth flow → JWT token from Google
2. Web3Auth Nodes verify JWT via Google JWKS endpoint
3. Nodes generate key share (1/3 of key), store at themselves
4. Device share (1/3) generated and encrypted in browser/app
5. Backup share (1/3) — can be recovery phrase, password, or social factor

For recovery, need 2 of 3 shares (2-of-3 threshold). Key reconstructed in-memory only at signing moment.

Web3Auth Integration with Viem

import { Web3Auth } from "@web3auth/modal";
import { EthereumPrivateKeyProvider } from "@web3auth/ethereum-provider";
import { createWalletClient, custom, http } from "viem";
import { mainnet } from "viem/chains";

const privateKeyProvider = new EthereumPrivateKeyProvider({
  config: { chainConfig: { chainId: "0x1", rpcTarget: RPC_URL } },
});

const web3auth = new Web3Auth({
  clientId: YOUR_WEB3AUTH_CLIENT_ID,
  web3AuthNetwork: "sapphire_mainnet", // production network
  privateKeyProvider,
});

await web3auth.init();

// "Sign in with Google" button
const provider = await web3auth.connect();

// Create walletClient as usual
const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(provider!),
});

const [address] = await walletClient.getAddresses();

Web3Auth + Account Abstraction

Web3Auth often combined with EIP-4337 for gasless experience. Web3Auth generates EOA-key which becomes smart wallet owner:

import { providerToSmartAccountSigner } from "permissionless";
import { signerToSimpleSmartAccount } from "permissionless/accounts";

// Web3Auth provider → signer → Smart Account
const smartAccountSigner = await providerToSmartAccountSigner(provider);
const smartAccount = await signerToSimpleSmartAccount(publicClient, {
  signer: smartAccountSigner,
  factoryAddress: FACTORY_ADDRESS,
  entryPoint: ENTRY_POINT_ADDRESS,
});

Now user: logged in via Google, got smart wallet address, transactions are free (Paymaster sponsors gas). Zero friction.

Privy: Emphasis on Embedded Wallets

Privy positions itself as "auth for crypto apps" with more emphasis on developer experience and embedded wallet concept. Wallet is created automatically on first login and bound to user account, not device.

Key Differences from Web3Auth

Privy stores key shares on its servers in encrypted form, user can recover access via email verification without seed phrase. Less decentralized than Web3Auth MPC, but simpler UX and sufficient for most consumer apps.

Unified auth — Privy combines in one SDK: social login (Google, Apple, Twitter, Discord), email/SMS OTP, and connecting external wallets (MetaMask, Coinbase Wallet). User can link all login methods to one account.

import { PrivyProvider, usePrivy, useWallets } from "@privy-io/react-auth";

// Provider wraps application
function App() {
  return (
    <PrivyProvider
      appId={YOUR_PRIVY_APP_ID}
      config={{
        loginMethods: ["google", "apple", "twitter", "email", "wallet"],
        embeddedWallets: {
          createOnLogin: "users-without-wallets",
        },
        appearance: {
          theme: "dark",
          accentColor: "#7B3FE4",
        },
      }}
    >
      <YourApp />
    </PrivyProvider>
  );
}

// Usage in components
function WalletButton() {
  const { login, logout, authenticated, user } = usePrivy();
  const { wallets } = useWallets();

  if (!authenticated) {
    return <button onClick={login}>Connect</button>;
  }

  // embedded wallet auto-created
  const embeddedWallet = wallets.find(w => w.walletClientType === "privy");

  return (
    <div>
      <p>{embeddedWallet?.address}</p>
      <button onClick={logout}>Disconnect</button>
    </div>
  );
}

Signing Transactions via Privy

import { useWallets } from "@privy-io/react-auth";
import { createWalletClient, custom } from "viem";

function useSendTransaction() {
  const { wallets } = useWallets();

  return async (to: string, value: bigint) => {
    const wallet = wallets.find(w => w.walletClientType === "privy");
    if (!wallet) throw new Error("No embedded wallet");

    await wallet.switchChain(8453); // Base

    const provider = await wallet.getEthereumProvider();
    const client = createWalletClient({
      chain: base,
      transport: custom(provider),
    });

    return client.sendTransaction({
      account: wallet.address as `0x${string}`,
      to: to as `0x${string}`,
      value,
    });
  };
}

Platform Comparison

Handling Edge Cases

User logged in from two devices — Web3Auth has no problems (MPC shares synchronized), Privy embedded wallet bound to account, not device. Problem occurs if user wants to export key — in Privy available via UI, in Web3Auth via getPrivateKey() method.

Account linking — user logged in via Google, then wants to add MetaMask. Privy supports linkWallet() natively. Web3Auth requires custom logic for mapping identities.

Server-side operations — if need to sign transactions without user participation (scheduled operations, batch processing), neither Web3Auth nor Privy suitable. Need separate server-side key (KMS or Fireblocks).

Typical Production System Architecture

User → Social Login (Google/Apple) → Web3Auth/Privy SDK
                                          ↓
                              Embedded Wallet (EOA)
                                          ↓
                              Smart Account (EIP-4337)
                                          ↓
                              Paymaster (gasless)
                                          ↓
                              Your dApp Contract

Full integration from scratch — 1–3 weeks depending on product complexity. Main time goes not to SDK integration (it's fast), but to: onboarding flow design, edge case handling, recovery access testing, and integration with your user system/authentication.