Web3Auth Integration for Social Login in Crypto Mobile Apps
Web3Auth solves classic crypto onboarding problem: user wants to log in via Google or Apple ID, but get non-custodial wallet. Nobody remembers seed phrases—they lose them. Web3Auth splits key pieces via MPC (Multi-Party Computation), no seed phrase required.
How Key Architecture Works
Web3Auth splits private key via tKey (threshold key) protocol. Google login stores key piece in Torus Network nodes, piece on user device, piece in cloud backup (iCloud / Google Drive). Recovering needs minimum 2 of 3 pieces—2-of-3 scheme.
User loses device → logs in via Google on new device → key recovers. No seed phrase. Important: not fully non-custodial—Torus Network holds one piece.
SDK Integration
Web3Auth provides web3auth-react-native-sdk for React Native and native wrappers for iOS/Android.
// React Native
import { Web3Auth, LOGIN_PROVIDER } from "@web3auth/react-native-sdk";
const web3auth = new Web3Auth(WebBrowser, {
clientId: "YOUR_CLIENT_ID",
network: "mainnet",
redirectUrl: "your-app-scheme://auth",
loginConfig: {
google: {
verifier: "your-google-verifier",
typeOfLogin: LOGIN_PROVIDER.GOOGLE,
clientId: "YOUR_GOOGLE_CLIENT_ID",
},
},
});
const login = async () => {
const state = await web3auth.login({
loginProvider: LOGIN_PROVIDER.GOOGLE,
mfaLevel: "optional",
});
const privateKey = web3auth.privKey; // hex string
// Create wallet from private key
const wallet = new ethers.Wallet(privateKey);
};
After getting privKey, create wallet via ethers.js or viem. Private key not stored directly on device—reconstructed per session, lives only in memory.
Verifier Setup in Dashboard
Before integration, create Custom Verifier in Web3Auth Dashboard. For Google: OAuth 2.0 Client ID from Google Cloud Console, verifier name. For Apple Sign In: additional setup via JWT verifier because Apple uses non-standard OIDC.
Deep Link / Universal Link configured for redirect after OAuth. Android: Intent Filter in AndroidManifest.xml:
<intent-filter android:autoVerify="true">
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
<data android:scheme="yourapp" android:host="auth" />
</intent-filter>
iOS: URL Scheme in Info.plist + handling in AppDelegate.application(_:open:options:).
What Can Go Wrong
Most common: redirect_uri_mismatch. OAuth provider (Google, Apple) rejects redirect to app URL scheme if not added to allowed list in provider console. Check both environments: development and production—different Client IDs, different redirect URIs.
Second: mfaLevel. Web3Auth supports optional second factor via device. If mfaLevel = "mandatory", user forced to set backup device on first login. For crypto apps with real assets—recommend "optional" with subsequent prompting.
Web3Auth integration with social login (Google + Apple)—1–3 weeks. Pricing determined individually.