> ## Documentation Index
> Fetch the complete documentation index at: https://base-a060aa97-danc-alpha-docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# useAuthenticate

> Cryptographically authenticate users with Sign In with Farcaster

Defined in [@coinbase/onchainkit](https://github.com/coinbase/onchainkit)

<Info>
  Provides cryptographically secure user authentication using Sign In with Farcaster (SIWF). Returns verified user identity and signature for secure operations.
</Info>

## Returns

<ResponseField name="user" type="AuthenticatedUser | null">
  Authenticated user object with verified identity, or null if not authenticated.

  <Expandable title="AuthenticatedUser properties">
    <ResponseField name="fid" type="string">
      Verified Farcaster ID of the authenticated user.
    </ResponseField>

    <ResponseField name="signature" type="string">
      Cryptographic signature proving user identity.
    </ResponseField>

    <ResponseField name="message" type="string">
      The signed message used for authentication.
    </ResponseField>
  </Expandable>
</ResponseField>

<ResponseField name="authenticate" type="() => Promise<AuthenticatedUser | null>">
  Function to trigger the authentication flow. Returns verified user data on success.
</ResponseField>

<RequestExample>
  ```tsx components/AuthButton.tsx
  import { useAuthenticate } from '@coinbase/onchainkit/minikit';
  import { useState } from 'react';

  export default function AuthButton() {
    const { user, authenticate } = useAuthenticate();
    const [isAuthenticating, setIsAuthenticating] = useState(false);

    const handleAuth = async () => {
      setIsAuthenticating(true);
      try {
        const authenticatedUser = await authenticate();
        if (authenticatedUser) {
          console.log('Authenticated user:', authenticatedUser.fid);
          // Save to your backend
          await saveUserSession(authenticatedUser);
        }
      } catch (error) {
        console.error('Authentication failed:', error);
      } finally {
        setIsAuthenticating(false);
      }
    };

    if (user) {
      return (
        <div>
          <p>✅ Authenticated as FID: {user.fid}</p>
          <button onClick={() => window.location.reload()}>
            Sign Out
          </button>
        </div>
      );
    }

    return (
      <button 
        onClick={handleAuth}
        disabled={isAuthenticating}
      >
        {isAuthenticating ? 'Authenticating...' : 'Sign In with Farcaster'}
      </button>
    );
  }
  ```

  ```tsx components/ProtectedFeature.tsx  
  import { useAuthenticate } from '@coinbase/onchainkit/minikit';

  export default function ProtectedFeature() {
    const { user, authenticate } = useAuthenticate();

    if (!user) {
      return (
        <div className="auth-required">
          <h3>Authentication Required</h3>
          <p>Please sign in to access this feature</p>
          <button onClick={authenticate}>
            Sign In with Farcaster
          </button>
        </div>
      );
    }

    return (
      <div className="protected-content">
        <h3>Welcome, {user.fid}!</h3>
        <p>This is a protected feature only available to authenticated users.</p>
      </div>
    );
  }
  ```
</RequestExample>

### Context vs Authentication

Use the right tool for the job:

```tsx components/SecurityExample.tsx
import { useAuthenticate, useMiniKit } from '@coinbase/onchainkit/minikit';

export default function SecurityExample() {
  const { user } = useAuthenticate(); // For security
  const { context } = useMiniKit();   // For UX 

  return (
    <div>
      {/* Safe: UX personalization with context */}
      {context.user.fid && (
        <p>Hi there, user {context.user.fid}!</p>
      )}
      
      {/* Safe: Security with authentication */}
      {user && (
        <SecureUserDashboard verifiedFid={user.fid} />
      )}
    </div>
  );
}
```

<Info>
  `useAuthenticate` provides cryptographic proof of user identity. Always verify signatures server-side for security-critical operations. Use `useMiniKit` context only for UX hints and analytics.
</Info>