# JWT signing

Keyelss mobile SDK can generate a signed a JWT containing a custom payload. You can use the signed JWT to implement [Dynamic Linking](https://docs.keyless.io/consumer/mobile-sdk-use-cases/guide-sca-dynamic-linking).

## Generate signed JWT

Pass `JwtSigningInfo` to the authentication to generate a signed JWT:

{% tabs %}
{% tab title="Android" %}

```kotlin
//Keyless adds a td claim to the JWTs containing the data you specify
val jwtSigningInfo = JwtSigningInfo(claimTransactionData = "<your custom data")

// if you want to authenticate with biometric
val biomAuthConfig = BiomAuthConfig(jwtSigningInfo = jwtSigningInfo)
// if you want to authenticate with pin
val pinAuthConfig = PinAuthConfig(pin = "1234", jwtSigningInfo = jwtSigningInfo)

// perform the authentication
Keyless.authenticate(
    configuration = biomAuthConfig, // pinAuthConfig if you use pin
    onCompletion = { /*TODO: process result*/ }
)
```

{% endtab %}

{% tab title="iOS" %}

```swift
//Keyless adds a td claim to the JWTs containing the data you specify
let jwtSigningInfo = JwtSigningInfo(claimTransactionData: "<your custom data>")

// if you want to authenticate with biometric
let biomAuthConfig = BiomAuthConfig(jwtSigningInfo: jwtSigningInfo)
// if you want to authenticate with pin
let pinAuthConfig = PinAuthConfig(pin: "1234", jwtSigningInfo: jwtSigningInfo)

// perform the authentication
Keyless.authenticate(
    configuration: biomAuthConfig, // pinAuthConfig if you use pin
    onCompletion : { /*TODO: process result*/ }
)
```

{% endtab %}

{% tab title="Flutter" %}

```dart
import 'package:keyless_flutter_sdk/keyless.dart';
import 'package:keyless_flutter_sdk/models/jwt_signing_info.dart';
import 'package:keyless_flutter_sdk/models/configurations/authentication_configuration.dart';

// Keyless adds a td claim to the JWTs containing the data you specify
final jwtSigningInfo = JwtSigningInfo("<your custom data>");

// if you want to authenticate with biometric
final biomAuthConfig = BiomAuthConfig(
    jwtSigningInfo: jwtSigningInfo
);

// if you want to authenticate with pin
final pinAuthConfig = PinAuthConfig(
    pin: "1234",
    jwtSigningInfo: jwtSigningInfo
);

try {
    // perform the authentication with either biometric or pin config
    final result = await Keyless.instance.authenticate(
        biomAuthConfig // or pinAuthConfig if you use pin
    );
    print("JWT signed successfully: ${result.signedJwt}");
} catch (error) {
    print("Authentication failed: $error");
}
```

{% endtab %}

{% tab title="React Native" %}

```typescript
    // Keyless adds a td claim to the JWTs containing the data you specify
    const jwtSigningInfo = new JwtSigningInfo('<your custom data>');

    // if you want to authenticate with biometric
    const biomAuthConfig = new BiomAuthConfig({
      jwtSigningInfo: jwtSigningInfo,
    });
    // if you want to authenticate with pin
    const pinAuthConfig = new PinAuthConfig({
      pin: '1234',
      jwtSigningInfo: jwtSigningInfo,
    });

    const result = await Keyless.authenticate(
      biomAuthConfig // or pinAuthConfig if you use pin
    );

    result.fold({
      onSuccess(data) {
        logConsole('Auth result success ' + JSON.stringify(data, null, 2));
      },
      onFailure(error) {
        logConsole('Auth result failure ' + JSON.stringify(error, null, 2));
      },
    });
```

{% endtab %}
{% endtabs %}

## User signing public key

The AuthenticationSuccess contains the following fields:

* `signedJwt`: the signed JWT.