> For the complete documentation index, see [llms.txt](https://docs.payments.thalescloud.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.payments.thalescloud.io/nfc-payment/implement-nfc-payment/make-payment/manage-payment-authentication/use-issuer-application-authentication.md).

# Use issuer application authentication

### Overview

In this model, the issuer application manages Android device authentication during payment.

Use this model when the issuer application must fully control the authentication UX.

{% hint style="warning" %}
Even if the authentication screan is managed by the issuer application, NFC Payment still relies oevice screen lock authentiction method (biomertric or device keyguard).
{% endhint %}

### Flow

Implement `ContactlessTransactionListener::onAuthenticationRequired()`.

The issuer application can use device credentials, biometric authentication, or another supported Android device authentication method.

When authentication succeeds, call `ContactlessTransactionListener::onDelegatedDeviceAuthenticationSucceeded(timeOfAuth)` as soon as possible.

Pass the authentication timestamp in milliseconds.

If the end user cancels the authentication step, call `ContactlessTransactionListener::onDelegatedDeviceAuthenticationCancelled()`.

### SDK

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

```java
ContactlessTransactionListener paymentCallback = new ContactlessTransactionListener() {
    @Override
    public void onAuthenticationRequired(@NonNull VerificationMethod method) {
        // The issuer application manages Android device authentication.

        // If authentication succeeds, provide the authentication timestamp.
        // Call this API as soon as possible so the end user still has enough
        // time to perform the second tap.
        D1PayConfigParams.getInstance()
            .getContactlessTransactionListener()
            .onDelegatedDeviceAuthenticationSucceeded(System.currentTimeMillis());

        // If the end user cancels authentication, cancel the transaction.
        D1PayConfigParams.getInstance()
            .getContactlessTransactionListener()
            .onDelegatedDeviceAuthenticationCancelled();
    }

    // ...
};

// Register the contactless transaction callback.
D1PayConfigParams configParams = D1PayConfigParams.getInstance();
configParams.setContactlessTransactionListener(paymentCallback);
```

{% endtab %}
{% endtabs %}


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