# Pre-authenticate

## Overview

The `preAuthenticate` method initiates the 3D Secure authentication flow.

## Request Fields

| Field             | Type          | Required | Description        |
| ----------------- | ------------- | -------- | ------------------ |
| `merchantOrderId` | String        | Yes      | Order reference    |
| `amount`          | Money         | Yes      | Transaction amount |
| `paymentMethod`   | PaymentMethod | Yes      | Card details       |
| `returnUrl`       | String        | Yes      | Redirect URL       |

## Response Fields

| Field                | Type   | Description                            |
| -------------------- | ------ | -------------------------------------- |
| `status`             | String | FRICTIONLESS, AUTHENTICATION\_REQUIRED |
| `authenticationData` | Map    | 3DS data                               |

## Example

```java
Map<String, Object> request = new HashMap<>();
request.put("merchantOrderId", "order_001");
request.put("amount", Map.of("minorAmount", 10000, "currency", "USD"));
request.put("returnUrl", "https://your-app.com/3ds/return");

Map<String, Object> response = authClient.preAuthenticate(request);
```