# Pre-authenticate

## Overview

The `pre_authenticate` method initiates the 3D Secure authentication flow. It determines whether frictionless or challenge-based verification is needed.

**Business Use Case:** Before processing a high-value transaction, initiate 3DS to reduce fraud liability.

## Purpose

| Scenario         | Benefit                   |
| ---------------- | ------------------------- |
| Fraud prevention | Shift liability to issuer |
| SCA compliance   | Meet EU requirements      |

## Request Fields

| Field               | Type          | Required | Description                 |
| ------------------- | ------------- | -------- | --------------------------- |
| `merchant_order_id` | str           | Yes      | Your unique order reference |
| `amount`            | Money         | Yes      | Transaction amount          |
| `payment_method`    | PaymentMethod | Yes      | Card details                |
| `return_url`        | str           | Yes      | URL to redirect after 3DS   |

## Response Fields

| Field                      | Type | Description                            |
| -------------------------- | ---- | -------------------------------------- |
| `connector_transaction_id` | str  | Connector's 3DS transaction ID         |
| `status`                   | str  | FRICTIONLESS, AUTHENTICATION\_REQUIRED |
| `authentication_data`      | dict | Device data for next step              |
| `redirection_data`         | dict | Challenge URL if required              |
| `status_code`              | int  | HTTP status code                       |

## Example

### SDK Setup

```python
from hyperswitch_prism import PaymentMethodAuthenticationClient

auth_client = PaymentMethodAuthenticationClient(
    connector='stripe',
    api_key='YOUR_API_KEY',
    environment='SANDBOX'
)
```

### Request

```python
request = {
    "merchant_order_id": "order_001",
    "amount": {
        "minor_amount": 10000,
        "currency": "USD"
    },
    "payment_method": {
        "card": {
            "card_number": {"value": "4242424242424242"},
            "card_exp_month": {"value": "12"},
            "card_exp_year": {"value": "2027"}
        }
    },
    "return_url": "https://your-app.com/3ds/return"
}

response = await auth_client.pre_authenticate(request)
```

### Response

```python
{
    "connector_transaction_id": "pi_3Oxxx...",
    "status": "FRICTIONLESS",
    "authentication_data": {
        "eci": "05",
        "cavv": "AAABBIIFmA=="
    },
    "status_code": 200
}
```

## Next Steps

* [authenticate](https://docs.hyperswitch.io/integrations/prism/python/payment-method-authentication-service/authenticate) - Complete the 3DS flow