# Authenticate

## Overview

The `authenticate` method executes the 3D Secure authentication step. For frictionless flows, it completes silently. For challenge flows, it presents the bank's authentication page.

**Business Use Case:** After initiating 3DS with preAuthenticate, this handles the actual authentication, managing customer interaction with the bank's page.

## Purpose

| Flow Type    | What Happens                      |
| ------------ | --------------------------------- |
| Frictionless | Completes without customer action |
| Challenge    | Presents bank challenge page      |

## Request Fields

| Field                | Type          | Required | Description                            |
| -------------------- | ------------- | -------- | -------------------------------------- |
| `merchantOrderId`    | string        | Yes      | Your unique order reference            |
| `amount`             | Money         | Yes      | Transaction amount                     |
| `paymentMethod`      | PaymentMethod | Yes      | Card details                           |
| `authenticationData` | object        | No       | Existing 3DS data from preAuthenticate |
| `returnUrl`          | string        | No       | URL to redirect after authentication   |

## Response Fields

| Field                    | Type   | Description                    |
| ------------------------ | ------ | ------------------------------ |
| `connectorTransactionId` | string | Connector's authentication ID  |
| `status`                 | string | AUTHENTICATED, FAILED, PENDING |
| `authenticationData`     | object | 3DS results (ECI, CAVV)        |
| `redirectionData`        | object | Challenge URL if needed        |
| `statusCode`             | number | HTTP status code               |

## Example

### SDK Setup

```javascript
const { PaymentMethodAuthenticationClient } = require('hyperswitch-prism');

const authClient = new PaymentMethodAuthenticationClient({
    connector: 'stripe',
    apiKey: 'YOUR_API_KEY',
    environment: 'SANDBOX'
});
```

### Request

```javascript
const request = {
    merchantOrderId: "order_001",
    amount: {
        minorAmount: 10000,
        currency: "USD"
    },
    paymentMethod: {
        card: {
            cardNumber: { value: "4242424242424242" },
            cardExpMonth: { value: "12" },
            cardExpYear: { value: "2027" }
        }
    },
    returnUrl: "https://your-app.com/3ds/return"
};

const response = await authClient.authenticate(request);
```

### Response - Frictionless

```javascript
{
    connectorTransactionId: "pi_3Oxxx...",
    status: "AUTHENTICATED",
    authenticationData: {
        eci: "05",
        cavv: "AAABBIIFmA=="
    },
    statusCode: 200
}
```

### Response - Challenge Required

```javascript
{
    connectorTransactionId: "pi_3Oxxx...",
    status: "PENDING",
    redirectionData: {
        url: "https://acs.bank.com/3ds/challenge",
        method: "POST"
    },
    statusCode: 200
}
```

## Next Steps

* [postAuthenticate](https://docs.hyperswitch.io/integrations/prism/node/payment-method-authentication-service/post-authenticate) - Validate authentication results
* [Payment Service](https://docs.hyperswitch.io/integrations/prism/node/payment-service) - Process payment with auth data