# Authentication

## Introduction

Regardless of how you choose to implement the Unipaas solution, you will need to perform one server-to-server call to initiate your connection with Unipaas.

## Server to server

**When it's used:**

* Hosted onboarding link
* Checkout page
* Pay-in API
* Account API
* Payout API

A basic authentication is enforced when performing an API request from your server to Unipaas. An authorization bearer header must be sent along with the `private_key,` provided to you in your portal account settings to access restricted API endpoints.

**Example of a checkout create API request:**

* cURL

  ```curl
  curl --location --request POST 'https://sandbox.unipaas.com/platform/pay-ins/checkout' \
  --header 'Content-Type: application/json' \
  --header 'Authorization: Bearer {{PRIVATE_KEY}}' \
  --data-raw '{
      "amount": 10,
      "currency": "GBP",
      "orderId": "1000456",
      "description": "Iphone case",
      "email": "test@test.com",
      "country": "GB",
       "items": [
      {
        "itemName": "Iphone case",
        "itemAmount" : 10,
        "vendorId" :"5ee8e655a65f08fcd71fe4d9",
        "platformFee" :  "15"

      }
       ]
  }'
  ```

## Client to server

**When it's used:** Onboarding Embedded UI

An OAuth 2.0 authorization is enforced when performing an API request from a client application such as a drop-in UI to Unipaas. For a client application to communicate with Unipaas without compromising your `private_key,` an OAuth 2.0 mechanism is used. This means before any API request from a client application; a temporary `accessToken` must be granted using the authorization API endpoint:

* cURL

  ```curl
  curl --request POST \
    --url https://sandbox.unipaas.com/platform/authorize \
    --header 'Accept: application/json' \
    --header 'Content-Type: application/json' \
    --header 'Authorization: Bearer {{private_key}}' \
    --data-raw '{
        "vendorId": "5140332a9d0ca8037a72c1812",
        "scopes": ["onboarding_write"]
     }'
  ```

Go Next[Platforms Overview](/docs/platform-overview/)