# Postman collection
source: https://developer.mastercard.com/mastercard-processing-mastercard/documentation/developer-tools/postman-collection/index.md

## Overview {#overview}

Postman is an application for easy RESTful API exploration. You can use Postman to test API calls multiple times without having to write code. You can save multiple sets of credentials to quickly test an API calls in the Sandbox and Production environments.

## Pre-requisites {#pre-requisites}

* [Postman account](https://www.postman.com/) (Sign up or log in)
* Mastercard Developers project with Sandbox and Production credentials  

> **What you will learn:**
>
> * Set up the Postman environment for Mastercard Processing APIs
> * Configure authentication for Mastercard Processing APIs
> * Configure payload encryption for Mastercard Processing APIs

## Step 1 - Import environment variables {#step-1---import-environment-variables}

Download the environment variables collection (JSON file) from
[sandbox.postman_environment.zip](https://static.developer.mastercard.com/content/mastercard-processing-mastercard/uploads/sandbox.postman_environment.zip) (2KB) created explicitly for the Mastercard Processing APIs Sandbox environment.

## Step 2 - Import the Postman collection {#step-2---import-the-postman-collection}

Download the Postman collection (JSON file) from
[mp_api_2.0_sandbox.postman_collection_v1.7.zip](https://static.developer.mastercard.com/content/mastercard-processing-mastercard/uploads/mp_api_2.0_sandbox.postman_collection_v1.7.zip) (51KB). The collection contains sample requests for testing the Mastercard Processing APIs in the Sandbox environment.
Warning: Storing API private keys directly in a Postman workspace is not secure, as it can be synced to the cloud when you are logged into your Postman account. To mitigate this risk, the provided Postman collection is explicitly configured to work with the dedicated Data Encryption Utility, ensuring that private keys remain stored only on your local machine.

## Step 3 -- Enabling authentication and encryption using data encryption utility {#step-3--enabling-authentication-and-encryption-using-data-encryption-utility}

The data encryption utility is a lightweight Java Spring Boot application that securely stores the certificates locally. It also performs all required encryption tasks, including JWE payload encryption.

The source code for the Mastercard Processing APIs data encryption utility is available at
[mp-data-encryption-utility-v1.5.0.zip](https://static.developer.mastercard.com/content/mastercard-processing-mastercard/uploads/mp-data-encryption-utility-v1.5.0.zip) (36KB).

* To configure and run the application, refer to the README.md file located in the root directory.

## Step 4 -- Setting up the base URL {#step-4--setting-up-the-base-url}

* In Postman, select the `sandbox` environment from the drop-down list.  

Once the data encryption utility is compiled and running locally, execute the desired API request in Postman. Postman automatically routes OAuth signing and payload encryption through the utility's local endpoint.