# Authentication
source: https://developer.mastercard.com/mastercard-processing-debit/documentation/api-basics-section/authentication/index.md

Mastercard Processing API uses one-legged OAuth 1.0a for authentication and authorization of client applications. For more information, refer to [Using OAuth 1.0a to Access Mastercard APIs](https://developer.mastercard.com/platform/documentation/security-and-authentication/using-oauth-1a-to-access-mastercard-apis/).  

We highly recommend using the Mastercard [client authentication libraries](https://github.com/Mastercard?q=oauth) available in several popular programming languages.