Many Web APIs require a Digital Signature to be provided with a message body to ensure the authenticity and integrity of the message. The Digital Signature (when combined with other measures) makes it possible to prove that the request was sent by a specific party, and that it has not been tampered with or modified in flight. But it adds complications to the process of manually poking an API with tools like Postman. In this article we describe how you can configure Postman to automatically Hash, Sign and Encode request bodies to generate a Digital Signature.