---
title: "Authentication"
source_url: https://docs.rapyd.net/en/authentication.html
lang: en
---

# Authentication

Most messages between the client and Rapyd are authenticated with the values of specific header parameters.

- REST requests and webhooks contain header parameters for authentication of the messages. See [Header Parameters](https://docs.rapyd.net/en/header-parameters.md "Header Parameters").
- The `signature` header parameter for REST requests is calculated according to a specific formula. See [Request Signatures](https://docs.rapyd.net/en/request-signatures.md "Request Signatures").
- The `signature` header parameter for webhooks is calculated according to a specific formula. The client can use this information as an additional layer of protection. See [Webhook Authentication](https://docs.rapyd.net/en/webhook-authentication.md "Webhook Authentication").

REST responses from Rapyd do not contain headers.

> **Note:**
>
> The formula for calculating the `signature` header parameter differs between REST requests and webhooks. The webhook formula excludes the HTTP method.