# CAS (Central Authentication Service)

## Introduction

> The CAS protocol is a simple and powerful ticket-based protocol. It involves one or many clients and one server. Clients are embedded in CASified applications (called “CAS services”) whereas the CAS server is a standalone component.

The Cas protocol makes it possible to implement the SSO authentication method that allows users to access web applications with a single sign-on.

The specification versions recognized are 3.0.3 and 2.0

[![cas_max_logo_0.png](https://bookstack.soffid.com/uploads/images/gallery/2022-08/scaled-1680-/cas-max-logo-0.png)](https://bookstack.soffid.com/uploads/images/gallery/2022-08/cas-max-logo-0.png)

---

[*https://apereo.github.io/cas/6.5.x/protocol/CAS-Protocol.html*](https://apereo.github.io/cas/6.5.x/protocol/CAS-Protocol.html)