# CAS Authentication ## 🔐 What is CAS authentication ? Using the [central authentication service](https://en.wikipedia.org/wiki/Central_Authentication_Service) (CAS) you can enable single-sign-on on your ngSurvey forms using a CAS server to authenticate the respondents. The CAS security item will automatically redirect the respondent to the CAS server if it can't find any ticket. If a ticket was found but the ticket was invalid it will ask the respondent to log back into the CAS server. ## 🔅 CAS properties * **`CAS URL`**URL of the server hosting your CAS. eg: * **`Allow multiple submissions`** can a respondent take part multiple time to the same survey. * **`Login message`** is the message that will be shown to the respondent on the login page that will allow him load the CAS server login page. This message will be shown if ngSurvey fails to authenticate automatically the user. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.ngsurvey.com/form-management/security/security-items/cas-authentication.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.