Optimal Authentication Service (OAS) by Optimal IdM is a hosted RESTful web service offering Authentication-as-a-Service (AaaS). OAS enables customers to perform various types and levels of authentications, including single authentication and multi-factor authentication (MFA). It can be deployed in any data center and is offered in a multi-tenant or isolated/dedicated environment. OAS integrates into applications using RESTful calls, the Optimal IdM.NET SDK, or a jQuery plugin.