Security model for RESTful application is need of Latest Architecture which is efficient and less in cost. During Research and development it is considered that this Security Model will be as light as REST architecture is where as effective enough to handle latest Security Issues. Federated Identity Management which is basic for Single Sign On (SSO) is also one of need in new security models. This Research introduced a Security Model for REST in which it would be able to Handle Federated Identity Management. JSON which is alternative for XML and also becoming popular in development due to easy to understand and human readability, it is also important to make sure this new proposed model adopt new technologies for which during development JSON is used. SAML is open source protocol but it is SOAP base, so our new RESTfull model base on SAML like structure with desire changes according to REST Architecture and also in place of XML, JSON form Data Assertion Packet were sent. We also tried to make sure our IdP which is handling every authentication and authorization processing shouldn't get over loaded also new purposed model should not be vulnerable to new security threats.