Architecture that utilizes the strong authentication mechanisms of network operators to provide authentication to mobile applications by identity federation. When a mobile client initiates request for access to an application outside the network operation infrastructure, the request is passed to an associated application secure token service. The application secure token service has an established trust and identity federation with the network operator. The application secure token service redirects the request to a network operator security token server, which then passes the request to a network operator authentication server for authentication against an operator identity service. Proof of authentication is then issued and returned from the network operator security token server to the application secure token service and the application, which allows the mobile client to access the application.