Abstract: Mobile operators presently offer services on behalf of service providers where such services are really carried out for the users. Mobile operators act as identity providers in this scenario, wherein service provider and identity provider share a unique identity to identify each particular user accessing a number of services. As the number of users accessing these services, and the number of services offered from different service providers increase, the storage required at the operator's network for such amount of user's identities becomes a problem. To overcome this and other problems, the present invention provides an identity Generator device arranged to generate a user's service indicator to identify the user between the service provider and the identity provider, the user's service indicator comprising a master user's identifier for identification of the user at the identity provider, and a service identifier indicating the services to be accessed at a given service provider.