A federation is a group of organizations or service providers which allow sharing of user identity information among each other based on a built trust. Its main goal is to enable Single Sign-On between different domains so enabling a user to authenticate himself only once and gain access to resources of multiple software systems. In the current web oriented information technology world, where an increasingly large number of services take place via the web, the federation framework provides means to enhance the user experience and to reduce the number of authentications a user will have to do while surfing between services of federated organizations. This thesis does a study of the federation concept, its specifications and some of the current software implementations for future references. In addition it studies the viability of federating the e-Catalunya platform. This is done with the development of a pilot test in which the e-Catalunya platform is prepared to form a single sign-on federation.