ABSTRACT
Nowadays, the users of fixed and mobile devices are able to use a huge amount of different services, most of them requiring some kind of authentication. Until now, the user had to have credentials for each service he aimed to use. Either he had to use them by hand, such as by writing his username and password when configuring them into a client application, or they were encased in a smart card, such as the Subscriber Identity Module (SIM) cards in mobile phones. The existence of several credentials is a problem due not only to its inconveniency for the user but also because provisioning these credentials to the users is expensive for the operators and other service providers (3GPP TR 33.919; 2011). For example, a third-party World Wide Web (WWW)-based service provider usually sends credentials via an email to the user and asks him to change the password. This, of course, is not very secure, and requires the user to choose an appropriate password and also to remember it. An example about the costs of provisioning for the operators is the distribution of SIM cards: they have to be manufactured and sent to the clients. They also have to be replaced when new services emerge and require a new kind of functionality.
