  Using communication services is a common part of everyday life in a personal
or business context. Communication services include Internet services like
voice services, chat service, and web 2.0 technologies (wikis, blogs, etc), but
other usage areas like home energy management and eMobility are will be
increasingly tackled. Such communication services typically authenticate
participants. For this identities of some kind are used to identify the
communication peer to the user of a service or to the service itself. Calling
line identification used in the Session Initiation Protocol (SIP) used for
Voice over IP (VoIP) is just one example. Authentication and identification of
eCar users for accounting during charging of the eCar is another example. Also,
further mechanisms rely on identities, e.g., whitelists defining allowed
communication peers. Trusted identities prevent identity spoofing, hence are a
basic building block for the protection of communication. However, providing
trusted identities in a practical way is still a difficult problem and too
often application specific identities are used, making identity handling a
hassle. Nowadays, many countries introduced electronic identity cards, e.g.,
the German "Elektronischer Personalausweis" (ePA). As many German citizens will
possess an ePA soon, it can be used as security token to provide trusted
identities. Especially new usage areas (like eMobility) should from the start
be based on the ubiquitous availability of trusted identities. This paper
describes how identity cards can be integrated within three domains: home
energy management, vehicle-2-grid communication, and SIP-based voice over IP
telephony. In all three domains, identity cards are used to reliably identify
users and authenticate participants. As an example for an electronic identity
card, this paper focuses on the German ePA.
