 Chapter XI Key Distribution and Management for Mobile Applications György Kálmán University Graduate Center – UniK, Norway Josef Noll University Graduate Center – UniK, Norway Copyright © 2008, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited. AbstrAct This chapter deals with challenges raised by securing transport, service access, user privacy, and ac- counting in wireless environments. Key generation, delivery, and revocation possibilities are discussed and recent solutions are shown. Special focus is on effciency and adaptation to the mobile environment. Device domains in personal area networks and home networks are introduced to provide personal digital rights management (DRM) solutions. The value of smart cards and other security tokens are shown and a secure and convenient transmission method is recommended based on the mobile phone and near-feld communication technology. A ProblEM of MEdIA AccEss On the dawn of ubiquitous network access, data protection is becoming more and more important. While in the past network connectivity was mainly provided by wired connections, which is still con- sidered the most secure access method, current and future users are moving towards wireless access and only the backbone stays connected by wires. In a wired environment, eavesdropping is existent, but not as spread and also not easy to implement. While methods exist to receive electromagnetic radiation from unshielded twisted pair (UTP) cables, a quite good protection can be achieved already by transport layer encryption or deploying shielded twisted pair (STP) or even fbre. New technologies emerged in the wireless world, and especially the IEEE 802.11 family has drastically changed the way users connect to net- works. The most basic requirements for new devices are the capability of supporting wireless service access. The mobile world introduced general packet radio service (GPRS) and third generation (3G) mobile systems provide permanent IP con- nectivity and provide together with Wi-Fi access points continuous wireless connectivity. Besides communications devices such as laptops, phones, also cars, machines, and home appliances nowadays come with wireless/mobile connectivity.