Nowadays, IP mobile devices need to employ a variety of different network access technologies to gain ubiquitous connectivity. This book reviews the authentication infrastructure challenges for Internet remote access supporting ubiquitous client mobility, and proposes a series of solutions obtained by adapting and reinforcing security techniques arising from different sources. The focus is on entity authentication protocols that can be carried both by the IETF PANA authentication carrier and by the EAP mechanisms, and possibly making use of an AAA infrastructure. The core idea is to adapt authentication protocols arising from the mobile telecommunications sphere to Internet remote access. A proposal is also given for Internet access using a public key based authentication protocol. The subsequent security analysis of the proposed protocols covers a variety of aspects, including: key freshness, DoS-resistance, and false-entity-in-the-middle attacks, in addition to identity privacy of users accessing the Internet via mobile devices. This book is destined to researchers or anyone else who is interested on authentication mechanisms for Internet remote access aiming ubiquitous mobility.