Today almost all big enterprise applications are§based on multi-tier Client-/Server architectures. In§such scenarios in particular it is very hard to§pinpoint the layer of clients, due to the fact that§the advancement in technology produces a lot of§different potential clients. A web-based client has§been of no importance fifteen years ago, but§certainly is one of the most important today. §§This vagueness in the client tier requires a new§approach in concerns of security. The server part of§a Client-/Server architecture needs to be extended in§order to provide secure remote access of mobile§client applications. Password-based systems, as they§happen to exist in the past, are considered to be§insufficient to meet today s security requirements.§§Smartcards are widely accepted, have proven to be§secure and technologically mature regarding the§problems mentioned above. JavaCard and the OpenCard§Framework enable the developer to program with a§high-level language on both the smartcard and the§terminal application level.