1.1 Introduction

Outsourcing is a primarily economic concept that many other sciences have adopted. In information technology (IT) the outsourcing of processing functions was extremely popular during the mainframe era, but has become less common over the last two decades. With the rise of the personal computer (PC), everyone wanted more and more powerful client computing devices. Less powerful clients and the outsourcing of special functions to dedicated server machines have regained popularity only recently. For enterprises a major business driver behind the latter process was the need for reduced total cost of ownership (TCO).

For the IT security space, the use of outsourcing can be summarized as follows: Even though the outsourcing of specific and specialized security functions to trusted third party (TTP) servers has been used for many years in specific areas of IT security (e.g., authentication), it was only at the beginning of the 1990s that this outsourcing became accepted for a wider range of security functions (such as key management...