Guenther Starnberger

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One crucial point in the implementation of botnets is the command and control channel, which is used by botmasters to distribute commands to compromised machines and to obtain results from previous commands. While the first botnets were mainly controlled by central IRC servers, recent developments have shown the advantages of a more decentralized approach(More)
The security of electronic transactions depends on the security of the user's terminal. An insecure terminal may allow an attacker to create or manipulate transactions. Several techniques have been developed that help to protect transactions performed over insecure terminals. TAN codes, security tokens, and smart cards prevent an attacker who obtained the(More)
Online auctions of governmental bonds and CO2 certificates are challenged by high availability requirements in face of high peak loads around the auction deadline. Traditionally, these requirements are addressed by cluster solutions. However, with strong requirements regarding hardware ownership and only a few auctions per owner per year hardware clusters(More)
Today's Internet-scale computing systems often run at a low average load with only occasional peak performance demands. Consequently, computing resources are often overdimensioned, leading to high costs. While load control techniques between clients and servers can help to better utilize a given system, these techniques can place a significant communication(More)
While it is widely recognized that security can be traded for performance and dependability, this trade-off lacks concrete and quantitative evidence. In this experience report we discuss (i) a concrete approach (temporal decoupling) to control the trade-off between those properties, and (ii) a quantitative and qualitative evaluation of the benefits based on(More)
A secure digital timestamp can assert the existence of a particular document at a specific point in time. While centralized timestamp servers show dependability drawbacks with respect to node or link failures, e.g., outages of the Internet connectivity, distributed timestamping protocols don't have these drawbacks, but are nowadays rarely seen in practice(More)
W IKIPEDIA, the free encyclopedia, is quickly increasing its influence on the Internet. More and more people link to it for term definitions, historical event descriptions and even the news. At the same time the content of the encyclopedia grows at a rapid rate. Together with the increasing amount of available information it is becoming difficult to(More)
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