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Abstract.The technique Private Information Retrieval (PIR) perfectly protects a user's access pattern to a database. An attacker cannot observe (or determine) which data element is requested by a user and so cannot deduce the interest of the user. We discuss the application of PIR on the World Wide Web and compare it to the MIX approach. We demonstrate particularly that in this context the method does not provide perfect security, and we give a mathematical model for the amount of information an attacker could obtain. We provide an extension of the method under which perfect security can still be achieved.

To mitigate global warming, the European Union aims at climate neutrality by 2050. In order to reach this, the transportation sector has to contribute especially, which accounts for about a quarter of the European greenhouse gas emissions. Herein, electricity-based fuels are a promising approach for reducing emissions. However, a large-scale deployment of electricity-based fuels has a significant impact on the power system due to high electricity demand and the requirement to use renewable energy sources in order to be sustainable. At the same time, this fuel production could offer additional flexibility for the power system. This article investigates the opportunities and challenges of electricity-based fuels and flexible electricity-based fuel production for the European power system. In a literature analysis, the pivotal role of electricity-based fuels for climate neutrality is confirmed. To analyze the impact of flexible fuel production, European power market simulations for the year 2035 are conducted. Results indicate that flexibilization leads to an increased integration of electricity based on renewable energy sources as well as reductions in both carbon dioxide emissions and total operational costs of the power system. However, very high flexibility levels also benefit high-emission power plants and may even lead to increased emissions.

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Business-to-business is the most important area in ECommerce. With the growth of this area, the importance of multimedia transfers increases as the business partners want to actually see each other during negotiations. In this paper, we will present an architecture that provides confidential multimedia transfers in the Internet, i.e. the transmitted data is protected against espionage from third parties by protecting the contents. Moreover, transmitted packets cannot be traced by observers in the Internet.