Contributions published at Communication Systems Group (Burkhard Stiller)

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Distributed Denial-of-Service (DDoS) attacks are one of the major causes of concerns for communication service providers. When an attack is highly sophisticated and no countermeasures are available directly, sharing hardware and defense capabilities become a compelling alternative. Future network and service management can base its operations on equally distributed systems to neutralize highly distributed DDoS attacks. A cooperative defense allows for the combination of detection and mitigation capabilities, the reduction of overhead at a single point, and the blockage of malicious traffic near its source. Main challenges impairing the widespread deployment of existing cooperative defense are: (a) high complexity of operation and coordination, (b) need for trusted and secure communications, (c) lack of incentives for service providers to cooperate, and (d) determination on how operations of these systems are affected by different legislation, regions, and countries. The cooperative Blockchain Signaling System (BloSS) defines an effective and alternative solution for security management, especially cooperative defenses, by exploiting Blockchains (BC) and Software-Defined Networks (SDN) for sharing attack information, an exchange of incentives, and tracking of reputation in a fully distributed and automated fashion. Therefore, BloSS was prototyped and evaluated through a global experiment, without the burden to maintain, design, and develop special registries and gossip protocols.

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In the last years, cryptocurrencies have becomeincreasingly popular along with their underlying distributedledger technology, referred to as a Blockchain (BC). Nowadays,a wide variety of BC implementations are available. However,the selection of a suitable implementation for a particularapplication or use case is complex because it requires technicalunderstanding of the underlying BC implementation aspects.Therefore, this paper proposes a Controlled Natural Language(CNL) to extends existing BC selection solutions to abstractunderlying implementation details. The approach allows thespecification abstract high-level policies, referred to as intents, inan English-based language. The approach is inspired by previousapproaches from the network management field. Moreover, astate machine-based refinement technique is proposed to refinethese intents into low-level BC selection policies. The resultsof the performance evaluation of the prototype implementationshow that the refinement process presents a minimal overhead.In addition, the perceived intuitiveness of the CNL by userswas assessed in a survey. The results of the survey suggest thattechnical and non-technical individuals benefit from an intent-based approach equally

In the last two decades the internet has changed many areas of our lives, especially in the way information is gathered[85]. This transition can also be seen in the realm of politics where Voting Advice Applications (VAA) have seen a major increase in usage[80]. However, these tools have not been spared with criticism. Research has shown that the recommendation strongly depends on the design choices in a VAA[76], e.g., the algorithm used in a VAA. Furthermore, even though some VAA providers publish their methodologies, there still is a lack of transparency, due to the central architecture these VAAs are built on. This bachelor's thesis tries to shed light on the situation in Switzerland by comparing four VAAs. This analysis includes a comparison and evaluation of the currently deployed VAAs, based on design criteria gathered from related work. Furthermore, the VAAs will also be assessed from a technical point of view, outlining the problems that come with the centralized architecture. As a possible solution to these problems, the final part of this thesis shows how a decentralized architecture in form of a Smart Contract architecture could look like. The findings of the comparison show that some Swiss VAAs have a significant lack of transparency in the disclosure of their processes. They further show that the design of the VAAs differ from provider to provider. From a technical standpoint, the thesis provides an alternate option to a centralized architecture, while also outlining the challenges that could come with this change.

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