Finished Theses

41 Entries found


Abstract of final thesis:

Apple Wireless Direct Link (AWDL) is a proprietary and undocumented 802.11 based peer-to-peer protocol. It is implemented in all of Apple's operating systems. In this thesis a reverse engineering method using binary analysis complemented by runtime analysis with traces and logs was applied. We found that each device in AWDL provides its own channel sequence. An elected master node is used to synchronize these sequences. Outside these windows of time, devices can use their wireless radio for other protocols or save energy by turning it off. Each node adapts its channel sequence, e.g. depending on network load, shifting the ratio between infrastructure and peer-to-peer Wi-Fi. This thesis also provides a first analysis of AWDL, includes the frame format documentation and presents a Wireshark dissector and a prototype implementation for AWDL.

[Abstract of final thesis] With wireless mobile IEEE 802.11a/g networks, collisions are currently inevitable despite effective counter measures. This work proposes an approach to detect the MAC addresses of transmitting stations in case of a collision, and measures its practical feasibility. Recognizing senders using cross-correlation in the time domain worked surprisingly well in simulations using Additive White Gaussian Noise (AWGN) and standard Matlab channel models.
Real-world experiments using software-defined radios also showed promising results in spite of decreased accuracy due to channel effects. During the experiments, various Modulation and Coding Schemes (MCSs) and scrambler initialization values were compared.  Knowledge about which senders were transmitting leading up to a collision could help develop new improvements to the 802.11 MAC coordination function, or serve as a feature for learning-based algorithms.

With the proliferation of numerous personal gadgets and smart devices, device pairing has become prominent in introducing security to such a diverse environment. Clearly, the process of secure device pairing is much more ambiguous than previously thought. This stems from the fact that there is no coherent vision of the pairing problem among the research community. To this end, we see that there is a plethora of various pairing protocols that have been proposed many of which are insecure or fail to work in practice. Clearly, there is no single winner in a device pairing race. 

Seeing the continuous increase in natural disasters around the world, many people are contemplating how to contribute helping those in need. Among them are several computer scientists who fulfil their share by developing technology which enables fast and reliable communication in disaster areas. We were inspired by their work and thus wanted to further improve the state-of-the-art. DTN is a specific technology which can be used for the creation of alternative networks in disaster areas, where conventional ones are unavailable due to the inevitable destructions implied by the disaster. Given that such technology is usually evaluated within network simulators we exclusively focus on improving the state-of-the-art of movement models and scenarios utilized within such simulators. The very random driven, and thus not realistic, state-of-the-art is improved by our contribution in the form of a fully designed, implemented, and evaluated realistic natural disaster movement model with underlying scenarios. The results of our evaluation indicate that previously published results might be too optimistic. Thus, further approximations to reality are inevitable for more accurate simulation of DTN, in the goal to ultimately obtain better and more realistic results.

Prof. Dr.-Ing. Matthias Hollick

Technische Universität Darmstadt
Department of Computer Science
Secure Mobile Networking Lab 

Mornewegstr. 32 (S4/14)
64293 Darmstadt, Germany

Phone: +49 6151 16-25472
Fax: +49 6151 16-25471

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