Finished Theses

47 Entries found


Todays wireless networks are imagined to rely on radio communication. With the emergence of light-emitting diodes (LEDs) for illumination, the possibility arose to modulate light at high frequencies to transmit data, termed as visible light communication (VLC). However, VLC still needs to mature, faces problems as such as portability and thus, is proposed to coexist with ubiquitous Wi-Fi. There is little practice-oriented research on this topic, as VLC in itself is not established and hardware capable of both technologies does not exist. Before hybrid networks can be adopted in commercial products, testbeds are required for development of standards.

In this thesis, VLC hardware from prior works was modified, simulated, and built. With the constructed VLC  channel, measurements of link blockage were carried out. Handover from VLC to Wi-Fi on layer 2 was designed and simulated, based on the previously made measurements. Furthermore, a combined VLC+Wi-Fi testbed was designed based on two software-defined radio (SDR) platforms. The design shows that a testbed can be realized at reasonable effort. In addition, the proposed testbed underlines the wide design space of heterogeneous networks.

Die Übertragung von Informationen mittels sichtbaren Lichtes, auch VLC genannt, ist eine altbekannte Methode. Durch die Fortschritt in der Lampen- und Sensorentechnik ist diese Art der Kommunikation wieder populär geworden. Durch die OpenVLC-Plattform wurde eine günstige Variante vorgestellt, um mit VLC zu experimentieren. Leider war der Treiber veraltet und war für höhere Geschwindigkeiten nicht stabil. Um die Hardware weiter nutzen zu können ist die Implementierung eines neuen Treibers nötig. Im Rahmen dieser Arbeit wird das unteren MAC-Layers eines neuen Treibers implementiert, welches Peer-to-Peer Verbindungen unterstützt, und die Möglichkeit bietet möglichst einfach den Umfang zu erweitern. Dabei wird der von IEEE 802.15.7 veröffentlichte Standard in Betracht gezogen.

Visible light communication describes the wireless transfer of data by using the visible light spectrum. VLC can be used to create small networks which can relieve existing WiFi and mobile networks. Due to

the fact that light does not cause electromagnetic interference it can be used in areas where conventional wireless networks are prohibited or restricted. To enable researchers to conduct experiments with the

VLC technology the OpenVLC project was created. It offers a Linux driver and a hardware extension for the BeagleBone Black. But their driver has severe stability issues and requires an outdated Linux kernel. In this thesis we develop a simple physical layer implementation for the OpenVLC hardware in form or a device driver. It implements parts of the IEEE 802.15.7 standard. Based on the existing implementation from the OpenVLC project we create an updated, more stable and higher performing version. Additionally we document the necessary configuration changes to allow the underlying operating system to deliver higher performance.

To secure the Internet of Things (IoT) while keeping its interoperability with today’s Internet is crucial to unleash the full potential of the IoT. Authentication and Authorization are fundamental guarantees to enable further security and operational challenges. To fulfill these guarantees in complex and diverse scenarios, we propose a solution based on the Authentication and Authorization for Constrained Environments (ACE) Framework, a token-based authorization, and authorization. Our solution, the IPsec profile for ACE, builds on the IPsec protocol suite and the Internet Engineering Task Force (IETF) IoT stack to provide network layer security and IPsec channel establishment based on token provisioning for constrained devices. The Direct Provisioning (DP) of Security Association (SA), symmetric-based authenticated establishment (Internet Key Exchange Protocol version 2 (IKEv2) in Pre-Shared Key (PSK) mode), and asymmetric key-based authenticated establishment (IKEv2 in Certificate-based Public Key (CPK) mode) are specified as ways to establish SAs, i.e., IPsec channels. We provide an implementation for Contiki, an Operating System (OS) for constrained devices such as the Zolertia Firefly. Furthermore, we evaluate our protocol design providing an lower bound for the performance of the profile. The evaluation includes network latency and processing time, energy consumption, memory footprint and packet sizes for the different SA establishment methods. The results provide a benchmark for the different protocol steps as well as aggregated measures for each of the evaluated setups. Our evaluation showed that the DP establishment has the smallest memory footprint and ACE packet size, and at the same time the highest performance. In the other hand, the authenticated establishment featuring IKEv2 in CPK mode, shows the largest memory footprint and packet size, together with the lowest performance of the three SA establishment methods. The trade-off regarding Random Access Memory (RAM) and Read-Only Memory (ROM) footprint, power consumption and network latency and processing time and security guarantees are also described.

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.


Absicherung von SCADA-Protokollen

Bachelor Thesis

The complexity of the technical processes in the industry increases more and more. The so-called SCADA (Supervisory Control and Data Acquisition) systems are often used to monitor these processes. As applications also include critical infrastructure, the security of these systems is very important. However, as previous research has pointed out several times, the security aspect is often realized insufficiently. In this thesis the Modbus TCP protocol is considered, which is widely used in the SCADA systems in the industry.

There already exist many approaches and research that deal with the basic cryptographic protocol weaknesses. Furthermore, the ability of internal attackers to send faulty instructions must be considered. In this thesis, a program is developed that allows filtering requests. For this purpose the user can determine constraints to deny faulty instructions.

The analysis has shown that the performance of the program depends on the rule configuration. Considering this aspect, the program is suitable for practical operation and definitely provides additional benefits in security to systems that communicate with Modbus TCP.


Tetra Security Analysis by Fuzzing

Master Thesis

We have a basic fuzzing framework for a digital trunked radio protocol. First tests showed that devices implementing this protocol have severe security issues, for example, freezing and rebooting devices with minor packet modifications is possible. Since this technology is used by emergency services and big companies, these security issues are very critical, and hence need to be revealed and fixed.

Your tasks:

  • Extend the fuzzing framework for more message types.
  • Do a structured analysis of multiple devices implementing the digital trunked radio protocol.

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. 

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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