Thesis Topics

Deterministic execution is crucial for state-machine replication, a fault-tolerance concept where multiple servers (replicas) execute the same requests. Replicas are then able to replace each other in case of faulty servers. In order to gain efficiency, multiple approaches for deterministic multithreading have been proposed, some of them by the Institute of Distributed Systems. The goal of this work is to evaluate multiple approaches and to measure their benefit, e.g. as speedup compared to a sequential solution. This has to be done with multiple workloads, of which some should be standard, e.g. the YCSB benchmark. Depending on the type of work the actual goals have to be adapted. As a Master's thesis, we expect contributions of the student in the direction of a qualified comparison which approaches are suitable for which workloads supported by measurements. Even specific workload creation may be required to underpin corner cases where a particular approach works best or worst.

State-machine replication is a fault-tolerance solution where multiple servers (replicas) execute the same requests. In order to manage the replicas, they have to handle complex replication protocols, a checkpoint mechanism etc. Obviously replicas have to communicate among each other and also with clients. As the currently available solutions are not really modular, we would like to build our own replication framework. As a first step there is a need for a messaging layer that is able to interconnect replicas and clients. Communication has to authenticated by various means (SSL, asymmetric and symmetric cryptography, message authentication codes). Further, the layer has to be aware of unavailable clients and replicas and to automatically reconnect as soon as these are back and up again. The communication layer should stick to gRPC fundamentals, e.g ProtocolBuffers but perhaps even more, to gain some interoperability and language independence. Part of the work is also an appropriate configuration concept, so that replicas know their buddy replicas and their key material. As part of a Master's thesis we would expect performance measurements and appropriate optimizations and the consideration of overload situations.

Subjective Logic (SL) is a mathematical framework for reasoning under uncertainty. It is useful for expressing opinions on how reliable information is (so-called Trust Opinions) and performing computations on these opinions. At our institute, we research applications of SL in the automotive domain, e.g. to express trust in data received from a sensor or from other vehicles. Current implementations of SL internally use floating-point arithmetic (IEEE 754) for performing calculations. However, IEEE 754 floating-point numbers are prone to introducing rounding errors. In safety-critical domains, failing to account for such errors might lead to catastrophic consequences. In this thesis/project, you will investigate the potential impact of floating-point errors in SL calculations and develop strategies to minimise it. You can choose your approach freely: whether you work theoretically (e.g. through a detailed study of literature) or practically (e.g. through implementing a test environment and explaining the observed effects) is up to you.

Abstract: Policy Languages such as XACML or ALFA are well-known and well-defined in the area of access control. With Zero Trust Service Function Chaining (ZTSFC) [https://journal.ub.tu-berlin.de/eceasst/article/view/1138], an advanced Zero Trust (ZT) architecture, new requirements came up for such Policy Languages. The goal of the thesis is to set up a list of this requirements, to identify missing features in existing policy languages. Based on this, the most promising policy language is to be extended by this missing features.

An autonomous vehicle is equipped with a variety of sensors that produce large quantites of data which the vehicle uses to run a lot of different safety-critical functions, such as Cooperative Adaptive Cruise Control or Park Assist. In this thesis, we focus on the trust between the vehicle computer and other in-vehicle components that it relies upon to provide non-compromised data as input to different safety-critical functions. The goal of the thesis is to build a tool that will automate building of in-vehicular trust models based on a system model of a vehicle. A system model of a simplified vehicle will first need to be built by using the System Modeling Language (SysML). This model will serve as an input to the automation tool that needs to output a trust model in form of a Subjective Trust Network. The methodology for building such trust models within the framework of Subjective Logic will be provided.

Service Function Chaining (SFC) is a technice to steer traffic through specific network services. To proof that the traffic was actually forwarded through the specified services, a Proof Of Transit (PoT) is used. In this project, different PoT approaches are compared and the most promising solution implemented in a HTTPS-based SFC environment.

Security assessments of networked systems require knowledge about the utilized communication protocol. For proprietary protocols without known specification and with only limited access to the end-points, the only source of information is the communication itself. To correctly conclude from the captured byte stream to message-formats, -types, and finally a protocol model, structure, message- and field-boundaries, data-type, and semantics need to be inferred. After an initial inference procedure, it is desirable to refine the existing protocol model. Actively probing an entity for the validity of message syntaxes allows to targetedly enhance the knowledge about the protocol. To do this efficiently a smart method of automatically generating test-cases depending on the current protocol model needs to be developed.