For any real-time system, being predictable with respect to time is a basic necessity. The combination of a preemptive execution model and a multiprocessor platform poses a challenge when analysing the predictability of a system. In this thesis, we present a new type of framework for the worst-case response time analysis for preemptive tasks scheduled on multiprocessor platforms. The proposed framework analyses this worst-case response time by building a schedule abstraction graph that abstracts all the execution scenarios that occur in the system. Since preemptive tasks scheduled on a multiprocessor platform creates a large state space of execution scenarios to explore, a schedule abstraction graph can easily face a state space explosion problem. A novel methodology has been introduced in this thesis, that allows us to eliminate state space explosion altogether. We used this new schedule abstraction graph framework to initially develop an analysis for uniprocessor platforms and compare it to the state-of-the-art. We then explain how the analysis can be extended from uniprocessor to multiprocessor platforms.

Modern times have seen an increasing use of networked control systems, in which plants and controllers may not necessarily have a direct link but instead be connected through a network, thereby closing control loops over multiple nodes.

The system may also be spread out spatially over a large area, and thus the associated network delays could greatly hamper control performance, potentially affecting the closed-loop stability of the system. In such scenarios, event-triggered control approaches could greatly reduce network congestion
by allowing a means for the controllers to send control loop computation packets over the network only when required, in an event-driven manner, rather than through periodic transmissions. However, in practice, the number of parallel channels is limited compared to the number of controllers and hence the transmission of packets needs to be scheduled carefully to avoid network conflicts.

This thesis explores using a network of timed (game) automata composed of models representing a networked control system’s control loops and its communication network. This reduces the scheduling problem of transmission of control loop computations to one of creating strategies using known algorithms, with the objective being to avoid network conflicts brought about by simultaneous transmissions. Furthermore, the proposed automata models also aim to reduce the conservatism of generated scheduling strategies by allowing the control loops a bounded number of retransmission attempts to send packets over the network in case it is already occupied. The concept is finally demonstrated in practice using simulated plants and controllers distributed over multiple machines connected via a physical CAN network.

As software security expert Bruce Schneier argues, the pervasive vulnerability of embedded systems today is structurally similar to the security crisis of PCs in the mid-1990s—only much worse. Embedded devices are ideal malware targets for several reasons. Firstly, Internet-connected devices are inherently more exposed to remote exploitation. Furthermore, embedded systems are notoriously difficult to update, regularly leading to unpatched vulnerabilities. Last but not least, many such devices operate in a mostly unattended fashion, which means that the timely discovery of compromise is unlikely. Hardening is the process of securing a system by reducing its surface of vulnerability. Hardening of the already deployed embedded devices that are connected to the internet is examined in this research. A method capable of automatically generating and enforcing security configuration based on the embedded system’s set of functions has been designed and implemented. The proposed system is dynamic, automatic, and seamless. Hardening level of such devices is measured through recognized security benchmarks. The objective is to harden the product as much as possible while maintaining its full functionality. This study concerns embedded systems using custom Linux-distribution software. The thesis was conducted in cooperation with Atos. OpenScape Business series X (OSBiz X) was used as a case study. OSBiz X is an embedded system used as a telephony center, with more than 150.000 systems already deployed worldwide. Implementing the system described above on OSBiz X significantly increased the hardening-level of the product while its functionality remained intact. Due to the case study’s scenario results, Atos plans to integrate the proposed system into the next version of OSBiz X’s official release. Finally, ongoing research about other internal organization’s products that could greatly benefit from this approach is being conducted.

Blockchains such as the Bitcoin facilitate the online transaction between users without an intermediate financial institution and can serve as a global currency. However, at the moment, blockchain solutions are suffering from low transaction throughput and high delays. For instance, the bitcoin network processes at most 7 transactions per second. Blockchain second layer solutions aim to solve this transaction scaling problem with the idea of creating off-chain transactions using payment channels. For a payment channel, the blockchain network is only required to initialize and terminate the channels. Otherwise, they can finalize transactions between pairs of users instantly without using the blockchain network. The Lightning Network is one such payment channel solution that creates an overlay network on top of the blockchain and routes payments across users. Currently, the Lightning network uses source routing to route payments from a source to a destination. However, source routing does not scale to large networks.

In this thesis, we begin by establishing the requirements for routing in the Lightning Network. Next, we analyze generic payment routing algorithms based on the set requirements and understand their limitations. Further, we design a routing algorithm for the Lightning Network that builds upon the key ideas found in the previous work. We, in particular, provide design solutions for computing transaction fees and communicating errors in a privacy-preserving manner. These problems were not addressed in any earlier works. Finally, we implement our algorithm in an active Lightning Network codebase. We evaluate it with regard to security, privacy, and performance requirements and also compare the same with the existing solution.

Automated generation of robot controllers using an Evolutionary Algorithm(EA) has received increasing attention in the last years as it has the potentialfor a reduction in the development time of a robot. Often these EAs generateNeural Networks (NNs) as robot controllers. Using a NN for automaticallygenerating robot controllers has two important downsides: 1.) A human isnot able to fully understand the inner working of a multi-layer NN, and 2.)a NN has only limited abilities to decompose a complex task into sub tasks.Both of these downsides can be addressed by using a State Machine (SM)instead of a NN as robot controller. Therefore, this thesis introduces an EAcalled Evolving State Machines As Controllers (ESMAC). ESMAC generatesSMs instead of NNs. A SM is understandable for humans because ofits modularity and allows for task decomposition by using a state for eachsub task. Furthermore, two extensions of ESMAC are proposed: adaptiveESMAC and selector ESMAC. Adaptive ESMAC aims to automatically determinesthe number of states with which the best tness for a task canbe achieved. Selector ESMAC replaces the transitions that are used in aSM to switch between states with a NN-based switching mechanism. This switching mechanism allows mutations to make more gradual changes to aSM's behaviours, which improves the performance of the EA. The performance of ESMAC is evaluated on two robotic tasks: come-and-go and phototaxis-with-obstacles. All three variants of ESMAC showequally good performance as a NN-based EA on the evaluated tasks. Thecontrollers generated with standard ESMAC and adaptive ESMAC hardlymake any state transitions and mainly use one state. However, controllers that do use multiple states appear to be more robust to changing scenarios and in noisy environments. Selector ESMAC is able to generate SMs-based controllers that have complementing states and, therefore, shows potentialfor decomposing a task into sub tasks.