A Distributed and Secure Self-Sovereign-Based Framework for Systems of Systems

Security and privacy are among the main challenges in the systems of systems. The distributed ledger technology and self-sovereign identity pave the way to empower systems and users' security and privacy. By utilizing both technologies, this paper proposes a distributed and self-sovereign-based framework for systems of systems to increase the security of such a system and maintain users' privacy. We conducted an extensive security analysis of the proposed framework using a threat model based on the STRIDE framework, highlighting the mitigation provided by the proposed framework compared to the traditional SoS security. The analysis shows the feasibility of the proposed framework, affirming its capability to establish a secure and privacy-preserving identity management system for systems of systems.

Fault Injection with Multiple Fault Patterns for Experimental Evaluation of Demand-Controlled Ventilation and Heating Systems

Heating, ventilation, and air-conditioning (HVAC) systems are large-scale distributed systems that can be subject to multiple faults affecting the electronics, sensors, and actuators, potentially causing high energy consumption, occupant discomfort, degraded indoor air quality and risk to critical infrastructure. Fault injection (FI) is an effective experimental method for the validation and dependability evaluation of such HVAC systems. Today's FI frameworks for HVAC systems are still based on a single fault hypothesis and do not provide insights into dependability in the case of multiple faults. Therefore, this paper presents modeling patterns of numerous faults in HVAC systems based on data from field failure rates and maintenance records. The extended FI framework supports the injection of multiple faults with exact control of the timing, locality, and values in fault-injection vectors. A multi-dimensional fault model is defined, including the probability of the occurrence of different sensor and actuator faults. Comprehensive experimental results provide insights into the system's behavior for concrete example scenarios using patterns of multiple faults. The experimental results serve as a quantitative evaluation of key performance indicators (KPI) such as energy efficiency, air quality, and thermal comfort. For example, combining a CO₂ sensor fault with a heater actuator fault increased energy consumption by more than 70%.

Adaptive and technology-independent architecture for fault-tolerant distributed AAL solutions

Today's architectures for Ambient Assisted Living (AAL) must cope with a variety of challenges like flawless sensor integration and time synchronization (e.g. for sensor data fusion) while abstracting from the underlying technologies at the same time. Furthermore, an architecture for AAL must be capable to manage distributed application scenarios in order to support elderly people in all situations of their everyday life. This encompasses not just life at home but in particular the mobility of elderly people (e.g. when going for a walk or having sports) as well. Within this paper we will introduce a novel architecture for distributed AAL solutions whose design follows a modern Microservices approach by providing small core services instead of a monolithic application framework. The architecture comprises core services for sensor integration, and service discovery while supporting several communication models (periodic, sporadic, streaming). We extend the state-of-the-art by introducing a fault-tolerance model for our architecture on the basis of a fault-hypothesis describing the fault-containment regions (FCRs) with their respective failure modes and failure rates in order to support safety-critical AAL applications.