Towards trustworthy self-optimization for distributed systems

Abstract. The increasing complexity of computer-based technical systems requires new ways to control them. The initiatives Organic Computing and Autonomic Computing address exactly this issue. They demand future computer systems to adapt dynamically and autonomously to their environment and postulate so-called self-* properties. These are typically based on decentralized autonomous cooperation of the system's entities. Trust can be used as a means to enhance cooperation schemes taking into account trust facets such as reliability. The contributions of this paper are algorithms to manage and query trust information. It is shown how such information can be used to improve self-* algorithms. To quantify our approach evaluations have been conducted

Reflective mobile agents in ubiquitous systems

Ubiquitäre Systeme werden als die nächste Generation der Computer gepriesen. Zukünftige Rechner werden unsichtbar und unaufdringlich in alltägliche Objekte integriert sein. Sie werden dem Menschen ungeahnte neue Dienste zur Verfügung stellen, indem sie Information aus der Umgebung sammeln und diese automatisch zur Unterstützung des Menschen verarbeiten. Um eine optimale Anpassung und damit einen angemessenen Mehrwert für den jeweiligen Benutzer bieten zu können, bedarf es auch persönlicher Informationen und der Information über den Aufenthaltsort des Benutzers. Mit neuen Arten von Geräten, wie Sensoren und wearables, und neuen Formen der Information wird zwangsläufig auch die Menge der Daten rapide ansteigen. Die effiziente Verarbeitung der Daten durch ein zentralisiertes System wird kaum mehr möglich. Das Paradigma der mobilen Agenten bietet eine komfortable Methode, persönliche Interessen des Benutzers und die Anforderungen eines ubiquitären dezentralen Systems zu vereinen. Mobile Agentensysteme bilden von Grunde auf die höchste Stufe der Dezentralisierung. Persönliche Informationen, wie Präferenzen, Vorlieben und Gewohnheiten, können von mobilen Agenten gekapselt und für ortsbasierte Dienste im Namen des Benutzers eingesetzt werden. Die Idee, die in dieser Arbeit vorgestellt wird, ist, dass der Benutzer von einem virtuellen Abbild in Form eines mobilen Agenten (so genannter reflektiver Agent) in der ubiquitären Umgebung begleitet wird. Der reflektive Agent kommt in einem neu entwickelten ubiquitären Agentensystem, dem Ubiquitous Mobile Agent System (UbiMAS), zum Einsatz. UbiMAS implementiert umfangreiche Sicherheitsfunktionen, die den reflektiven Agenten und damit die sensiblen persönlichen Daten des Benutzers schützen. Als ubiquitäre Umgebung wurde ein flexibles Bürogebäude mit elektronischen Türschildern, den Smart Doorplates, aufgebaut und für verschiedene Anwendungen der reflektiven Agenten eingesetzt. Im praktischen Einsatz und verschiedenen Präsentationen hat die Implementierung Funktionsfähigkeit gezeigt. UbiMAS wurde sowohl auf rechenstarken PCs, als auch auf mobilen PDAs eingesetzt, die drahtlos über WLAN oder Bluetooth kommunizierten. Allerdings ist die volle Sicherheitsfunktionalität von UbiMAS zu dem aktuellen Stand der Technologie nur auf PCs realisierbar.The next generation of computers will be embossed by ubiquitous systems. The computer will disappear behind daily things and will support people in their everyday life. New location-based services will be adapted to user preferences. For this the ubiquitous system needs to know user profiles, likings, habits, and the current location. The amount of data will rapidly rise with new types of devices, like sensors and wearables. The efficient processing of the data by a centralized system will not be possible anymore. The paradigm of mobile agents offers a convenient approach to combine personal interests of users and the requirements of a ubiquitous distributed system. Mobile agents build basically the highest stage of decentralisation. Personal information can be encapsulated by a mobile agent and can be used for location-based services on behalf of the user. The idea presented in this work is that a user is accomplished by a virtual reflection in form of a mobile agent in the ubiquitous environment. The reflective agent is used in a new developed ubiquitous mobile agent system called UbiMAS. UbiMAS implements several security functions that protect the reflective agent and therewith the sensitive personal data of the user. A flexible office building with smart doorplates is established as a ubiquitous environment where reflective agents perform different services. The implementation has proved functionality in practical usage and various presentations. UbiMAS was installed on high-performance PCs as well as on mobile PDAs that communicated wireless over WLAN or Bluetooth. However the full security functionality of UbiMAS is realisable only on PCs at the current stage of technology

Energy-Efficient and Secure System Architecture for Wireless Sensor Networks

Wireless Sensor Networks (WSN) have emerged as a new information-gathering paradigm based on the collaborative efforts of a large number of self-organized sensing nodes. These networks form the basis for many types of smart environments such as smart hospitals, intelligent battlefields, earthquake response systems, and learning environments. A set of applications, such as biomedicine, hazardous environment exploration, environmental monitoring, military tracking and reconnaissance surveillance, are the key motivations for the recent research efforts in this area. Different from traditional networks, sensor networks do impose a set of new limitations for the protocols designed for this type of networks. Devices in sensor networks have a much smaller memory, constrained energy supply, less process and communication bandwidth. Topologies of the sensor networks are constantly changing due to a high node failure rate, occasional shutdown and abrupt communication interferences. Because of the nature of the applications supported, sensor networks need to be densely deployed and have anywhere from hundred to thousands of sensing devices, which are orders of magnitude larger than traditional ad hoc mobile networks. In addition, energy conservation becomes the center of focus because of the limited battery capacity and the difficulty of recharge in the hostile environment. With fundamental difference between traditional networks and sensor networks, it is not appropriate and probably inefficient to port previous solutions for ad hoc networks into sensor networks with only incremental modifications. For ensuring the functionality of a sensor network, especially in malicious environments, security mechanisms are essential for all sensor networks. However, sensor networks differ from classical (wireless) networks and this consequently makes it harder to secure them. Reasons for this are resource constraints of the sensor nodes, the wireless multi-hop communication, and the possibility of node compromise. Since sensor nodes are often deployed in unattended or even hostile environments and are usually not equipped with tamper-resistant hardware, it is relatively easy to compromise a sensor node. By compromising a sensor node, an adversary gets access to all data stored on the node, such as cryptographic keys. This thesis discusses concepts and mechanisms to cope with energy efficiency and security issues in wireless sensor networks. The contribution of this work is to provide a novel system architecture for WSN which offers interfaces for diverse applications to directly control communication, topology, mobility, security, localization, and energy-saving based on predefined requirements

Context Prediction Based on Branch Prediction Methods

Ubiquitous systems use context information to adapt appliance behavior to human needs. Even more convenience is reached if the appliance foresees the user’s desires and acts proactively. This paper focuses on context prediction based on previous behavior patterns. The proposed prediction algorithms originate in branch prediction techniques of current high-performance microprocessors which are transformed to handle context prediction. We propose and evaluate the onelevel one-state, two-state, and multiple-state predictors, and the two-level two-state predictors with local and global first-level histories. Evaluation is performed by simulating the predictors with behavior patterns of people walking through a building as workload. The evaluations show that the proposed context predictors perform well but exhibit differences in training and retraining speed and in their ability to learn complex patterns

SecSens: security architecture for wireless sensor networks

In recent years, the potential range of applications for sensor networks is expanding. Their use has been consid-ered for safety critical areas such as: hospitals or power plants. The security comes more to the fore. This paper presents SecSens, an architecture that provides basic secu-rity components for wireless sensor networks. Since robust and strong security features require powerful nodes, Sec-Sens uses a heterogeneous sensor network. In addition to a large number of simple (cheap) sensor nodes providing the actual sensor tasks, there are a few powerful nodes (cluster nodes) that implement the required security features. The basic component of SecSens offers authenticated broadcasts to allow recipients to authenticate the sender of a message. To protect the sensor network against routing attacks, Sec-Sens includes a probabilistic multi-path routing protocol, which supports the key management and the authenticated broadcasts. SecSens also provides functions to detect forged sensor data by verifying data reports en-route. SecSens is successfully evaluated in a real test environment with two different kinds of sensor boards