ANSWER: AutoNomouS netWorked sEnsoR system

Sensor networks are expected to evolve into long-lived, open, ubiquitous, multi-purpose networked systems. We propose a new concept called AutoNomouS netWorked sEnsoR system (ANSWER) whose mission is to provide in situ users with real-time, secure information that enhances their situational and location awareness. To the best of our knowledge, solutions that accomplish this goal do not yet exist. ANSWER finds immediate applications to both overt and covert operations ranging from tactical battlefield surveillance to crisis management and homeland security. The architectural model of ANSWER is composed of a large number of sensors and of a set of (mobile) aggregation-and-forwarding nodes that organize and manage the sensors in their vicinity. In this paper we present the main features that enable ANSWER to effectively and efficiently provide secure, QoS-aware information services to in situ mobile users; namely, secure dynamic task-based networking and in-network storage to support application-level tasks and queries (each specified with desired QoS and security attributes), while hiding network-level details; and a model-based methodology exploiting QoS and security trade-offs for smart AFN mobility subject to application and network requirements and constraints. This new concept is in sharp departure from the prevalent view in NSS design that networking is independent of the task(s) at hand and information processing and storage are, primarily, the responsibility of remote entities.     

A service-centric model for wireless sensor networks

Most of the current research in wireless sensor networks (WSNs) is constraint driven and focuses on optimizing the use of limited resources (e.g., power) at each sensor. While such constraints are important, there is a energy for more general performance metrics to assess the effectiveness of WSNs. There is also a need for a unified formal model that would enable comparison of different types of WSNs and provide a framework for WSN operations. We propose a new service-centric model that focuses on services provided by a WSN and views a WSN as a service provider. A WSN is modeled at different levels of abstraction. For each level, a set of services and a set of metrics are defined. Services and their interfaces are defined in a formal way to facilitate automatic composition of services, and enable interoperability and multitasking of WSNs at the different levels. A two-way mapping between two neighboring levels is then defined as a decomposition (from higher to lower level) and composition (from lower to higher level). A composite mapping between metrics at different levels connects high-level, mission-oriented metrics and low-level, capability-oriented metrics. The service-centric model consists of mission, network, region, sensor, and capability layers. Each layer has associated semantics that use lower level components as syntactic units (except for the capability layer). Within each layer there are four planes or functionality sets; communication, management, application, and generational learning. The combination of layers and planes enables a service-based visualization paradigm that can provide better understanding of the WSN. The service-centric model provides a holistic approach to measuring and presenting WSNs effectiveness. In addition, it presents a general and flexible framework in which various more specific WSN models can be represented and evaluated.     

Dynamic key management in sensor networks

Numerous key management schemes have been proposed for sensor networks. The objective of key management is to dynamically establish and maintain secure channels among communicating nodes. Desired features of key management in sensor networks include energy awareness, localized impact of attacks, and scaling to a large number of nodes. A primary challenge is managing the trade-off between providing acceptable levels of security and conserving scarce resources, in particular energy, needed for network operations. Many schemes, referred to as static schemes, have adopted the principle of key predistribution with the underlying assumption of a relatively static short-lived network (node replenishments are rare, and keys outlive the network). An emerging class of schemes, dynamic key management schemes, assumes long-lived networks with more frequent addition of new nodes, thus requiring network rekeying for sustained security and survivability. In this article we present a classification of key management schemes in sensor networks delineating their similarities and differences. We also describe a novel dynamic key management scheme, localized combinatorial keying (LOCK), and compare its security and performance with a representative static key management scheme. Finally, we outline future research directions.     

μRACER: A Reliable Adaptive Service-Driven Efficient Routing Protocol Suite for Sensor-Actuator Networks

We present reliable adaptive service-driven efficient routing (muRACER), a routing protocol suite based on a novel service-oriented design for sensor-actuator networks where nodes expose their capabilities to applications as a service profile. A node's service profile consists of a set of services (i.e., sensing and actuation capabilities) that it provides and the quality-of-service (QoS) parameters associated with those services (delay, accuracy, freshness, etc.). muRACER uses an efficient service-aware routing approach that aggressively reduces downstream traffic (from the sink to the network's nodes) by translating service profiles into efficient paths for queries. To support QoS, muRACER dynamically adapts each node's routing behavior and service profile according to the current context of that node, i.e., number of pending queries and number and type of messages to be routed. Finally, muRACER improves end-to-end reliability through a scalable reputation-based approach in which each node is able to locally estimate the next hop of the most reliable path to the sink. Service- and context-aware reliable routing enhances the network's efficiency and effectiveness (satisfaction of applications' QoS requirements). We implemented muRACER on top of TinyOS and conducted several experiments that confirmed muRACER's ability with regard to each of its design objectives.     

Software visualization

The field of software visualization (SV) investigates approaches and techniques for static and dynamic graphical representations of algorithms, programs (code), and processed data. SV is concerned primarily with the analysis of programs and their development. The goal is to improve our understanding of inherently invisible and intangible software, particularly when dealing with large information spaces that characterize domains like software maintenance, reverse engineering, and collaborative development. The main challenge is to find effective mappings from different software aspects to graphical representations using visual metaphors. This paper provides an overview of the SV research, describes current research directions, and includes an extensive list of recommended readings.     

Training a Wireless Sensor Network

The networks considered in this paper consist of tiny energy-constrained commodity sensors massively deployed, along with one or more sink nodes providing interface to the outside world. Our contribution is to propose a scalable energy-efficient training protocol for nodes that are initially anonymous, asynchronous and unaware of their location. Our training protocol imposes a flexible and intuitive coordinate system onto the deployment area and partitions the anonymous nodes into clusters where data can be gathered from the environment and synthesized under local control. An important by-product of the training protocol is a simple and natural data fusion protocol as well as an energy-efficient protocol for routing data from clusters to the sink node. Being energy-efficient, our training protocol can be run on either a scheduled or ad-hoc basis to provide robustness and dynamic reconfiguration. We also outline a way of making the training protocol secure by using a parameterized variant of frequency hopping.     

SemWebDL: A privacy-preserving Semantic Web infrastructure for digital libraries

Recent advances in digital libraries have been closely intertwined with advances in Internet technologies. With the advent of the Web, digital libraries have been able to reach constituencies previously unanticipated. Because of the wide deployability of Web-accessible digital libraries, the potential for privacy violations has also grown tremendously. The much touted Semantic Web, with its agent, service, and ontology technologies, is slated to take the Web to another qualitative level in advances. Unfortunately, these advances may also open doors for privacy violations in ways never seen before. We propose a Semantic Web infrastructure, called SemWebDL, that enables the dynamic composition of disparate and autonomous digital libraries while preserving user privacy. In the proposed infrastructure, users will be able to pose more qualitative queries that may require the ad hoc collaboration of multiple digital libraries. In addition to the Semantic Web-based infrastructure, the quality of the response would rest on extraneous information in the form of a profile. We introduce the concept of communities to enable subject-based cooperation and search speedup. Further, digital libraries heterogeneity and autonomy are transcended by a layered Web-service-based infrastructure. Semantic Web-based digital library providers would advertise to Web services, which in turn are organized in communities accessed by users. For the purpose of privacy preservation, we devise a three-tier privacy model consisting of user privacy, Web service privacy, and digital library privacy that offers autonomy of perspectives for privacy definition and violation. We propose an approach that seamlessly interoperates with potentially conflicting privacy definitions and policies at the different levels of the Semantic Web-based infrastructure. A key aspect in the approach is the use of reputations for outsourcing Web services. A Web service reputation is associated with its behavior with regard to privacy preservation. We developed a technique that uses attribute ontologies and information flow difference to collect, evaluate, and disseminate the reputation of Web services.     

Service-Oriented Sensor-Actuator Networks [Ad Hoc and Sensor Networks]

Most approaches developed to query sensor-actuator networks (SANETs) are either application-specific or generic. Application-specific SANETs provide limited reusability, are not cost effective, and may require extensive reprogramming efforts to make the network able to serve new applications. Generic SANETs usually require that a sizeable code be deployed on the nodes regardless of the specific requirements of the application at hand. More important, they may not be optimized to fully exploit the specific characteristics and query patterns of a given application. In this article we introduce service-oriented SANETs (SOSANETs) as a novel approach to building customizable SANETs. SOSANETs provide the benefits of both application-specific SANETs (e.g., energy efficiency, scalability) and generic SANETs (e.g., reusability) and avoid most of their limitations. We implemented our approach in TinySOA, a SOSANET developed on top of TinyOS. We conducted an evaluation of TinySOA that included a comparison with TinyDB, an established query processing system for sensor networks. The obtained empirical results show that TinySOA outperforms TinyDB in many aspects including energy consumption, scalability, and response time.     

Location-Aware Combinatorial Key Management Scheme for Clustered Sensor Networks

Recent advances in wireless sensor networks (WSNs) are fueling the interest in their application in a wide variety of sensitive settings such as battlefield surveillance, border control, and infrastructure protection. Data confidentiality and authenticity are critical in these settings. However, the wireless connectivity, the absence of physical protection, the close interaction between WSNs and their physical environment, and the unattended deployment of WSNs make them highly vulnerable to node capture as well as a wide range of network-level attacks. Moreover, the constrained energy, memory, and computational capabilities of the employed sensor nodes limit the adoption of security solutions designed for wire-line and wireless networks. In this paper, we focus on the management of encryption keys in large-scale clustered WSNs. We propose a novel distributed key management scheme based on Exclusion Basis Systems (EBS); a combinatorial formulation of the group key management problem. Our scheme is termed SHELL because it is Scalable, Hierarchical, Efficient, Location-aware, and Light-weight. Unlike most existing key management schemes for WSNs, SHELL supports rekeying and, thus, enhances network security and survivability against node capture. SHELL distributes key management functionality among multiple nodes and minimizes the memory and energy consumption through trading off the number of keys and rekeying messages. In addition, SHELL employs a novel key assignment scheme that reduces the potential of collusion among compromised sensor nodes by factoring the geographic location of nodes in key assignment. Simulation results demonstrate that SHELL significantly boosts the network resilience to attacks while conservatively consuming nodes' resources.