Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed. <s> BIB001 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> Advances in technology introduce new application areas for sensor networks. Foreseeable wide deployment of mission critical sensor networks creates concerns on security issues. Security of large scale densely deployed and infrastructure less wireless networks of resource limited sensor nodes requires efficient key distribution and management mechanisms. We consider distributed and hierarchical wireless sensor networks where unicast, multicast and broadcast type of communications can take place. We evaluate deterministic, probabilistic and hybrid type of key pre-distribution and dynamic key generation algorithms for distributing pair-wise, group-wise and network-wise keys. <s> BIB002 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> Severe energy limitations, and a paucity of computation pose a set of difficult design challenges for sensor networks. Recent progress in two seemingly disparate research areas namely, distributed robotics and low power embedded systems has led to the creation of mobile (or robotic) sensor networks. Autonomous node mobility brings with it its own challenges, but also alleviates some of the traditional problems associated with static sensor networks. We illustrate this by presenting the design of the robomote, a robot platform that functions as a single mobile node in a mobile sensor network. We briefly describe two case studies where the robomote has been used for table top experiments with a mobile sensor network. <s> BIB003 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> Previous work on the coverage of mobile sensor networks focuses on algorithms to reposition sensors in order to achieve a static configuration with an enlarged covered area. In this paper, we study the dynamic aspects of the coverage of a mobile sensor network that depend on the process of sensor movement. As time goes by, a position is more likely to be covered; targets that might never be detected in a stationary sensor network can now be detected by moving sensors. We characterize the area coverage at specific time instants and during time intervals, as well as the time it takes to detect a randomly located stationary target. Our results show that sensor mobility can be exploited to compensate for the lack of sensors and improve network coverage. For mobile targets, we take a game theoretic approach and derive optimal mobility strategies for sensors and targets from their own perspectives. <s> BIB004 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> Recently, wireless sensor networks (WSN) have gained great popularity, mainly because they provide a low cost alternative to solving a great variety of real-world problems (Akyildiz, Su, & Sankarasubramaniam, 2003). Their low cost enableds the deployment of large amounts of sensor nodes (in the order of thousands, and in the future perhaps millions), which most of the time operate under harsh environments. WSN present extreme AbstrAct <s> BIB005 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> We present a programming model and distributed protocol to reprogram application-defined subsets of nodes in a wireless sensor network (WSN). the protocol operation is rooted in the use of social information inferred from the behavior of the individuals nodes are attached to. <s> BIB006 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> With sensor networks on the verge of deployment, security issues pertaining to the sensor networks are in the limelight. Though the security in sensor networks share many characteristics with wireless ad hoc networks, the two fields are rapidly diverging due to the fundamental differences between the make-up and goals of the two types of networks. Perhaps the greatest dividing difference is the energy and computational abilities. Sensor nodes are typically smaller, less powerful, and more prone to failure than nodes in an ad hoc network. These differences indicate that protocols that are valid in the context of ad-hoc networks may not be directly applicable for sensor networks. In this paper, we survey the state of art in securing wireless sensor networks. We review several protocols that provide security in sensor networks, with an emphasis on authentication, key management and distribution, secure routing, and methods for intrusion detection. Copyright © 2006 John Wiley & Sons, Ltd. <s> BIB007 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> As sensor networks are more and more being implemented in real world settings, it is necessary to analyze how the different requirements of these real-world applications can influence the security mechanisms. This paper offers both an overview and an analysis of the relationship between the different security threats, requirements, applications, and security technologies. Besides, it also overviews some of the existing sensor network standards, analyzing their security mechanisms. <s> BIB008 </s> Security in Mobile Wireless Sensor Networks – A Survey <s> I. INTRODUCTION <s> A SEA Swarm (Sensor Equipped Aquatic Swarm) is a collection of mobile underwater sensors that moves as a group with water current and enables 4D (space and time) monitoring of local underwater events such as contaminants and intruders. For prompt alert reporting, mobile sensors routes events to mobile sinks (i.e., autonomous underwater vehicles) via geographic routing that is known to be most efficient under mobility and scarce acoustic bandwidth. In order for a packet to be routed to the destination using geographical routing, it requires to know the location of the destination. This is accomplished by having a location service that returns the location of a requested node. Our goal is to design such location service for SEA Swarm. In this paper, we analyze various design choices to realize an efficient location service in SEA Swarm scenarios. We find that conventional ad hoc network location service protocols cannot be directly used, because the entire swarm moves along water current. We prove that maintaining location information in a 2D plane is a better design choice. Given this, we propose a bio-inspired location service called a Phero-Trail location service protocol. In Phero-Trail, location information is stored in a 2D upper hull of a SEA Swarm, and a mobile sink uses its trajectory (a la a pheromone trail of ants) projected to the 2D hull to maintain location information. This enables mobile sensors to efficiently locate a mobile sink. Our results show that Phero- Trail performs better than existing approaches. <s> BIB009
In recent years, Wireless Sensor Networks (WSNs) have been an extremely popular research area BIB001 . A WSN usually consists of a large number of different types of sensors that are able to monitor a wide variety of ambient conditions such as temperature, humidity, vehicular movement, pressure, noise levels, etc. The low cost of sensors makes it possible to deploy a large number of them to perform both military and civilian applications. However, the low cost of sensors also leads to severe resource constraints such as limited battery power, memory and low computation capability, and these constraints in turn introduce major obstacles to the implementation of traditional computer security approaches (such as public key cryptography) in a WSN. Moreover, the open nature and unattended operation of WSNs make the security defenses even more difficult. Because of these, WSN security issues, such as key management, message authentication, intrusion detection, etc. BIB005 - BIB002 , have recently gained a lot of attention. However, despite the static network topology, the traditional WSNs suffer from the following drawbacks: • Near-Sink sensors drain their energy faster than other sensors in the network because these sensors need to Manuscript received August 15, 2010 ; revised November 15, 2010; accepted January 15, 2011. Corresponding author: Xiaohu Ge, Email: xhge@mail.hust.edu.cn not only deliver their own data to the sink but also forward data originating from many other sensors (located farther away) towards the sink. As a consequence, the near-sink sensors could rapidly deplete their energy and then totally lose their functions. • Near-Sink sensors would attract more attacks than other sensors do because if enough near-sink sensors are compromised or lose function, sink reachability would be compromised. • In human being hostile areas, such as battle fields, volcanic areas, underwater zones, etc., sensors are usually deployed by airplanes or helicopters, creating the predicament of imprecise sensor location and coverage uncertainty. • Moreover, in the abovementioned areas, it may not be feasible to deploy a fixed sink (or base station). Additionally, we observe that in a large extent of existing WSN security literature (especially in the early research stage), it is assumed that sensors are both static and able to transmit sensed data at will (or anticipate an upload signal) to a trusted party, called a sink or base station, inside the network. However, this is not the case for all real-world WSN applications, for example in certain areas, such as the ocean surface  (sensors or sinks are mobile due to water current and wave conditions), underwater BIB009 (sensors or sinks are mobile because of the water current), patient monitoring  and wildlife monitoring BIB006 (sensors are mobile due to their attachment to patient or alive, moving animals). These new applications therefore require a new network topology in which either sinks or sensors are mobile or both of them are mobile. Thanks to the advances in robotics, it is possible to develop a variety of mobile nodes BIB003 to form a new type of WSNs known as Mobile Wireless Sensor Networks (MWSNs). In MWSNs, mobile nodes (essentially small robots with sensing, wireless communications, and mobility capabilities) are useful for applications such as adaptive sampling, improving network connectivity of static sensor deployment and event detection. In contrast to conventional static WSNs, targets that might never have been detected in a static WSN can now be detected by mobile sensors/sinks BIB004 due to sensors' (or sink's) mobility. Finally, mobility enables us to solve network connectivity problems caused by sensor failure or battery depletion. In brief, MWSNs differ from WSN in a way that the network topology of MWSNs is dynamic. Nevertheless, the unique properties of MWSNs pose many new challenges in security. Due to dynamic mobile network topology, security in MWSNs becomes more complicated. Thus, more exploratory studies are required with regard to the security issues involved. Aiming at providing deeper understanding of current security schemes in MWSNs, we provide in this paper a survey of the existing work in MWSN security that has been proposed in recent years, including a classification for these schemes. Furthermore, in certain topics such as location privacy and authentication, due to an absence of literature addressing security mechanisms in MWSNs, some classic schemes in traditional WSNs are addressed. In order to give a clue on this new research direction, we further highlight a few open questions that need be addressed, together with our suggestions on these topics. It is worth mentioning that this article does not focus on the common security issues of either traditional WSNs or MWSNs, but rather specifically addresses newly arisen issues due to the dynamic mobile network topology of MWSNs. Readers interested in common security issues of traditional WSNs and MWSNs may refer to a few existing surveys on security issues in WSNs BIB005 , BIB007 , BIB008 . In the remainder of the article, we discuss a number of security challenges unique to MWSNs. In Section II, we summarize the network architecture of MWSNs. The outline of the threat to models of MWSNs is addressed in Section III. The security requirements of MWSNs are listed in Section IV. In Section V, we review the existing schemes on MWSNs. A few new research directions in MWSNs are pointed out in Section VI. Finally, we offer a conclusion in Section VII.