A survey of security issues in wireless sensor networks <s> SECURE ROUTING PROTOCOLS <s> Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network. <s> BIB001 </s> A survey of security issues in wireless sensor networks <s> SECURE ROUTING PROTOCOLS <s> Future sensor networks will be composed of a large number of densely deployed sensors/actuators. A key feature of such networks is that their nodes are untethered and unattended. Consequently, energy efficiency is an important design consideration for these networks. Motivated by the fact that sensor network queries may often be geographical, we design and evaluate an energy efficient routing algorithm that propagates a query to the appropriate geographical region, without flooding. The proposed Geographic and Energy Aware Routing (GEAR) algorithm uses energy aware neighbor selection to route a packet towards the target region and Recursive Geographic Forwarding or Restricted Flooding algorithm to disseminate the packet inside the destina- <s> BIB002 </s> A survey of security issues in wireless sensor networks <s> SECURE ROUTING PROTOCOLS <s> We consider routing security in wireless sensor networks. Many sensor network routing protocols have been proposed, but none of them have been designed with security as a goal. We propose security goals for routing in sensor networks, show how attacks against ad-hoc and peer-to-peer networks can be adapted into powerful attacks against sensor networks, introduce two classes of novel attacks against sensor networks sinkholes and HELLO floods, and analyze the security of all the major sensor network routing protocols. We describe crippling attacks against all of them and suggest countermeasures and design considerations. This is the first such analysis of secure routing in sensor networks. <s> BIB003 </s> A survey of security issues in wireless sensor networks <s> SECURE ROUTING PROTOCOLS <s> Wireless sensor networks consist of small nodes with sensing, computation, and wireless communications capabilities. Many routing, power management, and data dissemination protocols have been specifically designed for WSNs where energy awareness is an essential design issue. Routing protocols in WSNs might differ depending on the application and network architecture. In this article we present a survey of state-of-the-art routing techniques in WSNs. We first outline the design challenges for routing protocols in WSNs followed by a comprehensive survey of routing techniques. Overall, the routing techniques are classified into three categories based on the underlying network structure: flit, hierarchical, and location-based routing. Furthermore, these protocols can be classified into multipath-based, query-based, negotiation-based, QoS-based, and coherent-based depending on the protocol operation. We study the design trade-offs between energy and communication overhead savings in every routing paradigm. We also highlight the advantages and performance issues of each routing technique. The article concludes with possible future research areas. <s> BIB004 </s> A survey of security issues in wireless sensor networks <s> SECURE ROUTING PROTOCOLS <s> There has been a lot of effort in the research on routing in mobile ad hoc networks in the last years. Promising applications of MANETs, e.g. in the automotive domain, are the drive for the design of inter-vehicle networks. So far, several projects in this field have chosen geographic routing approaches because of their outstanding performance and the possibility to support location-based applications like traffic warning functions. Having reached a reasonable functional level, a next step will be a deeper study of safety and security issues. ::: ::: With this paper, we dive into that area by assuming defective or malicious nodes that disseminate wrong position data. First, we have a look at the local problems that may arise from falsified position data, then we show the global effects on the routing performance by simulating malicious nodes. Simulation results show that the overall ratio of successfully delivered messages decreases, depending on the number of maliciously acting nodes, even up to approximately 30%. We conclude from this result that future work should take these threats into account in order to design more robust routing protocols. <s> BIB005
Many routing protocols have been specifically designed for WSNs. These routing protocols can be divided into three categories according to the network structure: flat-based routing, hierarchical-based routing, and location-based routing BIB004 . In flat-based routing, all nodes are typically assigned equal roles or functionality. In hierarchical-based routing, nodes play different roles in the network. In location-based routing, sensor node positions are used to route data in the network. Although many sensor network routing protocols have been proposed in literature, few of them have been designed with security as a goal. Lacking security services in the routing protocols, WSNs are vulnerable to many kinds of attacks. Most network layer attacks against sensor networks fall into one of the categories described above, namely: These attacks may be applied to compromise the routing protocols in a sensor network. For example, directed diffusion is a flat-based routing algorithm for drawing information from a sensor network BIB001 . In directed diffusion, sensors measure events and create gradients of information in their respective neighboring nodes. The base station requests data by broadcasting interest which describes a task to be conducted by the network. The interest is diffused through the network hop by hop, and broadcasted by each node to its neighbors. As the interest is propagated throughout the network, gradients are setup to draw data satisfying the query towards the requesting node. Each sensor that receives the interest sets up a gradient toward the sensor nodes from which it received the interest. This process continues until gradients are setup from the sources back to the base station. Interests initially specify a low rate of data flow, but once a base station starts receiving events it will reinforce one or more neighboring nodes in order to request higher data rate events. This process proceeds recursively until it reaches the nodes generating events, causing them to generate events at a higher data rate. Paths may also be negatively reinforced. Directed diffusion is vulnerable to many kinds of attacks if authentication is not included in the protocol BIB003 . For example, it is easy for an adversary to add himself/herself onto the path taken by a flow of events as described in the following: • The adversary can influence the path by spoofing positive reinforcements. After receiving and rebroadcasting an interest, an adversary could strongly reinforce the nodes to which the interest was sent while spoofing high-rate, low-latency events to the nodes from which the interest was received. • The adversary can replay the interests intercepted from a legitimate base station and list himself/herself as a base station. All events satisfying the interest will then be sent to both the adversary and the legitimate base station. By using the attacks above, the adversary can add himself/ herself onto the path and thus gain full control of the flow. The adversary can eavesdrop, modify, and selectively forward packets of his/her choosing. He/she can drop all forwarded packets and act as a sinkhole. Further, a laptop-class adversary can exert great influence on the topology by using a wormhole attack. The adversary creates a tunnel between a node located near a base station and a node located close to where events are likely to be generated. By spoofing positive or negative reinforcements, the adversary can push data flows away from the base station and towards the nodes selected by the adversary. Hierarchical and location based routing protocols not incorporating security services are also vulnerable to many attacks BIB003 . For example, location-based routing protocols such as Geographic and Energy Aware Routing (GEAR) BIB002 require location information to be exchanged between neighbors. However, location information can be misrepresented. Regardless of the adversary's actual location, he/she may advertise false position data to place himself/herself on the path of a known flow. Once on that path, the adversary can mount selective forwarding and Sybil attacks in the data flows. Simulations in BIB005 found that such attacks have great influence on the overall ratio of successfully delivered messages in the network. Secure routing in ad hoc networks is similar to that in sensor networks and has been well studied in the literature  . However, the defense mechanisms developed for ad hoc networks cannot be directly applied to sensor networks because of the differences between sensor and ad hoc networks discussed earlier. Ideally, a secure routing protocol should guarantee the integrity, authentication, and availability of messages in the presence of adversaries of arbitrary power. In the presence of only outsider adversaries, it is conceivable to achieve these idealized goals. However, in the presence of compromised nodes or insider adversaries, especially those with laptop class capabilities, it is most likely that some if not all of these goals are not fully attainable. In this situation, the best we can hope for is graceful degradation instead of a complete compromise of the network. To achieve the above goal requires that a routing protocol degrades no faster than a rate approximately proportional to the ratio of compromised nodes to total nodes in the network BIB003 . A secure routing protocol depends on an appropriate key management scheme in a WSN, which has been discussed earlier. Before a routing protocol starts, sensor nodes should have been loaded with proper keys (e.g., the key for confidentiality, authentication, etc.). One of the fundamental security services in sensor networks is broadcast authentication, which enables the base station to broadcast authenticated data to the entire sensor network. In this section, we first discuss the broadcast authentication problem and then review several secure routing schemes.