**1. Introduction**

Wireless sensor network (WSN), as shown in **Figure 1**, is a wireless interconnected network which consists of independently setup devices that monitor the conditions of its environment using sensors. WSNs are employed in a wide range of applications such as security surveillance, environmental monitoring, target tracking, military defense, intrusion detection, etc. Security in wireless sensor network is at a growing stage mainly not because of nonavailability of efficient security schemes, but most of the existing schemes are not suitable due to the peculiarity of WSNs. That is, WSNs' nodes have low computational capacity and energy constraint. In WSNs, sensor nodes have the ability to communicate with one another, but their primary task is to sense, gather, and compute data. These data are forwarded, via multiple hops, to a sink which may use it or relay it to other networks. To achieve an effective communication, WSNs need efficient routing protocols [2–6]. They facilitate communication in WSNs by discovering the appropriate routes for transmitting data and maintain the routes for subsequent

3.Multipath-based routing protocol

*DOI: http://dx.doi.org/10.5772/intechopen.84989*

*Wireless Sensor Networks (WSNs): Security and Privacy Issues and Solutions*

4.Location-based routing protocol

6.Mobility-based routing protocol

are examples of data-centric routing protocol [11, 12].

Data-centric routing protocol combines data arriving from various sensor nodes at a specific route. This eliminates redundancies and minimizes the total amount of data transmission before forwarding it to the base station. Directed diffusion, rumor routing, and sensor protocol for information via negotiation (SPIN) protocol

SPIN is a negotiation-based data-centric protocol for WSNs. Each node uses metadata to name its data, and negotiation is performed by a sensor node using its metadata. Hence, each node is able to negotiate whether to deliver data or not, in order to eliminate redundant data transmission throughout the network. After the negotiation, the sender transmits its data as shown in **Figure 2**; node A starts by broadcasting its hop request to its neighboring node B. Once the request is accepted, node A sends its data to B who then repeats this procedure. This is to find its neighboring node and hops the data to the neighboring node until the data reaches the destination. SPIN protocol saves energy due to the fact that each node only performs single hop. SPIN's hop request and acceptance packets prevent flooding attack on WSNs. Although SPIN protocol is good for lossless networks, it can also be

Hierarchical routing protocol classifies network nodes into hierarchical clusters. For each of the clusters, the protocol selects a node with high residual energy as the cluster head. The sensed data of each node in the cluster are transferred through the cluster heads of the clusters in the network [11]. The cluster node aggregates the sensed data of all the nodes in the cluster before sending it to the sink. Hierarchical routing protocol reduces the energy consumption through multi-hop transmission mode [13]. Also, data aggregation performed by the cluster head reduces traffic on

5.QoS-based routing protocol

**2.1 Data-centric routing protocol**

used for lossy or mobile networks.

**2.2 Hierarchical routing protocol**

**Figure 2.** *SPIN protocol.*

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**Figure 1.** *A typical wireless sensor networks (WSN) [1].*

transmissions. As a result of heterogeneity of WSNs' nodes, different protocols had been developed for different WSNs depending on the nature of the nodes and application. For instance, there are dedicated protocols for MWSNs and dedicated protocols for SWSNs.

There are two modes of transmission in WSN; single hop involves the source node sending its data packets to the destination within a hop. Meanwhile, WSNs' sensor nodes may rely on one another in order to relay packets to remote destinations. This mode of transmission is called multi-hop. Multi-hop is a routing phenomenon that involves the transfer of data between source and destination nodes with the cooperation of intermediary nodes. It enhances the performance of WSNs by allowing energy-depleted node to transfer data through its neighboring nodes along the routing path to the destination node. There are several security and privacy issues associated with multi-hop routing. Some of these issues like snooping, sinkhole, tampering Sybil, clone, wormhole, spoofing, etc. affect the integrity, availability, and data confidentiality of the WSNs.

Several security solutions had been proposed for WSNs; however, resource constraint of sensors makes some of these security solutions unfit for WSNs. This, therefore, makes their adoption in WSNs impossible. This is as a result of instability of the topology of most WSNs. Some of the WSNs, unlike some other networks, consist of mobile nodes that intermittently change the topology of the networks, therefore making it impossible for such mobile network to use existing protocol developed for static nodes. Also, large volume of data is transferred on the WSNs; this increases the traffic on the wireless communication infrastructure of WSN. All these show that security and privacy solutions of WSN must not only be lightweight in terms of the computational, communication, and energy overheads but also support aggregation and multi-hop in order to reduce the traffics and extend the life span of the networks. Meanwhile, most of the existing security solutions do not have these performance requirements [1, 7–10].
