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TopIntroduction
Sensor networks refer to a heterogeneous system combining tiny sensors and actuators with general-purpose computing elements. These tiny sensors have some limitations in power supplies, bandwidth, memory size, and energy (Wireless sensor networks, 2004; Akyildiz, Su, Sankarasubramaniam, & Cayirci, 2002), (Loveric & Sieffert). Thus, the resource-limited nature of sensor networks poses great challenges for security (Akyildiz et al., 2002). Furthermore, sensor networks can be used in a wide range of applications. For example, in the military, wireless sensor networks have been used for some applications such as sensing techniques for military commands, control, communications, computing, intelligence, surveillance, reconnaissance and targeting systems. In healthcare, sensor nodes can also be used for monitoring patients and assisting disabled individuals. In addition, there are lots of applications for wireless sensor networks (WSNs) including commercial applications for managing inventory, monitoring product quality, and monitoring disaster areas (Undercoffer, Avancha, Joshi, & Pinkston, 2002; Datema, 2005).
Because of the resource-constrained nature of WSNs, we should consider the best and the most suitable security mechanism against potential security threats (Walters, Liang, Shi, & Chaudhary, 2007). Generally, there are some serious limitations with current security mechanisms. In order to understand these limitations, it is essential to evaluate the differences between WSNs and general ad hoc networks (Lidong & Haas, 1999; Sakarindr & Ansari, 2007).
The most important differences between sensor networks and ad hoc networks include:
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The number of sensor nodes, which can be significantly higher in sensor networks compared to ad hoc network.Sensor nodes are densely deployed;
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Sensor nodes are prone to failures;
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The topology of a sensor network varies constantly;
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Sensor nodes use a broadcast communication. In contrast, most ad hoc networks are based on point-to-point communications;
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Sensor nodes are limited in power, computational capacities, and memory;
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Sensor nodes may not have global identification (ID) due to the large amount of overhead and high number of sensors.
This paper will discuss WSN limitation, the essential requirements for ensuring WSN security, requirements for secure sensor network protocols, potential attacks in different network layers, and some proposed countermeasures against these attacks.
TopWsn Limitations
Some basic limitations in WSNs are as follows (Du, Deng, Han, Chen, & Varshney, 2004; Shi & Perrig, 2004):
Limited Resources
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Limited Memory and Storage Space: A sensor is a really small device with just a low amount of memory and storage space for the code;
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Power Limitation: Since the sensors are battery operated, energy is the biggest limitation to wireless sensor capabilities.
Unreliable Communication
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Unreliable Transfer: The packet-based routing of the sensor network is connectionless and, thus, it can be unsafe. Packets may physically get harmed because of channel errors or dropped at highly congested nodes. As a result, packets are lost or may go missing;
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Conflicts: Since these networks communicate through broadcast, they are potentially unreliable even though the channel is not;
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Latency: Multi-hop routing, network congestion, and node processing can lead to greater latency in the network, making it difficult to achieve synchronization among sensor nodes.