# A Secure Protocol against Selfish and Pollution Attacker Misbehavior in Clustered WSNs  
[PERSON]  
1 Digital Security Lab, Sup'Com, University of Carthage, Tunis 2083, Tunisia; [EMAIL_ADDRESS] (R.A.); [EMAIL_ADDRESS] (S.G.)  
2 Mathls, XLIM, University of Limonges, 87032 Limoges, France; damien. energy consumption in the network, decreasing the nodes' connectivity and the network survival time. One way to preserve some battery power during communications involves the choice of network architecture and of the protocol used to route data from a sensor to the _BS_. A number of methods designed to handle security issues in _WSNs_ exploit network hierarchization and cluster-based routing [1]. Clustering a sensor network typically leads to possibilities for scaling, better control of nodes and energy efficiency gains provided by partitioning [2; 3]. Other ways to preserve battery power are sleep scheduling and energy harvesting. The former aims at minimizing the number of sensors to activate to cover a desired portion of the region of interest preserving the connectivity among sensors [4]. The latter aims to resolve the issue that the nodes are often unreachable after deployment and introduces the concept of renewable energy that can be harvested from the surrounding environment [5]. As mentioned before, _WSNs_ are vulnerable to several attacks, which can be classified into two types:inside attacks, performed by authorized nodes and outside attacks, performed by unauthorized nodes. Previous studies have shown that inside attacks are far more difficult to control than outside ones [6; 7]. Selfishness and pollution attacks are two forms of critical inside attacks, where nodes can easily launch a type of Denial of Service (_DoS_) in the first, or pollute data in transit to interrupt the normal functioning of the network, in the second. More specifically, in the former attack, selfish nodes refuse to relay packets and use network resources for their own benefit. This operation is one variety of a _DoS_ attack which can be performed in different ways [8] and has multiple forms [9]. In fact, a _DoS_ attack can also be achieved by congesting the network or draining the energy from its components [10]. This attack is considered one of the most frequent attacks in _WSNs_[11; 12]. In the latter attack, pollution attacker nodes modify native data packets or inject fake ones into the network. A pollution attack is potentially more damaging when applied in protocols for _WSNs_ based on network coding (_NC_) since it may have devastating impact on the data routing [13]. Figure 1 illustrates the aforementioned considered attacks. In a clustered network, if the misbehaving nodes that invoke a selfishness or a pollution attack are the _CH_ nodes, then the network will be more disordered and the consequences more serious. The _CH_s have a critical role in forwarding the cluster data to the _BS_[14]. _DoS_ and pollution attacks are challenging issues that aim to disable the service that a _WSN_ is supposed to provide, and create routing failure. This paper proposes a secure protocol for _WSNs_ that defends against the misbehavior of selfish and pollution attacker nodes in the network. It extends our previous work [15], which ensured confidentiality of exchanges in clustered _WSNs_ using an optimized (_NC_) technique. This extension provides a solution for preventing an attack on network avail  
Figure 1: The inside attacks performed on the _WSN_. ability as well as integrity. It also proposes attack detection and a punishment mechanism for malicious nodes causing the _DoS_ attack or the pollution attack. The solution takes advantage of the matrix format of keys specific to each sensor node used for confidential communication in [15] and implements a new scheme of _NC_ by adding data redundancy. It converts a file/message into a set of \(p\) pieces in such a way that the file/message can be reconstructed from any predefined subsets of \(t\) out of \(p\) pieces.