# TETES: Trust Based Efficient Task Execution Scheme for Fog Enabled Smart Cities
## 1 Introduction
Fog nodes utilize their resources in executing these tasks by considering them as legitimate tasks, resulting in increased task execution time for legitimate nodes. Differentiating between the legitimate and malicious offloaded tasks before their execution improves the performance of the fog nodes in executing legitimate tasks. Collecting trust values of all the nodes present in a network requires more time and overheads are also increased. To overcome this delay and control overheads, the network is divided into a number of clusters. Assessing legitimate node before the start of communication makes it more secure and increases the data reliability with improved quality of work [17; 18]. In order to assess data legitimacy, centralized authentication scheme is used to identify the malicious nodes data. However, it is not preferred in IoT based smart city environment due to following limitations. * Centralized scheme faces challenges in dynamic and evolving systems because it struggles to adapt quickly. * Decision making at the central level creates bottle neck resulting in a compromised communication environment. * Centralized authentication does not encourage the secure and cooperative environment. * There are increased number of inside threats in centralized systems where authentication decisions are primarily based on credentials. Classic centralized authentication scheme only identifies the malicious nodes that are not part of the member. However, there are many attacks from the malicious nodes which are also members of the network. IoT based smart cities applications demand adaptive and dynamic environment [19]. In such scenario, a trust based scheme is preferred over classic centralized authentication scheme. Malicious nodes being a member of the wireless network, offload complex tasks to compromise the execution efficiency of the fog node, because it consumes its processing resources in executing these malicious tasks. To improve the efficiency of fog node in task execution, it needs to find the tasks offloaded by a trusted node or not. A trust management system is designed to differentiate between legitimate and malicious tasks and improve the quality of the network by identifying malicious nodes. In this work, a Trust-based Efficient Task Execution Scheme (TETES) is proposed for fog nodes to effectively discard the tasks offloaded by fog malicious nodes and proposes an algorithm to efficiently execute the maximum number of legitimate tasks. The salient features of TETES are mentioned below. Figure 1: Fog enabled IoT network in smart cities. 1 Distribution of IoT networks attached with a fog node in small clustering units in order to minimize the delay and control overheads. 2 Trust management scheme to help fog node in evaluating the trust value of each IoT node in a cluster to differentiate between legitimate nodes and malicious nodes. 3 An efficient 0/1 knapsack-based task offloading scheme for fog nodes to execute a maximum number of offloaded tasks within a specified time. The rest of the paper is organized as: The previous research work relating to trust management in different prospects is discussed in Section 2. Sections 3 and 4 describe the system model and our proposed scheme respectively. Comparative analysis with extensive simulations and results are discussed in Sections 5 and 6 concludes our manuscript.