# Game theory-based Routing for Wireless Sensor Networks: A Comparative Survey
## 3 Game Theory-Based Routing Protocols in WSNs
### Routing Protocols Based on Noncooperative Games
#### 3.2.5 Energy-Aware Trust Derivation Scheme  
Security is a prime concern for a WSN-based IoT. The traditional routing protocols in most cases assume that the network environment is trustworthy, which is not pragmatic. The WSNs are deployed in remote places and are vulnerable to security attacks that are almost impossible to manage physically and may result in performance degradation, accompanied by a malfunction of the WSN. Cryptographic schemes can be a solution to deal with the security concerns, however, they are not feasible for memory-limited tiny sensor nodes with limited processing power. Because of the lesser complexity in computation and higher resistance in the internal attacks, trust evaluation [58; 59] is an effective solution for WSNs, contrary to cryptographic measures. [PERSON] et al. in their paper [32] designed an energy-aware trust derivation scheme for WSNs. The aim of this scheme was to decrease the energy consumption and latency of the network. The trust derivation process refers to the method of calculating the synthesis trust value. The synthesis trust value is based on the combination of the direct trust and collected indirect trust. The direct trust is computed when the nodes participating in data communication are directly observed for trustworthiness. Conversely, indirect trust is obtained based on the recommendation of the other nodes. Readers can refer to [60; 61; 62; 63] for further information about the trust derivation process. Initially, the authors of [32] provided a method to analyze the risk-strategy to simulate cooperation among the nodes. Subsequently, a trust derivation dilemma game (TDDG) was designed to decrease the overhead of the network. Finally, through simulations, it was demonstrated that the designed routing scheme could simultaneously ensure energy consumption and latency. In the designed routing protocol, a few sink nodes and several sensor nodes were distributed in the network area. A node in the network area could detect an event and transmit the data packet. End-to-end communication was achieved in a multi-hop way. Compared to normal sensor nodes, the sink nodes were assumed to be more trustworthy. Two types of attacks, active and passive, were tackled by the designed routing scheme. In passive attacks, the sensor nodes involved in routing passively gather sensitive information or behave in a selfish manner by not collaborating with other sensor nodes in the routing process. In the case of active attacks, the sensitive information is requested directly by the malicious nodes. This kind of attack directly harms the normal operation of the WSNs. Each sensor node in the network was responsible for observing the behavior of the nodes within its vicinity falling under the radio range. The observation results were used for the calculation of trust. A random node in the network had trust level \(T\) that was formed with direct trust \(T_{D}\) and indirect trust \(T_{I}\). The final trust computation results were used for secure routing and access control. The trust computation model that was used in the paper [32] was adopted from [64]. Figure 5 illustrates the trust deviation for an arbitrary node. In Figure 5, \(j\) represents the node being evaluated and \(i\) is the node that is conducting the evaluation. The hop-limited trust derivation procedure of the routing was as follows. The trust deviation process was initialized by a source node \(i\). The target was node \(j\). The node \(i\) broadcast a trust request packet towards node j. A hop-limit value was introduced to handle the overhead of the flooding mechanism. When a node received a trust request packet, it checked whether it had received an identical request. If it had, the packet was discarded within the shortest possible time. However, if the hop limit was greater than zero, the packet was rebroadcast. The node that obtained the trust request packet transmitted towards it should subsequently check if node \(j\) was its neighbor.