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Top1. Introduction
With the invention of new technologies, the adaptation of wireless ad-hoc networks has increased to large extent (Zhang et al., 2012), (Moussaoui et al, 2014). The ad-hoc networks have many important applications like WSN, IOT, MANET, VANET and FANET in different fields that attracts the researchers (Triparty et al., 2020), (Jiang et al., 2020), (Chen et al., 2020). Nodes or devices in these types of networks are capable of self-configuration without any centralized control to operate in the network (Mayti et al., 2017). Some networks involve movement of nodes making the network topology highly dynamic (Khan et al., 2017). The communication among nodes in such networks is achieved in multi hop manner. Intermediate nodes are used to set up a route between sender and receiver (Wei et al., 2014). However, these intermediates nodes may be malicious and can attack the network in many different ways in order to hamper communication in the network. Hence, the ad-hoc networks have more security issues than their counterparts.
Various mechanisms like routing based (Gupta et al., 2019), trust based (Huang et al., 2020), cluster based (Subba et al., 2015), sequence number based (Rajesh Babu & Usha, 2016), overhearing based (Kollati & Somasundaram, (2017), cross-layer based (Usha et al.,2017), cryptography and authentication, etc. are used by researchers to enhance the security of wireless ad-hoc networks. Out of all security mechanisms, trust based mechanisms have attracted the researchers more due to their preventive nature, effectiveness, accuracy and scalability. Trust based systems can deal with simple as well as smart or intelligent attacks like co-operative blackhole (Singh et al., (2021) and grayhole attacks (Khanna & Sachdeva, 2019). One more advantage of trust based frameworks is that they can work in collaboration with other mechanisms and integrate seamlessly with base routing protocols to provide all-inclusive security in smart networks (Alnumay et al., 2019).
Trust based mechanisms support both prevention and detection of malicious nodes in a network (Hammamouche et al., 2018), (Zhang et al., 2019). Prevention is achieved through forming routes that are more trustworthy. For detection, trust based mechanisms periodically update the trust value of all the active nodes to detect the malicious nodes. In trust based system, we can continuously observe the performance and behavioural patterns of neighbouring nodes in the network (Bhasin et al., 2020). If any malicious node is found during this periodic check, that node(s) is marked malicious and information related to it is broadcasted in the network and as a result that node becomes isolated in the network. Trust based frameworks enhances the overall performance of network in terms Quality of Service, robustness, packet delivery ratio, and throughput.