# Context-Aware Trust and Reputation Routing Protocol for Opportunistic IoT Networks
## 2 Related Work  
In this section, representative routing schemes for OpploT networks are discussed [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. In [6], [PERSON] and [PERSON] proposed the Epidemic routing protocol for OppsNets, where the eventual message delivery from a source node to a destination node is achieved via random pairwise exchanges of messages among the nodes based on a flooding strategy, minimizing the total resources consumed during message delivery. In such an approach, a summary vector is exchanged among the relay nodes to identify the data packets residing at that buffer. Based on this, a mechanism is then invoked, which enables every data packet to eventually reach every node and get sent to the intended destination. However, since there are multiple copies of the same data packet in the network, this raises a resource consumption issue, which might lead to possible network congestion. In [9], [PERSON] et al. proposed a method for identifying malevolent nodes within the OppNet ecosystem, which depends on the infrastructure nodes and established cryptography mechanism. The proposed secured algorithm makes use of this cryptographic technique in trust-based routing for guaranteeing the participation of more nodes in the routing process, by building confidence in their participation. Simulation experiments are conducted, and confirming the effectiveness of the proposed scheme can enhance the network performance in terms of the considered performance metrics. While the proposed method effectively identifies malevolent nodes and enhances network performance through cryptographic techniques in trust-based routing, it relies heavily on infrastructure nodes and an established cryptographic framework. This dependency could limit its applicability in fully decentralized or resource-constrained OppNet environments where infrastructure support and computational resources for cryptographic operations are not readily available. In [10], [PERSON] et al. proposed a trust-based routing scheme for OppNets, which consists of two steps: data retrieval and data transfer. The data retrieval step is meant to identify and then maintain each node's data transfer, whereas the data transfer step is meant to process the prediction of a safe path to be used for the transmission of the data packets to the destination node. With this strategy, nodes do, however, consume a lot of energy. This strategy involves significant energy consumption by nodes during the data retrieval and transfer steps, which may limit its practicality in energy-constrained environments such as mobile or battery-powered devices. In [11], [PERSON] et al. proposed a modified multi-path distance vector (MMDV) protocol for OppNets and designed a trustworthy and secure mechanism for transmitting the data amid a blackhole threat. In their approach, the messages are split up into several paths to get to their destinations, and the transmission of the messages is secured using a homomorphic encryption algorithm. Simulation results are provided, validating the effectiveness of the MMDV protocol in terms of packet delivery and network throughput. The splitting of messages into multiple paths increases computational and communication overhead, which may pose challenges in resource-constrained OppNet environments. Additionally, the reliance on homomorphic encryption could introduce delays due to its computational intensity. In [7], [PERSON] et al. proposed a trust reputation evaluation mechanism for wireless sensor networks (referred to as a beta-based Trust and Reputation Evaluation System (BTRES), which can be applied to OppNets. Such a mechanism relies on the use of the beta distribution to simulate the reputation of a node after monitoring its behavior, and then calculate its trust value and credibility. The trust values of nodes are then utilized to guide the selection of appropriate nodes that participate in the message-routing process.