# Blockchain-Based Lightweight Trust Management in Mobile Ad-Hoc Networks
## 1 Introduction  
Unlike conventional networks, mobile ad-hoc networks (MANETs) are cooperative networks composed of mobile nodes. Without any fixed infrastructure or centralized administration [1], the nodes randomly move and communicate with each other both directly via wireless connections and indirectly via communication with other nodes outside the wireless range through relay nodes. This mode of communication induces the multi-hop phenomenon [2], where intermediate nodes act as routers for relaying packets to destination nodes. Consequently, several routing protocols for MANETs have emerged, including optimized link state routing (OLSR), ad-hoc on-demand distance vector routing (AODV), and dynamic source routing (DSR). Based on these routing protocols, the nodes themselves choose a routing path to the destination and forward packets [3; 4]. Based on their flexibility and robustness, regardless of geographic location or proximity to infrastructure [5], MANETs are applicable to various interactive application scenarios, including military battlefields, commercial sectors, and other civilian environments. In military scenarios [6],while MANETs can provide information network technology for soldiers and vehicles through scattered devices on the battlefield, an enemy can compromise devices and make the network vulnerable, allowing them to disseminate malicious information, discard sensitive information in multi-hop scenarios, or extract critical data. Additionally, in after-war scenarios, an enemy can continue to scatter devices in an attempt to obstruct recovery operations or coordinate sudden attacks. MANETs are also widely applied in the commercial sector, as well as in emergency and rescue operations following natural disasters. During emergency and rescue operations, MANETs are also prone to vulnerabilities. For example, when multiple countries cooperate to recover from natural disasters, the data that some of the countries prefer to secure as private and sensitive could be exposed through MANETs [7]. Securing communications in MANETs is one of the biggest challenges for system architects. There are a variety of attacks that can occur in every network layer (the attacks that MANETs are vulnerable to are classified in Table 1). Although it is desirable to introduce effective security solutions that can reveal attackers in a network and there are several existing MANET security solutions, attack prevention is even more desirable. To minimize malicious actions, it is necessary to introduce an effective trust system in MANETs to achieve various system objectives, including reliability, scalability, and availability [8]. To introduce trust into communication networks under critical conditions, system designers should consider various perspectives (e.g., node heterogeneity, rapid changes in network topology, a lack of predefined trust relationships, and the resource-constrained environment of mobile nodes [9]). In MANETs, trust management has been introduced in various forms, including trust establishment [10], trust updating, and trustworthiness [8]. Some researchers have introduced an authentication mechanism [11] to ensure links are safe prior to communicating within the network. However, because MANETs are continuously changing [12], the owner of a secret key could be a malicious entity, even if there are no malicious outsiders with unauthorized identities. Furthermore, it is difficult to control the authentication process through a single node. Generally, trust operations are limited to local access, which introduces the problems of incompleteness and vagueness. Hence, it is critical to reconfigure networks seamlessly and consistently. In this paper, we propose a blockchain-based trust establishment system that provides distributed, consistent, and tamper-proof trust to nodes in MANETs. Blockchain as a potential solution for trust management, it has been actively researched in various fields, including wireless networks [13] and the internet-of-things (IoT).