# Blockchain-Assisted Adaptive Reconfiguration Method for Trusted UAV Network
## 2 Related Work
As special MANETs, the mission environments of UAV networks are mostly complex and non-secure, requiring more secure network reconfiguration methods. To increase the security of routes, the re-routing adds the evaluation of node reputation. In [19], a reputation-based ant colony optimization method is designed to identify low reputation nodes by modifying the target source routing protocol (DSR) to resist grey hole attacks. Ref. [20] evaluates the reputation of nodes through cooperation between them during the route request process as a reference for route selection. Ref. [21] also evaluates the reputation of nodes, discarding requests from untrustworthy nodes to avoid flooding attacks on routing requests. In [22; 23; 24] reputation assessment of node behavior and inclusion of node trustworthiness conditions in existing routing protocols to exclude such nodes when reconfiguring network routes. The above routing protocols consider security issues and circumvent low trustworthiness nodes during network routing configuration, improving the security of the routes, but also increasing the computational overhead of all participating nodes and limiting the network size. The decentralized, de-trusted and tamper-proof nature of blockchain technology fits well with a distributed MANET network with no management center and no infrastructure. Refs. [25; 26] introduces blockchain to MANET. Using a subset of nodes to validate routing actions taken by other nodes and using the distributed consensus mechanism of the blockchain network to accumulate the reputation of each node. Specifically, we use the heterogeneous difficulty of proof-of-work to represent the trustworthiness of verification and design a scoring system to isolate malicious nodes by distributed consensus, and route reconfigurations to directly avoid malicious nodes. However, this direct approach with a traditional blockchain is overwhelming for resource-constrained MANET nodes, with proof-of-work (POW) computation consumption, progressively increasing block storage, and its synchronous update method on the blockchain increasing bandwidth overhead. Ref. [27] creates a distributed management system of trust and rewards in MANET that detects uncooperative nodes via the blockchain. However, this virtual network requires a \"mining node\" to perform the large consuming calculations such as consensus, which the peer-to-peer lightweight nodes in the UAV network cannot handle. Most of the above research results reconfigure MANETs at the network layer through the dynamic selection of routes. Furthermore, in insecure environments, malicious nodes still exist in the network and each reconfiguration requires an unnecessary increase in operational overhead. The introduced permissionless blockchain, where any node enters the network indiscriminately, increases communication and storage overhead and the proof-of-work consensus approach is unaffordable for UAV networks with limited node resources. Ref. [27] uses blockchains to build global management systems that reorganize the network to exclude uncooperative nodes. Thus, introducing a blockchain to globally manage node trust in distributed UAV networks is a feasible approach. Table 1 shows a performance comparison of the MANET network reconfiguration methods, focusing on security, scalability and the overheads of computation, communication and storage. [PERSON], [PERSON] et al. in [28] proposed a blockchain-enhanced data collection framework where UAVs are used to assist in data collection from sensor nodes in large-scale monitoring scenarios in wireless sensor networks. A Merkle tree-based UAV authentication mechanism is designed to ensure the security of data transmission. The scheme determines the authenticity of the collected data by verifying the legitimacy of the UAV node identity. Query verification using Merkle evidence is also time-consuming when the number of drone nodes increases, especially when given a non-existent piece of evidence.