# Integrating Blockchains with the IoT: A Review of Architectures and Marine Use Cases
## 5 Discussion  
This paper has explored the integration of blockchain technology with the IoT in marine environments, specifically within the MIoT and IoUT. These systems face unique challenges, such as a limited communication bandwidth, high latency, and a lack of standardization across protocols and device interoperability, all due to the demanding nature of these environments [16; 17; 18]. However, integrating blockchains into these IoT systems can introduce additional complexities, including increased energy consumption, storage limitations, and potential latency issues [9; 19; 20]. If not managed attentively, the blockchain's computational demands may amplify these existing challenges or even create new ones, complicating the development of reliable and efficient IoT solutions for marine environments [14; 20]. Existing work has highlighted that computing paradigms such as edge and fog computing are crucial to the development of reliable BIoT systems [3; 30], as they enable local data processing that reduces latency and conserves bandwidth--especially important in marine and underwater contexts with limited resources. A key focus of this work has been the examination of various solutions that actively implement these computing paradigms to address specific challenges within the MIoT and IoUT. For example, [PERSON] et al. [25] utilize cloud and fog layers within a blockchain framework, while [PERSON] [26] incorporatesSDN and fog, and [PERSON] et al. [24] leverage edge computing combined with federated learning. These examples demonstrate how recommended computing models are effectively used in marine and underwater IoT environments. In addition to these computing paradigms, this work also examined these solutions regarding the consensus mechanisms and blockchain platforms chosen to meet the unique demands of the MIoT and IoUT. Lightweight nodes are essential components, allowing these systems to operate efficiently without overwhelming the limited processing capabilities of typical IoT devices [3]. While some solutions utilize platforms such as Ethereum and Hyperledger ([PERSON] et al. [51]), custom solutions are prevalent--even modified Ethereum solutions, such as \"BCTrust\" [21]--due to the specificity of the MIoT and IoUT domains. These custom implementations often avoid resource-intensive PoW architectures, which are unsuitable for constrained marine IoT environments. Additionally, several solutions incorporate the IPFS to manage data in a decentralized manner. For instance, [PERSON] [14] integrates Ethereum with IPFS to enable decentralized storage, ensuring integrity and secure transmission. Likewise, [PERSON] et al. [28] use the IPFS alongside AI and onion routing to enhance communication security, particularly in underwater vehicle networks where the risk of intrusion is higher. This focus on consensus algorithms reveals a wide array of choices, strategically adapted to the constraints of marine environments. In this respect, [PERSON] et al. [25] employ modified PoS protocols to reduce resource consumption, while [PERSON] et al. [22] utilize PoA\({}_{2}\) to enhance energy efficiency during device migration. Other solutions implement protocols such as modified PoW [26], PoA\({}_{1}\)[23], and PoQ [24], demonstrating a range of approaches designed to balance energy efficiency and security. A noteworthy consideration is that many of these solutions were developed prior to Ethereum, in September 2022, transitioning from a PoW to a PoS consensus mechanism (known as the Merge) [56]. With Ethereum being more energy-efficient, future blockchain-based MIoT and IoUT systems may adopt it more widely as a platform. Had PoS been available earlier, Ethereum might have seen broader adoption in these contexts. However, customized solutions and private/permissioned networks could continue to dominate due to the specific needs of each use case.