# A Survey on Emerging Blockchain Technology Platforms for Securing the Internet of Things
## 2 Related Work  
This section provides a summary of existing works and a table to compare 15 review and survey papers, comprising four journal articles and 11 conference papers. Most of these papers delve into fundamental aspects of blockchain and IoT, examining intersections and contemporary research directions. Many of these papers expand on their analyses by concentrating on specific areas or topics (tagged Focus) within IoT-BC systems. Adaptation of Blockchain (BC) in IoT, its challenges, and solutions are a major focus of [23; 24; 25]. [PERSON] et al. [24] additionally focused on Industrial IoT (IIoT). These papers discuss the basic structure and main features of blockchain and its application in the IoT and IIoT. [PERSON] et al. [25] reviewed the use of blockchain in IoT applications and provided a taxonomy that covers various aspects such as platforms, recent advances, challenges, and future research directions. Their work gave insights into several blockchain platforms and the contribution they can make to IoT networks. [PERSON] et al. [26] provided an overview of IoT blockchains, including their architectures, communication protocols, applications, and traffic models. They discussed the network structures and protocols of popular IoT blockchain systems, compared different consensus algorithms, and analysed the traffic distribution in P2P and blockchain systems. They also emphasised the need for regulation and development policies to guide the integration of IoT and blockchain technology. Overviews and reviews of IoT-BC integration and use-cases can be found in [27; 28; 29]. [PERSON] et al. [29] and [PERSON] et al. [30] additionally investigated issues encountered after IoT blockchain integration, focusing on aspects like system efficiency in terms of resource limitations and scalability. [PERSON] et al. [27] reviewed blockchain-based platforms  
Figure 4: PRISMA literature search flow. from the perspective of IoT use cases. They introduced an evaluation framework to select a suitable blockchain platform for a given IoT application based on its specific requirements. They discussed different IoT use cases and their functional and non-functional requirements, emphasising the need for a clear understanding of the requirements to identify an appropriate blockchain platform. [PERSON] et al. [PERSON] _et al._ (2018) discussed the integration of blockchain with IoT networks. They evaluated current research in this area and proposed an architectural framework that is structured around a system comprising three distinct layers: the device layer, the dew-blockchain layer, and the cloudlet-blockchain layer. Security perspectives surrounding IoT-BC integration are seen in ([PERSON] _et al._, 2018; [PERSON] _et al._, 2019; [PERSON] _et al._, 2020; [PERSON] _et al._, 2020). [PERSON] and [PERSON] [PERSON] and [PERSON] (2019) conducted a critical review of blockchain-based wireless sensor networks (WSN), focusing on the security concerns in WSN and the adoption of blockchain in comparison with other research reviews. [PERSON] et al. [PERSON] _et al._ (2019) and [PERSON] and [PERSON] [PERSON] and [PERSON] (2020) reviewed security problems in IoT, the proposed solutions using blockchain, the status of blockchain adoption in IoT, and their challenges. Table 1 provides a comparison of selected state-of-the-art surveys and review papers related to IoT security using blockchain. These papers were carefully looked at, considering their key focus (which represents the authors' research focus), reviewed work count (which is the number of works reviewed by their author), limitations, and recommendations for future work. There was a clear gap in the security perspective of IoT-BC in the work; also, the components of BC that enhance security in IoT are given less attention and, in some works, not discussed. These are part of the issues addressed in this work. While the existing reviewed papers focused on a few concepts of security benefits in blockchain IoT, the current paper goes in depth.