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The Internet of Things (IoT) is a new technology that uses a collection of smart devices to collect data from the physical world and then transfer it via the internet to be exchanged, processed, and stored. The collected data is used to extract information and act upon the physical world using actuators and smart appliances (Cherif et al., 2020). IoT is used today in several domains including transportation systems, smart energy management, and environmental monitoring (Bangui et al., 2019). IoT added intelligent features like interconnection, monitoring and remote control to a wide range of applications, such as smart homes, smart buildings and cities facilitating daily life (Moreno et al., 2017; Chang et al., 2021). Further, IoT has supported healthcare systems to face the coronavirus (COVID-19) pandemic and treat patients (Benali & Maamri, 2021). It assists healthcare agencies in monitoring individuals and avoiding the virus spread. (Kumar et al., 2020).
Nevertheless, the global economic impact of IoT and its giant amount of confidential data expose it to cyber-attacks, making its security a valuable asset. With such enormous business value, IoT must deliver its revenues while meeting effectively its business objectives and goals (Sacke, 2019). Furthermore, security and privacy present major issues because it deals with very sensitive and private data. On the one hand, an IoT system must ensure the security of user data. On the other hand, IoT devices are vulnerable to cyber-attacks due to their limited capacities. As a result, it is essential to address IoT security and privacy (Benali & Maamri, 2021).
To keep IoT systems secure, several solutions are proposed to solve the aforementioned problems (Benali & Maamri, 2021). In this context, Blockchain is a critical technology that has seen significant success in IoT security (Lao et al., 2021). Blockchain (or BC) is the fundamental technology that enables the existence of cryptocurrencies, and Bitcoin was the first use case (Dorri et al., 2016). Satoshi Nakamoto developed Bitcoin in 2008, which is an electronic cash system allowing payment exchange without requiring a third party (Nakamoto, 2008; Reyna et al., 2018). Blockchain is a tamper-resistant record of shared data that does not require central control, which builds strong trust among all authorized network members (Lao et al., 2021; IBM, 2021). Today, Blockchain spreads rapidly in many non-financial areas including the verification of location proof, transportation, telecommunications, healthcare, and IoT (Dorri et al., 2019; IBM, 2022; Lao et al., 2021). However, Blockchain integration with IoT has many challenges mainly due to their conflicted natures. It demands computing power and produces delays (Dorri et al., 2016), meanwhile, most IoT devices have limited resources (Cherif et al., 2020). This contradiction leads to many challenges in mining, storage, scalability, and consensus reaching (Reyna et al., 2018).
Blockchain has been used to suggest Blockchain-based architectures, such as the architecture to ensure security in IoT presented by Dorri et al. (2016). They propose an architecture consisting of three tiers: local network, overlay network, and cloud. In the local network, all transactions are processed by a miner and stored in a local ledger. The miner checks the policy header to authorize or deny a transaction. The policy header is similar to a permissions list and it is defined using a specific structure (Dorri, Kanhere, Jurdak, & Gauravaram, 2017). Therefore, the policy structure plays an important role in transaction handling and affects the system’s security and performance.