## 4 Decentralization in IoT Security
### Blockchain Solutions and IoT Security  
A blockchain and smart-contract-based IoT system was developed by [PERSON] et al. [93]. The created architecture makes use of blockchain technology and a cryptocurrency system to replace the regular cloud server in the IoT. IoT-related transactions and activities are kept in blocks so that every user in the system is able to verify them. On the other hand, smart contracts are implemented for actions in accordance with predetermined policies and roles. The examination of the framework proved the extensive safety of IoT applications. [PERSON] et al. [94] proposed a blockchain-empowered IoT network architecture that is strong, lightweight, and distributed. The architecture is reliable for various activities, e.g., transaction recording, user authentication, access control, etc. [PERSON] et al. [93] presented a system in which IoT devices can verify each other's identities and exchange data securely thanks to blockchain technology. However, not all authentication methods for enhancing the security of IoT data transfer were considered in the study. In [95], [PERSON] et al. presented an authentication system that makes use of blockchain technology and networked identities. Blockchain anonymity was used to assess the system's block speed and performance time. Using a connection protocol, [PERSON] et al. [96] proposed a blockchain system. The proposed protocol proved effective in ensuring the security of IoT network endpoints. It also included a blockchain-based network protocol to provide cryptographically secured authentication and validation of inter-IoT terminals and access to platforms. According to [PERSON] et al. [97], integrating AI with blockchain helped further the objective of safe and scalable IoT systems. For large-scale data analytics tasks in IoT applications, the proposed architecture provides precise, centralized, secure, private, and low-latency options. Latency and insufficient computing power are addressed to some extent but not fully. [PERSON] et al. [98] presented a blockchain framework that aims to continuously ensure the security of IoT systems without human intervention. [PERSON] et al. [99] studied different types of IoT computing devices using a fundamental four-layer IoT blockchain modeling strategy, which includes perceptual, network, blockchain, and application layers. As a proof of concept, they proposed testing a fully automated trading device built on the Ethereum blockchain. As demonstrated by the developed model, blockchain has enhanced the confidentiality, verifiability, and safety of IoT applications. Considering privacy preservation in IoT, [PERSON] et al. [100] designed a blockchain-based thin-client system to address the IoT's authentication and privacy issues. Because of the suggested method, the issue of thin-client devices' limited storage space can be remedied. The trustworthiness of the plan was also verified by means of a comprehensive security examination. However, further study is needed to completely grasp how smartphones are impacted by the computational load of thin clients. Another blockchain technology was introduced by [PERSON] et al., in [101], to ensure security and privacy. A wide range of IoT systems can now be resistant to attacks because of the proposed blockchain-based methods. Blockchain technology further makes it easier to implement IoT activities across different domains and layers, e.g., from the fundamental (data collection) layer to the higher (communication and applications) layers. There are also many works focusing on using blockchain for the security of e-business or financial IoT. For instance, [PERSON] et al. [102] presented a blockchain-empowered system for safeguarding financial and trading transactions in the IoT. The presented method builds a peer neighborhood network to make the blockchain ledger easily fetched by all users. After putting the suggested method through its paces, the universal peers, the size of ledgers, and the weight of blocks can be effectively decreased.