The Internet of Things (IoT) is one of the popular domains in real-time analytics, ma-chine learning, ubiquitous computing, commodity sensors, and embedded systems where remote smart devices play notable roles in smart homes and industry. The information from emerging IoT environments like remotely-controlled objects, autonomous vehicles (AVs), and energy management can produce a huge amount of data. Moreover, under-standing the security in a scalable decentralized IoT environment is a significant issue.Decentralization has become popular again in the world since cryptocurrencies started to be a part of businesses. Therefore, researchers invested in upgrading resources to increase the reliability of these systems among people when most of the activities and human works are now managed by smart electronic devices remotely. Distributed ledgers, Distributed Hash Tables (DHTs), and blockchain technologies are proper decentralized technologies that improve system security, scalability, and trustworthiness. Blockchains contain a group of connected blocks that are digitally signed transactions stored in a decentralized fashion. The DHT technology is another decentralized solution that helps applications keep files and information immutable in a decentralized manner to mitigate the high cost of storage without memory limitations.In this thesis, we argue for a decentralized systems paradigm and, in conjunction with IoT and the blockchain. Our contributions are as follows. First, we introduce the term networks and service architectures and how it is possible to use blockchain in the real world. We consider different architectures in IoT systems and show the blockchain en-counter with the IoT and the resulting behavior. Second, we detect most of the frequent types of attacks in IoT related to using blockchain in the systems. We also describe how the blockchain works and illustrate a variety of security problems in systems. Fur-thermore, we discuss how the blockchain solves security problems by comparing different blockchains and explain how users handle their communication without third-party de-pendence. As our third contribution, we propose a novel architecture that consists of finding global identification in distributed applications and enable decentralized systems to be more secure with the help of blockchain technology. We also validate the proposed architecture and novel decentralized application development to evaluate high efficiency by combining blockchain, DHT, and biometric technologies.

High-level systems need identification techniques, where higher security and scalability are considered requirements. Identification plays a significant role in systems where smart electronic devices increase in zero trust and open environments like decentralized systems. Also, decentralization has emerged as one of the most exciting domains in recent years, again after the first Internet was invented. Besides, decentralization in identification systems has gained popularity worldwide since cryptocurrencies became part of businesses. Distributed Ledger Technology (DLT) and Distributed Hash Tables (DHT) can be appropriate decentralized solutions that improve identification to be much more secure, scalable, and trustworthy.

The decentralized nature of DLT and DHT ensures no single point of failure, making them highly resilient to attacks. Blockchain as a DLT solution can help devices communicate with each other securely and trustably by storing an immutable history of transactions, providing an additional layer of security to identification systems. DHT senable applications to keep files and information immutable in a decentralized manner. DHTs ensure that the data is replicated across multiple nodes, making it highly resilient to data loss. Moreover, mitigating high storage costs without memory limitations is the target of these technologies. In this context, a decentralized system paradigm that combines systems with DLT and DHTs can be highly beneficial.

This thesis argues for such a paradigm, and the contributions include introducing the term decentralized networks and architectures and demonstrating the feasibility of using blockchain as a DLT solution in real-world scenarios. These scenarios can be applied to the Internet of Things (IoT) or other Peer to Peer networked systems. We explore different architectures in various systems and analyze the interaction in blockchain. This thesis contributes to developing decentralized identification systems that provide users’ trust in an open environment. It presents the challenges associated with decentralized identification, including registry and storage issues, and proposes solutions using DLT and DHT. The immutability of DLT and DHTs provides fast and secure solutions for decentralized identification systems. In particular, we show that a DHT-based architecture is feasible to maintain decentralization while avoiding memory constraints. However, there is still room for improvement in terms of performance. Our investigation shows that combining DHTs with blockchain in decentralized identifiers improves performance.

By concealing blocks in the private blockchain, we show that query performance is better than other DHT and public blockchain-based solutions without concealed information. Moreover, our results show that DHT performs better than the public blockchain for scenarios with many records.

These findings highlight the importance of selecting the appropriate technology for decentralized identification systems, considering the specific use case and the number of records to be stored.

We also consider different decentralized identification systems and platforms built based on the recommendation of W3C Decentralized Identifiers (DIDs). We found low-efficiency issues using this technology, resulting from leveraging public DLT in the data registry part of DIDs. That model has searching time problems if the DLT grows. Finally, this thesis helps to analyze these issues and find better solutions. By choosing the right technology, we can ensure that decentralized identifiers are efficient, secure, and scalable, which enables users to trust them in an open environment.