Blockchain gets its name from being a series of blocks that are linked together to form a chain. Once the information has been added to the chain, it cannot be changed. There are several consensus protocols, and each of them is chosen based on the type of blockchain and the system requirements. With the rapid urbanization of the world, several economic, social, and environment-related issues have been raised. Smart cities are an emerging concept that holds the solution to these urban problems. Blockchain is such an innovation that can promote the development of smart cities. Along with its application in the internet of things, smart cities, and logistics, blockchain truly is state-of-the-art technology. Here, the authors aim to provide an in-depth look into this relatively new technology, beginning with blockchain's fundamentals and then covering the applications, issues, and future scope.
TopIntroduction
Blockchain (Wright, 2019)is a prominent and trending technology in distributed ledger technology (DLT)(Sakız & Gencer, 2019). This technology holds the characteristics of an immutable, decentralized, and sharable database. It is an innovation that hits a breakthrough in secure computing, making all the transactions decentralized. Blockchain enables users to communicate and make transactions among themselves without any third party making it more secure. It is the building block of Bitcoin. Both of them were invented in 2008 by Satoshi Nakamoto and implemented in 2009 for open source after releasing the code. Owing to blockchain technology's several benefits, it is in high demand(Gupta et al., 2020; et al., 2018).
Blockchain spread across various application domains included the financial sector, traffic management, risk management, healthcare, and other social services(Pilkington, 2016; Xu et al., 2019) . It also can be used in digital assets, remittance and online payment, smart contracts, public services, hyper-ledger, insurance, supply chain management, reputation systems, and security services(Labazova et al., 2019). Blockchain technology uses particular consensus algorithms for creating a balanced distributed ledger inside the network. The transaction information is stored chronologically inside the blocks which are interlinked in a chain. The entire ledger or database is stored as multiple copies across all the nodes of the peer-to-peer network. Blockchain can be public or private, with private ones requiring permission from the owner for someone to join(Tasca & Tessone, 2017).
There are mainly two types of blockchain: the public or permissionless blockchain and the private or permissioned blockchain. Examples of public Blockchain include the Bitcoin or Ethereum platform, which allows anyone to join in on the network(Vujičić et al., 2018). Private Blockchain pre-verifies its participants within the network. Usually, they are known to each other. A hybrid kind is a mixture of both that utilizes the advantageous characteristics of each type of blockchain. The applicability of various blockchain types depends on the nature of the application(Hao et al., 2018; Ismail & Shehab, 2019) . This paper facilitates potential readers with the following –
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Latest pieces of literature and their contribution related to blockchain survey
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A detailed overview of blockchain fundamentals
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A precise description fo consensus algorithms used in the blockchain network
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Explanation of state-of-the-art applications related to blockchain
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A Categorical representation of blockchain’s future research direction.
The rest of the paper is organized as section 2 contains the blockchain fundamentals. This part includes blockchain characteristics, block structure, blockchain architecture, and a comparative overview of various blockchain types. Section 3 includes a brief description of various consensus algorithm principles used in blockchain. Section 4 consists of the application related to blockchain in various sectors. Section 5 consists of a well-defined categorical representation of future research direction, and section 6 concludes the paper.
TopLiterature Survey
Since the inception of blockchain technology, several surveys have been conducted. Those surveys focused on specific attributes of blockchain technology. The surveys and their contributions are given below in Table 1 –