Blockchain and Deep Learning for Smart Healthcare E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 664

Veröffentlichungsjahr: 2023

Beschreibung

BLOCKCHAIN and DEEP LEARNING for SMART HEALTHCARE The book discusses the popular use cases and applications of blockchain technology and deep learning in building smart healthcare. The book covers the integration of blockchain technology and deep learning for making smart healthcare systems. Blockchain is used for health record-keeping, clinical trials, patient monitoring, improving safety, displaying information, and transparency. Deep learning is also showing vast potential in the healthcare domain. With the collection of large quantities of patient records and data, and a trend toward personalized treatments. there is a great need for automated and reliable processing and analysis of health information. This book covers the popular use cases and applications of both the above-mentioned technologies in making smart healthcare. Audience Comprises professionals and researchers working in the fields of deep learning, blockchain technology, healthcare & medical informatics. In addition, as the book provides insights into the convergence of deep learning and blockchain technology in healthcare systems and services, medical practitioners as well as healthcare professionals will find this essential reading.

Leseprobe

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Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])

Blockchain and Deep Learning for Smart Healthcare

Edited by

Akansha Singh

School of Computer Science Engineering and Technology, Bennett University, Greater Noida, India

Anuradha Dhull

Department of Computer Science Engineering, The NorthCap University, Gurugram, India

and

Krishna Kant Singh

Delhi Technical Campus, Greater Noida, India

This edition first published 2024 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2024 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.

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Library of Congress Cataloging-in-Publication Data

ISBN 978-1-119-79174-4

Cover image: Pixabay.ComCover design by Russell Richardson

Preface

The value of blockchain technology in the healthcare market is expected to surpass $1.6 billion by 2025. Blockchain technology is poised to revolutionize more than just payment and cryptocurrency. Many vertical industries will be reshaped by the new trusted data models enabled and inspired by the blockchain—healthcare is no exception. In fact, healthcare may hold the greatest opportunities for the meaningful use of the technology. Early pioneers have explored some of the first use cases for medical payments, electronic health records, HIPAA/data privacy, drug counterfeiting, and credentialing of healthcare professionals. The research has just begun to scratch the surface in how to automate the complexities of today's healthcare systems and design new systems that focus on trust, transparency, and the alignment of incentives.

Healthcare as an industry has unique requirements associated with security and privacy due to additional legal requirements to protect patients’ medical information. In the Internet age where sharing of records and data becomes more prevalent with cloud storage and the adoption of mobile health devices, so too does the risk of malicious attacks and the risk of private information being compromised as it is shared. As health information is becoming more easily obtained through smart devices, and patients are traveling to multiple doctors, the sharing and privacy of this information are a concern. The unique requirements the healthcare industry is facing are in the form of authentication, interoperability, data sharing, the transfer of medical records, and considerations for mobile health. The disruptive integration of blockchain technology with Deep Learning techniques will reveal the answers to the many potential problems associated with the healthcare sector.

This book is based on two of the most emerging fields—blockchain technology and Deep Learning—applied to the healthcare sector. The book will be an essential guide to all academicians, researchers, and industry individuals who are working in their related field. This book will provide insights into the convergence of Deep Learning and blockchain technology in healthcare system and services.

There are a number of books available in Deep Learning and blockchain technology individually. There is no such book available that focuses on the application of Deep Learning and blockchain technology in the healthcare system. Thus, this book is unique in terms of the topics and related content it covers. The readers from a large domain will be interested in the book as it covers three major fields. Moreover, it will be appealing for the readers who tend to do research in this field as the book covers the latest research topics.

The EditorsOctober 2023

Part 1BLOCKCHAIN FUNDAMENTALS AND APPLICATIONS

1Blockchain Technology: Concepts and Applications

Hermehar Pal Singh Bedi1*, Valentina E. Balas2, Sukhpreet Kaur1 and Rubal Jeet1

1Department of Computer Science and Engineering, Chandigarh Engineering College, Landran, Mohali, Punjab, India

2Department of Automatics and Applied Software, University of Arad, Arad Romania

Abstract

Many new technologies evolve and deplete over time, but the most significant technological innovation in recent years has been blockchain technology, which not only has changed almost all aspects of life but also could incorporate all the existing technologies. In this chapter, we will be elaborating all the concepts of blockchain technology and try to understand its purpose in today’s world. We will also look into its use cases especially from a security point of view. As we delve a bit more into the details, we will be looking into the workings of blockchain technology, the different types of blockchains available depending on the network and the consensus mechanism, its structure, and the opportunities for blockchains. Lastly, we will also be exploring some of the challenges that blockchain is facing due to public perception and also the future prospects of blockchain technology.

Keywords: Blockchain, cryptocurrency, smart contracts, decentralized applications

1.1 Introduction

The proposal of a protocol similar to that of blockchain was proposed by cryptographer David Chaum in his dissertation “Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups” in 1982 [1]. In 1991, researchers Haber et al. and Stornetta et al. have illustrated the algorithms on a secured chain of blocks very effectively using cryptography [2, 3]. Nakamoto et al. introduced the method of decentralized blockchain in 2008. He used blockchain for all the transactions made on the Bitcoin network using a ledger in a public domain. Originally, Satoshi Nakamoto used the words “block” and “chain” as two different words, but later were combined to make a single word, “blockchain”.

Blockchain technology is interpreted by many IT professionals as the biggest innovative technological research in today’s digital world in terms of secured assets. Blockchain is the technique of sharing the ledger, which is also one of the best techniques of decentralization of both catalogs and accounts on big data [4]. It is a shared and immutable, i.e., unchangeable and incorruptible, ledger that clears the path for the procedure of documenting the transactions made and tracking the different transactions and assets of any network related to any business. Assets can be of two types: tangible and intangible.

Tangible assets:

These are the physical assets that can be touched such as property, money, vehicles, etc.

Intangible assets:

These are the assets that do not exist in real life but have real-life monetary value such as the crypto-currency, patents, trademarks, etc.

When the defined network is decentralized, then different nodes are used to write, share, and lock the consistent transactions in a distributed ledger [5]. Blockchain works similarly, with the difference being that the data in blockchain are organized into chronological and cryptographical linked blocks, and it also uses different types of mechanisms based on consensus and smart contracts [6].

1.2 Blockchain Types

Broadly, there are four types of blockchains available, which are shown in Figure 1.1.

Figure 1.1 Types of blockchains available.

Public blockchains

are the blockchains that do not require any permissions and are not managed by any company or individual. In public blockchains, anyone can become the node. Public blockchains are purely decentralized and hence allows equal access of blockchains to each and every node. Moreover, each node has the right to create and validate a block of data. There are different blockchains available in the public domain, including Bitcoin, Ethereum, and Litecoin. Mostly, the public blockchains are used for exchanging and mining cryptocurrencies. Public blockchains are criticized by many because of security reasons as the information in the public domain can be accessed by anyone joining the network [

7

]. In public blockchains, all the nodes are treated equally and none of the nodes available on the network have any special privileges. We can interchangeably use permissionless and public blockchain [

8

]. The public blockchain features access in real-life examples [

9

].

Private blockchains

or managed or permissioned blockchains are blockchains that require some permissions, which are managed or controlled by some company or an individual. In managed blockchains, the company or the individual who owns the blockchain grants permissions and makes the decision in creating the nodes. It is not necessary that each node enjoys the same rights similar to public blockchains. They are not purely decentralized as not all the information is available to the public. Ripple and Hyperledger are the examples of permissioned or managed blockchain technologies available. The terms “permissioned” and “private” are used interchangeably [

8

]. All the nodes in this blockchain have different rights for using the services of the network, which includes data accessing, reading, and making transactions, all limited to an individual or some company. The use cases of private blockchains have been increasing [

8

].

Consortium blockchain

is a managed and permissioned blockchain that is managed by a group of organizations rather than an individual. Consortium blockchain is more decentralized as compared to private blockchain, which results in high security. Consortium blockchain is mostly used in the financial services industry and supply chain sectors. Quorum and Corda are examples of consortium blockchains. In a consortium blockchain, all the nodes have different rights for using the services of the network, and it is all limited to the company.

Hybrid blockchain

is a singly managed blockchain, which also requires the oversight of some other public blockchains for the validation of transactions. Transactions made in hybrid blockchains are kept private, which can be verified whenever required by enabling access through a smart contract. A hybrid blockchain allows organizations to establish a private and secured system that requires permissions alongside a public permissionless system, which enables them to administer and decide about the level of rights to be given to each member for accessing the data. Either it can be made private with restricted rights or it can be made public [

10

]. XinFin is an example of a hybrid blockchain.

Some of the papers also divide the blockchain into only two types, depending on their architecture:

Permissioned

Permissionless

Permissioned blockchains include the blockchain networks, in which all the nodes do not have the right to access, read, write, and transact, but all these facilities are limited to some company or individual. Permissioned blockchains include both private and consortium blockchains discussed above and are also sometimes referred to as private blockchains [8]. They use QuorumChain and majority voting consensus, because of which they are faster than permissionless blockchains [11]. Permissioned blockchains are comparatively more secured than public or permissionless blockchains as not all the nodes can access the data available on the network.

Figure 1.2 Types of blockchains.

Table 1.1 Comparison of different blockchains [13].

Property

Public blockchain

Private blockchain

Consortium blockchain

Consensus determination

All different nodes in the network

Only limited to one network of company

Only selected nodes

Type: Permissionless/Permissioned

Permissionless

Permissioned

Permissioned

Security

Secured as it is immutable.

Less secured as it is mutable and can be tempered.

Less secured as it is mutable and can be tempered.

Identity

Anonymous identity [

12

]

Known identity of users [

12

]

Known identity of users [

12

]

Consensus Type

Proof of work

QuorumChain

QuorumChain and majority voting

Permissionless blockchains include the blockchain networks, in which all the nodes are treated equally, have access to all the information on the network, and can broadcast the transaction on the network. Public blockchains include the public blockchain discussed above and are also sometimes referred to as permissionless blockchains [8]. It uses proof-of-work (PoW) consensus, which ensures that all the nodes are only permitted to take any decision if they reach consensus. This also has an adverse effect of slowing down the network [11].

Thus, the types of blockchains available can be classified into two types and then further divided into subtypes as shown in Figure 1.2.

The differences between different types of blockchains are illustrated in Table 1.1.

1.3 Consensus

In blockchain, the consensus is the procedure by which all the shareholders agree on one common thing. These shareholders are known as full nodes; only these full nodes validate each transaction entering the blockchain network. All the blockchains have their own algorithms for the development of consensus; this is because different blockchains are meant for different purposes such as trading, storing data, and security systems [14]. Consensus is also sometimes referred to as the driving force of the blockchains. Depending on the type of blockchain, the consensus is determined as in public blockchains; all the nodes are consensus determinants, whereas in private blockchains, only selected nodes are consensus determinants. There are different types of consensuses like PoW and QuorumChain, developed by JP Morgan. The PoW consensus is used in Bitcoin blockchain.

PoW consensus mechanism: It is a security algorithm and is used to provide a consensus to a new block entering the network. PoW sets some instructions called a protocol for mining. Mining is the process of solving the computational problems, which are in coordination with the PoW protocol. The nodes that want to take part in the mining have to follow the PoW protocol for the affixation. In such cases, nodes have to choose the block that has the largest hash value, and only then can it attach the block [15]. Initial blockchains were implemented using the PoW consensus mechanism. Popular blockchains Bitcoin and Ethereum are both based on the PoW consensus mechanism [16].

Proof-of-stake (PoS) consensus mechanism: It is a security algorithm that is used to provide a consensus to a new block entering the network. PoS also sets some instructions called a protocol for mining. In PoS, the trusted nodes or entities work together to add records into the PoS protocol and to accept the block on the blockchain network; the trusted nodes go through the voting process [15]. Nowadays, in the PoS consensus mechanism, solution hunting has been completely removed and the nodes are now selected based on the stake they have instead of the traditional computational problem solving [16]. Popular blockchains like Cardano and Algorand are based on the PoS consensus mechanism.

Proof-of-concept (PoX) consensus mechanism: This consensus mechanism was basically developed to overcome the problems that were faced by the PoW consensus mechanism. These were (1) to improve the performance in terms of security and incentives and (2) to use computational resources in a better way. Various different consensus mechanisms require the solving of mathematical problems like usage of proof of exercise in evaluating product problems in matrices or finding solutions of various functions in proof of useful work [16].

Hybrid consensus mechanism: These mechanisms use PoW–PoS combinations of consensus mechanisms to form a new kind of consensus mechanisms. One such example of hybrid consensus mechanism is the proof-of-activity (PoA) consensus mechanism as it uses PoW for the creation of a block and PoS for verification of a block and adding the transactions [16]. Blockchains like Casper and Peercoin are based on the hybrid consensus mechanism. Table 1.2 provides the comparison of the two mostly used consensus mechanism i.e., PoW and PoS.

Table 1.2 Differences between PoW and PoS consensus mechanisms.

Property

PoW

PoS

Criterion for selection

Solving computational problems

Stake based

Block generation speed

Slow

Fast

Power consumption

More

Less

Transaction speed

Slow

Fast

1.4 How Does Blockchain Work?

The record list of blockchain is growing very rapidly, and these lists of records are known as blocks. In other words, the blocks can be defined as the database, as in this database, all the transactions made are recorded and cannot be manipulated. Hence, a blockchain can be referred to as a chain of blocks, as it is used to transfer the information or to make transactions from one person to another as illustrated in Figure 1.3. The very first block of this mechanism is called the genesis block. The unique hash codes have been assigned to each block, which helps in the detection of the right block. Hash code acts as the fingerprint of the human hand. Each block in the chain has three parts: Data; Hash, which can be addressed to as the address of the node or block; and Hash of the preceding block. This makes this process an even more secured way of making payments and transferring data. This is because if the hash and data get manipulated, then all the succeeding blocks will become invalid and the transaction will not be executed. The blocks are used as servers and they are stored in the nodes. The data between the nodes are shared continuously as all nodes are connected to each other. Hence, all the data are preserved as the nodes can store and spread the data. Therefore, the nodes can be said to be the fundamental unit of blockchain, without which it cannot be formed.

The following steps are involved in making a particular transaction using blockchain technology:

Step 1: Input and Authentication: In this step, the authorized user will input a transaction, and that transaction should be authenticated first.

Step 2: Formation of a Block: After successful authentication of the transaction, a block is generated, which represents a specific transaction.

Step 3: Transferring Data: Now, once a block has been created, the same information is shared among the nodes of the network.

Figure 1.3 Mechanism of a blockchain.

Step 4: Consensus: Authorized nodes now verify the transaction and adds it to the existing blockchain.

Step 5: Distribution: In this step, all the information is updated across the network, after which the transaction is finalized.

Figure 1.4 represents a sample transaction made on the blockchain network. Firstly, the input for the transaction is declared. After the input, the transaction becomes the node, which is further broadcasted to all other nodes available on the network for consensus. After broadcasting, the consensus step takes place if the block is accepted by all or majority of the nodes (depending on type of consensus), then finally when the transaction is completed through all the steps, that block is added to the network chain.

Figure 1.4 All steps included to make a transaction on a blockchain network.

1.5 Need of Blockchain

There are many reasons to use blockchain technology:

Security:

Blockchain is a secured way of doing transactions and storing the data, as it is immutable and it is almost impossible to hack the blockchain network due to the hash code. If a block gets hacked, then also all the succeeding blocks are inaccessible, preventing the loss of all the data available.

Transparency:

All the changes made to the public blockchain are viewable to the public.

Reliability:

Blockchain verifies the identity of all the users, preventing the duplicity and making it a more secured place for sharing data.

Self-Reliant:

Blockchain allows the users to be self-reliant and self-sufficient in making the transactions; i.e., without the need of any mediator, the money can be transferred from one person to another.

Decentralized:

Blockchain is a decentralized technology, meaning that it is not governed by any single party, which guarantees that all transactions are verified and the valid transactions are added gradually.

1.6 Uses of Blockchain

Humanitarian aid, a project started by the United Nations world food program in January 2017, was developed in villages of the Sindh region of Pakistan. The data of the beneficiaries who received money, daily bread, and all other types of transactions were registered on a blockchain to guarantee security and transparency of this process [17].

There are different types of use cases in blockchain technology across the various sectors of the society:

Government Sector:

During the COVID-19 pandemic, the governments conducted elections by organizing e-Voting using blockchain. Even blockchain is used in transnational personalized governance services and digitization of documents.

Financial Sector:

Cryptocurrency and the digital currency are used in blockchain in almost every financial sector. Other than these, blockchain is also used to make payments and remittance.

Health Sector:

Blockchain technology is being utilized as an efficient method to address healthcare concerns. It can be used for observation, pregnancies, risk data management of medical scripts, supply chains, data exchange, and directing an investing pill for medical use. There are different cases such as the practitioner’s license, billing insurances, sharing medical records with patients, and clinical trials that can benefit from blockchain technology [

18

].

Market:

In markets, the blockchain is used for making the billing system, for transferring data, and in the supply chain management.

Internet of Things:

Blockchain technology is a secured way of transferring data between different parties. Blockchain allows the devices to operate securely and autonomously.

Authorship:

Blockchain technology is also used for confirming and preserving the authorships to the artists.

Big Data:

The combination of blockchain and big data leads to more efficient analytics. This is because of three main reasons:

Security:

The data cannot be tempered by blockchain; hence, we can ensure the security of data in all terms.

Transparency:

The source or the initial point of the data can be easily traced as it is stored on blockchain.

Flexibility:

Since blockchain can store both structured and unstructured kinds of data, it makes the model more flexible and hence accurate.

Information Security:

Since the data available on blockchain are decentralized and integrated, they prevent data breach, identity theft, and cyberattacks, thereby securing the data from any misuse.

1.7 Evolution of Blockchain

There have been advancements in the usage of blockchain, depending on which the blockchain can be divided into three parts, which is demonstrated in Figure 1.5:

Phase 1: Cryptocurrency: The very first phase of blockchain or the phase that gave birth to blockchain was cryptocurrency, which started during 2008–2009 with the origin of the famous Bitcoin by Satoshi Nakamoto.

Phase 2: Smart Contracts: The second phase of the blockchain started with the development of Ethereum, which leads to the development of smart contracts from 2013 to 2015. These are the computer programs or the software stored on the blockchain, which started working when the predefined conditions are met. Smart contracts are used as the alternative for traditional contracts. The government voting system and the supply chain are examples of smart contracts.

Phase 3: Blockchain 3.0: The third or the current phase of the blockchain is the development of the decentralized applications, which started in 2018. In this phase, different applications started to integrate with the blockchain. The codes for these applications are running on a dispersed network that is connected peer-to-peer at their backend. Peepeth, a social media application, and Cryptokitties, a decentralized game, are examples of decentralized applications. Decentralized applications are abbreviated as DApps.

All these phases of blockchain are discussed in detail below.

Phase 1: Blockchain in CryptocurrenciesCryptocurrencies are encrypted data strings that denote a unit of currency. They are based on blockchain technology and are digital currencies. Bitcoin is believed to be the first and the largest cryptocurrency in the world, followed by Ethereum. The use of blockchain in cryptocurrencies was part of the first or the initial phase of using blockchain. Cryptocurrencies are also believed to be the source of blockchain. Today, there are more than 2000 different cryptocurrencies circulating, with a total market capital of around 900 billion dollars [19]. Some examples of cryptocurrencies are Bitcoin (BTC), Ether (ETH), Dogecoin (DOGE), Binance coin (BNB), Cardano (ADA), Litecoin (LTC), Polkadot (DOT), and Solana (SOL).

Figure 1.5 Evolution of blockchain.

Bitcoin: It is a digital currency that is decentralized in nature, developed by Nakamoto et al. in 2008. Bitcoin is also sometimes referred to as a programmed coin or a digital coin. Bitcoin is believed to be the first originator of the blockchain technology. Bitcoin uses the digital ledger to keep track and execute the transactions, which works on the principle of blockchain. In total, Bitcoin has a supply capping of 21 million, meaning only 21 million Bitcoins can be mined. Mining is the procedure of finding and updating the transaction to the Bitcoin’s public ledger of the already completed transactions. The researcher describes the programmed coin as a technology of digital signatures. To avoid the problem of double spending, a trusted central authority known as mint can be introduced. The main function of mints would be to check all the transactions for double spending, but introducing the mints was similar to banks, and to overcome this, each transaction was made public, and to avoid any conflicts in the future, the participants are required by the network to agree with the history of the transactions [20].

Blockchain in Bitcoin

Transactions in Bitcoin: Transactions are made after the verification of the hash function of the transaction is done in the past and the public key of the next owner. All transactions are done digitally. Digital signatures are the private keys, which are unique to all the users. The first owner’s public key and the digital signature of the first owner available on the block of the second owner are verified in order to successfully transfer the Bitcoins. Thus, a single block of Bitcoin contains three sub-blocks that are the current owner’s public key, the hash, and the digital signatures of the previous owner.

Timestamp Server: To make participants agree on the order of transactions of the competing transactions, Satoshi Nakamoto proposed a method consisting of three steps.

Step 1: The competent transactions are grouped together.

Step 2: The hash of the transactions made was computed and published to an external outlet with a large audience like a newspaper.

Figure 1.6 Transaction in Bitcoin [20].

Step 3: As more transactions are recorded, and thus more blocks are added, each new hash/digest will be computed from the current block AND the previous hash/digest. Since hashes cannot be reversed, if block B’s hash can be computed from block A’s hash, it proves that block A came before block B [21].

Figure 1.6 shows the process of how a transaction is made a Bitcoin, as was proposed by Satoshi Nakamoto [20].

PoW: In Bitcoin, a PoW network, which is almost identical to that of Adam Back’s Hashcash, has been used instead of the newspaper. The PoW has been implemented by increasing a nonce (number only used once) in the block. Its value is increased until it reaches zero bits, which is the requirement of PoW [20].

Networking: The following steps are involved in the networking of the Bitcoin:

Step 1: Every node on the network of blockchain has the information of all transactions since it is broadcasted to them.

Step 2: Each and every node gathers new transactions within a block.

Step 3: All nodes work on locating a harder PoW for its block.

Step 4: Upon the successful finding of PoW, the information related to the block is broadcasted to the whole network by the concerned node.

Step 5: After the validation of the transactions of the block, the nodes will accept that block into the network.

Step 6: Acceptance of a block by the node is expressed by using the hash function of the accepted block and then generating the following blocks in the chain [20].

Ethereum: Ethereum (ETH) is a blockchain-based decentralized smart contract, which was developed by V. Buterin, G. Wood, and C. Hoskinson in 2013 and was launched in July 2015. ETH cryptocurrency is second in market capitalization after the Bitcoin. All the concepts of the transaction-based machines are built using ETH only [21]. Ethereum’s native cryptocurrency is Ether, which a user must spend as a cost of processing a transaction on the ETH network. Ethereum is also an example of public cryptocurrency and hence does not require any permission and is not managed by any company or individual. Ethereum is built using the Solidity and Vyper smart contract languages. ETH is used for Decentralized Finance (DeFi) and the Non-Fungible Tokens (NFTs).

1.8 Blockchain in Ethereum

Ethereum Virtual Machine (EVM): EVMs are basically stack-based architecture having a stack size of 256 bits and do not follow the standard Von Neumann Architecture. Instead of storing the codes in random access memory (RAM) or storage, it stores the data in the virtual read-only memory (ROM) and hence interacts only with specific instructions [22].

Ethereum Accounts: In ETH, the term “Accounts” is described as the state of the objects that have a 20-byte address. Each account has four fields:

Number only used once (nonce) counter to make sure that the transactions are not processed repeatedly;

The current balance of account in ETH;

The contract code of the account, which is the hash function of root; and

The account’s codehash.

There are two types of accounts in ETH

Externally owned accounts:

The different types of private keys are used to own these accounts; moreover, they do not have any association with any type of code. All the messages can be forwarded by them after creating and signing a transaction [

23

].

Contract accounts:

They are associated with different codes and these accounts are owned by the contract code as well. In these types of accounts, communication is done using messages and the code is activated after receiving the message, which, in turn, allows the account to read and write transactions in the internal storage. Using this method, messages are sent to different accounts in the network [

23

].

Gas: Gas is the fee required to conduct any transaction on the ETH network. The only payment method acceptable to pay the gas is in Ether, the native cryptocurrency of the ETH network.

Gas Price: This quantitative parameter gives the value any account will spend on each and every unit of gas. It basically gives the value of Ether. It is measured in gwei, where 1 gwei = 0.000000001 Ether [21, 22].

Gas Limit: It is the capacity that each and every transaction can consume in terms of gas units.

Transaction Fees = Gas Price * Gas Limit [24]

In ETH, all the transactions consist of blocks grouped together and they contain three parts:

Block header:

It contains the following information: parentHash, ommersHash, beneficiary, stateRoot, transactionsRoot, receiptsRoot, difficulty, number, gasLimit, gasUsed, logsBloom, nonce, extradata, timestamp, and mixHash.

Information about set of transactions

Set of other block headers for the current block ommers

: Ommers are the blocks whose parent is equal to the current block’s parent’s parent.

Transactions in Ethereum: Transactions are the instructions given by the account holder to the network. When an account holder sends an instruction or makes a transaction, the ETH network is appropriately updated. Each transaction alters the EVM, and then this information is shared with all the nodes in the network. After the broadcast, miners initiate the transaction and pass on the changes made to all other nodes [25].

State Transaction Function: The basic structure behind the workings of the ETH is as follows:

Step 1: Check the credibility of transaction

Step 2: Calculate the transaction fee

Step 3: The transaction fee is deducted from the account of the sender and the nonce counter is incremented. If there is insufficient balance, then exit.

Step 4: For each byte in the transaction, some quantity of gas is subtracted.

Step 5: Release the transaction amount into the receiver’s account. If no receiver’s account is found, then create one. If the receiver has a contract account, then run the code stored in the smart contract account. The code is executed until it is completed or until some type of failure occurs.

Step 6: If the transaction is unsuccessful due to insufficient balance or due to some failure, then all types of updates and changes done so far are returned back and fees are refunded to the sender [23].

Table 1.3 explains the differences between the Bitcoin network and the Ethereum network of blockchain.

Litecoin: Litecoin (LTC) is a cryptocurrency that was developed by Charles Lee in 2011. It is denoted by a silver coin in reference to the Bitcoin, which was earlier named as the gold coin [27]. It used the source code of Bitcoin after making some changes. The main difference between LTC and Bitcoin is the processing time of transaction made, which is about 2.5 min in LTC and 10 min in Bitcoin. Moreover, the mining of Bitcoin requires fast computing and processing along with a high electricity consumption, whereas LTC does not require such high configuration. It only requires an ordinary computer [27].

Table 1.3 Comparison of different blockchain networks [26].

Property

Bitcoin network

Ethereum network

Currency

Bitcoin

Ether

Latency

10 min

12–14 s

Throughput

7 Tx/s

9–10 Tx/s

Application

Bitcoin only has a financial application

Ethereum does not have only financial application, it is also used for smart contracts

Programming language

C++

Solidity

Dogecoin: Dogecoin (DOGE), referred to as the memecoin, was developed by Billy Markus, a programmer by profession in Portland, Oregon. It was officially released in December 2013. DOGE was created as a “fun cryptocurrency”, which could reach a broader demographic area than the Bitcoin. DOGE was created as a rival coin to Bitcoin. DOGE is based on the already existing structure of Luckycoin, which is the system of rewarding for mining a block of coin. This system of rewarding was changed in 2014 to the static block reward. Luckycoin was based on the Litecoin technology of the cryptocurrency discussed above. Earlier, the supply of DOGE was limited to 100 billion, but later it was decided and announced that there will be no capping on the total number of coins; hence, the DOGE network will produce infinite coins. DOGE is even faster than the Litecoin, which has a processing time of around 2.5 min. DOGE reduced the processing time to 1 min [28]. This is the only reason that Tesla CEO Elon Musk said “DOGE is a way better crypto coin than Bitcoin when it comes to the transactions per day” [29].

Ripple: Ripple (XRP) was developed by Open Coin in 2012. XRP is also a payment system and a cryptocurrency similar to Bitcoin. XRP is very fast in comparison to other systems. It is because it is able to transfer money to other users in the network within a couple of seconds using this network [27].

Phase 2: Blockchain in Smart ContractsSmart contracts lead to the next phase of the blockchain. They are basically the software, as they are intended to execute and document legally relevant events in the terms of a contract automatically. In smart contracts, the buyer’s and seller’s information is directly inscribed into the code. They are operated using the virtual machines that dedicatedly worked for them. These machines use ledgers that are distributed in nature and are embedded in a blockchain [30]. The various components include the program code, storage, and a balance [31]. A smart contract can be made and used by any node available on the blockchain by simply pushing a transaction onto the blockchain. They can be developed and deployed on various blockchain networks such as Bitcoin and Ethereum. Deploying a smart contract on ETH is easy as compared to that on Bitcoin as Bitcoin uses the bytecode scripting language, which is based on stacks, making it less compatible [32], whereas in ETH, there are two types of accounts as discussed above. All accounts under this category are coordinated by the logic of program code, state, storage, and balance. EVM supports the smart contracts by interpreting the compiled source code, which is converted into the bytecode. Each node executes the same instruction to run a smart contract [31]. There were some challenges related to the scalability of smart contracts in both of these blockchain networks, which was overcome by the Hyperledger fabric. The major difference between Hyperledger and Bitcoin or ETH is based on permissions only. The former is a permissioned blockchain network whereas the latter is a permissionless blockchain network.

1.9 Advantages of Smart Contracts

They have many advantages, because of which they are gaining popularity. Some of the advantages of smart contracts are listed below:

Security:

Since these are based on blockchain, they use the best data encryption, which is also used in cryptocurrencies, making it one of the most secured ways of transacting.

Speed:

Since smart contracts work on the software codes, they are very fast, which helps prevent the wastage of time and also manual labor.

Accuracy:

Smart contracts omit the need to fill the forms manually, which reduces the risk of errors and hence making it more accurate. Smart contracts store all the terms and conditions, so they can be used later.

Efficiency:

Because of the speed and the accuracy of the smart contracts, they become more efficient. Better efficiency results in creating more transactions per unit time.

Eco-friendly:

As smart contracts are based on software and reduce the use of paper, they are eco-friendly.

Transparency:

All the terms and conditions are clearly mentioned and visible to both parties, which reduces the risk of dispute between the parties.

Backup:

They have the advantage that they are able to record the details of each transaction for backup, so that they can be easily accessible in the future [

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].

1.10 Use Cases of Smart Contracts

Smart contracts are being used for several different things such as:

Online Voting System:

Smart contracts are a secured way of conducting a poll as it does not allow the manipulation of transactions made (votes casted in this case). All the votes that are cast by the nodes are protected by ledgers, so it is difficult to decode and manipulate.

Supply Chain:

In supply chain, the different applications included are management systems related to inventory and the automation of payments and tasks.

Financial Sector:

Different tools are integrated for book-keeping, which, in turn, reduced the possibility of manipulation of any type of records [

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1.11 Real-Life Example of Smart Contracts

Suppose you are buying any property and you sent the payment to the seller in cryptocurrency. The seller sends you a receipt, which is stored in virtual contract. The seller is supposed to send you the digital key to access the receipt by a certain date. If the seller has not sent you the key on the specified date, then the refund would automatically be initiated by the blockchain. If the seller has sent you the key before the specified date, then the key would be delivered to you and the money you transacted would be deposited into the seller’s account.

1.12 Blockchain in Decentralized Applications

Decentralized applications are open-source software, which works on peer-to-peer blockchain networks instead of a single computer [35]. Decentralized applications are abbreviated as DApps. Most of the times, DApps are built on the Ethereum blockchain network, due to which DApps are becoming more popular. The major benefit of using a DApp is that it is easily accessible. Also, it does not have any point of failure [34]. It is not necessary for a DApp to run on a blockchain network. Some of the DApps that do not run on the blockchain network are Tor, BitTorrent, and Popcorn Time [36]. DApps that run on the blockchain technology are Peepeth, a social media application, and Cryptokitties.

Recently, a new concept of metaverse is also gaining popularity. Metaverse is simply the network of three-dimensional (3D) virtual worlds that focuses on connecting the society. Metaverse is also a type of new social media, wherein the public can literally feel like they are present in some other world with some other people around them. Metaverse is also a type of DApp. Metaverse applications are built using the blockchain network. Most common examples of DApps built using the multi-metaverse interplanetary scenario are Fortnite and Solana. Solana is also a blockchain, which, like many other blockchain networks, has its own money known as SOL [37]. Recently, Facebook has also been renamed to Meta. Meta comes from the same term metaverse.

1.12.1 Advantages of DApps

Security:

If any of the node is working on the network, then the network will be available, because of which it is very difficult for hackers to hack the node and hence making the network one of the most secured technologies [

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].

Data Integrity: