Mastering Blockchain - Third Edition

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By Imran Bashir
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About this book

Blockchain is the backbone of cryptocurrencies, with applications in finance, government, media, and other industries. With a legacy of providing technologists with executable insights, this new edition of Mastering Blockchain is thoroughly revised and updated to the latest blockchain research with four new chapters on consensus algorithms, Serenity (the update that will introduce Ethereum 2.0), tokenization, and enterprise blockchains.

This book covers the basics, including blockchain’s technical underpinnings, cryptography and consensus protocols. It also provides you with expert knowledge on decentralization, decentralized application development on Ethereum, Bitcoin, alternative coins, smart contracts, alternative blockchains, and Hyperledger.

Further, you will explore blockchain solutions beyond cryptocurrencies such as the Internet of Things with blockchain, enterprise blockchains, tokenization using blockchain, and consider the future scope of this fascinating and disruptive technology.

By the end of this book, you will have gained a thorough comprehension of the various facets of blockchain and understand their potential in diverse real-world scenarios.

Publication date:
August 2020



Decentralization is not a new concept. It has been in use in strategy, management, and government for a long time. The basic idea of decentralization is to distribute control and authority to the peripheries of an organization instead of one central body being in full control of the organization. This configuration produces several benefits for organizations, such as increased efficiency, expedited decision making, better motivation, and a reduced burden on top management.

In this chapter, the concept of decentralization will be discussed in the context of blockchain. The fundamental basis of blockchain is that no single central authority is in control of the network. This chapter will present examples of various methods of decentralization and ways to achieve it. Furthermore, the decentralization of the blockchain ecosystem, decentralized applications, and platforms for achieving decentralization will be discussed in detail. Many exciting applications and ideas emerge from the decentralized blockchain technology, such as decentralized finance and decentralized identity, which will be introduced in this chapter.


Decentralization using blockchain

Decentralization is a core benefit and service provided by blockchain technology. By design, blockchain is a perfect vehicle for providing a platform that does not need any intermediaries and that can function with many different leaders chosen via consensus mechanisms. This model allows anyone to compete to become the decision-making authority. A consensus mechanism governs this competition, and the most famous method is known as Proof of Work (PoW).

Decentralization is applied in varying degrees from a semi-decentralized model to a fully decentralized one depending on the requirements and circumstances. Decentralization can be viewed from a blockchain perspective as a mechanism that provides a way to remodel existing applications and paradigms, or to build new applications, to give full control to users.

Information and communication technology (ICT) has conventionally been based on a centralized paradigm whereby database or application servers are under the control of a central authority, such as a system administrator. With Bitcoin and the advent of blockchain technology, this model has changed, and now the technology exists to allow anyone to start a decentralized system and operate it with no single point of failure or single trusted authority. It can either be run autonomously or by requiring some human intervention, depending on the type and model of governance used in the decentralized application running on the blockchain.

The following diagram shows the different types of systems that currently exist: central, distributed, and decentralized. This concept was first published by Paul Baran in On Distributed Communications: I. Introduction to Distributed Communications Networks (Rand Corporation, 1964):


Figure 2.1: Different types of networks/systems

Centralized systems are conventional (client-server) IT systems in which there is a single authority that controls the system, and who is solely in charge of all operations on the system. All users of a centralized system are dependent on a single source of service. The majority of online service providers, including Google, Amazon, eBay, and Apple's App Store, use this conventional model to deliver services.

In a distributed system, data and computation are spread across multiple nodes in the network. Sometimes, this term is confused with parallel computing. While there is some overlap in the definition, the main difference between these systems is that in a parallel computing system, computation is performed by all nodes simultaneously in order to achieve the result; for example, parallel computing platforms are used in weather research and forecasting, simulation, and financial modeling. On the other hand, in a distributed system, computation may not happen in parallel and data is replicated across multiple nodes that users view as a single, coherent system. Variations of both of these models are used to achieve fault tolerance and speed. In the parallel system model, there is still a central authority that has control over all nodes and governs processing. This means that the system is still centralized in nature.

The critical difference between a decentralized system and distributed system is that in a distributed system, there is still a central authority that governs the entire system, whereas in a decentralized system, no such authority exists.

A decentralized system is a type of network where nodes are not dependent on a single master node; instead, control is distributed among many nodes. This is analogous to a model where each department in an organization is in charge of its own database server, thus taking away the power from the central server and distributing it to the sub-departments, who manage their own databases.

A significant innovation in the decentralized paradigm that has given rise to this new era of decentralization of applications is decentralized consensus. This mechanism came into play with Bitcoin, and it enables a user to agree on something via a consensus algorithm without the need for a central, trusted third party, intermediary, or service provider.

We can also now view the different types of networks shown earlier from a different perspective, where we highlight the controlling authority of these networks as a symbolic hand, as shown in the following diagram. This model provides a clearer understanding of the differences between these networks from a decentralization point of view:

Figure 2.2: Different types of networks/systems depicting decentralization from a modern perspective

The preceding diagram shows that the centralized model is the traditional one in which a central controller exists, and it can be viewed as a depiction of the usual client/server model. In the middle we have distributed systems, where we still have a central controller but the system comprises many dispersed nodes. On the right-hand side, notice that there is no hand/controller controlling the networks.

This is the key difference between decentralized and distributed networks. A decentralized system may look like a distributed system from a topological point of view, but it doesn't have a central authority that controls the network.

The differences between distributed and decentralized systems can also be viewed at a practical level in the following diagrams:

Figure 2.3: A traditional distributed system comprises many servers performing different roles

The following diagram shows a decentralized system (based on blockchain) where an exact replica of the applications and data is maintained across the entire network on each participating node:

Figure 2.4: A blockchain-based decentralized system (notice the direct P2P connections and the exact replicas of blocks)

A comparison between centralized and decentralized systems (networks/applications) is shown in the following table:





Service provider

All users



Distributed, different topologies



More secure

High availability



Fault tolerance

Basic, single point of failure

Highly tolerant, as service is replicated

Collusion resistance

Basic, because it's under the control of a group or even single individual

Highly resistant, as consensus algorithms ensure defense against adversaries

Application architecture

Single application

Application replicated across all nodes on the network


Consumers have to trust the service provider

No mutual trust required

Cost for consumer



The comparison in the table only covers some main features and is not an exhaustive list of all features. There may be other features of interest that can be compared too, but this list should provide a good level of comparison.

Now we will discuss what methods can be used to achieve decentralization.


Methods of decentralization

Two methods can be used to achieve decentralization: disintermediation and competition. These methods will be discussed in detail in the sections that follow.


The concept of disintermediation can be explained with the aid of an example. Imagine that you want to send money to a friend in another country. You go to a bank, which, for a fee, will transfer your money to the bank in that country. In this case, the bank maintains a central database that is updated, confirming that you have sent the money. With blockchain technology, it is possible to send this money directly to your friend without the need for a bank. All you need is the address of your friend on the blockchain. This way, the intermediary (that is, the bank) is no longer required, and decentralization is achieved by disintermediation. It is debatable, however, how practical decentralization through disintermediation is in the financial sector due to the massive regulatory and compliance requirements. Nevertheless, this model can be used not only in finance but in many other industries as well, such as health, law, and the public sector. In the health industry, where patients, instead of relying on a trusted third party (such as the hospital record system) can be in full control of their own identity and their data that they can share directly with only those entities that they trust. As a general solution, blockchain can serve as a decentralized health record management system where health records can be exchanged securely and directly between different entities (hospitals, pharmaceutical companies, patients) globally without any central authority.

Contest-driven decentralization

In the method involving competition, different service providers compete with each other in order to be selected for the provision of services by the system. This paradigm does not achieve complete decentralization. However, to a certain degree, it ensures that an intermediary or service provider is not monopolizing the service. In the context of blockchain technology, a system can be envisioned in which smart contracts can choose an external data provider from a large number of providers based on their reputation, previous score, reviews, and quality of service.

This method will not result in full decentralization, but it allows smart contracts to make a free choice based on the criteria just mentioned. This way, an environment of competition is cultivated among service providers where they compete with each other to become the data provider of choice.

In the following diagram, varying levels of decentralization are shown. On the left side, the conventional approach is shown where a central system is in control; on the right side, complete disintermediation is achieved, as intermediaries are entirely removed. Competing intermediaries or service providers are shown in the center. At that level, intermediaries or service providers are selected based on reputation or voting, thus achieving partial decentralization:

Figure 2.5: Scale of decentralization

There are many benefits of decentralization, including transparency, efficiency, cost saving, development of trusted ecosystems, and in some cases privacy and anonymity. Some challenges, such as security requirements, software bugs, and human error, need to be examined thoroughly.

For example, in a decentralized system such as Bitcoin or Ethereum where security is normally provided by private keys, how can we ensure that an asset or a token associated with these private keys cannot be rendered useless due to negligence or bugs in the code? What if the private keys are lost due to user negligence? What if due to a bug in the smart contract code the decentralized application becomes vulnerable to attack?

Before embarking on a journey to decentralize everything using blockchain and decentralized applications, it is essential that we understand that not everything can or needs to be decentralized.

This view raises some fundamental questions. Is a blockchain really needed? When is a blockchain required? In what circumstances is blockchain preferable to traditional databases? To answer these questions, go through the simple set of questions presented below:



Recommended solution

Is high data throughput required?


Use a traditional database.


A central database might still be useful if other requirements are met. For example, if users trust each other, then perhaps there is no need for a blockchain. However, if they don't or trust cannot be established for any reason, blockchain can be helpful.

Are updates centrally controlled?


Use a traditional database.


You may investigate how a public/private blockchain can help.

Do users trust each other?


Use a traditional database.


Use a public blockchain.

Are users anonymous?


Use a public blockchain.


Use a private blockchain.

Is consensus required to be maintained within a consortium?


Use a private blockchain.


Use a public blockchain.

Is strict data immutability required?


Use a blockchain.


Use a central/traditional database.

Answering all of these questions can help you decide whether or not a blockchain is required or suitable for solving the problem. Beyond the questions posed in this model, there are many other issues to consider, such as latency, choice of consensus mechanisms, whether consensus is required or not, and where consensus is going to be achieved. If consensus is maintained internally by a consortium, then a private blockchain should be used; otherwise, if consensus is required publicly among multiple entities, then a public blockchain solution should be considered. Other aspects, such as immutability, should also be considered when deciding whether to use a blockchain or a traditional database. If strict data immutability is required, then a public blockchain should be used; otherwise, a central database may be an option.

As blockchain technology matures, there will be more questions raised regarding this selection model. For now, however, this set of questions is sufficient for deciding whether a blockchain-based solution is suitable or not.

Now we understand different methods of decentralization and have looked at how to decide whether a blockchain is required or not in a particular scenario. Let's now look at the process of decentralization, that is, how we can take an existing system and decentralize it. First, we'll briefly look at the different ways to achieve decentralization.


Routes to decentralization

There are systems that pre-date blockchain and Bitcoin, including BitTorrent and the Gnutella file-sharing system, which to a certain degree could be classified as decentralized, but due to a lack of any incentivization mechanism, participation from the community gradually decreased. There wasn't any incentive to keep the users interested in participating in the growth of the network. With the advent of blockchain technology, many initiatives are being taken to leverage this new technology to achieve decentralization. The Bitcoin blockchain is typically the first choice for many, as it has proven to be the most resilient and secure blockchain and has a market cap of nearly $166 billion at the time of writing. Alternatively, other blockchains, such as Ethereum, serve as the tool of choice for many developers for building decentralized applications. Compared to Bitcoin, Ethereum has become a more prominent choice because of the flexibility it allows for programming any business logic into the blockchain by using smart contracts.

How to decentralize

Arvind Narayanan and others have proposed a framework in their book Bitcoin and Cryptocurrency Technologies that can be used to evaluate the decentralization requirements of a variety of issues in the context of blockchain technology. The framework raises four questions whose answers provide a clear understanding of how a system can be decentralized:

  1. What is being decentralized?
  2. What level of decentralization is required?
  3. What blockchain is used?
  4. What security mechanism is used?

The first question simply asks you to identify what system is being decentralized. This can be any system, such as an identity system or a trading system.

The second question asks you to specify the level of decentralization required by examining the scale of decentralization, as discussed earlier. It can be full disintermediation or partial disintermediation.

The third question asks developers to determine which blockchain is suitable for a particular application. It can be Bitcoin blockchain, Ethereum blockchain, or any other blockchain that is deemed fit for the specific application.

Finally, a fundamental question that needs to be addressed is how the security of a decentralized system will be guaranteed. For example, the security mechanism can be atomicity-based, where either the transaction executes in full or does not execute at all. This deterministic approach ensures the integrity of the system. Other mechanisms may include one based on reputation, which allows for varying degrees of trust in a system.

In the following section, let's evaluate a money transfer system as an example of an application selected to be decentralized.

Decentralization framework example

The four questions discussed previously are used to evaluate the decentralization requirements of this application. The answers to these questions are as follows:

  1. Money transfer system
  2. Disintermediation
  3. Bitcoin
  4. Atomicity

The responses indicate that the money transfer system can be decentralized by removing the intermediary, implemented on the Bitcoin blockchain, and that a security guarantee will be provided via atomicity. Atomicity will ensure that transactions execute successfully in full or do not execute at all. We have chosen the Bitcoin blockchain because it is the longest established blockchain and has stood the test of time.

Similarly, this framework can be used for any other system that needs to be evaluated in terms of decentralization. The answers to these four simple questions help clarify what approach to take to decentralize the system.

To achieve complete decentralization, it is necessary that the environment around the blockchain also be decentralized. We'll look at the full ecosystem of decentralization next.


Blockchain and full ecosystem decentralization

The blockchain is a distributed ledger that runs on top of conventional systems. These elements include storage, communication, and computation.

There are other factors, such as identity and wealth, which are traditionally based on centralized paradigms, and there's a need to decentralize these aspects as well in order to achieve a sufficiently decentralized ecosystem.


Data can be stored directly in a blockchain, and with this fact it achieves decentralization. However, a significant disadvantage of this approach is that a blockchain is not suitable for storing large amounts of data by design. It can store simple transactions and some arbitrary data, but it is certainly not suitable for storing images or large blobs of data, as is the case with traditional database systems.

A better alternative for storing data is to use distributed hash tables (DHTs). DHTs were used initially in peer-to-peer file sharing software, such as BitTorrent, Napster, Kazaa, and Gnutella. DHT research was made popular by the CAN, Chord, Pastry, and Tapestry projects. BitTorrent is the most scalable and fastest network, but the issue with BitTorrent and the others is that there is no incentive for users to keep the files indefinitely. Users generally don't keep files permanently, and if nodes that have data still required by someone leave the network, there is no way to retrieve it except by having the required nodes rejoin the network so that the files once again become available.

Two primary requirements here are high availability and link stability, which means that data should be available when required and network links also should always be accessible. Inter-Planetary File System (IPFS) by Juan Benet possesses both of these properties, and its vision is to provide a decentralized World Wide Web by replacing the HTTP protocol. IPFS uses Kademlia DHT and Merkle Directed Acyclic Graphs (DAGs) to provide storage and searching functionality, respectively. The concept of DHTs and DAGs will be introduced in detail in Chapter 4, Public Key Cryptography.

The incentive mechanism for storing data is based on a protocol known as Filecoin, which pays incentives to nodes that store data using the Bitswap mechanism. The Bitswap mechanism lets nodes keep a simple ledger of bytes sent or bytes received in a one-to-one relationship. Also, a Git-based version control mechanism is used in IPFS to provide structure and control over the versioning of data.

There are other alternatives for data storage, such as Ethereum Swarm, Storj, and MaidSafe. Ethereum has its own decentralized and distributed ecosystem that uses Swarm for storage and the Whisper protocol for communication. MaidSafe aims to provide a decentralized World Wide Web. All of these projects are discussed later in this book in greater detail.

BigChainDB is another storage layer decentralization project aimed at providing a scalable, fast, and linearly scalable decentralized database as opposed to a traditional filesystem. BigChainDB complements decentralized processing platforms and filesystems such as Ethereum and IPFS.


The Internet (the communication layer in blockchain) is considered to be decentralized. This belief is correct to some extent, as the original vision of the Internet was to develop a decentralized communications system. Services such as email and online storage are now all based on a paradigm where the service provider is in control, and users trust such providers to grant them access to the service as requested. This model is based on the unconditional trust of a central authority (the service provider) where users are not in control of their data. Even user passwords are stored on trusted third-party systems.

Thus, there is a need to provide control to individual users in such a way that access to their data is guaranteed and is not dependent on a single third party. Access to the Internet (the communication layer) is based on Internet Service Providers (ISPs) who act as a central hub for Internet users. If the ISP is shut down for any reason, then no communication is possible with this model.

An alternative is to use mesh networks. Even though they are limited in functionality when compared to the Internet, they still provide a decentralized alternative where nodes can talk directly to each other without a central hub such as an ISP.

An example of a mesh network is Firechat, which allows iPhone users to communicate with each other directly in a peer-to-peer fashion without an Internet connection. More information is available at

Now imagine a network that allows users to be in control of their communication; no one can shut it down for any reason. This could be the next step toward decentralizing communication networks in the blockchain ecosystem. It must be noted that this model may only be vital in a jurisdiction where the Internet is censored and controlled by the government.

As mentioned earlier, the original vision of the Internet was to build a decentralized network; however, over the years, with the advent of large-scale service providers such as Google, Amazon, and eBay, control is shifting toward these big players. For example, email is a decentralized system at its core; that is, anyone can run an email server with minimal effort and can start sending and receiving emails. There are better alternatives available. For example, Gmail and Outlook already provide managed services for end users, so there is a natural inclination toward selecting one of these large centralized services as they are more convenient and free to use. This is one example that shows how the Internet has moved toward centralization.

Free services, however, are offered at the cost of exposing valuable personal data, and many users are unaware of this fact. Blockchain has revived the vision of decentralization across the world, and now concerted efforts are being made to harness this technology and take advantage of the benefits that it can provide.

Computing power and decentralization

Decentralization of computing or processing power is achieved by a blockchain technology such as Ethereum, where smart contracts with embedded business logic can run on the blockchain network. Other blockchain technologies also provide similar processing-layer platforms, where business logic can run over the network in a decentralized manner.

The following diagram shows an overview of a decentralized ecosystem. In the bottom layer, the Internet or mesh networks provide a decentralized communication layer. In the next layer up, a storage layer uses technologies such as IPFS and BigChainDB to enable decentralization. Finally, in the next level up, you can see that the blockchain serves as a decentralized processing (computation) layer. Blockchain can, in a limited way, provide a storage layer too, but that severely hampers the speed and capacity of the system. Therefore, other solutions such as IPFS and BigChainDB are more suitable for storing large amounts of data in a decentralized way. The Identity and Wealth layers are shown at the top level. Identity on the Internet is a vast topic, and systems such as bitAuth and OpenID provide authentication and identification services with varying degrees of decentralization and security assumptions:

Figure 2.6: Decentralized ecosystem

The blockchain is capable of providing solutions to various issues relating to decentralization. A concept relevant to identity known as Zooko's Triangle requires that the naming system in a network protocol is secure, decentralized, and able to provide human-meaningful and memorable names to the users. Conjecture has it that a system can have only two of these properties simultaneously.

Nevertheless, with the advent of blockchain in the form of Namecoin, this problem was resolved. It is now possible to achieve security, decentralization, and human-meaningful names with the Namecoin blockchain. However, this is not a panacea, and it comes with many challenges, such as reliance on users to store and maintain private keys securely. This opens up other general questions about the suitability of decentralization to a particular problem.

Decentralization may not be appropriate for every scenario. Centralized systems with well-established reputations tend to work better in many cases. For example, email platforms from reputable companies such as Google or Microsoft would provide a better service than a scenario where individual email servers are hosted by users on the Internet.

There are many projects underway that are developing solutions for a more comprehensive distributed blockchain system. For example, Swarm and Whisper are developed to provide decentralized storage and communication for Ethereum. We will discuss Swarm and Ethereum in more detail in Chapter 13, Ethereum Development Environment.

With the advent of blockchain technology, it is now possible to build software versions of traditional physical organizations in the form of Decentralized Organizations (DOs) and other similar constructs, which we will examine in detail shortly.

Moreover, with the emergence of the decentralization paradigm, different terminology and buzzwords are now appearing in the media and academic literature, which we will explore in the next section.


Pertinent terminology

The following concepts are worth citing in the context of decentralization. The terminology introduced here is often used in the literature concerning decentralization and its applications.

Smart contracts

A smart contract is a software program that usually runs on a blockchain. Smart contracts do not necessarily need a blockchain to run; however, due to the security benefits that blockchain technology provides, blockchain has become a standard decentralized execution platform for smart contracts.

A smart contract usually contains some business logic and a limited amount of data. The business logic is executed if specific criteria are met. Actors or participants in the blockchain use these smart contracts, or they run autonomously on behalf of the network participants.

More information on smart contracts will be provided in Chapter 10, Smart Contracts.

Autonomous agents

An Autonomous Agent (AA) is an artificially intelligent software entity that acts on the behalf of its owner to achieve some desirable goals without requiring any or minimal intervention from its owner.

Decentralized organizations

DOs are software programs that run on a blockchain and are based on the idea of actual organizations with people and protocols. Once a DO is added to the blockchain in the form of a smart contract or a set of smart contracts, it becomes decentralized and parties interact with each other based on the code defined within the DO software.

Decentralized autonomous organizations

Just like DOs, a decentralized autonomous organization (DAO) is also a computer program that runs on top of a blockchain, and embedded within it are governance and business logic rules. DAOs and DOs are fundamentally the same thing. The main difference, however, is that DAOs are autonomous, which means that they are fully automated and contain artificially intelligent logic. DOs, on the other hand, lack this feature and rely on human input to execute business logic.

Ethereum blockchain led the way with the introduction of DAOs. In a DAO, the code is considered the governing entity rather than people or paper contracts. However, a human curator maintains this code and acts as a proposal evaluator for the community. DAOs are capable of hiring external contractors if enough input is received from the token holders (participants).

The most famous DAO project is The DAO, which raised $168 million in its crowdfunding phase. The DAO project was designed to be a venture capital fund aimed at providing a decentralized business model with no single entity as owner. Unfortunately, this project was hacked due to a bug in the DAO code, and millions of dollars' worth of ether currency (ETH) was siphoned out of the project and into a child DAO created by hackers. A major network change (hard fork) was required on the Ethereum blockchain to reverse the impact of the hack and initiate the recovery of the funds. This incident opened up the debate on the security, quality, and need for thorough testing of the code in smart contracts in order to ensure their integrity and adequate control. There are other projects underway, especially in academia, that are seeking to formalize smart contract coding and testing.

Currently, DAOs do not have any legal status, even though they may contain some intelligent code that enforces certain protocols and conditions. However, these rules have no value in the real-world legal system at present. One day, perhaps an AA (that is, a piece of code that runs without human intervention) commissioned by a law enforcement agency or regulator will contain rules and regulations that could be embedded in a DAO for the purpose of ensuring its integrity from a legalistic and compliance perspective. The fact that DAOs are purely decentralized entities enables them to run in any jurisdiction. Thus, they raise a big question as to how the current legal system could be applied to such a varied mix of jurisdictions and geographies.

Decentralized autonomous corporations

Decentralized autonomous corporations (DACs) are similar to DAOs in concept, though considered to be a subset of them. The definitions of DACs and DAOs may sometimes overlap, but the general distinction is that DAOs are usually considered to be nonprofit, whereas DACs can earn a profit via shares offered to the participants and to whom they can pay dividends. DACs can run a business automatically without human intervention based on the logic programmed into them.

Decentralized autonomous societies

Decentralized autonomous societies (DASes) are a concept whereby an entire society can function on a blockchain with the help of multiple, complex smart contracts and a combination of DAOs and decentralized applications (DApps) running autonomously. This model does not necessarily translate to a free-for-all approach, nor is it based on an entirely libertarian ideology; instead, many services that a government commonly offers can be delivered via blockchains, such as government identity card systems, passports, and records of deeds, marriages, and births. Another theory is that, if a government is corrupt and central systems do not provide the levels of trust that a society needs, then that society can start its own virtual one on a blockchain that is driven by decentralized consensus and transparency. This concept might look like a libertarian's or cypherpunk's dream, but it is entirely possible on a blockchain.

Decentralized applications

All the ideas mentioned up to this point come under the broader umbrella of decentralized applications, abbreviated to DApps. DAOs, DACs, and DOs are DApps that run on top of a blockchain in a peer-to-peer network. They represent the latest advancement in decentralization technology.

DApps at a fundamental level are software programs that execute using either of the following methods. They are categorized as Type 1, Type 2, or Type 3 DApps:

  1. Type 1: Run on their own dedicated blockchain, for example, standard smart contract based DApps running on Ethereum. If required, they make use of a native token, for example, ETH on Ethereum blockchain.

    For example, Ethlance is a DApp that makes use of ETH to provide a job market. More information about Ethlance can be found at

  2. Type 2: Use an existing established blockchain. that is, make use of Type 1 blockchain and bear custom protocols and tokens, for example, smart contract based tokenization DApps running Ethereum blockchain.An example is DAI, which is built on top of Ethereum blockchain, but contains its own stable coins and mechanism of distribution and control. Another example is Golem, which has its own token GNT and a transaction framework built on top of Ethereum blockchain to provide a decentralized marketplace for computing power where users share their computing power with each other in a peer-to-peer network.

    A prime example of Type 2 DApps is the OMNI network, which is a software layer built on top of Bitcoin to support trading of custom digital assets and digital currencies. More information on the OMNI network can be found at

    More information on the Golem network is available at

    More information on DAI is available at

  3. Type 3: Use the protocols of Type 2 DApps; for example, the SAFE Network uses the OMNI network protocol.

More information on the SAFE Network can be found at

Another example to understand the difference between different types of DApps is the USDT token (Tethers). The original USDT uses the OMNI layer (a Type 2 DApp) on top of the Bitcoin network. USDT is also available on Ethereum using ERC20 tokens. This example shows that a USDT can be considered a Type 3 DApp, where the OMNI layer protocol (a Type 2 DApp) is used, which is itself built on Bitcoin (a Type 1 DApp). Also, from an Ethereum point of view USDT can also be considered a Type 3 DApp in that it makes use of the Type 1 DApp Ethereum blockchain using the ERC 20 standard, which was built to operate on Ethereum.

More information can be found about Tether at

In the last few years, the expression DApp has been increasingly used to refer to any end-to-end decentralized blockchain application, including a user interface (usually a web interface), smart contract(s), and the host blockchain. The clear distinction between different types of DApps is now not commonly referred to, but it does exist. Often, DApps are now considered just as apps (blockchain apps) running on a blockchain such as Ethereum, Tezos, NEO, or EOS without any particular reference to their type.

There are thousands of different DApps running on various platforms (blockchains) now. There are various categories of these DApps covering media, social, finance, games, insurance, and health. There are various decentralized platforms (or blockchains) running, such as Ethereum, EOS, NEO, Loom, and Steem. The highest number of DApps currently is on Ethereum.

Requirements of a DApp

For an application to be considered decentralized, it must meet the following criteria. This definition was provided in a whitepaper by Johnston et al. in 2015, The General Theory of Decentralized Applications, DApps:

  1. The DApp should be fully open source and autonomous, and no single entity should be in control of a majority of its tokens. All changes to the application must be consensus-driven based on the feedback given by the community.
  2. Data and records of operations of the application must be cryptographically secured and stored on a public, decentralized blockchain to avoid any central points of failure.
  3. A cryptographic token must be used by the application to provide access for and incentivize those who contribute value to the applications, for example, miners in Bitcoin.
  4. The tokens (if applicable) must be generated by the decentralized application using consensus and an applicable cryptographic algorithm. This generation of tokens acts as a proof of the value to contributors (for example, miners).

Generally, DApps now provide all sorts of different services, including but not limited to financial applications, gaming, social media, and health.

Operations of a DApp

Establishment of consensus by a DApp can be achieved using consensus algorithms such as PoW and Proof of Stake (PoS). So far, only PoW has been found to be incredibly resistant to attacks, as is evident from the success of and trust people have put in the Bitcoin network. Furthermore, a DApp can distribute tokens (coins) via mining, fundraising, and development.

Design of a DApp

A DApp—pronounced Dee-App, or now more commonly rhyming with app—is a software application that runs on a decentralized network such as a distributed ledger. They have recently become very popular due to the development of various decentralized platforms such as Ethereum, EOS, and Tezos.

Traditional apps commonly consist of a user interface and usually a web server or an application server and a backend database. This is a common client/server architecture. This is visualized in the following diagram:

Figure 2.7: Traditional application architecture (generic client/server)

A DApp on the other hand has a blockchain as a backend and can be visualized as depicted in the following diagram. The key element that plays a vital role in the creation of a DApp is a smart contract that runs on the blockchain and has business logic embedded within it:

Figure 2.8: Generic DApp architecture

Note that the frontend in either a DApp or app architecture can either be a thick client, a mobile app, or a web frontend (a web user interface). However, it is usually a web frontend commonly written using a JavaScript framework such as React or Angular.

The following comparison table highlights the key properties of and differences between these different types of decentralized entities:






Legal status


































Optional tokens


Use case dependent

Having covered the main concepts of DApps, it will be useful to explore some specific examples.

DApp examples

Examples of some DApps are provided here.


This application provides the facility to manage Know Your Customer (KYC) data securely and conveniently based on smart contracts.


This is a decentralized peer-to-peer network that enables commercial activities directly between sellers and buyers instead of relying on a central party, such as eBay or Amazon. It should be noted that this system is not built on top of a blockchain; instead, distributed hash tables are used in a peer-to-peer network to enable direct communication and data sharing among peers. It makes use of Bitcoin and various other cryptocurrencies as a payment method.

More information regarding Open Bazaar is available at


This is the decentralized equivalent of Uber. It allows peer-to-peer ride sharing and users to be incentivized by proof of movement, and they can earn Zooz coins.

More information on Lazooz is available at

Many other DApps have been built on the Ethereum blockchain and are showcased at

Now that we have covered the pertinent terminology, DApps, and relevant examples, let's now look at what platforms can be used to build and host DApps.


Platforms for decentralization

Today, there are many platforms available for decentralization. In fact, the fundamental feature of blockchain networks is to provide decentralization. Therefore, any blockchain network, such as Bitcoin, Ethereum, Hyperledger Fabric, or Quorum, can be used to provide a decentralization service. Many organizations around the world have introduced platforms that promise to make distributed application development easy, accessible, and secure. Some of these platforms are described as follows.


Ethereum tops the list as being the first blockchain to introduce a Turing-complete language and the concept of a virtual machine. This is in stark contrast to the limited scripting language in Bitcoin and many other cryptocurrencies. With the availability of its Turing-complete language, Solidity, endless possibilities have opened for the development of decentralized applications. This blockchain was first proposed in 2013 by Vitalik Buterin, and it provides a public blockchain to develop smart contracts and decentralized applications. Currency tokens on Ethereum are called ethers.


This is a project for the decentralized Internet introduced in 2006. This is not a blockchain, but a decentralized and autonomous network.

MaidSafe provides a SAFE (Secure Access for Everyone) network that is made up of unused computing resources, such as storage, processing power, and the data connections of its users. The files on the network are divided into small chunks of data, which are encrypted and distributed randomly throughout the network. This data can only be retrieved by its respective owner. One key innovation of MaidSafe is that duplicate files are automatically rejected on the network, which helps reduce the need for additional computing resources needed to manage the load. It uses Safecoin as a token to incentivize its contributors.

More information on MaidSafe is available at


Lisk is a blockchain application development and cryptocurrency platform. It allows developers to use JavaScript to build decentralized applications and host them in their respective sidechains. Lisk uses the Delegated Proof of Stake (DPOS) mechanism for consensus, whereby 101 nodes can be elected to secure the network and propose blocks. It uses the Node.js and JavaScript backend, while the frontend allows the use of standard technologies, such as CSS3, HTML5, and JavaScript. Lisk uses LSK coin as a currency on the blockchain. Another derivative of Lisk is Rise, which is a Lisk-based DApp and digital currency platform. It offers greater focus on the security of the system.


This is a blockchain protocol launched in January 2018, with its own cryptocurrency called EOS. EOS raised an incredible 4 billion USD in 2018 though its Initial Coin Offering (ICO). They key purpose behind EOS is, as stated by its founders, to build a decentralized operating system. Its throughput is significantly higher (approx. 3,996 transactions per second (TPS)) than other common blockchain platforms, such as Bitcoin (approx. 7 TPS) and Ethereum (approx. 15 TPS).

A practical introduction to these platforms and some others are provided in this book's bonus content pages, which can be found here:

Due to fast-paced innovation and the natural evolution of these platforms and blockchain in general, many innovative trends have emerged, which we explore in the next section.


Innovative trends

With the growth of blockchain, several ideas have emerged that make use of the decentralized property of blockchain to provide more user centric and fully decentralized services. Some of the key ideas in this space are decentralized web, decentralized identity, and decentralized finance. We will explore these ideas one by one as follows.

Decentralized web

Decentralized web is a term that's used to describe a vision of the web where no central authority or set of authorities will be in control. The original intention of the Internet was indeed decentralized, and the development of open protocols such HTTP, SMTP, and DNS meant that any individual could use these protocols freely, and immediately become part of the Internet. This is still true; however, with the emergence of a layer above these protocols called the Web layer introduced a more service-oriented infrastructure, which inevitably led to large profit-seeking companies taking over. This is evident from the rise of Facebook, Google, Twitter, and Amazon, which of course provide excellent user services but at the cost of a more controlled, centralized, and closed system.

Once intended and developed as decentralized, open and free protocols are now being dominated by powerful commercial entities around the world, which has resulted in major concerns around privacy and data protection. These types of business models do work well and are quite popular due to the high level of standardization and services provided, but they pose a threat to privacy and decentralization due to the dominance of only a handful of entities on the entire Internet.

With blockchain, it is envisioned that this situation will change as it will allow development of the decentralized Internet, or the decentralized web, or Web 3 for short, which was the original intention of the Internet.

We can review the evolution of the Web over the last few decades by dividing the major developments into three key stages, Web 1, Web 2, and Web 3.

Web 1

This is the original World Wide Web, which was developed in 1989. This was the era when static web pages were hosted on servers and usually only allowed read actions from a user's point of view.

Web 2

This is the era when more service-oriented and web-hosted applications started to emerge. E-commerce websites, social networking, social media, blogs, multimedia sharing, mash-ups, and web applications are the main features of this period. The current Web is Web 2, and even though we have a richer and more interactive Internet, all of these services are still centralized. Web 2 has generated massive economic value and provides services that are essential for day-to-day business, personal use, social interactions, and almost every walk of life, but privacy concerns, the need for trusted third parties, and data breaches are genuine issues that need to be addressed. Common examples of centralized Web 2 services include Twitter, Facebook, Google Docs, and email services such Gmail and Hotmail.

Web 3

This is the vision of the decentralized internet or web that will revolutionize the way we use the internet today. This is the era that will be fully user-centric and decentralized without any single authority or a large organization or internet company in control. Some examples of Web 3 are as follows:

  • Steemit: This is a social media platform based on the Steem blockchain and STEEM cryptocurrency. This cryptocurrency is awarded to contributors for the content they have shared, and the more votes they get, the more tokens they earn. More information is available at
  • Status: This is a decentralized multipurpose communication platform providing secure and private communication. More information is available at
  • IPFS: This is a peer-to-peer hypermedia/storage protocol that allows storage and sharing of data in a decentralized fashion across a peer-to-peer network. More information is available at

Other fast-growing trends include decentralized identity and decentralized finance, which we introduce next.

Decentralized identity

Another trend that has gained massive popularity recently is decentralized identity. Identity is a sensitive and difficult problem to solve. Currently, due to the dominance of large Internet companies and other similar organizations, the identity of a user is not in control of the identity holder and this often leads to privacy issues. Decentralized identity gives control of identity credentials back to identity holders and enables them to control when and how they share their credentials and with whom.

A prime example of such an initiative is that Microsoft has built a decentralized identity network called Identity Overlay Network (ION) on top of Bitcoin blockchain. This infrastructure is based on work done for decentralized identity at W3C and the Decentralized Identity Foundation. Similar initiatives have also been taken by IBM and other organizations around the world.

More information regarding ION is available at

Information regarding the Decentralized Identify Foundation is available at

Information regarding decentralized identifiers (DIDs) is available at

Decentralized finance (DeFi)

DeFi could be the killer app of the decentralized revolution that everyone has been waiting for. Traditionally, finance is a business that is almost impossible to do without the involvement of a trusted third party. It can either be a bank or some other financial firm; consumers have to trust a central authority to do business on their behalf and provide the services.

There are rules, policies, procedures, and strict regulations that govern this ecosystem. This control and management is of paramount importance for the integrity of the entire financial ecosystem. Still, since there is always a central party that is required in every single transaction consumers do, this approach has some disadvantages.

Some main disadvantages are listed as follows:

  • Access barrier: Access to financial services and banking requires a rigorous onboarding process involving KYC and other relevant checks and procedures. Even though this is extremely important for the integrity of the existing financial system, it can become a barrier at times for millions of unbanked people all around the world, especially in third world countries.
  • High cost: Financial services can be costly in some scenarios, especially investment-related activities, and could be seen as a barrier toward entering the financial services industry.
  • Transparency issues: There are concerns around transparency and trust due to the proprietary nature of the financial industry.
  • Siloed: Most current financial industry solutions are proprietary and are owned by their respective organization. This results in interoperability issues where systems from one organization are unable to talk with another.

DeFi comes with a number of advantages, such as inclusion, easy access, and cheaper services; however, it has its own challenges. These drawbacks must be addressed for further adoption of this novel paradigm of financial services:

  • Underdeveloped ecosystem: This ecosystem is still developing and requires more effort to improve usability and adoption.
  • Too technical: As some users may find understanding and handling all financial transactions and jargon a bit daunting, adopting a DeFi platform may take some time and educational effort.
  • Lack of regulation: This is a genuine and clear concern because without the existence of any regulatory framework, this ecosystem can be used for illegal activities. Moreover, trusting the code alone, instead of traditional paper contracts with established financial institutions, is seen as a major problem, especially by consumers who are used to traditional financial systems.
  • Human error: On a blockchain, human errors can result in serious implications. Especially on DeFi systems or cryptocurrency blockchains, any human negligence can result in serious implications, such as financial loss. Moreover, due to the lack of regulation (relative to traditional finance), such an issue can have an even greater detrimental impact.

    Note that human error can occur in any system, and blockchain is not immune either. Generally, a blockchain is regarded as a tamper-proof, all-secure, and decentralized platform due to its security promises. However, this perception can give the wrong impression. For example, for a general user who perhaps doesn't understand the underlying technology and associated limitations, human errors may go unnoticed, and users may innocently accept everything as accurate, due to blockchain being the source of ultimate truth! Therefore, human errors must be minimized as much as possible. It is essential to perform validation checks in DApps, especially on user interfaces where users might be entering different types of data. For example, it should be ensured at the user interface level that account details (addresses) are correct (at least the format of the address) to reduce the possibility of loss of funds. Not much can be done afterward, for example, if funds are sent to the wrong address.

    Other types of human errors might include, but are not limited to, sending funds to incompatible wallets, not appropriately protecting account information, and not understanding how to use DApps' frontends correctly.

DeFi applications are used in a broad spectrum of use cases, including loans, decentralized exchanges (DEXs), derivatives, payments, insurance, and assets. All of these use cases have one thing in common, which is that there is no central authority in control and participants (that is, users) on DeFi platforms conduct business directly with each other without the involvement of any intermediaries. This may sound like a utopian fantasy, but the DeFi revolution is happening right now and there is almost 5 billion USD (at the time of writing) of value locked in the DeFi system. This large amount of locked value is a clear indication that the usage of DeFi applications is quite significant and is expected to only increase.

You can find the latest rankings and analytics of the DeFi protocol on this excellent website:

Uses cases of all these developments and further details will be introduced later in Chapter 19, Blockchain—Outside of Currencies.

In this section, we discussed some innovative trends, including decentralized web and DeFi; however, these are not the only applications of blockchain technology. Some other emerging trends include the convergence of different technologies with blockchain, which can open new vistas for further innovation such as artificial intelligence and the Internet of Things (IoT). We will cover these topics in Chapter 22, Current Landscape and What's Next.



This chapter introduced the concept of decentralization, which is the core service offered by blockchain technology. Although the concept of decentralization is not new, it has gained renewed significance in the world of blockchain. As such, various applications based on a decentralized architecture have recently been introduced.

The chapter began with an introduction to the concept of decentralization. Next, decentralization from the blockchain perspective was discussed. Moreover, ideas relating to the different layers of decentralization in the blockchain ecosystem were introduced. Several new concepts and terms have emerged with the advent of blockchain technology and decentralization from the blockchain perspective, including DAOs, DACs, and DAPPs. Finally, some innovative trends and examples of DApps were presented.

In the next chapter, fundamental concepts necessary to understanding the blockchain ecosystem will be presented. Principally cryptography, which provides a crucial foundation for blockchain technology.

About the Author
  • Imran Bashir

    Imran Bashir has an M.Sc. in Information Security from Royal Holloway, University of London, and has a background in software development, solution architecture, infrastructure management, and IT service management. He is also a member of the Institute of Electrical and Electronics Engineers (IEEE) and the British Computer Society (BCS). Imran has extensive experience in both the public and financial sectors, having worked on large-scale IT projects in the public sector before moving to the financial services industry. Since then, he has worked in various technical roles for different financial companies in Europe's financial capital, London.

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Wonderful, very complete book!
Good in-depth reference on blockchain technology
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