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Building Blockchain Projects
Building Blockchain Projects

Building Blockchain Projects: Building decentralized Blockchain applications with Ethereum and Solidity

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Building Blockchain Projects

Understanding Decentralized Applications

Almost all of the Internet-based applications we have been using are centralized, that is, the servers of each application are owned by a particular company or person. Developers have been building centralized applications and users have been using them for a pretty long time. But there are a few concerns with centralized applications that make it next to impossible to build certain types of apps and every app ends up having some common issues. Some issues with centralized apps are that they are less transparent, they have a single point of failure, they fail to prevent net censorship, and so on. Due to these concerns, a new technology emerged for the building of Internet-based apps called decentralized applications (DApps). In this chapter, we will learn about decentralized apps.

In this chapter, we'll cover the following topics:

  • What are DApps?
  • What is the difference between decentralized, centralized, and distributed applications?
  • Advantages and disadvantages of centralized and decentralized applications.
  • An overview of the data structures, algorithms, and protocols used by some of the most popular DApps
  • Learning about some popular DApps that are built on top of other DApps.

What is a DApp?

A DApp is a kind of Internet application whose backend runs on a decentralized peer-to-peer network and its source code is open source. No single node in the network has complete control over the DApp.

Depending on the functionality of the DApp, different data structures are used to store application data. For example, the Bitcoin DApp uses the blockchain data structure.

These peers can be any computer connected to the Internet; therefore, it becomes a big challenge to detect and prevent peers from making invalid changes to the application data and sharing wrong information with others. So we need some sort of consensus between the peers regarding whether the data published by a peer is right or wrong. There is no central server in a DApp to coordinate the peers and decide what is right and wrong; therefore, it becomes really difficult to solve this challenge. There are certain protocols (specifically called consensus protocols) to tackle this challenge. Consensus protocols are designed specifically for the type of data structure the DApp uses. For example, Bitcoin uses the proof-of-work protocol to achieve consensus.

Every DApp needs a client for the user to use the DApp. To use a DApp, we first need a node in the network by running our own node server of the DApp and then connecting the client to the node server. Nodes of a DApp provide an API only and let the developer community develop various clients using the API. Some DApp developers officially provide a client. Clients of DApps should be open source and should be downloaded for use; otherwise, the whole idea of decentralization will fail.

But this architecture of a client is cumbersome to set up, especially if the user is a non-developer; therefore, clients are usually hosted and/or nodes are hosted as a service to make the process of using a DApp easier.

What are distributed applications?
Distributed applications are those applications that are spread across multiple servers instead of just one. This is necessary when application data and traffic becomes huge and application downtime is not affordable. In distributed applications, data is replicated among various servers to achieve high availability of data. Centralized applications may or may not be distributed, but decentralized applications are always distributed. For example, Google, Facebook, Slack, Dropbox, and so on are distributed, whereas a simple portfolio site or a personal blog are not usually distributed until traffic is very high.

Advantages of decentralized applications

Here are some of the advantages of decentralized applications:

  • DApps are fault-tolerant as there is no single point of failure because they are distributed by default.
  • They prevent violation of net censorship as there is no central authority to whom the government can pressurize to remove some content. Governments cannot even block the app's domain or IP address as DApps are not accessed via a particular IP address or domain. Obviously the government can track individual nodes in the network by their IP address and shut them down, but if the network is huge, then it becomes next to impossible to shut down the app, especially if the nodes are distributed among various different countries.
  • It is easy for users to trust the application as it's not controlled by a single authority that could possibly cheat the users for profit.

Disadvantages of decentralized applications

Obviously, every system has some advantages and disadvantages. Here are some of the disadvantages of decentralized applications:

  • Fixing bugs or updating DApps is difficult, as every peer in the network has to update their node software.
  • Some applications require verification of user identity (that is, KYC), and as there is no central authority to verify the user identity, it becomes an issue while developing such applications.
  • They are difficult to build because they use very complex protocols to achieve consensus and they have to be built to scale from the start itself. So we cannot just implement an idea and then later on add more features and scale it.
  • Applications are usually independent of third-party APIs to get or store something. DApps shouldn't depend on centralized application APIs, but DApps can be dependent on other DApps. As there isn't a large ecosystem of DApps yet, it is difficult to build a DApp. Although DApps can be dependent on other DApps theoretically, it is very difficult to tightly couple DApps practically.

Decentralized autonomous organization

Typically, signed papers represent organizations, and the government has influence over them. Depending on the type of organization, the organization may or may not have shareholders.

Decentralized autonomous organization (DAO) is an organization that is represented by a computer program (that is, the organization runs according to the rules written in the program), is completely transparent, and has total shareholder control and no influence of the government.

To achieve these goals, we need to develop a DAO as a DApp. Therefore, we can say that DAO is a subclass of DApp.

Dash, and the DAC are a few example of DAOs.

What is a decentralized autonomous corporation (DAC)?
There is still no clear difference between DAC and DAO. Many people consider them to be the same whereas some people define DAC as DAO when DAO is intended to make profits for shareholders.

User identity in DApps

One of the major advantages of DApps is that it generally guarantees user anonymity. But many applications require the process of verifying user identity to use the app. As there is no central authority in a DApp, it become a challenge to verify the user identity.

In centralized applications, humans verify user identity by requesting the user to submit certain scanned documents, OTP verification, and so on. This process is called know your customer (KYC). But as there is no human to verify user identity in DApps, the DApp has to verify the user identity itself. Obviously DApps cannot understand and verify scanned documents, nor can they send SMSes; therefore, we need to feed them with digital identities that they can understand and verify. The major problem is that hardly any DApps have digital identities and only a few people know how to get a digital identity.

There are various forms of digital identities. Currently, the most recommended and popular form is a digital certificate. A digital certificate (also called a public key certificate or identity certificate) is an electronic document used to prove ownership of a public key. Basically, a user owns a private key, public key, and digital certificate. The private key is secret and the user shouldn't share it with anyone. The public key can be shared with anyone. The digital certificate holds the public key and information about who owns the public key. Obviously, it's not difficult to produce this kind of certificate; therefore, a digital certificate is always issued by an authorized entity that you can trust. The digital certificate has an encrypted field that's encrypted by the private key of the certificate authority. To verify the authenticity of the certificate, we just need to decrypt the field using the public key of the certificate authority, and if it decrypts successfully, then we know that the certificate is valid.

Even if users successfully get digital identities and they are verified by the DApp, there is a still a major issue; that is, there are various digital certificate issuing authorities, and to verify a digital certificate, we need the public key of the issuing authority. It is really difficult to include the public keys of all the authorities and update/add new ones. Due to this issue, the procedure of digital identity verification is usually included on the client side so that it can be easily updated. Just moving this verification procedure to the client side doesn't completely solve this issue because there are lots of authorities issuing digital certificates and keeping track of all of them, and adding them to the client side, is cumbersome.

Why do users not verify each other's identity?
Often, while we do trading in real life, we usually verify the identity of the other person ourselves or we bring in an authority to verify the identity. This idea can be applied to DApps as well. Users can verify each other's identity manually before performing trade with each other. This idea works for specific kinds of DApps, that is, for DApps in which people trade with each other. For example, if a DApp is a decentralized social network, then obviously a profile cannot be verified by this means. But if the DApp is for people to buy/sell something, then before making a payment, the buyer and seller can both verify each other's identity. Although this idea may seem fine while doing trading, when you think practically, it becomes very difficult because you may not want to do identity verification every time you trade and everyone not knows how to do identity verification. For example, if the DApp is a cab-booking app, then you will obviously not want to perform identity verification before booking a cab every time. But if you trade sometimes and you know how to verify identity, then it's fine to follow this procedure.

Due to these issues, the only option we are currently left with is verifying user identity manually by an authorized person of the company that provides the client. For example, to create a Bitcoin account, we don't need an identification, but while withdrawing Bitcoin to flat currency, the exchanges ask for proof of identification. Clients can omit the unverified users and not let them use the client. And they can keep the client open for users whose identity has been verified by them. This solution also ends up with minor issues; that is, if you switch the client, you will not find the same set of users to interact with because different clients have different sets of verified users. Due to this, all users may decide to use a particular client only, thus creating a monopoly among clients. But this isn't a major issue because if the client fails to properly verify users, then users can easily move to another client without losing their critical data, as they are stored as decentralized.

The idea of verifying user identity in applications is to make it difficult for users to escape after performing some sort of fraudulent activity, preventing users with a fraud/criminal background from using the application, and providing the means for other users in the network to believe a user to be whom the user is claiming to be. It doesn't matter what procedure is used to verify user identity; they are always ways for users to represent themselves to be someone else. It doesn't matter whether we use digital identities or scanned documents for verification because both can be stolen and reused. What's important is just to make it difficult for users to represent themselves to be someone else and also collect enough data to track a user and prove that the user has done a fraudulent activity.
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Key benefits

  • Create powerful, end-to-end applications for Blockchain using Ethereum
  • Write your first program using the Solidity programming language
  • Change the way you think and design your applications by using the all new database-Blockchain

Description

Blockchain is a decentralized ledger that maintains a continuously growing list of data records that are secured from tampering and revision. Every user is allowed to connect to the network, send new transactions to it, verify transactions, and create new blocks, making it permission-less. This book will teach you what blockchain is, how it maintains data integrity, and how to create real-world blockchain projects using Ethereum. With interesting real-world projects, you will learn how to write smart contracts which run exactly as programmed without any chance of fraud, censorship, or third-party interference, and build end-to-e applications for blockchain. You will learn about concepts such as cryptography in cryptocurrencies, ether security, mining, smart contracts, solidity, and more. You will also learn about web sockets, various API services for Ethereum, and much more. The blockchain is the main technical innovation of bitcoin, where it serves as the public ledger for bitcoin transactions.

Who is this book for?

This book is for JavaScript developers who now want to create tamper-proof data (and transaction) applications using Blockchain and Ethereum. Those who are interested in cryptocurrencies and the logic and database empowering it will find this book extremely useful.

What you will learn

  • Walk through the basics of the blockchain technology
  • Implement blockchain s technology and its features, and see what can be achieved using them
  • Build DApps using Solidity and Web3.js
  • Understand the geth command and cryptography
  • Create Ethereum wallets
  • Explore consortium blockchain
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Table of Contents

9 Chapters
Understanding Decentralized Applications Chevron down icon Chevron up icon
Understanding How Ethereum Works Chevron down icon Chevron up icon
Writing Smart Contracts Chevron down icon Chevron up icon
Getting Started with web3.js Chevron down icon Chevron up icon
Building a Wallet Service Chevron down icon Chevron up icon
Building a Smart Contract Deployment Platform Chevron down icon Chevron up icon
Building a Betting App Chevron down icon Chevron up icon
Building Enterprise Level Smart Contracts Chevron down icon Chevron up icon
Building a Consortium Blockchain Chevron down icon Chevron up icon

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J. Canada Jan 06, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
FINALLY an actual book on Ethereum that get's down to it and doens't waste time explaining extremely basic concepts of blockchain, etc.This book is written for programmers/coders, etc., people who learn something by playing with it. I'm only about 20% in, but this book reads like a recipe cookbook (like the O'reiley series).Not for crypto tourists (the short-term trader speculators that are screwing up the market).
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John and Margarita Cherri Aug 22, 2017
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Good book
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Amazon Customer Aug 23, 2017
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Good Book, with clear explanations
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Cesar A. Lòpez Aug 14, 2018
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Good for intermediate level
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Suvam Patel Jun 28, 2017
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Fantastic!
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