Ethereum cookbook over 100 recipes covering ethereum based tokens, games, wallets, smart contracts, protocols, and dapps

He has authored the book Ethereum Smart Contract Development and engages in occasional pro-bono consultation on blockchain implementation.. Debugging a smart contract using Truffle Getti

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Ethereum Cookbook

Over 100 recipes covering Ethereum-based tokens, games, wallets, smart contracts, protocols, andDapps

Manoj P R

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BIRMINGHAM - MUMBAI

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Ethereum Cookbook

All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented However, the information contained in this book is sold without warranty, either express or implied Neither the author(s) nor Packt Publishing or its dealers and distributors, will be held liable for any damages caused or alleged to have been caused directly or indirectly by this book.

Packt Publishing has endeavoured to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals However, Packt Publishing cannot guarantee the accuracy of this information.

Commissioning Editor: Pravin Dhandre

Acquisition Editor: Namrata Patil

Content Development Editor: Eisha Dsouza

Technical Editor: Ishita Vora

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Indexer: Aishwarya Gangawane

Graphics: Jisha Chirayil

Production Coordinator: Nilesh M ohite

First published: August 2018

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To my father.

– Manoj

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Contributors

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About the author

Manoj P R is a tech-savvy person who has been working with distributed ledger technology for more

than three years His passion for the latest technology trends in the market has made him an avid

learner and contributor in this space He specializes in Ethereum, JavaScript, and Go A self-taughtprogrammer, Manoj started his programming career as a freelancer during his early academic life Hehas developed many scalable enterprise blockchain solutions for various clients across the globe He

is currently associated with Conduent Labs as a Blockchain SME He loves solving real-life

problems using technology and is a lively contributor towards open source projects Apart from

work, Manoj likes traveling and writing

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About the reviewer

Mayukh Mukhopadhyay is an assistant consultant at Tata Consultancy Services who works on the

big data and revenue assurance projects of the world's oldest telecommunication company, where he

tames messy data to generate tangible insights He has authored the book Ethereum Smart Contract

Development and engages in occasional pro-bono consultation on blockchain implementation He has

a master's in Software Engineering from Jadavpur University and is an executive MBA candidate atIIT Kharagpur

I want to thank my daughter, Abriti, who, even at the tender age of 11 months, supports her papa and his foolish endeavours.

To my wife, Mrittika, all I want to say is, "Despite our superficial differences, we share the same soul."

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If you're interested in becoming an author for Packt, please visit authors.packtpub.com and apply today

We have worked with thousands of developers and tech professionals, just like you, to help themshare their insight with the global tech community You can make a general application, apply for aspecific hot topic that we are recruiting an author for, or submit your own idea

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About the author

About the reviewer

Packt is searching for authors like you

Preface

Who this book is for

What this book covers

To get the most out of this book

Download the example code files Download the color images Conventions used

Geth Parity There's more

Setting up a node and participating in a network Getting ready

How to do it

Working with the JavaScript console

Getting ready How to do it

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MetaMask MyCrypto Ethereum wallet–Mist Using block explorer

How to do it

Structs 

Enums Control structures in Solidity

How to do it

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Writing functions in solidity

Using storage and memory efficiently

Using MetaMask as an injected provider

Writing data into a smart contract

There's more

Watching events from your DApp

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Sending a raw transaction

There's more

Batch requests using web3.js

Interacting with Ethereum using JSON-RPC

Other ways to interact with your contract

Nethereum Web3J

4 The Truffle Suite

There's more

Compiling smart contracts

Advanced Truffle configuration

Migration and deployment in Truffle

Interacting with your contract

There's more

Debugging a smart contract using Truffle

Writing tests for smart contracts

Writing tests in JavaScript Writing tests in Solidity Building DApps and APIs using Truffle

Package management in Truffle

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EthPM npm There's more

Getting started with Drizzle

There's more

Using HD wallet in Truffle

5 Tokens and ICOs

Creating a token that can be burnt

Getting ready How to do it…

There's more…

Creating an ERC223 token

Building your own Initial Coin Offering Getting ready

How to do it…

Adding features to the ICO contract

There's more…

Providing bonus tokens to investors

There's more…

Whitelisting users for the crowdsale

There's more…

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Accepting crypto payments for the crowdsale Getting ready

How to do it…

MetaMask Shapeshift BTC Relay Creating a wallet that supports all ERC20 tokens Getting ready

There's more…

Asset tracking and movement

Creating a basic game on Ethereum

Building a decentralized lottery on Ethereum Getting ready

Affiliating programs to attract more users Getting ready

require() revert() assert() Abstract and interface contracts

Abstract contracts Interface contracts Managing contracts from other contracts

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There's more

Contract inheritance in solidity

Creating libraries in solidity

How it works

There's more

Function as a type in solidity

Understanding solidity assembly

There's more

Implementing multisig wallets in solidity

8 Smart Contract Security

Introduction

Integer overflow and underflow

There's more

Re-entrancy attack

The parity hack

Forcing Ether to a contract

There's more

Use of private variables

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Transaction-Ordering Dependence (TOD)

Call to the unknown

DoS using loops

Security analysis tools for solidity

Uninitialized storage pointer in solidity

Best practices in solidity

Implementing an application-specific wallet Getting ready

How to do it…

What if you find a bug after deployment?

Generating random numbers in Solidity

Keeping contracts simple, modular, and up to date Getting ready

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How to do it…

Watching Bitcoin transactions using BTCRelay

Scheduling Ethereum transactions using an alarm clock Getting ready

How to do it…

Using the openzeppelin library

11 Miscellaneous

Introduction

Using Vyper to write smart contracts

There's more

Debugging smart contracts with Remix

Deploying contracts using Remix

Generating documentation for solidity code

Writing better code with the help of a linter

Sharing solidity code with others

Other Books You May Enjoy

Leave a review - let other readers know what you think

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With this practical guide, you will learn how to set up Ethereum and connect to a network, write anddeploy quality smart contracts, use Truffle and Ganache to manage your development, create yourown Tokens and ICOs, build decentralized games and organization, create your own wallet thatsupports multiple tokens, and much more

You'll also learn about the security vulnerabilities that can arise and various other protocols ofEthereum Moving on, you’ll learn the various design decisions and tips to make your applicationscalable and secure With this book and the advanced topics it covers, you can get well versed withthe Ethereum principles and ecosystem

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Who this book is for

If you want to set up an Ethereum blockchain network, write and deploy smart contracts, build

decentralized applications (DApps) or facilitate peer-to-peer transaction, then this book is for you It

is recommended that the readers should be familiar with basic blockchain concepts and knowledge ofJavaScript and NodeJS

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What this book covers

Chapter 1, Getting Started, covers the very basics of Ethereum and its tools You will find the steps

required to set up and run a network and interact with it

Chapter 2, Smart Contract Development, contains a set of recipes that will help you write smart

contracts It also covers the steps to compile, deploy, and test the contracts that you have written

Chapter 3, Interacting with the Contract, covers the topics that are essential for building a

decentralized application (DApp) that can interact with blockchain and the contracts

Chapter 4, The Truffle Suite, explains a popular tool in the Ethereum ecosystem This chapter also

explains the use cases that will help you to have a better development workflow and build betterDApps

Chapter 5, Tokens and ICOs, covers the topics necessary for you to build your own Ethereum-based

token and distribute it through ICO

Chapter 6, Games and DAOs, takes you through a series of interesting recipes that will help you create

your own decentralized game or organization

Chapter 7, Advanced Solidity, contains more advanced recipes about the smart contract language that

will help you to achieve more complex tasks efficiently in the Blockchain

Chapter 8, Smart Contract Security, is designed to help you understand more about the common

vulnerabilities and ways to avoid them It also takes you through the set of tools you can use to

analyze the code

Chapter 9, Design Decisions, contains the recipes to help you decide between the common design

questions you may come across while developing a fully functional DApp

Chapter 10, Other Protocols and Applications, walks you through some of the other Ethereum

protocols and applications that might come in handy while building your DApp

Chapter 11, Miscellaneous, includes a few additional recipes that can help you build better DApps.

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To get the most out of this book

It is recommended to have a basic idea about blockchain and its concepts to get the most out of thisbook This book does not cover the basics of how blockchain works but focuses more on workingwith Ethereum

Basic knowledge of JavaScript and NodeJS would be good to have since interaction with Ethereumhappens mostly through JavaScript Support for other languages is also explained

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Download the example code files

You can download the example code files for this book from your account at www.packtpub.com If youpurchased this book elsewhere, you can visit www.packtpub.com/support and register to have the filesemailed directly to you

You can download the code files by following these steps:

1 Log in or register at www.packtpub.com

2 Select the SUPPORT tab

3 Click on Code Downloads & Errata

4 Enter the name of the book in the Search box and follow the onscreen instructions

Once the file is downloaded, please make sure that you unzip or extract the folder using the latestversion of:

WinRAR/7-Zip for Windows

Zipeg/iZip/UnRarX for Mac

7-Zip/PeaZip for Linux

The code bundle for the book is also hosted on GitHub at https://github.com/PacktPublishing/Ethereum-Cookb ook In case there's an update to the code, it will be updated on the existing GitHub repository

We also have other code bundles from our rich catalog of books and videos available at https://github com/PacktPublishing/ Check them out!

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Download the color images

We also provide a PDF file that has color images of the screenshots/diagrams used in this book Youcan download it here: http://www.packtpub.com/sites/default/files/downloads/EthereumCookbook_ColorImages.pdf

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Conventions used

There are a number of text conventions used throughout this book

CodeInText: Indicates code words in text, database table names, folder names, filenames, file

extensions, pathnames, dummy URLs, user input, and Twitter handles Here is an example: "Mount thedownloaded WebStorm-10*.dmg disk image file as another disk in your system."

A block of code is set as follows:

pragma solidity ^0.4.21;

contract HelloWorld {

function printSomething() returns (string) {

return "hello world";

string textToPrint = "hello world";

function changeText(string _text) public {

Bold: Indicates a new term, an important word, or words that you see onscreen For example, words

in menus or dialog boxes appear in the text like this Here is an example: "Select System info from theAdministration panel."

Warnings or important notes appear like this.

Tips and tricks appear like this.

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Get in touch

Feedback from our readers is always welcome

General feedback: Email feedback@packtpub.com and mention the book title in the subject of your

message If you have questions about any aspect of this book, please email us at questions@packtpub.com

Errata: Although we have taken every care to ensure the accuracy of our content, mistakes do

happen If you have found a mistake in this book, we would be grateful if you would report this to us.Please visit www.packtpub.com/submit-errata, selecting your book, clicking on the Errata Submission Formlink, and entering the details

Piracy: If you come across any illegal copies of our works in any form on the Internet, we would be

grateful if you would provide us with the location address or website name Please contact us at

copyright@packtpub.com with a link to the material

If you are interested in becoming an author: If there is a topic that you have expertise in and you

are interested in either writing or contributing to a book, please visit authors.packtpub.com

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Please leave a review Once you have read and used this book, why not leave a review on the sitethat you purchased it from? Potential readers can then see and use your unbiased opinion to makepurchase decisions, we at Packt can understand what you think about our products, and our authorscan see your feedback on their book Thank you!

For more information about Packt, please visit packtpub.com

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Getting Started

In this chapter, we will cover the following recipes:

Choosing a client for Ethereum

Setting up a node and participating in a networkWorking with the JavaScript console

Saving time and money with INFURA

Creating your own private Ethereum networkCreating a blockchain network for developmentUsing Azure Ethereum as a service

Using MetaMask and other wallets

Using block explorer

Understanding everything about accounts

Installing a solidity compiler

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It is really important to understand how to configure and work with various implementations of theEthereum protocol before developing applications in it There are several flavors, which can be usedinterchangeably for development, testing, and deployment Keywords in Ethereum might be very new

to a person who is just getting started, so it is important to understand and use the tools and services

in the Ethereum ecosystem

Ethereum is a distributed public ledger, like Bitcoin Bitcoin acts more like a peer-to-peer electroniccash system, whereas Ethereum is a decentralized platform for building applications Ethereum has abuilt-in Turing complete programming language (solidity), which can be used to write smart

contracts This means that Ethereum has a broader application than other traditional

blockchains Ethereum also has a cryptocurrency (Ether), which can be traded for value or to pay thetransaction fee for applications and services in Ethereum

POW (Proof of Work), POS (Proof of Stake), IBFT (Istanbul Byzantine Fault Tolerance), Raft, and so on are

different commonly used consensus algorithms These algorithms are used to achieve agreement on a data value among distributed systems Each algorithm has their own advantages and disadvantages, and various blockchain platforms use them based on their requirements.

A smart contract is a computer program that outlines the rules in a relationship Smart contracts workexactly as intended and cannot be changed at a later point in time Once deployed, these smart

contracts cannot be changed This gives users trust and transparency With the help of Ethereum smartcontracts, you can create your own tradable tokens, raise funds for your startup, build a decentralizedorganization, or even make a fun game

The recipes in this chapter will primarily focus on Ethereum configuration and platform tools, whichwill help the reader understand more about the Ethereum ecosystem before starting to develop

applications

While the recipes in this chapter will give you an overview of Ethereum and working with various clients, we

encourage you to adopt this proposal according to your needs Since the software used is still in development and gaining in popularity, some organization's policies and antivirus software will prevent you from using this In such cases, it is typically a good idea to discuss this with your IT security department—if your company happens to have one—well in advance, to prevent lengthy discussions later on.

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Choosing a client for Ethereum

In this recipe, we will focus on installing various clients that implement the Ethereum protocol Thiswill help you learn what each client has to offer, and will enable you to choose and work with anefficient implementation based on your requirements

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Getting ready

If you are using macOS, you will need homebrew to install the packages

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How to do it

There are several clients that implement the Ethereum protocol and we will mainly focus on geth and

parity You can get more information about the remaining protocols from the official Ethereum

documentation (http://www.ethdocs.org/)

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Geth is the official Go implementation of Ethereum:

1 To install geth on macOS, the easiest way to follow is using homebrew Run the following

commands in your Terminal to download and install geth:

brew tap ethereum/ethereum

brew install ethereum

This command will install the latest stable version of geth on your Mac If you want toinstall the development version of geth, then add the devel flag to the install command:

brew install ethereum devel

2 To install geth on Ubuntu, run the following commands:

sudo apt-get install software-properties-common sudo add-apt-repository -y ppa:ethereum/ethereum sudo apt-get update

sudo apt-get install ethereum

3 If you are using Windows, it is suggested to download the binary from https://geth.ethereum.org/dow nloads/ and install it by double-clicking the geth.exe file

4 Verify the installation by running the geth command:

geth version

It will show the current client details, as displayed here:

Since geth is a development version and still gaining in popularity, some antivirus software may consider it a virus Also, make sure that you are not violating your organization's policies by using this software.

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bash <(curl https://get.parity.io -kL)

2 If you are using Windows, then download the binary releases from https://github.com/paritytech/par ity/releases and install them You can also see supported binaries for other operating systems aswell

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Setting up a node and participating in a

network

Here, you will learn how to set up a node using the geth command-line tool You will also see how toconnect to a public network and perform operations such as ledger syncing and mining

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