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- Herausgeber: Packt Publishing
- Kategorie: Fachliteratur
- Sprache: Englisch
Ethereum is a public, blockchain-based distributed computing platform featuring smart contract functionality. This book is your one-stop guide to blockchain and Ethereum smart contract development.
We start by introducing you to the basics of blockchain. You'll learn about hash functions, Merkle trees, forking, mining, and much more. Then you'll learn about Ethereum and smart contracts, and we'll cover Ethereum virtual machine (EVM) in detail. Next, you'll get acquainted with DApps and DAOs and see how they work. We'll also delve into the mechanisms of advanced smart contracts, taking a practical approach.
You'll also learn how to develop your own cryptocurrency from scratch in order to understand the business behind ICO. Further on, you'll get to know the key concepts of the Solidity programming language, enabling you to build decentralized blockchain-based applications. We'll also look at enterprise use cases, where you'll build a decentralized microblogging site.
At the end of this book, we discuss blockchain-as-a-service, the dark web marketplace, and various advanced topics so you can get well versed with the blockchain principles and ecosystem.
Das E-Book können Sie in Legimi-Apps oder einer beliebigen App lesen, die das folgende Format unterstützen:
Seitenzahl: 277
Veröffentlichungsjahr: 2018
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Ethereum Smart Contract Development
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Contributors
About the author
Mayukh Mukhopadhyay started his career as a BI developer. After the 2008-09 financial crisis, he was at Tata Consultancy Services for one of their Fortune 500 clients in the telecom sector. Holding a master's in software engineering from Jadavpur University, he is presently working as a data insight developer, where he focuses on applying data science and machine learning to raw telecom equipment logs to generate business insights. He has a varied list of academic interests, ranging from audio signal processing, structural bioinformatics, and bio-inspired algorithms to consciousness engineering. Apart from being an Oracle Certified Specialist, he is a Certified Bitcoin Professional, recognized by C4 (Crypto Currency Certification Consortium). He tries to apply blockchain as a technology to different business domains.
To my guide @JUDr Parama Bhaumik —your lectures on distributed systems were my main inspiration while writing this book.
To my professional network connections Ivan Liljeqvist, Dug Campbell, Mahesh Murthy, Kaushik Sathupadi, Ravinder Deol, Narayan Prusty, and Thomas Wiesner—thanks for your blogs and vlogs. This book is as much your creation as it is mine.
About the reviewer
Daniel Kraft studied applied mathematics and theoretical physics in Graz, Austria, where he obtained his PhD from the University of Graz in 2015. After that, he started as a software engineer in Zurich, Switzerland. He has been very interested in Bitcoin and cryptocurrencies since 2011 and involved in Bitcoin development since 2013. Since 2014, he has been the main developer for Namecoin and Huntercoin, and has successfully reimplemented both on top of the modern Bitcoin Core code base. Wherever possible, Daniel also contributed improvements to the upstream Bitcoin Core. He has published multiple research articles in peer-reviewed journals, two of them directly related to cryptocurrency.
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Table of Contents
Title Page
Copyright and Credits
Ethereum Smart Contract Development
Dedication
Packt Upsell
Why subscribe?
PacktPub.com
Contributors
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
Get in touch
Reviews
Blockchain Basics
Understanding distributed systems
The Byzantine Generals' Problem
Losing strategy
Winning strategy
The CAP theorem
Consensus in distributed systems
Understanding the hash function and the Merkle tree
Understanding a blockchain–a developer and trader's perspective
Inside a block
Blockchain mining and forking
Blockchains – evolution, generations, and hype
Summary
Grokking Ethereum
Understanding Ethereum
The notion of decentralization
The Ethereum ecosystem
Mist
Decentralized applications
Middleware
Swarm
Whisper
EVM
Hardware clients and internet
Turing completeness and the magic sauce
Ethereum block, mining, and forking
The Ethereum wallet and client interface
Summary
Hello World of Smart Contracts
A smart contract in seven lines of code
Remix in a nutshell
Increment and decrement operations using Solidity
Coding a loop
Raising an issue on GitHub
Smart contract on a private blockchain
Writing the genesis block
Building a private blockchain
Connecting MIST browser using geth
Mining ethers in a private blockchain
Deploying smart contracts on our private chain
Summary
A Noob's Guide to DApps and DAO
Understanding DApps
Steps to develop a DApp
Architecture of a DApp
What is ethercast?
btcrelay.org
oraclize.it
the-pitts-circus.com
Understanding the design of DAO
The rise and fall of DAO
Summary
Deep-Diving into Smart Contracts
What makes a contract "smart"?
Definition and design
Role of code in a smart contract
Basic anatomy of a smart contract design
Smart contract optimization
Smart contract auditing and compliance
Designing a voting DApp
Summary
Solidity in Depth
Need for solidity
Nuances, syntax, and features of solidity
Pragma, import, and comments
Class properties of a contract
Functions
Events
Inheritance
Libraries
Expression and control structures
Units and variables
Optimizer and debugging options
Parity hack demystified
Summary
Primer on Web3.js
Web3.js in the Ethereum ecosystem
Running a smart contract using Web3.js
API structure of Web3.js
Designing an ownership contract
Summary
Developing a Cryptocurrency from Scratch
Token versus coin
ERC20 token development using Truffle
Arbitrage trading for cryptocurrencies
The ICO story
Fiat2Crypto and Crypto2Crypto exchange
Parity hack returns
Summary
Enterprise Use Cases
Banking and payments
Insurance
Supply chain management
Forecasting and prediction market
Charity
Public benefits
Energy management
Art and music
Retail
Real estate
Cyber security
Crowdfunding
Networking and the Internet of Things
Voting
Government
Private transport and ride sharing
Cloud storage
Healthcare
Smart contract use cases
Insurance
Trade finance
Derivatives
Securities
Accounts
Digital identity
Record-keeping
Loans and mortgages
Legal
Supply chain
Clinical trials
Terminal disease research
Decentralized microblogging
Administrative and security constraints
TwtAccount.sol
TwtRegistry.sol
Service setup on the private blockchain
Reading tweets
Summary
BaaS and the Dark Web Market
Playful privacy
Types of blockchain
Private blockchains
Public blockchains
Consortium blockchains
Blockchain-as-a-service
Enterprise platforms for BaaS
IBM Hyperledger
Microsoft Azure EBaaS
Amazon Eris
Dark web marketplace
Project smartCV
Summary
Advanced Topics and the Road Ahead
Common design patterns
Restricting access
Token systems
Factory pattern
Registries
Voting systems
DACs and DAS
Ethereum improvement proposal
Rational behind EIPs
Types of EIP
EIP life cycle
EIP template
Consortium blockchains
Case study on R3 Corda
Tangle beyond blockchain
Shortcomings of a blockchain
Tangle demystified
Iota GitHub analysis
Purchase and storage of Iota
Summary
Other Books You May Enjoy
Leave a review - let other readers know what you think
Preface
If you are reading this line, I want to congratulate you because you have already overcome the most difficult hurdle in the pursuit of the understanding blockchain, and specifically, Ethereum smart contracts. This hurdle is the overwhelming hype surrounding this promising yet premature technology and trying to know what is really going on under the hood.
I am a software developer, and through my book, which you are viewing in your electronic device or physically holding in your hand, we will together embark on a fascinating journey through this enigmatic and revolutionary technology.
The chapters in this book have been arranged in an incremental fashion. We start with a gentle introduction to blockchain using the familiar bitcoin, and quickly dive into the world of Ethereum and the major players in its ecosystem.
Then we proceed to do some hands-on coding of a typical "Hello World" smart contract. We then take on the subject of decentralized autonomous organizations, decentralized applications, and smart contract optimization. We also analyze two famous multi-million-dollar hacks that recently occurred in the Ethereum community, along with the preventive measures employed to avoid them in future.
We then move on to the intricacies of the solidity programming language and web3.js library.
The final chapters mainly deal with the development of standardized tokens, the concept of initial coin offering, potential enterprise use cases of smart contracts, designing a decentralized micro-blogging platform, and surfing the dark web marketplace.
We conclude the book by providing primers on advanced topics with promising future prospects such as graph-based DLTs and quantum secured blockchains.
At the onset, I want to have a clear understanding between us. Even though I am the author of this book and it is my sole responsibility to present the facts as accurately as possible in this book, in no possible way do I consider myself as the sole authority on this subject.
As my reader, I want you to realize that I am just another overenthusiastic fellow learner who will try to assist you with your pursuit of knowledge by introducing the optimal amount of information required to kick-start your journey. And I will make you aware of the hurdles and pitfalls I faced along the way so that you can learn from my mistakes.
Enough said. Let's start our journey to blockchain and get our hands dirty with Ethereum Smart Contract Development.
Happy reading!
Who this book is for
This book is dedicated to novice programmers, solution architects, and blockchain enthusiasts who want to build powerful, robust, and optimized smart contracts using solidity from scratch and in combination with other open source JavaScript libraries. If you want to build your own extensive, decentralized applications that can smartly execute on a blockchain, then this book is what you need! An open and inquisitive mind is a necessary and sufficient prerequisite. Some preliminary knowledge of data structures, object-oriented programming, networking concepts, and cryptography is a plus and will help the reader to understand the concepts presented in this book.
What this book covers
Chapter 1, Blockchain Basics, will serve as a warm-up session about blockchain before we deep dive into Ethereum and smart contract development. To really appreciate blockchain, we must understand the two founding pillars on which blockchain as a technology is firmly grounded: distributed systems and cryptography. Once we have covered these two core concepts, we try to understand a blockchain from two different perspectives: as a software developer and as a trader of financial instruments. Then we probe into the internal logical architecture of a block in the blockchain, focusing the bitcoin block structure, and get a gentle introduction to the mining and forking process. We conclude the chapter by discussing how blockchain has evolved in recent years and clearly marking out its current position in the technological hype cycle.
Chapter 2, Grokking Ethereum, will help us to understand the meaning of decentralization and whether Ethereum is truly decentralized. We will also cover its core technological stack and get familiarized with various jargon, such as Mist, EVM, Swarm, Whisper, Ether, and Gas. We will briefly discuss the notion of a Turing-complete language. We'll then revisit forking, mining, and block architecture from the perspective of Ethereum. We'll end this chapter by getting a notion of Ethereum wallets and client interfaces, which will serve as a firm base for smart contract development.
Chapter 3, The Hello World of Ethereum Smart Contract, provides a hands-on guide to developing our first smart contract. As an unspoken tradition of a software developer, we start with a "Hello World" program. Then we try some basic arithmetic increment and decrement operations using a contract. We then learn how to code a loop inside a smart contract and how to raise an issue in GitHub. We end this chapter by creating our own private blockchain right from the genesis block, attach it with Geth, and use the Mist browser to deploy one of the smart contracts we studied in this chapter, after mining some ethers.
Chapter 4, A Noob's Guide to DApps and DAOs, develops our understanding towards decentralized applications from a developer's perspective. We introduce the high-level steps to develop a decentralized application. Then we explore a unique marketplace called ethercast, which serves as an aggregator of several DApps. We then move on to design a decentralized autonomous organization. We conclude this chapter with a retrospection of the infamous DAO hack, which led to the ETH/ETC split, from a purely technical perspective.
Chapter 5, Deep-Diving into Smart Contracts, digs deeper into smart contract designs. We start by understanding the textbook definition of a smart contract. Then we move on to understand different smart contract models and the role of code in a smart contract. We go through the basic anatomy of a smart contract and see how a smart contract works. Then we shift our focus to advanced topics such as smart contract optimization, auditing, and ERC20 compliance. We conclude the chapter with a hands-on drill of building a voting DApp.
Chapter 6, Solidity in Depth, is all about the Turing complete solidity language on the Ethereum blockchain. We will start by probing into the design decision of why we really need a new language like solidity. The next sections will cover the nuances of the solidity language and the basic syntax used in it. Specifically, we'll cover contract-oriented features, functions and events, inheritance, libraries, expressions, control structures, units, and variables. Then we'll look at the optimizer and debugging options. We will conclude this chapter by analyzing the code flaw that led to the recent parity wallet hack in the Ethereum blockchain, which stole around $30 million worth of ethers.
Chapter 7, Primer on Web3.js, introduces a special application programming interface library written in JavaScript. This interface connects our web browser with the Ethereum blockchain node. We will begin this chapter by understanding the difference between Geth, Web3.js, and Mist. Then we will learn how to import this API library and get connected with Geth. We will then explore the API structure inside the web3.js library. We'll conclude the chapter by studying the design of an ownership contract.
Chapter 8, Developing Cryptocurrency from Scratch, provides a hands-on tutorial to develop an ERC20 standardized token using the Truffle framework. We then dive in to the concepts of initial coin offering (ICO) and how to identify genuine ICOs among fake and Ponzi schemes. The chapter concludes by discussing various token conversion process and pair-trading concepts.
Chapter 9, Enterprise Use Cases, provides some exciting and promising use cases of Ethereum smart contracts. We also discuss the design of a decentralized micro-blogging platform using solidity.
Chapter 10, BaaS and the Dark Web Market, introduce us to the blockchain framework of Microsoft and IBM. We conclude this chapter by discussing the difference between the Conventional Web and the Dark Web (.onion website and TOR) and how to safely browse the Dark Web to find use cases of cryptocurrencies.
Chapter 11, Advanced Topics and the Road Ahead, deals with exciting topics such as graph-based DLTS with a focus on Tangle, quantum secured blockchain, Ethereum improvement protocols, consortium blockchains, distributed autonomous societies, and common design patterns for solidity.
To get the most out of this book
Inform the reader of the things that they need to know before they start, and spell out what knowledge you are assuming
Some preliminary knowledge of data structures, object-oriented programming, networking concepts, and cryptography is a plus but not mandatory
Download the example code files
You can download the example code files for this book from your account at www.packtpub.com. If you purchased this book elsewhere, you can visit www.packtpub.com/support and register to have the files emailed directly to you.
You can download the code files by following these steps:
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The code bundle for the book is also hosted on GitHub athttps://github.com/PacktPublishing/Ethereum-Smart-Contract-Development. 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 athttps://github.com/PacktPublishing/. Check them out!
Download the color images
We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: http://www.packtpub.com/sites/default/files/downloads/EthereumSmartContractDevelopment_ColorImages.pdf.
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: "Open your Google Chrome browser and type remix solidity in Google, as shown in Figure 3.1."
A block of code is set as follows:
{"jsonrpc":"2.0","method":"eth_coinbase","params":[],"id": 67}
Any command-line input or output is written as follows:
$ geth --datadir=./chaindata/ init genesis.json
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: "Click on the Create button as highlighted in Figure 3.7. Voila! You just created your smart contract."
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Blockchain Basics
This chapter will serve as a warm-up session about blockchain before we dive into Ethereum and smart contract development. To really appreciate blockchain, we must understand the two pillars on which blockchain, as a technology, is firmly grounded: distributed systems and cryptography. Once we have tackled these two core concepts, we will try to understand blockchain from two different perspectives: one as a software developer and another as a trader of financial instruments. Then, we'll probe into the internal logical architecture of a block in blockchain, focusing on the bitcoin block structure and get a gentle introduction to the mining and forking process.
We conclude the chapter by discussing the evolution of blockchain as a technology in recent years, three generations of blockchain technology, and the current position of blockchain on the gartner hype cycle.
After studying this chapter, you will be able to:
Understand the foundation of
blockchain
technology
Appreciate
blockchain
as a developer and a trader
Discuss the basic structure of a bitcoin block
Know about
blockchain
mining and forking and understand the evolution, generations, and hype surrounding
blockchain
Understanding distributed systems
To understand a distributed system, we need to first distinguish it from traditional centralized systems. Traditional centralized systems consist of two main components: the client and the server. In the simplest setup, the client is the one who makes a request for getting a job done, and a server is the one who gets it done. This was how web 1.0 operated; the one we started calling the World Wide Web. For example, you placed a search request on Google search engine, and it gave you back a set of web links and summarized results.
Now, if two clients want to communicate between each other, they have to place request via the server, which serves as the middleman. A second example might be, for instance, if I send you a message from the client app of my mobile, this message is pushed to the WhatsApp server, which then notifies your client app about my message. Once you see my message, your client app sends back an acknowledgement signal in terms of a blue double tick to my client app, again using the WhatsApp server. This is how the present internet operates and we call it web 2.0, the advent of the social network. In both of these examples, we can see the centralized system works just fine. In Figure 1.1, this centralized setup is represented by the left-side lego block setup. The aggregated middle blocks represent the server, whereas the circumferential isolated blocks represent the clients. However, these centralized servers are generally owned by business organizations and can be influenced by a criminal entity or central authority to leak private data while the clients communicate. To overcome this fundamental flaw, peer-to-peer networking (web 3.0) came into practice (for example, BitTorrent). These were distributed systems, as depicted in the right of Figure 1.1, where each node can be a client or server or both and are not distinguishable from other nodes. Even though these systems were good at privacy, they faced challenges like the Byzantine Generals' Problem and the CAP theorem, which we will discuss in the subsequent sections.
The Byzantine Generals' Problem
Imagine a time during the dark ages, where a pirate ship is under attack. There are 200 pirates aboard the pirate ship surrounded by six army ships of 50 warriors each, who've anchored, surrounding the pirate ship. Each army ship is commanded by a captain. The 300 warriors can easily overpower the 200 pirates aboard the pirate ship. However, if they don't all attack simultaneously, there is a very real risk that the warriors will be outnumbered by the pirates and they'll go on to lose the battle.
So, how can the captains all agree on the same time to attack the pirate ship? These days, we'd simply need a quick group video-conference call, and the captains would have to agree to attack at 22:00 hours (10 PM).
However, back in the dark ages, things were a little more complicated:
The 22:00 attack message could only be passed on by a sailor on a small boat. He has to sail around each army ship, visiting each captain in turn to confirm.
Any captain may be a traitor and in league with the pirates in the pirate ship.
Losing strategy
Captain 1 decides to attack at 22:00. He sends his sailor out with the message (22:00 attack) to deliver to Captain 2. Upon arrival, Captain 2 reads the message, notes the time of the attack, and sends a message that also says 22:00 attack. He sends the sailor on to share the message with Captain 3. However, we have a problem. Captain 3 is a traitor. He wants the attack to fail. So, when he gets the message, he rips it up and replaces it with a new message that says 21:00 attack (9 PM). The sailor continues unaware. Captain 4 now receives a message saying 21:00 attack. He notes the time, signs the message saying 21:00 attack and sends this on to Captain 5, who then sends the same message to Captain 6. Now, the message has gone around everyone, but we have a problem. The dishonest captain has disrupted the result. We now have three captains (4, 5, and 6) with 150 warriors attacking the pirate ship at 21:00. Expecting others to join them, they instead get outnumbered and overpowered by the 200 pirates. The victorious pirates now stream out of the pirate ship and join forces with the treacherous Captain 3. Suddenly, the two remaining captains (1 and 2) have only 100 warriors and find themselves fighting 200 pirates plus 50 traitors. Unfortunately, the pirates and traitors win.
Winning strategy
Captain 1 wants to send the same message (attack at 22:00). However, this time, there are two new rules he must obey:
He must spend 10 minutes preparing any new message for it to be valid
He must include the history of every previous message in every new message
So, let's see what happens this time. As before, Captain 1 sends the message (22:00 attack) with the sailor on the boat. This time, however, it is different for Captain 2, because he knows two things for certain:
The message must have taken 10 minutes to prepare
There are no previous messages, so it must be the truth (even if Captain 1 is a traitor and put in the wrong time, it doesn't matter; if the majority of captains followed this suggestion and went with a 22:00 attack time, they would still outnumber those in the pirate ship and win the battle)
So, now it is time for Captain 2 to send a message. As required, he spends 10 minutes preparing the new message and he embeds Captain 1's message into his own. The sailor then sets off with this message (now in fact, it is two messages chained together as the second has the first embedded within it). Now it gets to Captain 3.
Remember, he's the traitor. So, what does he do? Last time, he changed the message to 21:00 attack so that captains 4, 5, and 6 would attack early and get overpowered. Now, however, he can't because, under the new rules, he has only 10 minutes to prepare a message for Captain 4. He has two options:
Cheat by changing the message to 21:00 attack. To do this, he needs to (a) spend 10 minutes creating his message and then (b) spend an extra 2 x 10 minutes working to create replacement 21:00 attack messages from Captains 1 and 2 to embed these into his message and carry out this 30 minutes of work within the next 10 minutes to avoid the other captains knowing that he's a traitor.
Admit defeat and prepare the 22:00 attack message during those 10 minutes.
In other words, every captain has got no more than 10 minutes to provide the next captain with something that would take more than 10 minutes to fake if they were trying to be dishonest. If they can't deliver it within 10 minutes, everyone knows they're dishonest and ignores them, rendering their attempts to mislead others useless.
The CAP theorem
Before stating the CAP theorem, let's try to understand consistency, availability, and partition tolerance using a real-world problem.
As a married person, I know how pathetic a person's life can become if they forget important dates like the birthday and anniversary of their spouse (in most cases, the husband is the culprit, but that is a separate discussion). One of my friends, let's call him Kaushik, saw an opportunity in this and opened up a start-up, HappySpouse.com, to address this issue. During a typical business day, Kaushik (K) and his customer (C) would have the following conversation:
K: Hello from HappySpouse.com. How may I help you?
C: Hey, I want you to remember my wife's birthday.
K: Sure! When is it?
C: September 3.
K: (Writing it down on a page exclusive for C.) Stored. Call me any time to remind you of your spouse's birthday again!
C: Thank you!
K: No problem! Your credit card has been charged with $0.05.
Kaushik's idea was so simple, needed nothing but a notebook and phone, yet so effective that it rolled off like an avalanche. VC firms started pouring in funds. He also started getting hundreds of calls every day. That's where the problem started. Now, more and more of his customers had to wait in the queue to speak to him. Most of them even hung up, tired of the waiting tone. Besides, when he was sick for a day and could not come to work, he lost a whole day of business. Not to mention all those unsatisfied customers who wanted information on that day. So, Kaushik decided to scale up and bring in his wife to help him.
He started with a simple plan to solve his availability to customers:
He and his wife both got an extension phone
Customers still dialed the same number
A PBX routed the customer calls to whoever was free at that moment
A few weeks went by smoothly. One fine morning, he got a call from one of his old customers, Joey (J):
J: Hello, am I speaking to Kaushik from HappySpouse.com?
K: Hi Joey, great you remembered us. What can I do for you?
J: Can you tell me when our anniversary was?
K: Sure. 1 sec, Joey (looking up in his notebook, there was no entry on Joey's page). Joey, I have only your spouse's birthday here.
J: Holy cow! I just called you guys yesterday! (Cuts the call!)
How did that happen? Was Joey lying? Kaushik thought about it for a second and the reason hit him! Yesterday, did Joey's call reach his wife? He goes to his wife's desk and checks her notebook. Sure enough, it's there. He tells this to his wife and she realizes the problem too. What a terrible flaw in this distributed setup! This setup was not consistent!
