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Prefácio
A primeira vez que ouvi falar em bitcoin foi em meados de 2011. Minha reação imediata foi mais ou menos essa "Pfft! Dinheiro de nerd!" e eu ignorei-o por mais seis meses, sem compreender a sua importância. Esta é uma reação que eu tenho observado com frequência entre muitas das pessoas mais inteligentes que conheço, o que me dá algum consolo. A segunda vez que me deparei com bitcoin, em uma lista de discussão, eu decidi ler o seu "manual de instruções" oficial, a white page, escrito pelo seu criador, Satoshi Nakamoto, para ver do que se tratava. Ainda me lembro do momento em que eu terminei de ler essas nove páginas, quando eu percebi que bitcoin não era simplesmente uma moeda digital, mas uma rede de confiança que também poderia servir de base para aplicações muito mais avançadas do que apenas moedas. Após constatar que o bitcoin não é dinheiro, mas sim uma rede de confiança descentralizada, comecei uma viagem de quatro meses para devorar cada pedaço de informação que eu poderia encontrar sobre o assunto. Eu me tornei obcecado e encantado, gastando 12 ou mais horas por dia colado ao monitor, lendo, escrevendo, codificando e aprendendo o máximo que pude. Após pular muitas refeições, saí desse período de obsessão 20 quilos mais leve e determinado a dedicar-me a trabalhar com bitcoin.
Two years later, after creating a number of small startups to explore various bitcoin-related services and products, I decided that it was time to write my first book. Bitcoin was the topic that had driven me into a frenzy of creativity and consumed my thoughts; it was the most exciting technology I had encountered since the Internet. It was now time to share my passion about this amazing technology with a broader audience.
This book is mostly intended for coders. If you can use a programming language, this book will teach you how cryptographic currencies work, how to use them, and how to develop software that works with them. The first few chapters are also suitable as an in-depth introduction to bitcoin for noncoders—those trying to understand the inner workings of bitcoin and cryptocurrencies.
The leafcutter ant is a species that exhibits highly complex behavior in a colony super-organism, but each individual ant operates on a set of simple rules driven by social interaction and the exchange of chemical scents (pheromones). Per Wikipedia: "Next to humans, leafcutter ants form the largest and most complex animal societies on Earth." Leafcutter ants don’t actually eat leaves, but rather use them to farm a fungus, which is the central food source for the colony. Get that? These ants are farming!
Although ants form a caste-based society and have a queen for producing offspring, there is no central authority or leader in an ant colony. The highly intelligent and sophisticated behavior exhibited by a multimillion-member colony is an emergent property from the interaction of the individuals in a social network.
Nature demonstrates that decentralized systems can be resilient and can produce emergent complexity and incredible sophistication without the need for a central authority, hierarchy, or complex parts.
Bitcoin is a highly sophisticated decentralized trust network that can support a myriad of financial processes. Yet, each node in the bitcoin network follows a few simple mathematical rules. The interaction between many nodes is what leads to the emergence of the sophisticated behavior, not any inherent complexity or trust in any single node. Like an ant colony, the bitcoin network is a resilient network of simple nodes following simple rules that together can do amazing things without any central coordination.
The following typographical conventions are used in this book:
- Italic
- Indicates new terms, URLs, email addresses, filenames, and file extensions.
- Constant width
- Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.
- Constant width bold
- Shows commands or other text that should be typed literally by the user.
- Constant width italic
- Shows text that should be replaced with user-supplied values or by values determined by context.
This icon signifies a tip, suggestion, or general note.
This icon indicates a warning or caution.
The examples are illustrated in Python, C++, and using the command line of a Unix-like operating system such as Linux or Mac OS X. All code snippets are available in the GitHub repository in the code subdirectory of the main repo. Fork the book code, try the code examples, or submit corrections via GitHub.
All the code snippets can be replicated on most operating systems with a minimal installation of compilers and interpreters for the corresponding languages. Where necessary, we provide basic installation instructions and step-by-step examples of the output of those instructions.
Some of the code snippets and code output have been reformatted for print. In all such cases, the lines have been split by a backslash () character, followed by a newline character. When transcribing the examples, remove those two characters and join the lines again and you should see identical results as shown in the example.
All the code snippets use real values and calculations where possible, so that you can build from example to example and see the same results in any code you write to calculate the same values. For example, the private keys and corresponding public keys and addresses are all real. The sample transactions, blocks, and blockchain references have all been introduced in the actual bitcoin blockchain and are part of the public ledger, so you can review them on any bitcoin system.
This book is here to help you get your job done. In general, if example code is offered with this book, you may use it in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.
We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Mastering Bitcoin by Andreas M. Antonopoulos (O’Reilly). Copyright 2015 Andreas M. Antonopoulos, 978-1-449-37404-4.”
Some editions of this book are offered under an open source license, such as CC-BY-NC (creativecommons.org), in which case the terms of that license apply.
If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at [email protected].
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