Bitcoin and Cryptocurrency Technologies 比特币和数字货币技术

说到底，还是打算翻译一遍了，3~6个月时间吧，在区块链如此疯狂的情况下，我居然还在这样慢悠悠的学习这么基础的技术，也算佩服我自己，总是跟不上节拍。

再次决定翻译的原因是，中文版的翻译确实看不下去了，我有强迫症，还是自己翻译舒服点。

2018-06-27

Arvind Narayanan, Joseph Bonneau, Edward Felten,
Andrew Miller, Steven Goldfeder
with a preface by Jeremy Clark
Draft — Feb 9, 2016
草稿——2016年2月9日

Feedback welcome! Email: bitcoinbook@lists.cs.princeton.edu
欢迎反馈！
For the latest draft and supplementary materials including programming assignments,
see our Coursera course .
如果想看最新的草稿和包含编程任务的补充材料，请看我们的课程。
The official version of this book will be published by Princeton University Press in 2016.
If you’d like to be notified when it’s available, please sign up here .
本书的官方版本即将在2016年普林斯顿大学出版社出版，如果你想收到出版通知，请登录。

[TOC]

Introduction to the book 本书简介

There’s a lot of excitement about Bitcoin and cryptocurrencies. Optimists claim that Bitcoin will fundamentally alter payments, economics, and even politics around the world. Pessimists claim Bitcoin is inherently broken and will suffer an inevitable and spectacular collapse.
比特币和数字货币有很多令人激动的特点。乐观主义者认为比特币将从根本上改变全世界的支付方式、经济甚至政治，而悲观主义者则认为比特币注定会破产，并将遭受不可避免的、惊人的崩溃。

Underlying these differing views is significant confusion about what Bitcoin is and how it works. We wrote this book to help cut through the hype and get to the core of what makes Bitcoin unique.
正因为对比特币及其工作原理的困惑，才导致这些迥异观点的产生。我们写这本书是为了除去炒作噱头，揭示到底是什么让比特币如此地独一无二。

To really understand what is special about Bitcoin, we need to understand how it works at a technical level. Bitcoin truly is a new technology and we can only get so far by explaining it through simple analogies to past technologies.
为了真正理解比特币的特别之处，我们需要从技术角度了解它是如何工作的。比特币确实是一项新技术，通过简单地类比一些过去的技术来诠释它是不够深入的。

We’ll assume that you have a basic understanding of computer science — how computers work, data structures and algorithms, and some programming experience. If you’re an undergraduate or graduate student of computer science, a software developer, an entrepreneur, or a technology hobbyist, this textbook is for you.
我们假定你有计算机科学基础——计算机工作原理、数据结构、算法和一些编程经验。如果你是计算机科学的本科生或研究生、软件开发者、企业家或技术爱好者，那么本书适合你。

In this book we’ll address the important questions about Bitcoin. How does Bitcoin work? What makes it different? How secure are your bitcoins? How anonymous are Bitcoin users? What applications can we build using Bitcoin as a platform? Can cryptocurrencies be regulated? If we were designing a new cryptocurrency today, what would we change? What might the future hold?
本书会讨论一些关于比特币的关键问题。比特币是如何工作的？为什么它与众不同？你的比特币够安全么？匿名程度？我们可以通过比特币作为平台构建什么样的应用？数字货币能否被监管？如果我们现在设计一个数字货币，我们会做哪些改进？未来会如何发展？

Each chapter has a series of homework questions to help you understand these questions at a deeper level. In addition, there is a series of programming assignments in which you’ll implement various components of Bitcoin in simplified models. If you’re an auditory learner, most of the material of this book is also available as a series of video lectures. You can find all these on our Coursera course . You should also supplement your learning with information you can find online including the Bitcoin wiki, forums, and research papers, and by interacting with your peers and the Bitcoin community.
每一章都有一系列家庭作业，用来帮你在一个更深的程度上理解这些问题。此外，还有一系列编程任务，你可以在简化模型中实现比特币的各种组件。如果你喜欢看视频课程，本书提供的大部分学习材料都有视频讲座，你可以在我们课程主页找到它们。你也可以通过其他方式来巩固你的学习，比如：维基百科、论坛、研究论文、与同学或比特币社区中其他人进行讨论。

After reading this book, you’ll know everything you need to be able to separate fact from fiction when reading claims about Bitcoin and other cryptocurrencies. You’ll have the conceptual foundations you need to engineer secure software that interacts with the Bitcoin network. And you’ll be able to integrate ideas from Bitcoin into your own projects.
读完本书，你应该能够分辨出比特币或其他数字货币材料或新闻的真假，设计出能和比特币网络进行安全交互的软件，也可以将比特币地思想整合到你自己的工程项目中。

A note of thanks 感谢

We’re immensely grateful to the students who helped develop programming assignments and to everyone who provided feedback on the drafts of this book. Princeton students Shivam Agarwal, Miles Carlsten, Paul Ellenbogen, Pranav Gokhale, Alex Iriza, Harry Kalodner, and Dillon Reisman, and Stanford students Allison Berke, Benedikt Bünz, and Alex Leishman deserve special praise. We’re also thankful to Dan Boneh and Albert Szmigielski.

Preface — The Long Road to Bitcoin 序言——比特币的漫漫长路

The path to Bitcoin is littered with the corpses of failed attempts. I’ve compiled a list of about a hundred cryptographic payment systems, both e-cash and credit card based technologies, that are notable in some way. Some are academic proposals that have been well cited while others are actual systems that were deployed and tested. Of all the names on this list, there’s probably only one that you recognize — PayPal. And PayPal survived only because it quickly pivoted away from its original idea of cryptographic payments on hand-held devices!

通往比特币的道路，充满了无数失败的尝试。我收集了大约一百种加密支付系统的列表，它们基于电子现金和信用卡技术，并在一些方面具有显著的成就。其中一些事被广泛引用的学术研究成果，另一些则是实际部署和测试的系统。在这个列表上，可能你只知道一个——贝宝（PayPal）。然而贝宝之所以幸存，是因为它及时改变了最初在移动设备上进行支付的想法。

ACC	CyberCents	iKP	MPTP	Proton
Agora	CyberCoin	IMB-MP	Net900	Redi-Charge
AIMP	CyberGold	InterCom	NetBill	S/PAY
Allopass	DigiGod	pin	NetCard	Sandia
b-money	Digital	Silk	Road	Javien
BankNet	e-Comm	Karma	NetCheque	Semopo
Bitbit	E-GoId	LotteryTickets	NetFare	SET
Bitgold	Ecash	Lucre	No3rd	SET2G0
Bitpass	eCharge	Magic	Money	One
C-SET	eCoin	Mandate	PayMe	Trivnet
CAFÉ	Edd	MicroMint	PayNet	TUB
CheckFree	eVend	Micromoney	PayPal	Twitpay
ClickandBuy	First	Virtual	MilliCent	PaySafeCard
ClickShare	FSTC	Electronic	Check	Mini-Pay
CommerceNet	Geldkarte	Minitix	PayWord	Wallie
CommercePOiNT	Globe	Left	MobileMoney	Peppercoin
CommerceSTAGE	Hashcash	Mojo	PhoneTicks	WorldPay
Cybank	HINDE	Mollie	Playspan	X-Pay
CyberCash	iBill	Mondex	Polling

表0.1 一些优秀的电子支付系统和方案

There’s a lot to learn from this history. Where do the ideas in Bitcoin come from? Why do some technologies survive while many others die? What does it take for complex technical innovations to be successfully commercialized? If nothing else, this story will give you an appreciation of how remarkable it is that we finally have a real, working payment mechanism that’s native to the Internet.

这段历史有很多值得学习的地方。比特币的想法从何而来？为什么一些技术成功而另一些却失败？如何将复杂的技术创新成功商业化？即便不关心这些，比特币发展的故事仍然会告诉你，基于互联网且真正有效的支付系统，它的诞生是多么的不容易。

Traditional financial arrangements 传统金融体系

Back in time before there were governments, before there was currency, one system that worked for acquiring goods was barter. Let’s say Alice wants a tool and Bob wants medicine. If each of them happen to have what the other person needs, then they can swap and both satisfy their needs.

在政府和货币出现之前，人们用以物易物的方式进行交易。假设Alice需要工具，而Bob需要药品。如果他们都有对方需要的物品，那么，他们就可以进行交换，满足各自的需求。

On the other hand, let’s say Alice has food that she’s willing to trade for a tool, while Bob, who has a tool, doesn’t have any need for food. He wants medicine instead. Alice and Bob can’t trade with each other, but if there’s a third person, Carol, who has medicine that she’s willing to trade for food, then it becomes possible to arrange a three-way swap where everyone gets what they need.

但是，如果Alice想用食物来交换工具，同时，Bob拥有工具，需要药品却不需要食物。这种情况下，Alice和Bob无法直接进行交易。如果这时存在第三个人，Carol有药品并且需要食物，那么这三个人就可以进行交易取得各自所需的物品。

The drawback, of course, is coordination —— arranging a group of people, whose needs and wants align, in the same place at the same time. Two systems emerged to solve coordination: credit and cash. Historians, anthropologists, and economists debate which of the two developed first, but that’s immaterial for our purposes.

显而易见，这种交易方式的难点在于，在同一时间同一地点组织一群人进行交易。关于解决这个难题，有两种解决方案：信用和现金。历史学家、人类学家和经济学家经常为二者谁更早出现而争论不休，不过这不是本书的讨论范围。

In a credit-based system, in the example above, Alice and Bob would be able to trade with each other. Bob would give Alice the tool and Bob gets a favor that’s owed to him. In other words, Alice has a debt that she needs to settle with Bob some time in the future. Alice’s material needs are now satisfied, but she has a debt that she’d like to cancel, so that’s her new “want”. If Alice encounters Carol in the future, Alice can trade her food for Carol’s medicine, then go back to Bob with the medicine and cancel the debt.

对于上面的例子，如果采用信用体系，Alice和Bob是有可能进行交易的。Bob会给Alice工具，同时Alice欠Bob一个人情。换句话说，Alice欠下一笔债务，并在将来的某一天偿还给Bob。Alice的工具需求马上得到满足，但欠下一笔债务，她会想尽快还清，这样，“还债”就是她新的需求了。如果Alice在未来某天遇到了Carol，Alice可以用她的事务和Carol交换药品，然后用药品偿还欠Bob的债务。

On the other hand, in a cash-based system, Alice would buy the tool from Bob. Later, she might sell her food to Carol, and Carol can sell her medicine to Bob, completing the cycle. These trades can happen in any order, provided that the buyer in each transaction has cash on hand. In the end, of course, it’s as if no money ever changed hands.

另一方面，如果采用现金体系，Alice会购买从Bob那里购买工具，并且向Carol出售食物，而Carol可以出售她的药品给Bob，进而完成一个循环。只要每个人手里有足够的现金，交易顺序是无关紧要的。并且，完成交易后，每个人手里的现金就像是没有变化过一样。

Neither system is clearly superior. A cash-based system needs to be “bootstrapped” with some initial allocation of cash, without which no trades can occur. A credit-based system doesn’t need
bootstrapping, but the drawback is that anyone who’s owed a debt is taking on some risk. There’s a chance that the other person never comes back to settle the debt.

很难说这两种体系哪个更加优越。现金体系的问题是，最开始必须分配现金，否则无法发生交易。信用体系没有先决条件，但是债务人存在不偿还债务的可能，因此要使得交易发生，债权人就必须承担一定的风险。

Cash also allows us to be precise about how much something is worth. If you’re bartering, it’s hard to say if a tool is worth more than medicine or medicine is worth more than food. Cash lets us use numbers to talk about value. That’s why we use a blended system today — even when we’re using credit, we measure debt in the amount of cash it would take to settle it.

使用现金有另外一个好处是，可以衡量物品的价值。以物易物时，我们很难说工具比药品值钱，或者药品就比食物值钱。现金让我们用数字就可判断物品的价值。实际上，两种体系我们都在使用——即使采用信用进行交易，我们也会用现金的数字来衡量应当偿还债务的金额大小。

These ideas come up in many contexts, especially online systems where users trade virtual goods of some kind. For example, peer-to-peer file-sharing networks must deal with the problem of
“freeloaders,” that is, users who download files without sharing in turn. While swapping files might work, there is also the issue of coordination: finding the perfect person who has exactly the file you want and wants exactly the file you have. In projects like MojoNation and academic proposals like Karma, users get some initial allocation of virtual cash that they must spend to receive a file and earn when they send a copy of a file to another user. In both cases, one or more central servers help keep track of users’ balances and may offer exchange services between their internal currency and traditional currency. While MojoNation did not survive long enough to implement such an exchange, it became the intellectual ancestor of some protocols used today: BitTorrent and Tahoe-LAFS.

这些交易观点在许多场合都有所应用，特别是用户在线上系统中使用虚拟物品进行交易时。比如：在点对点文件分享系统中，很可能遇到只下载却不分享的用户。也许进行文件交换是个可行的方案，但如何找到两个人恰好拥有对方需要的文件，也是个难题。在一些项目如MojiNation或学术猜想Karma中，用户可以获得一些初始虚拟货币，然后，下载文件时花费一定的虚拟货币给提供该文件的人，提供文件时又可以获得别人的虚拟货币。不管是下载还是提供文件，都会有一个或多个服务器记录跟踪用户的账户余额，并且提供虚拟货币和真实货币之间的兑换功能。虽然MojoNation在提供兑换功能之前就消失了，但它确实是今天BitTorrent和Tahoe-LAFS等协议的前身。

The trouble with credit cards online 网络信用卡的弊端

Credit and cash are fundamental ideas, to the point that we can sort the multitude of electronic payment methods into two piles. Bitcoin is obviously in the “cash” pile, but let’s look at the other one first.

信用和现金是非常基本的概念，许多电子支付方式都可以划分为其中某一类。比特币显然属于现金，但我们先谈谈基于信用的电子支付方式。

Credit card transactions are the dominant payment method that is used on the web today. If you’ve ever bought something from an online seller such as Amazon, you know how the arrangement goes. You type in your credit card details, you send it to Amazon, and then Amazon turns around with these credit card details and they talk to the “system”—a financial system involving processors, banks, credit card companies, and other intermediaries.

信用卡是现在主流的线上支付方式。如果你曾经在像是亚马逊这样的网上商店购买过东西，那你一定很熟悉使用信用卡的流程。你输入信用卡信息发送给亚马逊，亚马逊会将收到的这些信息发给系统——包括信息处理、银行、信用卡公司或其他中介。

On the other hand, if you use something like PayPal, what you see is an intermediary architecture. There’s a company that sits between you and the seller, so you send your credit card details to this intermediary, which approves the transaction and notifies the seller. The intermediary will settle its balance with the seller at the end of each day.

如果你使用的像贝宝这类的支付工具，会有很明显的中介式结构。会有一家公司夹在你和商家之间，你将信用卡信息发送给中介，中介核对交易信息并且通知商家，并会在每天结束时统一和商家进行结算。

What you gain from this architecture is that you don’t have to give the seller your credit card details, which can be a security risk. You might not even have to give the seller your identity, which would improve your privacy as well. The downside is that you lose the simplicity of interacting directly with the seller. Both you and the seller might have to have an account with the same intermediary.

这一结构的优势在于，你无需把信用卡信息发给商家，避免了一定的风险。而且，你也无需向商家提供个人身份信息，同样保护了你的个人隐私。然而劣势在于，增加了交易的复杂性，你无法和商家直接交互，并且，你和商家都必须在中介开设账户。

Today most of us are comfortable with giving out our credit card information when shopping online, or at least we’ve grudgingly accepted it. We’re also used to companies collecting data about our online shopping and browsing activity. But in the 1990s, the web was new, standards for protocol-level encryption were just emerging, and these concerns made consumers deeply uncertain and hesitant. In particular, it was considered crazy to hand over your credit card details to online
vendors of unknown repute over an insecure channel. In such an environment, there was a lot of interest in the intermediary architecture.

如今，我们已经习惯在进行线上交易时提供信用卡信息，至少勉强算是接受了。我们也习惯了网络公司在我们网上购物或浏览商品时收集我们的信息。但是在1990年代，互联网刚刚兴起，数据加密协议也刚开始发展，那时，消费者对网上购物的安全性感到担忧和不大情愿。尤其是，将你的信用卡信息通过网络上不安全的渠道交给商家，这简直无法想象。在这样的环境下，中介式交易结构开始崭露头角。

A company called FirstVirtual was an early payment intermediary, founded in 1994. Incidentally, they were one of the first companies to set up a purely virtual office with employees spread across the country and communicating over the Internet — hence the name.

在1994年，一家叫第一虚拟的网络公司成立了，它是较早成立的中介支付机构。正如它的名字一样，它也是第一家完全虚拟办公、通过网络交流、员工遍布全国的公司。

FirstVirtual’s proposed system was a little like PayPal’s current system but preceded it by many years. As a user you’d enroll with them and provide your credit card details. When you want to buy something from a seller, the seller contacts FirstVirtual with the details of the requested payment, FirstVirtual confirms these details with you, and if you approve your credit card gets billed. But two details are interesting. First, all of this communication happened over email; web browsers back in the day were just beginning to universally support encryption protocols like HTTPS, and the multi-party nature of payment protocol added other complexities. (Other intermediaries took the approach of encoding information into URLs or using a custom encryption protocol on top of HTTP.) Second, the customer would have ninety days to dispute the charge, and the merchant would receive the money only after three months! Today the merchant does get paid immediately, but, there still is the risk that the customer will file a chargeback or dispute the credit card statement. If that happens, the merchant will have to return the payment to the credit card company.

唉，不想翻译了，太慢了，每天一页，也没有耐心了，，，仔细看书书吧，如此反复无常，能成什么事？

我现在状态很差，不是很有耐心仔细琢磨每一句的译文，就让我很气馁，既然不愿意认真翻译，那干嘛还要翻译，很丢人，知道吧。

不自在，压力很大，迷茫，未来不知道往那里走了，想做区块链，也不知道怎么入手，怎么应用，怎么在这世上挺过各种大风大浪？？所以就开始迷了，，，