• 什么是比特币
• 概述
• 加密哈希函数
• 数字签名
• 交易记录
• 工作证明
• 交易区块链
• 货币供应
• 交易区块链的安全性

# 什么是比特币？

Bitcoin: What is it?

## 视频原文翻译

But what I wanted to do in this video is talk about what a bitcoin is in more general terms and what differentiating characteristics they have compared to other approaches. 这个视频，我想讨论普遍意义上的比特币，以及它与其他方法相比，有什么样的特点。
So for starters, bitcoin is just an electronic payment system. 从一开始，比特币只是一种电子支付系统。
By electronic payment system, I mean it’s just a vehicle, a conduit, by which two parties can transact over the internet. 所谓的电子支付系统，就是一个工具，一个管道，可以让两个人通过网络进行交易。
I call these parties Alice and Bob. 现在，有两个人，分别是爱丽丝和鲍勃。
And let’s say Alice for whatever reason wants to give money to Bob over the internet. 爱丽丝想通过网络转钱给鲍勃。
And this may be because she owes Bob money, or maybe Bob is a merchant and Alice is buying something from Bob. Or maybe Bob is a not-for-profit, and Alice is making a donation to Bob. 无论为了什么，可能是爱丽丝欠鲍勃钱；也可能鲍勃是一个商家，爱丽丝从鲍勃那里购买了一些东西；甚至，也可能鲍勃是一个公益机构，爱丽丝想做慈善捐款。
So there could be many reasons why Alice is trying to pay Bob over the internet in some capacity. 他们可以有很多种理由，总之，爱丽丝想尝试通过网络付钱给鲍勃。
Now, if Bob is willing to accept bitcoins, which are a form of electronic payments, then Alice can go ahead and send Bob some value in bitcoins. 现在，鲍勃愿意接受电子支付的方式——比特币，然后爱丽丝就可以发给鲍勃一定价值的比特币。
And really, a bitcoin transaction between Alice and Bob amounts to a specially constructed sequence of numbers that Alice will basically send over to Bob. And this will be done entirely over the internet. 实际上，爱丽丝和鲍勃之间的比特币交易，爱丽丝发送给鲍勃的是一串特殊结构的数列，并且全部的过程通过互联网完成。
These numbers will have certain mathematical properties. They make it hard for someone to really defraud the system or to conduct some type of nefarious action on the system. 这些数字，有一定的数学性质，让人们难以做违法的事情。
And the way that Alice is actually going to conduct this transaction in practice is either by installing a special piece of software, which we call a bitcoin client, or she can work with a third-party service that can handle these mechanics for her. 在实际交易中，爱丽丝可以选择自己安装一个软件——比特币系统，进行交易，也可以选择通过第三方服务，帮助她进行交易。
But in either case, either the client or the service is going to generate these numbers for Alice. 但是无论哪一种，都会生出一串数列。
And on the flip side, Bob will also typicall either have a piece of software installed or he’ll use a third-party service that will take these numbers and allow him to do something else with those numbers. 另外一方面，鲍勃也要安装一个软件或是通过第三方服务对得到的比特币进行处理。
For example, Bob can in turn buy something on his own with those numbers, or he can trade those numbers in for real money and so on and so forth. 他可以用比特币给自己买些东西，或是兑换成现金等等。
Now, one of the first questions you might have– and I kind of alluded to this earlier– is why would Bob even want to accept bitcoins in the first place? 现在，你也许有个问题，也是我之前提到过的问题——为什么鲍勃在一开始就愿意接受比特币呢？
After all, a bitcoin is just a bunch of numbers. What intrinsic value would it conceivably have? 毕竟，比特币只是一串数字。它有着什么样的内在价值？
And it turns out, quite surprisingly, that bitcoins actually have real-world value. 令人惊讶的是，实际上，比特币有现实价值。
There are more and more merchants popping up each day who accept bitcoins for transactions. 每天，有越来越多的商家愿意接受比特币交易。
There are also bitcoin exchanges, places where you can go and exchange bitcoins for more mainstream currencies. 也有比特币交易场所，在那里，你可以将比特币换作更主流的货币。
And some of exchanges include– the major one is one called Mt.Gox. And at Mt.Gox you could exchange a bitcoin for a euro or yen or dollar and so on and so forth. 主要的一个交易场所是Mt.Gox，在Mt.Gox，你可以将比特币换做欧元、日元或是美元。
Now the current price of a bitcoin, the current value of a bitcoin in US dollars as of this video, is approximately US$100 per bitcoin. 现在，一个比特币的价值大概为100美金。（PS：翻译时价为$9559.03）
That number is fluctuating. This is a new currency, and there’s going to be some fluctuation. 这是一种新货币，它的价值是波动的，也会持续波动下去。
But as people understand the currency better, the hope is that that fluctuation will decrease. 随着人们对比特币的理解，这个波动会逐渐平缓。
But I think ultimately, the thing to keep in mind is that the value of a bitcoin is going to be derived from the faith that you have in the value of what you can procure with that bitcoin. 但是我认为，归根结底，比特币的价值源自你对比特币价值的信念。
It’s just like you would for a dollar, a euro or yen. The faith that you have in that currency’s value is how you value that currency. 这就像你对一美元、一欧元或是一日元一样，你对他们的价值认知源于你的信念。
Now another question you might have is why do people even bother with bitcoins in the first place. 现在，另一个问题是，为什么人们要接受它？
Aren’t there other more standard ways? 没有其他的标准方法吗？
Why couldn’t Alice and Bob use Paypal? 为什么不用Paypal？
Why couldn’t they use a credit card number to transact? 为什么不用信用卡去交易？
Why couldn’t Alice just sent Bob an electronic check? 为什么不用电子支票？
Why not use one of these other approaches that are more well understood, that are more mainstream, that are more established? 为什么不用更主流、更容易理解、更成熟的方法呢？
Why on earth would you possibly want to mess with a good thing? 为什么将事情搞得如此复杂？
So it turns out that there are a few properties of bitcoins that are worth noting. 因此，比特币一定有某些特性值得注意。
For starters, there’s privacy. It turns out that within the bitcoin ecosystem, within the bitcoin network, people can transact without divulging who they are in the real world. 首先是关于隐私的问题。事实证明，在比特币生态中，在比特币的网络上，人们可以不泄露真实世界中的身份进行交易。
From the perspective of bitcoin, Alice’s identity is just going to be a sequence of numbers. 从比特币的角度看，爱丽丝的身份是一串数字。
And that sequence of numbers is effectively going to function like a pseudonym for Alice. 这串序列会像化名一样起作用。
And that sequence of numbers has nothing to do with your real-world identity. 不会与真实世界相关联。
Nobody needs to know this is Alice transacting. All they need to worry about is their pseudonym within the system. And this is kind of but not quite like what you would get if you bought something using cash. 没有人需要知道在交易的是爱丽丝，还是别人。他们只会担心系统内的假名。这和你用现金的感觉是不同的。
In that capacity, when you buy something using cash, then you don’t have to provide any details or proof regarding who you are in the real world. 以这种身份，当你用现金买东西的时候，你不用提供任何真实世界的身份证明。
And that’s different from, let’s say, using a credit card, where you have to provide your name and your billing address and so on. 如果是使用卡，你必须提供你的姓名和账户等等。
Or let’s say providing an electronic check, where you need to tie that electronic check, typically your bank account details. 如果是电子支票，你需要绑定电子支票，通常需要你的账户信息。
Now, I do want to also mention here that sometimes when you have a cash list or a transaction that uses cash, there is now the possibility that people might try to use these transactions for malicious purposes to buy illicit goods and services. 现在，我想说的是，当你有一个现金或是交易的账单的时候，就会有人想要利用这些交易，购买非法商品和服务。
That definitely is a risk that occurs when you provide anonymity and privacy. 这无疑是提供姓名和隐私的风险。
But there are certainly legitimate reasons why somebody might want to conduct a transaction privately and not have the whole world know what they’re transacting. 所以，这也是为什么人们想私下交易，而不想让别人知道他们在做什么。
Another property of bitcoin is that it’s open. 比特币的特性就是开放。
Literally anyone can get involved. 任何人都可以参与其中
Literally anyone who was an internet connection can make a bitcoin transaction. 任何人都可以通过互联网进行比特币交易。
And all you need to do to get started is, as I alluded to earlier, is download this special bitcoin client. 你开始要做的只是下载一个比特币的客户端。
And the bitcoin client, or for that matter you can use a service like Mt.Gox which will effectively do the same work as a client for you. 你也可以使用Mt.Gox服务，帮助你做同等的操作。
But the short of it is that anyone who has a bitcoin client or who has an account with an exchange like Mt.Gox can engage in bitcoin transactions. 但不足之处是，任何有比特币客户端的人，或是有像Mt.Gox交易所账户的人，都可以参与比特币交易。
That transaction, the details of it, the mechanics of it will be transparent to the user. 这个交易的细节、机制将会对用户透明
All the user has to worry about– all Alice needs to worry about– is how much money she has and whether she can give that money to Bob. 所有的这些用户，就像爱丽丝，他们需要担心的是她有多少钱，以及如何将这些钱转给Bob。
The actual software underneath will take care of all the underlying mechanics of making that transaction work. 软件将会处理所有的底层机制。
Now, this is different. When you think about a traditional currency like a dollar, if I want to transact something online, typically I need a bank account, I need a credit card, and so on and so forth. 现在，事情变得不一样了。当你用使用传统的货币，比如美元，如果想在网络上进行交易，需要银行账户、信用卡等等。
Then we often take it for granted that there are people out there who may not have access to a credit card, who may not have a bank account. 然后，我们想当然的认为，有些人没有信用卡，没有银行账户。
For example, in the United States alone it turns out–and I just looked this up– the number of households without a bank account, I read it, is somewhere north of about 8%. It’s pretty high. 比如，我刚刚查到的，在美国，没有银行卡的人数占8%，这是非常高的比例。
There are a lot of people out there who wouldn’t be able to conduct a traditional internet transaction, but who can conduct a transaction using bitcoin. And by the way, there are people using bitcoin all over the world. And literally it doesn’t matter where you are in the world, as long as you have an internet connection, you can start transacting bitcoins. 有很多人不能进行传统的互联网交易，但是可以进行比特币交易。世界各地的人都有人在用比特币交易，无论你在哪里，只要你有网络，就可以用比特币进行交易。
Now, another property of bitcoin that’s worth mentioning is that it’s decentralized. 比特币的另一个性质，就是分散性。
There’s no bank or centralized entity that can really control what’s happening in the bitcoin ecosystem. It’s all done in this kind of ad hoc fashion. 没有任何一个银行或是中央的实体可以操控比特币的生态。这一切，都是以这种特别的方式进行的。
And what that means is that when you do a transact–or when Alice transacts with Bob over the internet, that transaction doesn’t have to go through a third party. 这样意味着你在交易的时候，或是爱丽丝在交易的时候，不会经过第三方。
There’s no bank that gets in the way of that transaction. And that can have certain benefits as well. 没有银行将会干扰你们的交易，这是有一定好处的。
For example, that means that no one entity can directly control the money supply of bitcoins. That also means that no one entity can see your assets. Or for that matter, no one entity can reverse a transaction, which is definitely desirable for certain merchants. 比方说，任何一个实体都无法直接控制比特币的货币供应量，任何人也无法查看你的账户资产。或者，就这一点而言，没有实体可以逆转交易，这对商家来说是非常有用的。
Some merchants might not be able to conduct business online because of fraud concerns. 为了防止欺诈，有些商家无法在网上开展业务。
And if you have a system where the transactions cannot be charged back easily, then from the merchant’s perspective, they may be able to inhibit fraud and thereby that might enable their business entirely online. 如果有这样一个系统，交易很难被改变，那么从他们的角度看，他们也会能够将业务全部变为线上业务。
Now I want to point out that this last property of decentralization definitely causes concern among some people or not in bitcoin after all. 现在，我想指出分散的最后一个特性，可能有部分人或是没有人会关注的。
When you think about it, a central authority like a bank does perform an important function in the context of a traditional currency. 仔细想想，一个中心集权的，像是银行，在传统货币背景下发挥了重要作用。
For example, banks might validate currencies. They might validate transactions against fraud. Now, in bitcoin, this validation is basically done in a decentralized way by the other parties, the other nodes, in the bitcoin network. 比如，银行会验证货币。他们会确认是否为交易气站。现在，在比特币中，这种验证是基于分散在各个地方的比特币网络。
Now, the goal of the remaining videos in this series is to walk through the underlying mechanics of bitcoin transactions and really how they’re validated, even though the system is decentralized. And there are some pretty amazing techniques that are used to make all this work. So I suspect that at this point, you may have a ton of questions about bitcoin, and that’s entirely to be expected. 现在，本系列的剩余视频的目的，是了解比特币的系统机制以及它是如何进行分布式的验证的。同时，也有一些令人惊叹的科技，来完成这些工作。我认为在这点上，你会有很多问题，这是意料之中的。
Bitcoin is a very complex protocol. It has many moving parts. And I think it’s critical when you’re trying to understand something as complex and wrap your head around something as sophisticated as bitcoin, it’s important to get exposed to all the parts first so that you can ultimately get a flavor for how they fit together. 比特币是一个非常复杂的协议。它分为了很多部分。当你想尝试了解这些复杂如麻的内容时，关键的是首先要接触所有的部分，然后你才可以了解它们是如何结合在一起的。
And hopefully the other videos in this series will help you to understand these different parts and along the way address many of the questions that you might have. 也希望本系列视频将会帮助你理解这些不同部分，解决您可能遇到的某些问题。

# 概述

Bitcoin: Overview

# 加密哈希函数

Bitcoin: Cryptographic hash functions

# 数字签名

Bitcoin: Digital signatures

# 交易记录

Bitcoin: Transaction records

# 工作证明

Bitcoin: Proof of work

# 交易区块链

Bitcoin: Transaction block chains

# 货币供应

Bitcoin: The money supply

# 交易区块链的安全性

Bitcoin: The security of transaction block chains