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揭秘比特币工作原理 – 译学馆
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揭秘比特币工作原理

Bitcoin: How Cryptocurrencies Work

现在 有一种价值数百美元的货币 但它不是
Say there’s a coin that’s currently worth hundreds of U.S. dollars, but it’s not made
由黄金 白金或者其他贵重金属制成的
of gold, or platinum, or any precious metal.
事实上 它不是那种你能抓在手里或是放进储蓄罐的硬币
In fact, it’s not the kind of coin you can hold in your hand or stick in a piggy bank.
它是一种数字货币 只以电子的形式存在
It’s a digital currency, which means it only exists electronically.
我说的是比特币
I’m talking about bitcoin.
比特币不像其他货币
Bitcoin doesn’t work like most money.
它不附属于国家或政府 所以它没有中央发行机构
It isn’t attached to a state or government, so it doesn’t have a central issuing authority
或监察机构
or regulatory body.
基本上这就意味着没有哪个机构来能够决定什么时候制造更多的比特币
Basically, that means there’s no organization deciding when to make more bitcoins, figuring
制造多少 记录它们在哪儿 或是调查诈骗
out how many to produce, keeping track of where they are, or investigating fraud.
所以比特币是如何作为一种货币运行的呢 它们有价值吗?
So how does bitcoin work as a currency, or have any value at all?
没有网络和密码 比特币就不会
Well, bitcoin wouldn’t exist without a whole network of people and a little thing called
存在
cryptography.
事实上 有时它被认为是世界上第一种加密货币
In fact, it’s sometimes described as the world’s first cryptocurrency.
接下来会说明是它如何运作的
And here’s how it works.
比特币完全是数字货币 你可以在全球对等网络中
Bitcoin is a fully digital currency, and you can exchange bitcoins between computers in
兑换比特币
a worldwide peer-to-peer network.
大多数对等网络的主要目的是共享 比如让人们
The whole point of most peer-to-peer networks is sharing stuff, like letting people make
拷贝正版音乐或是下载电影
copies of super legal music or movies to download.
如果比特币是数字货币 怎么阻止你伪造赝品
If bitcoin is a digital currency, what’s stopping you from making a bunch of counterfeit
并且借此发财呢?
copies and becoming fabulously wealthy?
不像mp3或者视频文件 一个比特币不是可复写的一行数据
Well, unlike a mp3 or a video file, a bitcoin isn’t a string of data that can be duplicated.
比特币其实是被称作区块链的巨大的全球的账簿的入口
A bitcoin is actually an entry on a huge, global ledger called the blockchain, for reasons
接下来一分钟我们会给出解释
we’ll get to in a minute.
每一次比特币交易都会被区块链记录
The blockchain records every bitcoin transaction that has ever happened.
直到2016年末 整个账户有大约107千兆字节的数据
And, as of late 2016, the complete ledger is about 107 gigabytes of data.
所以当你给某个人比特币的时候 并不像是你给他们一堆
So when you send someone bitcoins, it’s not like you’re sending them a bunch of
文件
files.
而是你在账簿上写下交易——比如说
Instead, you’re basically writing the exchange down on that big ledger – something like,
迈克尔给汉克5个比特币
“Michael sends Hank 5 bitcoins.”
现在 也许你正在想 “但是 等等
Now, maybe you’re thinking, “But, wait.
你说过比特币没有记录一切的中央机构!”
You said bitcoin doesn’t have a central authority to keep track of everything!”
即使区块链有中央记录的功能 但没有官方人员
Even though the blockchain is a central record, there’s no official group of people who
更新账簿并且像银行那样追踪每个人的货币去向——它被分散了
update the ledger and keep track of everybody’s money like a bank does – it’s decentralized.
事实上 每个人都能更新区块链中出现的新交易
In fact, anybody can volunteer to keep the blockchain up to date with all the new transactions.
许多人这么做了
And a ton of people do.
它运作着是因为有许多人做了相同的记录
It all works because there are lots of people keeping track of the same thing, to make sure
以保证所有的交易都是精确的
all transactions are accurate.
比如 想象你正在和朋友们玩扑克 但是没有人有筹码
Like, imagine you’re playing a game of poker with some pals, but none of you have poker
你们的现金都在家里
chips, and you left your cash at home.
桌子上没有现金 所以你们中有几个人拿出了一些笔记本
There’s no money on the table, so a few of you get out some notebooks, and start writing
开始写下谁下了多少赌注 谁赢了 谁输了
down who bets how much, who wins, and who loses.
每个人都不信任其他人 所以每个人分开保管他们的账簿
You don’t completely trust anyone else, so everyone keeps their ledgers separately.
每局游戏结束后 你们比较各自所写下的看是否一致
And at the end of every hand, you all compare what you’ve written down.
这样的话 如果有人犯错 或是试图作弊得到额外的钱
That way, if someone makes a mistake, or tries to cheat and snag some extra money for themselves,
记录不一致一下就被发现了
that discrepancy is caught.
几局之后 关于资金流动的记录 你也许写满了
After a couple hands, you might fill up a page of your notebook with notes about the
一页纸
money movement.
你可以把每一页看作一个“交易区块”
You can think of each page as a “block of transactions.”
最终 你的笔记本会有数页信息——相当于一连串的
Eventually, your notebook will have pages and pages of information – a chain of those
区块
blocks.
也就是:区块链
Hence: blockchain.
现在 如果成千上万人分散地维护比特币区块链
Now, if thousands of people are separately maintaining the bitcoin blockchain, how are
所有的账簿是如何保持同步的呢?
all the ledgers kept in sync?
继续我们的扑克类比:把整个比特币对等网络看作
To stick with our poker analogy: think of the entire bitcoin peer-to-peer network as
一个有着数百万人的无比巨大的扑克桌
a really huge poker table with millions of people.
虽然只是一些人兑换货币 但是许多人都在记录账簿
Some are just exchanging money, but lots of volunteers are keeping ledgers.
所以当你想给或收钱 你需要告知桌上的每个人
So when you want to send or receive money, you have to announce it to everyone at the
这样记录者们能够更新他们的账簿
table, so the people keeping track can update their ledgers.
每次交易 你要告诉比特币网络一些东西
So for every transaction, you’re announcing a couple of things to the bitcoin network:
你的账号 交易对象的账号 以及
your account number, the account number of the person you’re sending bitcoins to, and
比特币交易数量
how many bitcoins you want to send.
所有保存区块链副本的用户会把你的交易记录加到
And all of the users who are keeping copies of the blockchain will add your transaction
现有的区块
to the current block.
一群人记录交易看起来像是一个很好的安全措施
Having a bunch of people keep track of transactions seems like a pretty good security measure.
但是如果交易比特币只要发送几个账号 那看起来
But if all it takes to send bitcoins is a couple of account numbers, that seems like
也许是一个安全问题
it might be a security problem.
对于普通货币是个很大的问题——试想不法分子
It’s a huge problem with regular money – just think about all the ways criminals try to
试图盗取他人信用卡信息各种方式
steal other people’s credit card information.
对于比特币 没有中央银行监察异状阻止犯罪
And with bitcoin, there’s no central bank to notice anything weird going on to shut
比如你突然花光毕生积蓄买
down fraud, like if it looked like suddenly you spent your entire life savings on beef
牛肉干
jerky.
因此什么能阻止汉克假扮我 并把我所有的比特币
So what’s stopping Hank from pretending he’s me and just sending himself all of
给他自己呢?
my bitcoins?
因为密码学 比特币是相当安全的 这也是为什么它被认为是一种加密货币
Bitcoins are kept pretty safe thanks to cryptography, which is why it’s considered a cryptocurrency.
具体来说 比特币能保持安全是依靠组块信息形成的密钥
Specifically, bitcoin stays secure because of keys, which are basically chunks of information
能被用来加密消息 如“嘿 这真的
that can be used to make mathematical guarantees about messages, like “hey, this is really
是我!”
from me!”
当你在比特币网络建立一个账户 也许你已经听过这个账户被叫作
When you create an account on the bitcoin network, which you might have heard called
“钱包” 那个账户链接两个独特的密钥:一个是私钥 一个
a “wallet,” that account is linked to two unique keys: a private key, and a public
公钥
key.
私钥能存储一些数据并且做好标记 也就是常说的
In this case, the private key can take some data and basically mark it, also known as
签名 这样其他人有需要的话就可以识别那些签名
signing it, so that other people can verify those signatures later if they want.
比方说我想发送这么一个消息到比特币网络 “迈克尔给
So let’s say I want to send a message to the network that says, “Michael sends 3
奥利维亚3个比特币”
bitcoins to Olivia.”
我用只有我能使用其他人无法复制的私钥
I sign that message using my private key, which only I have access to, and nobody else
签名这条消息
can replicate.
然后我把签名消息发送到比特币网络 每个人都能用我的公钥
Then, I send that signed message out to the bitcoin network, and everyone can use my public
验证我的签名
key to make sure my signature checks out.
这样的话 所有记录比特币交易的人把我的交易加到
That way, everyone keeping track of all the bitcoin trading knows to add my transaction
他们的区块链副本上
to their copy of the blockchain.
也就是说 如果公钥生效了 就证明那条消息用我的私钥签名的
In other words, if the public key works, that’s proof that the message was signed by my private
并且是我想发送的消息
key and is something I wanted to send.
不像手写的签名 或是信用卡卡号 这个身份证明不能
Unlike a handwritten signature, or a credit card number, this proof of identity isn’t
被专职骗子伪造
something that can be faked by a scam artist.
在每次交易过程中确认比特币交易对象
The “who” part of each transaction is obviously important, to make sure the right
显然是很重要的
people are swapping bitcoins.
但是“何时”交易也很重要
But the “when” matters, as well.
举个例子 如果你的银行账户里有一千美元 然后想要买两个
If you had a thousand dollars in your bank account, for example, and tried to buy two
售价一千美元的东西 银行会通过第一笔交易
things for a thousand dollars each, the bank would honor the first purchase and deny the
拒绝第二笔
second one.
如果银行没有那么做 你一笔钱能用很多次
If the bank didn’t do that, you’d be able to spend the same money multiple times.
听上去很妙 但也很可怕
Which … might sound awesome, but it’s also terrible.
金融系统不能像那样运作 因为这样的话没人会得到回报
A financial system can’t work like that, because no one would get paid.
因此如果我只有支付给奥利维亚或者汉克中任意一位的钱 但是我试图支付给他们两人
So if I only have enough money to pay Olivia or Hank, but I try to pay them both, there’s
比特币系统内部有个核查系统
a check built into the bitcoin system.
首先比特币网络和你的钱包会自动检查你之前的交易以确保
Both the bitcoin network and your wallet automatically check your previous transactions to make sure
你有足够的比特币
you have enough bitcoins to send in the first place.
但随着时间也许会有另一个问题:
But there’s another problem that might happen with timing:
因为世界上许多人都保存区块链的副本
Because lots of people are keeping copies of the blockchain all over the world, network
网络延时意味着你不会以相同顺序收到交易请求
delays mean that you won’t always receive the transaction requests in the same order.
现在你要从一群有着略微不同区块的人中做出选择
So now you’ve got a bunch of people with a bunch of slightly different blocks to pick
但是他们都不一定是错的
from, but none of them are necessarily wrong.
那么 比特币
Okay, bitcoin.
怎么解决这个问题呢?
How do you solve that problem?
结果是 事实上就是解决问题:
Turns out, it’s by actually solving problems.
解决数学问题
Math problems.
为了在区块链上增加交易区块 每个维护账户的人需要解决
To add a block of transactions to the chain, each person maintaining a ledger has to solve
一种特殊的由加密哈希函数形成的数学问题
a special kind of math problem created by a cryptographic hash function.
哈希函数是将一种将任意输入值转化为固定输出值
A hash function is an algorithm that takes an input of any size, and turns it into an
的算法
output with a fixed size.
例如说 你输入一串数字
For example, let’s say you had this string of numbers as your input
我们的示例哈希函数把所有的数字加到一起
And our example hash function says to add all of the numbers together.
所以 这样的话 输出结果就是10
So, in this case, the output would be 10.
哈希函数很适合密码学是因为有了输入值之后
What makes hash functions really good for cryptography is that when you’re given an
很容易找到相应的输出值
input, it’s really easy to find the output.
但是很难用一个输出来计算出原始的输入
But it’s really hard to take an output and figure out the original input.
即使是在这个超简单的例子中 也有很多串数字可以加起来得到
Even in this super simple example, there are lots of strings of numbers that add up to
10
10.
唯一找出输入是“1-2-3-4”的办法是猜直到你
The only way to figure out that the input was ‘1-2-3-4’ is to just guess until you
得到正确答案
get it right.
如今 比特币使用的哈希函数被叫做SHA256 代表
Now, the hash function that bitcoin uses is called SHA256, which stands for Secure Hash
安全散哈希算法哈希值大小为256位
Algorithm 256-bit.
它最初是由美国国家安全局开发的
And it was originally developed by the United States National Security Agency.
特别设计用于解决SHA256哈希问题的电脑平均花费
Computers that were specifically designed to solve SHA256 hash problems take, on average,
大约十分钟推测每个哈希问题的答案
about ten minutes to guess the solution to each one.
那意味着他们从数十亿个推测中得到
That means they’re churning through billions and billions of guesses before they get it
正确答案
right.
无论谁先解答了哈希问题把下一个交易区块加到区块链中
Whoever solves the hash first gets to add the next block of transactions to the blockchain,
一个新的需要解决的问题就会产生
which then generates a new math problem that needs to be solved.
如果许多人大致在同一时间制作区块 那么网络会选择一个
If multiple people make blocks at roughly the same time, then the network picks one
以保持区块链地持续建立 逐渐形成最长最可靠的链
to keep building upon, which becomes the longest, and most trusted chain.
没被选择的区块链分支上的所有交易会放回库中
And any transactions in those alternate branches of the chain get put back into a pool to be
加入之后的区块
added onto later blocks.
这些志愿者花了成千上万美元在用来解决SHA256问题的电脑上
These volunteers spend thousands of dollars on special computers built to solve SHA256
花高额电费来保持这些机器运行
problems, and run their electricity bills up sky high to keep those machines running.
但是为什么呢?
But why?
维护区块链他们得到了什么呢?
What do they get out of maintaining the blockchain?
只是社区服务?
Is it just community service?
比特币有个内部系统会回报他们
Well, bitcoin actually has a built-in system to reward them.
现在 每次你成功把一个区块加到区块链中 就会凭空产生12.5个新比特币
Today, every time you win the race to add a block to the blockchain, 12 and a half new
并且奖励进你的账户
bitcoins are created out of thin air, and awarded to your account.
事实上 你也许知道比特币账簿保管人的另一个名字:矿工
In fact, you might know the bitcoin ledger-keepers by another name: miners.
这是因为保持区块链的更新就像在哈希问题中挥动十字鹤嘴锄
That’s because keeping the blockchain updated is like swinging a proverbial pickaxe at those
希望发现丰富的矿藏
hash problems, hoping to strike it rich.
当2009年比特币刚被创造时 他们本来没有任何价值
When bitcoins were first created in 2009, they didn’t really have any perceived value.
几十个比特币等价于一堆便士
Tens of bitcoins would have been worth the same as a bunch of pennies.
然而到了2016年11月10日 一个比特币价值708美元
As of November 10th, 2016, though, one bitcoin is worth 708 US dollars.
所以12.5比特币价值8850美元
So 12 and a half bitcoins are worth 8,850 dollars.
变化真是很大
That’s a nice chunk of change!
每一个现有的比特币被创造来奖励一个比特币矿工
Every single bitcoin that exists was created to reward a bitcoin miner.
除了巨额支出 当他们增加新区块的交易 矿工们基本上
Besides the big payout when they add a new block of transactions, miners are also essentially
每次都能从加入账簿的交易上收获一小笔小费
tipped a very small amount for each transaction they add to the ledger.
值得注意的是每产生21万区块后 增加一个新的区块 比特币的数目
It’s also worth noting that every 210,000 blocks, the number of coins generated when
减少一半
a new block is added goes down by half.
所以一开始奖励50比特币 然后降到25 然后降到12.5
So what started as a reward of 50 bitcoins decreased to 25, then 12 and a half.
几年后将会只有6比特币 并且持续下降
It’ll only be around 6 bitcoins in a couple more years, and keep decreasing.
最终 一个区块里有足够多的交易 仍然值得矿工们
Eventually, there will be so many transactions in a block, that it’ll still be worthwhile
去赚取小费
for miners to mostly be paid in tips.
根据现在的规划 最后的比特币——大约是第2100万个
According to current projections, the last bitcoin – probably around the 21 millionth
比特币——会在2140年被开采出来
coin – will be mined in the year 2140.
比特币数目减少就如同
This decreasing number of bitcoins is actually modelled off the rate at which things like
从地球挖出的金子
gold are dug out of the earth.
所以比特币的限制供给将会随时间推移提升它们的
And the idea is that keeping the supply of bitcoins limited will raise their value over
价值
time.
所以 投资比特币是个好主意吗?
So, is investing in bitcoin a good idea?
这就不是科学秀能解答的问题了
Now that’s… not really a SciShow kind of question.
比特币依然不稳定并且是试验性的
Bitcoin is still volatile, and experimental.
很多人爱它 也有很多人认为它注定失败
A lot of people love it, and a lot of people think it’s doomed to fail.
我们只是觉得这很有趣让并且它让我们知道密码学接下来
We just think it’s an interesting idea, and it makes us wonder what cryptography might
能给我们带来什么
do for us next.
感谢观看本期科学秀节目本期内容由Patron上的支持者提供
Thanks for watching this episode of SciShow, brought to you by our patrons on Patreon.
如果你想支持科学秀 请上网站patreon.com/scishow
If you want to help support this show, just go to patreon.com/scishow.
不要忘了去youtube.com/scishow 订阅哦
And don’t forget to go to youtube.com/scishow and subscribe!

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比特币这种数字货币是什么,它是如何运作的,它有什么价值,安全性如何,让我们一起了解下吧!

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