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