of gold, or platinum, or any precious metal.

金，或鉑，或任何貴金屬製作而成

In fact, it’s not the kind of coin you can hold in your hand or stick in a piggy bank.

事實上，它不是你可以拿在手中 或是存在小豬撲滿裡的那種硬幣

It’s a digital currency, which means it only exists electronically.

它是一種數位貨幣，這意味著 它只有電子形式的存在

I’m talking about bitcoin.

我正是在說比特幣

Bitcoin doesn’t work like most money.

比特幣運作方式不像常見的錢幣

It isn’t attached to a state or government, so it doesn’t have a central issuing authority

它不是依附在國家或政府 因此它不具有中心化的發放單位

or regulatory body.

或監管機構

Basically, that means there’s no organization deciding when to make more bitcoins, figuring

基本上，這意味著沒有組織能夠 決定發行更多的比特幣或計畫

out how many to produce, keeping track of where they are, or investigating fraud.

要發行的數量，也無法追蹤比特幣的流向 或調查欺詐行為

So how does bitcoin work as a currency, or have any value at all?

那麼，身為電子貨幣的Bitcoin 到底是怎麼運作和賦予自身的價值呢？

Well, bitcoin wouldn’t exist without a whole network of people and a little thing called

簡單說，比特幣需要一大群在網路上的人們和

cryptography.

密碼學

In fact, it’s sometimes described as the world’s first cryptocurrency.

事實上，比特幣有時被描述為 世界上第一個加密貨幣

And here’s how it works.

以下是它的運作原理

Bitcoin is a fully digital currency, and you can exchange bitcoins between computers in

比特幣是一種全數位化貨幣 你可在以電腦之間交換比特幣

a worldwide peer-to-peer network.

透過全世界的點對點網絡

The whole point of most peer-to-peer networks is sharing stuff, like letting people make

大多數的點對點網絡是用來 分享檔案，像是讓人們

copies of super legal music or movies to download.

下載"超級合法"的音樂或電影

If bitcoin is a digital currency, what’s stopping you from making a bunch of counterfeit

如果比特幣是一種數位貨幣 有什麼可以阻止你複製出一堆假幣

copies and becoming fabulously wealthy?

然後變得超級富有？

Well, unlike a mp3 or a video file, a bitcoin isn’t a string of data that can be duplicated.

老實說，這不像是MP3音樂或影片檔 比特幣並一個可以被複製的一段資料

A bitcoin is actually an entry on a huge, global ledger called the blockchain, for reasons

比特幣實際存在於一本分佈於全世界 的巨大帳本稱為區塊鏈，其原因

we’ll get to in a minute.

我們會在一分鐘後談到這點

The blockchain records every bitcoin transaction that has ever happened.

區塊鏈會記錄每一筆已經發生過的比特幣交易資訊。

And, as of late 2016, the complete ledger is about 107 gigabytes of data.

截至2016年年底，完整的帳本約有 約107 GB的數據

So when you send someone bitcoins, it’s not like you’re sending them a bunch of

所以，當你發送給某人一些比特幣時 你並不是送給了他們一些

files.

檔案

Instead, you’re basically writing the exchange down on that big ledger – something like,

相反的，你其實是寫了一筆紀錄 在那個大帳本 - 類似:

“Michael sends Hank 5 bitcoins.”

“邁克爾·漢克發送了5個比特幣”

Now, maybe you’re thinking, “But, wait.

現在也許你在想，“但是，等等

You said bitcoin doesn’t have a central authority to keep track of everything!”

你剛說過比特幣不具有中央化的機構 在掌管這些資訊！"

Even though the blockchain is a central record, there’s no official group of people who

但儘管區塊鏈是一個中心化的記錄 並沒有所謂官方的單位

update the ledger and keep track of everybody’s money like a bank does – it’s decentralized.

向銀行一樣更新帳本和追蹤每個人的錢 - 這是所謂的的分散化

In fact, anybody can volunteer to keep the blockchain up to date with all the new transactions.

事實上，任何人都可以保留一份 區塊鏈上所有即時新增的交易資料

And a ton of people do.

而且有不計其數的人在做這件事

It all works because there are lots of people keeping track of the same thing, to make sure

比特幣之所以能運作正是因為有很多人 一直在確認帳本上的資訊，以確保

all transactions are accurate.

所有交易是正確無誤的

Like, imagine you’re playing a game of poker with some pals, but none of you have poker

這就像，想像一下你正在與 一些好朋友玩撲克牌遊戲，但沒有人

chips, and you left your cash at home.

帶來籌碼 而且現金都放在家裡

There’s no money on the table, so a few of you get out some notebooks, and start writing

大家都沒有錢，所以 你們幾個拿出了筆記本，並開始紀錄

down who bets how much, who wins, and who loses.

誰下注多少，誰贏，誰輸

You don’t completely trust anyone else, so everyone keeps their ledgers separately.

你不能完全信任對方， 所以每個人都分別紀錄它們的帳本

And at the end of every hand, you all compare what you’ve written down.

而在每局結束時，大家拿出各自的帳本出來比較

That way, if someone makes a mistake, or tries to cheat and snag some extra money for themselves,

這樣一來，如果有人記錯帳，或嘗試 欺騙而暗中佔有不屬於自己的錢

that discrepancy is caught.

這種差異就會被抓到

After a couple hands, you might fill up a page of your notebook with notes about the

又過了幾局之後，你可能已經寫滿一整頁

money movement.

資金的移動資訊

You can think of each page as a “block of transactions.”

你可以把每一頁想像成為交易清單的“區塊“

Eventually, your notebook will have pages and pages of information – a chain of those

最終，你的筆記本將包含了一頁一頁的交易資訊 - 也就是一條連續鏈狀的

blocks.

區塊

Hence: blockchain.

因此稱作：區塊鏈

Now, if thousands of people are separately maintaining the bitcoin blockchain, how are

現在，如果成千上萬的人分別 持有比特幣的區塊鏈副本，如何

all the ledgers kept in sync?

讓所有帳本保持同步？

To stick with our poker analogy: think of the entire bitcoin peer-to-peer network as

回想一下我們的撲克牌比喻：試著把 整個比特幣的點對點網絡想像為

a really huge poker table with millions of people.

數以百萬計的人坐在一張非常巨大的撲克桌

Some are just exchanging money, but lots of volunteers are keeping ledgers.

有些人只是換錢，但很多 志願者只是保管著帳本

So when you want to send or receive money, you have to announce it to everyone at the

所以當你要發送或接收錢的時候， 你必須把這些資訊公佈在帳本上給大家知道

table, so the people keeping track can update their ledgers.

所以大家就可以即時更新他們的帳本

So for every transaction, you’re announcing a couple of things to the bitcoin network:

因此在每一筆交易，你必須宣布 幾件事情到比特幣網絡上：

your account number, the account number of the person you’re sending bitcoins to, and

您的帳戶號碼，要接收比特幣的帳戶號碼，和

how many bitcoins you want to send.

多少個比特幣要發送。

And all of the users who are keeping copies of the blockchain will add your transaction

然後所有保管著區塊鏈的人會在 上面增加一筆您發送的交易

to the current block.

到當下的區塊中

Having a bunch of people keep track of transactions seems like a pretty good security measure.

有一堆人持續在關注著交易 似乎是一個相當不錯的安全措施

But if all it takes to send bitcoins is a couple of account numbers, that seems like

但是，如果發送比特幣時都需要同時透漏帳號號碼

it might be a security problem.

這可能會成為一個安全性問題。

It’s a huge problem with regular money – just think about all the ways criminals try to

這在常見的錢幣運作上是個大問題 - 想想犯罪分子總是試圖

steal other people’s credit card information.

盜取他人的信用卡資訊

And with bitcoin, there’s no central bank to notice anything weird going on to shut

而回到比特幣，沒有中央銀行在 隨時把關可疑的詐騙交易

down fraud, like if it looked like suddenly you spent your entire life savings on beef

像是你突然就把你畢生的積蓄花在一條

jerky.

牛肉乾上

So what’s stopping Hank from pretending he’s me and just sending himself all of

所以要怎麼防止漢克假裝用我的名義把

my bitcoins?

我的比特幣都轉出？

Bitcoins are kept pretty safe thanks to cryptography, which is why it’s considered a cryptocurrency.

這就要感謝密碼學將比特幣保護得很好 也就是為什麼它被認為是加密貨幣

Specifically, bitcoin stays secure because of keys, which are basically chunks of information

具體來說，比特幣能夠保證安全是因為 有著所謂的金鑰，它們基本上是一段資訊

that can be used to make mathematical guarantees about messages, like “hey, this is really

可用於數學方法驗證的訊息 譬如“嘿，這

from me!”

真的是從我本人送出的訊息！”

When you create an account on the bitcoin network, which you might have heard called

當你對創建一個比特幣帳戶，你可能聽說過所謂的

a “wallet,” that account is linked to two unique keys: a private key, and a public

一個“錢包”，該帳戶連接著 兩把獨特的金鑰：一把私鑰

key.

一把公鑰

In this case, the private key can take some data and basically mark it, also known as

在此情況下，私鑰可以加上一些資料 並將其標記，這動作也被稱為

signing it, so that other people can verify those signatures later if they want.

簽署，以便其他人後續可以驗證這些簽名

So let’s say I want to send a message to the network that says, “Michael sends 3

因此，如果當我想將消息發送到網絡上時 譬如:“邁克爾·發送3個

bitcoins to Olivia.”

比特幣給奧利維亞“。

I sign that message using my private key, which only I have access to, and nobody else

此時我用我的私鑰簽署這份消息 只有我有能夠解密他，而且也沒有人

can replicate.

可以複製這份消息。

Then, I send that signed message out to the bitcoin network, and everyone can use my public

然後，我發送這份簽署後的訊息到 比特幣的網絡，每個人都可以使用我的公鑰

key to make sure my signature checks out.

確保我的簽署送出。

That way, everyone keeping track of all the bitcoin trading knows to add my transaction

這樣的話，每個有在關注比特幣交易訊息的人 都會知道要把我發布的交易

to their copy of the blockchain.

加入他們的區塊鏈副本。

In other words, if the public key works, that’s proof that the message was signed by my private

換句話說，如果公鑰能夠成功解密 這就證明該消息是由我個人用私鑰簽署

key and is something I wanted to send.

的訊息，確實是我本人發布的訊息

Unlike a handwritten signature, or a credit card number, this proof of identity isn’t

不同於手寫的簽名，或是信用卡號碼 這種身分識別的方法

something that can be faked by a scam artist.

無法被詐騙者所偽造

The “who” part of each transaction is obviously important, to make sure the right

每筆交易中是“誰”的部分顯然是最重要的部分 這才能確保正確的

people are swapping bitcoins.

雙方可以交換比特幣。

But the “when” matters, as well.

但關於“何時”的問題也很重要。

If you had a thousand dollars in your bank account, for example, and tried to buy two

如果你的銀行帳戶有一千元，並試圖買

things for a thousand dollars each, the bank would honor the first purchase and deny the

兩份各為一千元的物品 銀行會接受第一份的交易並拒絕

second one.

第二份交易。

If the bank didn’t do that, you’d be able to spend the same money multiple times.

如果銀行沒有做到這一點，你就可以 重複花費同樣的錢。

Which … might sound awesome, but it’s also terrible.

這......聽起來真棒，但它也很糟糕。

A financial system can’t work like that, because no one would get paid.

這樣的金融系統不可能正常運作 因為沒有人會拿得到錢

So if I only have enough money to pay Olivia or Hank, but I try to pay them both, there’s

所以如果我僅擁有可以支付奧利維亞或漢克其中一位的錢，但我試圖同時支付給他們兩個的話

a check built into the bitcoin system.

比特幣系統有一套檢查機制。

Both the bitcoin network and your wallet automatically check your previous transactions to make sure

無論是比特幣網絡或你的錢包都會自動 檢查您以前的交易，以確保

you have enough bitcoins to send in the first place.

你有足夠的比特幣的可以支付

But there’s another problem that might happen with timing:

但有時可能會發生另一個時間上的問題

Because lots of people are keeping copies of the blockchain all over the world, network

因為在世界各地都有人保管區塊鏈副本，而網絡

delays mean that you won’t always receive the transaction requests in the same order.

的延遲時間意味著每個人 不會總是以一樣的順序收到發布的交易資訊

So now you’ve got a bunch of people with a bunch of slightly different blocks to pick

於是現在你有了一堆人和 一堆有點差異的區塊資訊要選擇

from, but none of them are necessarily wrong.

但它們都不一定是錯的

Okay, bitcoin.

好吧，比特幣

How do you solve that problem?

你要怎麼解決這個問題？

Turns out, it’s by actually solving problems.

答案是，真的來"解決問題"

Math problems.

數學問題

To add a block of transactions to the chain, each person maintaining a ledger has to solve

要將交易資訊添加到區塊鏈上時 每一位區塊鏈維護者需要去解決

a special kind of math problem created by a cryptographic hash function.

一種由雜湊函數製造的特殊數學問題

A hash function is an algorithm that takes an input of any size, and turns it into an

雜湊函數是一種演算法，輸入一份 任何大小的資料進後可以變成一份

output with a fixed size.

固定大小的資料輸出

For example, let’s say you had this string of numbers as your input

例如，假設你輸入這個字串

And our example hash function says to add all of the numbers together.

而我們這邊舉例的雜湊函數說要 把所有的數字加在一起

So, in this case, the output would be 10.

因此，在這種情況下，輸出將會是10

What makes hash functions really good for cryptography is that when you’re given an

雜湊函數在密碼學上的強項是，當你給予

input, it’s really easy to find the output.

輸入時，它很容易就可以算得出結果。

But it’s really hard to take an output and figure out the original input.

但是要從結果回推回去 原始輸入的資料卻是相當困難

Even in this super simple example, there are lots of strings of numbers that add up to

即使在剛剛超級簡單的例子 就有非常多的數字加起來可以是

10.

10

The only way to figure out that the input was ‘1-2-3-4’ is to just guess until you

唯一能找出原始輸入的方法就是 '1-2-3-4'的一直猜測，直到你

get it right.

猜到對的那組數字。

Now, the hash function that bitcoin uses is called SHA256, which stands for Secure Hash

現在，比特幣使用的雜湊函數是 所謂的SHA256，這代表安全雜湊

Algorithm 256-bit.

演算法有256位元的長度。

And it was originally developed by the United States National Security Agency.

它最初是由美國國家安全局開發

Computers that were specifically designed to solve SHA256 hash problems take, on average,

解SHA256 函數問題的電腦被設計在需要平均

about ten minutes to guess the solution to each one.

約十分鐘可以猜測到一個解答

That means they’re churning through billions and billions of guesses before they get it

這意味著他們需要經過上百萬次的猜測後 才有辦法猜中對的答案

right.

00:06:54,370 --> 00:06:58,710 誰第一個解決了雜湊函數的問題 就可以在區塊鏈上增加區塊

Whoever solves the hash first gets to add the next block of transactions to the blockchain,

然後就生成一個新的雜湊數學問題需要解決

which then generates a new math problem that needs to be solved.

如果數個人幾乎同時篹出解答，則網路將選出一個

If multiple people make blocks at roughly the same time, then the network picks one

持續保持增加區塊而成為最長的的鏈 也就是最值得信賴的區塊鏈

to keep building upon, which becomes the longest, and most trusted chain.

而在存在於那些其他分支區塊鏈的交易資訊必須被放回交易池

And any transactions in those alternate branches of the chain get put back into a pool to be

等待再被加入後續的區塊鏈中

added onto later blocks.

許多志願者花費數千美元 在特殊的電腦來解決這些SHA256問題

These volunteers spend thousands of dollars on special computers built to solve SHA256

且需要付出非常高的電費來保持這些機器運作

problems, and run their electricity bills up sky high to keep those machines running.

但這是為了什麼？

But why?

是什麼讓他們願意出來維護區塊鏈?

What do they get out of maintaining the blockchain?

難道僅僅是社群服務？

Is it just community service?

其實，比特幣系統有內建獎勵機制

Well, bitcoin actually has a built-in system to reward them.

如今，每一次算出解答 而得以添加新區塊到區塊鏈上時，12塊半的

Today, every time you win the race to add a block to the blockchain, 12 and a half new

新比特幣將被無中生有地 創造並授予那位算出解答的比特幣帳戶

bitcoins are created out of thin air, and awarded to your account.

事實上，你可能早已經知道這些 比特幣帳本維護者的別名：礦工

In fact, you might know the bitcoin ledger-keepers by another name: miners.

這是因為一直努力保持區塊鏈不斷更新區塊的人們就像是對著雜湊函數揮動著十字鎬

That’s because keeping the blockchain updated is like swinging a proverbial pickaxe at those

希望能挖到一塊大金礦而致富的礦工

hash problems, hoping to strike it rich.

當比特幣系統在2009年首次建立時 他們其實沒有什麼真正的價值

When bitcoins were first created in 2009, they didn’t really have any perceived value.

數十比特幣當時也只和一堆便士差不多

Tens of bitcoins would have been worth the same as a bunch of pennies.

如今2016年11月10日 1比特幣可兌換708美元

As of November 10th, 2016, though, one bitcoin is worth 708 US dollars.

所以，12塊半比特幣相當等同於8850美元

So 12 and a half bitcoins are worth 8,850 dollars.

這是一個非常大的改變

That’s a nice chunk of change!

每一個比特幣都是被創造來獎勵礦工

Every single bitcoin that exists was created to reward a bitcoin miner.

除了礦工每增加一個新的區塊獲得的高額獎勵 礦工也可以

Besides the big payout when they add a new block of transactions, miners are also essentially

在將每一筆交易放入區塊中時領取些微的交易手續費

tipped a very small amount for each transaction they add to the ledger.

另外值得一提的是，每隔21萬 區塊產生時，每次新區塊產生硬幣的數量

It’s also worth noting that every 210,000 blocks, the number of coins generated when

會降至一半

a new block is added goes down by half.

所以一開始是50比特幣的獎勵 下降到25，然後12塊半。

So what started as a reward of 50 bitcoins decreased to 25, then 12 and a half.

過幾年後就會剩6塊的獎勵，並繼續下降

It’ll only be around 6 bitcoins in a couple more years, and keep decreasing.

最終，區塊裡將會有越來越多的交易 使得礦工還是可以從

Eventually, there will be so many transactions in a block, that it’ll still be worthwhile

交易的手續費中獲得報酬

for miners to mostly be paid in tips.

根據目前的預測，最後一枚比特幣 - 可能會是第兩百一十萬枚

According to current projections, the last bitcoin – probably around the 21 millionth

的硬幣 - 且將在2140年被產生

coin – will be mined in the year 2140.

比特幣的這種數量減少的設計其實是在仿造

This decreasing number of bitcoins is actually modelled off the rate at which things like

從土被挖出來的黃金

gold are dug out of the earth.

而這個想法是，限制比特幣的產出 將使其價值隨著時間而增加

And the idea is that keeping the supply of bitcoins limited will raise their value over

所以

time.

投資在比特幣是一個好主意嗎？

So, is investing in bitcoin a good idea?

這......不是SciShow會探討的問題

Now that’s... not really a SciShow kind of question.

比特幣依然不夠穩定且帶有些實驗性質

Bitcoin is still volatile, and experimental.

很多人喜歡它 但也很多人認為這是注定要失敗的

A lot of people love it, and a lot of people think it’s doomed to fail.

我們認為這是一個有趣的想法 它使我們好奇密碼未來學可能

We just think it’s an interesting idea, and it makes us wonder what cryptography might

為我們帶來什麼樣的變化

do for us next.

感謝您收看這集的SciShow 這集由Patreon贊助商所贊助

Thanks for watching this episode of SciShow, brought to you by our patrons on Patreon.

如果你想幫助支持這個節目 快去看看 patreon.com/scishow

If you want to help support this show, just go to patreon.com/scishow.

而且不要忘了訂閱youtube.com/scishow

And don’t forget to go to youtube.com/scishow and subscribe!