Name: 有沒有想過比特幣（和其他加密貨幣）實際工作？ (Ever wonder how Bitcoin (and other cryptocurrencies) actually work?)
Uploaded: 2017-10-19T18:44:18.000Z
Duration: 26 min 21 s

程度副詞

it's a fully digital currency with no government to issue it;

它是一種完全數字化的貨幣，沒有政府來發行它。

and that no banks need to manage accounts and verify transactions;

而銀行不需要管理賬戶和核實交易。

and also that no one really knows who invented it.

也沒有人真正知道是誰發明的。

And yet, many people don't know the answer to this question, at least not in full.

然而，很多人都不知道這個問題的答案，至少不知道完整的答案。

and to make sure that the technical details underlying the answer actually feel motivated,

並確保回答的基礎技術細節實際感受到動力。

what we're going to do is walk through step by step

我們要做的是通過一步步走過。

how you might have invented your own version of Bitcoin.

你是如何發明你自己版本的比特幣的。

We'll start with you keeping track of payments with your friends using a communal ledger.

我們將從您使用公共賬本與您的朋友一起跟蹤付款開始。

And then, as you start to trust your friends and the world around you less and less,

然後，當你開始越來越不信任你的朋友和周圍的世界。

and if you're clever enough to bring in a few ideas from cryptography

如果你足夠聰明，可以從密碼學中引入一些想法

what you end up with is what's called a "cryptocurrency".

你最終得到的是所謂的 "加密貨幣"。

You see, Bitcoin is just the first implemented example of a cryptocurrency.

你看，比特幣只是加密貨幣的第一個實施例。

And now, there are thousands more on exchanges with traditional currencies.

而現在，在與傳統貨幣的交流中，還有成千上萬的人。

Walking the path of inventing your own can help to set the foundations

走自己的發明之路，可以幫助打下基礎

for understanding some of the more recent players in the game

用於瞭解一些最近在遊戲中的玩家。

and recognizing when and why there's room for different design choices.

並認識到何時和為何有不同的設計選擇空間。

In fact, one of the reasons I chose this topic is that

事實上，我選擇這個題目的原因之一是

in the last year, there's been a huge amount of attention and investment

在過去的一年裡，有大量的關注和投資。

and, well, honestly hype directed at these currencies.

以及，說實話，針對這些貨幣的炒作。

And I'm not going to comment or speculate on the current or future exchange rates,

而我也不會去評論或猜測當前或未來的匯率。

anyone looking to buy a cryptocurrency should really know what it is.

任何想買加密貨幣的人都應該真正知道它是什麼。

And I don't just mean in terms of analogies with vague connections to gold mining,

我不僅僅是指與金礦開採有模糊聯繫的類比。

I mean an actual direct description of what the computers are doing

我的意思是直接描述計算機正在做的事情。

when we send, receive and create cryptocurrencies.

當我們發送、接收和創建加密貨幣時。

One thing worth stressing, by the way, is that

順便說一句，有一點值得強調，那就是......。

even though you and I are going to dig into the details here,

you don't actually need to know those details if you just want to use the cryptocurrency,

如果你只是想使用加密貨幣，你其實並不需要知道這些細節。

just like you don't need to know the details of what happens under the hood when you swipe a credit card.

就像你不需要知道刷卡時的細節一樣。

Like any digital payment, there're lots of user-friendly applications that

就像任何數字支付一樣，有很多用戶友好的應用程序，這

let you just send and receive the currencies without thinking about what's going on.

讓您只需發送和接收貨幣，而無需考慮發生了什麼。

The difference is that the backbone underlying this

所不同的是，這個基礎的骨幹。

is not a bank that verifies transactions.

Instead, it's a clever system of decentralized trust-less verification

相反，它是一個聰明的去中心化的無信任驗證系統。

based on some of the math born in cryptography.

基於密碼學中誕生的一些數學。

I want you to actually set aside the thought of cryptocurrencies and all that just for a few minutes.

我希望你能真正放下對加密貨幣和所有這些的想法，就幾分鐘。

We're going to begin the story with something more down-to-earth: ledgers and digital signatures.

我們要從更平實的東西開始講起：賬本和數字簽名。

If you and your friends exchange money pretty frequently,

如果你和你的朋友經常交換錢。

you know, paying your share of the dinner bill and such,

你知道，支付你的晚餐賬單等份額。

it can be inconvenient to exchange cash all the time.

所以，你可以保留一個公共賬本

that records all of the payments that you intend to make some point in the future.

它記錄了你在未來某個時間點上打算支付的所有款項。

你知道，愛麗絲付給鮑勃20美元。

鮑勃付給查理40美元，這樣的事情。

This ledger is going to be something public and accessible to everyone,

這個賬本將是公開的東西，每個人都可以使用。

like a website, where anyone can go and just add newlines.

就像一個網站，任何人都可以去那裡，只需添加新行。

And let's say that at the end of every month,

you all go together, look at the list of transactions and settle up.

你們一起去，看看交易清單，然後結算。

If you spent more than you received, you put that money in the pot;

如果你花的錢比你收到的多，你就把這些錢放進鍋裡。

and if you received more than you spent, you take that money out.

如果你收到的錢比你花的多，你就把這些錢拿出來。

So the protocol for being part of this very simple system might look like this:

是以，成為這個非常簡單的系統的一部分的協議可能是這樣的。

and at the end of every month you all get together and settle up.

每個月末，你們都會聚在一起解決。

Now, one problem with a public ledger like this is that anyone can add a line,

現在，這樣的公共賬本有一個問題，就是任何人都可以增加一行。

so what's to prevent Bob from going in writing "Alice pays Bob $100" without Alice approving?

所以，什麼是防止鮑勃去寫 "愛麗絲支付鮑勃100美元 "沒有愛麗絲準許？

How are we supposed to trust that all of these transactions

Well, this is where the first bit of cryptography comes in: digital signatures.

好吧，這就是密碼學的第一點：數字簽名。

the idea here is that Alice should be able to add something next to that transaction

這裡的想法是，Alice應該能夠在該事務旁邊添加一些東西。

that proves that she has seen it and that she's approved of it.

這證明她已經看過了，而且她也認可了。

And it should be infeasible for anyone else to forge that signature.

而其他人要偽造這個簽名應該是不可能的。

At first, it might seem like a digital signature shouldn't even be possible.

乍一看，似乎數字簽名根本就不應該存在。

I mean, whatever data makes up that signature can just be read and copied by a computer,

我的意思是，不管是什麼數據組成的簽名，都可以被電腦讀取和複製。

Well, the way this works is that everyone generates what's called a "public key - private key pair",

好吧，工作方式是每個人都會生成一個所謂的 "公鑰-私鑰對"。

each of which looks like some string of bits.

每一個看起來都像一些比特的字符串。

The "private key" is sometimes also called a "secret key",

so that we can abbreviate it as "sk", while abbreviating the public key is "pk".

這樣我們就可以將其縮寫為 "sk"，而將公鑰縮寫為 "pk"。

Now as the name suggests, this secret key is something you want to keep to yourself.

現在顧名思義，這把祕鑰是你想留給自己的東西。

In the real world, your handwritten signature looks the same no matter what document you're signing.

在現實世界中，無論你簽署什麼文件，你的手寫簽名看起來都是一樣的。

But a digital signature is actually much stronger,

because it changes for different messages.

It looks like some string of ones and zeros, commonly something like 256 bits;

它看起來像一些1和0的字符串，通常是256位的東西。

completely changes what the signature on that message should look like.

完全改變了該消息上的簽名應該是什麼樣子。

producing a signature involves a function that depends both on the message itself and on your private key.

產生簽名涉及到一個函數，這個函數既取決於資訊本身，也取決於你的私鑰。

The private key ensures that only you can produce that signature,

私鑰可以確保只有你能產生該簽名。

and the fact that it depends on the message

means that no one can just copy one of your signatures and then forge it on another message.

意味著沒有人可以複製你的一個簽名，然後在另一條資訊上偽造。

Hand-in-hand with this is a second function used to verify that a signature is valid.

與此相配合的是第二個用於驗證簽名是否有效的函數。

And this is where the public key comes into play.

to indicate if this was a signature produced by the private key

來表明這是否是由私鑰產生的簽名

associated with the public key that you're using for verification.

I won't go into the details of how exactly both these functions work,

這兩個功能的具體工作原理我就不多說了。

but the idea is that it should be completely infeasible to find a valid signature

但這個想法是，它應該是完全不可能找到一個有效的簽名。

Specifically, there's no strategy better than just guessing and checking random signatures,

具體來說，沒有什麼策略比只猜測和檢查隨機簽名更好。

which you can check using the public key that everyone knows.

你可以用大家都知道的公鑰來檢查。

Now think about how many signatures there are with a length of 256 bits,

現在想想有多少個長度為256位的簽名。

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有沒有想過比特幣（和其他加密貨幣）實際工作？ (Ever wonder how Bitcoin (and other cryptocurrencies) actually work?)

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