But what is a blockchain?

但什麼是區塊鏈？

How do they work, what problems do they solve and how can they be used?

它們是如何工作的，解決什麼問題的？ 以及如何使用它們？

Like the name indicates, a blockchain is a chain of blocks that contains information.

就像名字所示，區塊鏈是一種 包含資訊的區塊鏈。

This technique was originally described in 1991 by a group of researchers and was originally

這項技術最初描述於 1991年由一組研究人員提出，最初是

intended to timestamp digital documents so that it’s not possible to backdate them

旨在對數字文件進行時間標記，以便 不可能回溯它們的日期

or to tamper with them.

或對其進行篡改。

Almost like a notary.

幾乎像一個公證員。

However it went by mostly unused until it was adapted by Satoshi Nakamoto in 2009 to

然而，它基本上沒有被使用，直到它 在2009年由中本聰改編為

create the digital cryptocurrency Bitcoin.

創造了數字加密貨幣比特幣。

A blockchain is a distributed ledger that is completely open to anyone.

區塊鏈是一種分佈式賬本，它可以 是完全對任何人開放的。

They have an interesting property: once some data has been recorded inside a blockchain,

它們有一個有趣的特性：一旦一些 數據已經被記錄在區塊鏈裡面。

it becomes very difficult to change it.

就很難改變它。

So how does that work?

那麼，這又是怎麼做到的呢？

Well, let’s take a closer look at a block.

好吧，我們來仔細看看一個區塊。

Each block contains some data, the hash of the block and the hash of the previous block.

每個塊都包含一些數據，哈希值為 塊和前一個塊的哈希值。

The data that is stored inside a block depends on the type of blockchain.

塊中存儲的數據取決於 在區塊鏈的類型上。

The Bitcoin blockchain for example stores the details about a transaction in here, such

比如比特幣區塊鏈存儲的是 交易的細節在這裡，如

as the sender, receiver and amount of coins.

作為發件人、收件人和幣的數量。

A block also has a hash.

一個區塊也有一個哈希。

You can compare a hash to a fingerprint.

你可以將哈希值與指紋進行比較。

It identifies a block and all of its contents and it's always unique, just as a fingerprint.

它可以識別一個塊和它的所有內容。 而且它總是獨一無二的，就像指紋一樣。

Once a block is created, it’s hash is being calculated.

一旦一個區塊被創建，它的哈希值就會被。 計算的。

Changing something inside the block will cause the hash to change.

改變塊內的一些東西會導致 的哈希值來改變。

So in other words: hashes are very useful when you want to detect changes to blocks.

所以換句話說：哈希是非常有用的。 當你想檢測塊的變化時。

If the fingerprint of a block changes, it no longer is the same block.

如果一個區塊的指紋發生了變化，它就會 不再是同一個區塊。

The third element inside each block is the hash of the previous block.

每個區塊內的第三個元素是 前一個區塊的哈希值。

This effectively creates a chain of blocks and it’s this technique that makes a blockchain

這就有效地形成了一個區塊鏈 而正是這種技術，使得區塊鏈中的

so secure.

如此安全。

Let's take an example.

我們舉個例子。

Here we have a chain of 3 blocks.

這裡我們有一個由3個區塊組成的鏈條。

As you can see, each block has a hash and the hash of the previous block.

如你所見，每個區塊都有一個哈希值和 前一個區塊的哈希值。

So block number 3 points to block number 2 and number 2 points to number 1.

所以第3塊指向第2塊 而2號則指向1號。

Now the first block is a bit special, it cannot point to previous blocks because it's the

現在，第一個區塊有點特殊，它不能 指向以前的塊，因為它是

first one.

第一個。

We call this the genesis block.

我們把這叫做元神塊。

Now let's say that you tamper with the second block.

現在我們假設你篡改了第二個 塊。

This causes the hash of the block to change as well.

這將導致該塊的哈希值發生變化 也是。

In turn that will make block 3 and all following blocks invalid because they no longer store

反過來，這將使第3塊和所有後續的 塊無效，因為它們不再存儲

a valid hash of the previous block.

前一個區塊的有效哈希值。

So changing a single block will make all following blocks invalid.

是以，改變一個區塊將使下面所有的 塊無效。

But using hashes is not enough to prevent tampering.

但使用哈希值並不足以防止 篡改。

Computers these days are very fast and can calculate hundreds of thousands of hashes

現在的電腦速度非常快，可以 計算數十萬次的哈希值

per second.

為第二。

You could effectively tamper with a block and recalculate all the hashes of other blocks

你可以有效地篡改塊 並重新計算其他塊的所有哈希值。

to make your blockchain valid again.

以使你的區塊鏈再次有效。

So to mitigate this, blockchains have something called proof-of-work.

所以為了緩解這種情況，區塊鏈有一些 稱為工作證明。

It's a mechanism that slows down the creation of new blocks.

這是一種減緩創造的機制 的新區塊。

In Bitcoins case: it takes about 10 minutes to calculate the required proof-of-work and

以比特幣為例：大約需要10分鐘時間 以計算所需的工作證明和

add a new block to the chain.

在鏈上添加一個新的塊。

This mechanism makes it very hard to tamper with the blocks, because if you tamper with

這種機制使其很難被篡改。 塊，因為如果你篡改。

1 block, you'll need to recalculate the proof-of-work for all the following blocks.

1塊，你需要重新計算工作證明。 以下所有區塊：

So the security of a blockchain comes from its creative use of hashing and the proof-of-work

所以區塊鏈的安全性來自於 它創造性地使用了散列和工作證明。

mechanism.

機制。

But there is one more way that blockchains secure themselves and that's by being distributed.

但還有一種方式，就是區塊鏈 確保自己的安全，那就是通過被分配。

Instead of using a central entity to manage the chain, blockchains use a peer-to-peer

而不是使用一箇中央實體來管理 鏈，區塊鏈使用的是點對點。

network and anyone is allowed to join.

網絡，任何人都可以加入。

When someone joins this network, he gets the full copy of the blockchain.

當有人加入這個網絡時，他得到的是 區塊鏈的完整副本。

The node can use this to verify that everything is still in order.

節點可以用這個來驗證所有的東西。 仍在有序進行。

Now let's see what happens when someone creates a new block.

現在讓我們看看當有人創建了 一個新的區塊。

That new block is send to everyone on the network.

這個新的區塊被髮送到每個人在 網絡。

Each node then verifies the block to make sure that it hasn't been tampered with.

然後，每個節點都會驗證該區塊，以使 確保它沒有被篡改。

If everything checks out, each node adds this block to their own blockchain.

如果一切正常，每個節點都會添加這個 塊到自己的區塊鏈。

All the nodes in this network create consensus.

這個網絡中的所有節點都會產生共識。

They agree about what blocks are valid and which aren't.

他們同意哪些區塊是有效的和 哪些不是。

Blocks that are tampered with will be rejected by other nodes in the network.

被篡改的區塊將被拒絕。 由網絡中的其他節點。

So to successfully tamper with a blockchain you'll need to tamper with all blocks on the

所以要想成功篡改區塊鏈 你需要篡改所有的區塊在

chain, redo the proof-of-work for each block and take control of more than 50% of the peer-to-peer

鏈，為每個區塊重新做工作證明。 並控制了50%以上的點對點。

network.

網絡。

Only then will your tampered block become accepted by everyone else.

只有這樣，你的篡改區塊才會變成。 被大家接受。

This is almost impossible to do!

這幾乎是不可能做到的！

Blockchains are also constantly evolving.

區塊鏈也在不斷髮展。

One of the more recent developments is the creation of smart contracts.

最近的發展之一是 智能合約的創建。

These contracts are simple programs that are stored on the blockchain and can be used to

這些合同是簡單的程序，是 存儲在區塊鏈上，並可用於?

automatically exchange coins based on certain conditions.

自動換幣 條件：

More on smart contracts in a later video.

更多關於智能合約的內容，在後面的視頻中會有介紹。

The creation of blockchain technology peaked a lot of people’s interest.

區塊鏈技術的產生達到了頂峰 很多人的興趣。

Soon, others realized that the technology could be used for other things like storing

很快，其他人意識到，該技術 可以用來做其他事情，比如存儲

medical records, creating a digital notary or even collecting taxes.

醫療記錄，創建數字公證 甚至收稅。

So now you know what a blockchain is, how it works on basic level and what problems

那麼現在你知道什麼是區塊鏈了吧，如何做到的？ 它的基本工作原理和問題是什麼

it solves.

它解決了。

Want to learn how you can implement a simple blockchain with Javascript?

想了解如何實現一個簡單的 用Javascript實現區塊鏈？

Then checkout this video here.

那就在這裡看看這個視頻吧。

And as always: thank you very much for watching.

並一如既往地表示：非常感謝您的觀看。