极简入门：什么是区块链？

区块的第一个元素是数据。区块中所保存的数据与区块链的类型有关。例如，比特币区块链中的区块保存了相关的交易信息，包括卖家，买家，以及交易比特币的数量。

The first element of the block is data. The data stored in the block is related to the type of block chain. For example, blocks in the bitcoin block chain contain relevant transaction information, including sellers, buyers, and the number of bitcoins traded.

区块的第二个元素是哈希值。每个区块包含了一个哈希值，这个哈希值是唯一的，它用来标识一个区块和它所包含的所有内容。一旦某个区块被创建，它的哈希值就相对应的被计算出来了。改变区块中的某些内容会使得哈希值改变。所以换句话说：当你想要检测区块中内容的改变时，哈希值对你就很有帮助。如果一个区块的指纹改变了，那它就再也不是之前的区块了。

The second element of the block is the Hashi value. Each block contains a Hashi value, which is the only one that identifies a block and everything it contains. Once a block is created, its Hashi value is calculated. Changes in some of its contents change the Hashi value. So, in other words, if you want to detect changes in the content of a block, the Hashi value is very helpful to you. If the fingerprint of a block changes, it is no longer the previous block.

区块的第三个元素是前一个区块的哈希值。这个元素使得区块之间可以形成链接，并且能够使得区块链十分的安全。

The third element of the block is the Hashi value of the previous block. The element

举个例子假设我们有一条区块链包含3个区块。如图所示，每个区块包含了一个自己的哈希值以及前一个区块的哈希值。3 号区块指向 2 号区块，2 号区块又指向 1 号区块。但是 1 号区块有点特殊，它不能指向前一个区块，因为它是第一个区块。我们把1号区块叫做创世区块。

For example, let's assume that we have a chain of blocks containing three blocks. As the figure shows, each block contains its own Hashi value and the Hashi value of the previous block. Block No. 3 points to block No. 2 and block No. 2 points to block No. 1. But block No. 1 is a little special, and it does not point forward to a block because it is the first block. We call block No. 1 a creative block.

那么，现在我们假设你篡改了第二个区块。这将导致第二个区块的哈希值改变，那么 3 号区块存储的数据就是错误的、非法的。而 3 号区块存储的数据一旦是非法的，后面的区块也一定是非法的。

Now, let's assume that you tampered with the second block. This will lead to a change in the Hashi value of the second block, so that the data stored in block 3 is wrong and illegal. And once the data stored in block 3 are illegal, the rest must be illegal.

所以如果一个人想要篡改区块链中任何一个区块，它必须修改这个区块以及这个区块之后的所有区块。这将是一个很繁重的任务。

So if a person wants to tamper with any of the blocks in the block chain, it has to modify the block and all the blocks that follow it. This will be a huge task.

但是，仅仅使用哈希值的方法不足以防止用户篡改区块。因为现在的计算机运算速度已经足够强大，并且能够每秒计算成千上万的哈希值。你完全可以篡改一个区块并且重新计算其他的区块的哈希值，这样就使得你的区块再次变得合法。

However, the use of Hashi values alone is not enough to prevent users from tampering with blocks. Because the computer is already strong enough to calculate thousands of Hashi values per second. You can completely alter one block and recalculate the other, making your block legal again.

所以为了减少这种风险，区块链还采用了一种技术叫做工作量证明。这是一种减缓新区块创建过程的机制。

So in order to reduce this risk, the block chain also uses a technology called workload certification, which is a mechanism to slow down the process of creating new blocks.

在比特币区块链中，大概需要花费10分钟来完成所要求的工作量证明，并且添加一个新的区块到区块链中。这个机制使得区块链的篡改更加困难，因为一旦你篡改了一个区块，你需要重新计算所有后续的区块的工作量证明。

In the Bitcoin block chain, it takes about 10 minutes to complete the required workload certification and to add a new block to the block chain. This mechanism makes it more difficult to tamper with the block chain, because once you have tampered with a block, you need to recalculate all subsequent blocks.

所以区块链技术的安全性主要来自于哈希值以及工作量证明机制。

The security of block chain technology is mainly derived from Hashi values and the workload certification mechanism.

但是，区块链还有一种机制来保护自身的安全性，那就是分布式。相对于用一个中心化的实体来管理区块链网络，区块链采用的是一种peer-to-peer网络，并且所有人都可以加入。当有人加入这个网络时，他就会得到整个区块链的复制。这个人就可以以此来验证是否所有的区块还是合法未篡改的。

But there is also a mechanism in the block chain to protect its security, that is, distribution. Rather than managing the block chain network with a centralized entity, the block chain is a peer-to-peer network that is accessible to all. When someone joins the network, he gets a copy of the whole block chain. This is how the person can verify whether all the blocks are legal and unaltered.

那么接下来我们就来看看，当某人创建了一个新的区块时，会发生哪些改变这个新的区块会被发送给网络上的所有人。每个人再验证这个区块以确保这个区块没有被篡改过。如果所有的东西都被检验正确之后，那么每个人就都会把这块新的区块加到自己的区块链上。

So let's see, when someone creates a new block, what happens to this new block is sent to everyone on the network. Everyone checks the block to make sure it's not tampered with. If everything is tested correctly, everyone adds the new block to their own chain.

我们可以称之为，网络上的所有人达成了「共识」。他们认同网络中那些区块是合法的，哪些是不合法的。那些被篡改过的区块将会被网络上的其他用户拒绝。所以，要成功篡改一个区块链，你需要篡改区块链上的所有区块，重新完成每个区块的工作量证明，并且控制区块链网络中超过50%的用户。

We can call it the "consensus" of all the people on the network. They agree that the blocks in the network are legal and what are illegal. The altered blocks will be rejected by the other users on the network. So, in order to successfully tamper with a block chain, you need to tamper with all the blocks in the block chain, complete the workload proof of each block, and control more than 50% of the users in the block chain network.

只有这样，你篡改的区块才会被所有人承认。但实际上，这基本上是不可能做得到的！

Only then will the blocks that you have tampered with be recognized by everyone. But, in fact, this is essentially impossible!

看到这里，你可以尝试着回答下面几个问题：

Here, you can try to answer the following questions:

• 什么是区块链？

区块链由区块和链组成，每个区块由数据、哈希值、前一个区块的哈希值三个部分组成。

The block chain consists of blocks and chains, each consisting of three parts of the data, the Hashi value and the Hashi value of the previous block.

• 区块链为什么需要挖矿（工作量证明）？

通过挖矿（工作量证明）可以避免坏人的恶意破解，增加其破解的时间成本和经济成本。

Mining (proven workload) avoids malicious break-ups and increases the time and economic costs of break-ups.

• 区块链为什么很安全？

区块链安全是因为其不可更改特性和分布式特性。即如果要修改区块链中的数据，你需要完成下面两件事情：第一，你需要计算出修改区块之后的所有区块的哈希值，这需要非常庞大的计算能力。第二，你需要让超过50%的区块链用户同意你的修改。同时完成上面两件事情基本上是不可能的，所以区块链很安全。