加密货币是什么？
（转载自阮一峰老师博客，目的只是自己收藏新技术知识，并非用于任何商业用途）去年，比特币暴涨，其他币也像雨后春笋一样冒出来，已经有1000多种了。
Last year, Bitcoin surged, and other coins came out like the spring of the rain, and there were more than 1,000.
很多人都在问，加密货币（cryptocurrency）的时代，真的来临了吗？将来会不会人类不再使用美元、人民币，改用加密货币？那么多品种，我应该使用哪一种币？要不要现在就去投资一些？
Many ask, is it true that the age of cryptography has come? Will mankind stop using the dollar, the renminbi, instead of the encrypted currency? So many varieties, which currency should I use? Do you want to invest now?
这些问题的答案，我也想知道，就花了很多时间查阅资料、研究协议。前两周发表的《区块链入门教程》和《比特币入门教程》，是我的学习心得。但是，那两篇教程主要介绍基本概念、探讨协议的可行性，没回答一个根本的问题：加密货币到底是什么？
I would also like to know the answers to these questions. 下面就是我对这个问题的思考。阅读之前，如果你已经了解区块链和比特币，那很好；如果不了解，也没关系，本文不涉及技术，只讨论最基本的原理。 Here's what I'm thinking about. Before you read it, it's good if you already know about block chains and bitcoin; if you don't know, it's okay, it's not about technology, it's about basic principles. 一、钱是什么？ I. What's the money? 我们都知道，人民币是钱，美元是钱，金银财宝是钱。我问一个问题，它们为什么能成为钱？ We all know that the renminbi is money, the dollar is money, and the treasure is money. Let me ask you a question. Why can they be money? 你可能回答，因为它们有价值，或者是价值的代表。但是，有价值的东西多了，为什么只有这些品种成为了钱？ You might answer because they're valuable, or because they're a representative of value. But there's more to it. Why is it that these varieties are the only ones that make money? 答案很容易想到，因为人们普遍相信（认同）它们的价值，其他东西的价值难以得到普通认同，无法成为钱。比如，邮票的价值就没有普遍的认同，除了集邮爱好者，其他地方都不能当钱用。一般来说，认同的人越多，这种钱的通用性就越高。 The answer is easy to imagine, because there is a general belief in their value, that the value of other things is difficult to obtain in common and cannot become money. For example, there is no universal recognition of the value of stamps, which cannot be used for money other than by collectors. In general, the greater the number of people who agree, the greater the generality of the money. 我曾经去俄罗斯旅行，当地货币是卢布。可是，一旦离开俄国，没人相信它的购买力，所以卢布离开俄国就没用了。相反，全世界人民都相信美元的价值，所以全世界都能用。我用美元付账的时候，我发现那些俄国人都很满意。 I traveled to Russia, and the local currency was the rubles. But once I left Russia, no one believed in its purchasing power, so the rubles left Russia. On the contrary, people all over the world believed in the value of the dollar, so the world could use it. When I paid the dollar, I found those Russians satisfied. 所以，钱的本质，或者说货币的本质，就是它的可信性。它必须使人们相信，它是有价值的，然后才能成为钱，才能被收藏和支付。 So, the essence of money, or money, is its credibility. It has to make people believe that it's worth it before it becomes money, and it can be collected and paid for. 二、可信性 II. Credibility 为什么钱必须是可信的？因为对方必须相信它的价值，否则你没法支付出去。那么，接下来的问题就是，可信的东西是否就是钱？ Why does money have to be credible? Because the other side has to believe in its value, otherwise you can't pay it. So the next question is, is that what is credible is money? 我的回答是 Yes。一样东西能否成为钱，只取决于人们是否相信它的价值，至于它是不是真的有价值，根本不重要。 My answer is yes. Whether or not something becomes money depends on whether people believe in its value or not, it doesn't matter at all. 如果马云在一张纸条上写"这张纸条价值10000元"，下面签了他的名，并且附上防伪标记。你说这纸条是钱吗？我跟你保证，这就是钱，你用来支付，人们都会接受，马云等同于发行了一种新的纸币。 If Maun wrote "This note is worth $10,000" on a note, and signed his name below, with a security mark. Do you think this note is money? I promise you, it's money, you pay it, people will accept that Maun is equivalent to issuing a new banknote. 比特币也是如此，它是什么，其实不太重要。重要的是，它必须保证自己是可信的，这样才能让足够的人相信它的价值，然后才能成为钱。 And so is Bitcoin, what it is, it's not really important. The important thing is that it has to be credible so that enough people believe in its value and then become money. 三、比特币的可信性 III. The credibility of Bitcoin 比特币要解决的核心问题，就是创造一种可信的数字凭证。由于这种凭证可信，所以能够当做货币。 The core issue to be addressed by Bitcoin is the creation of a credible digital document. can be used as a currency because of its credibility. 比特币的技术基础是加密学，因为只有加密学才能保证它的可信性。一旦加密被破解，它就没法当作货币了。这也是这一类数字凭证被称为"加密货币"的原因。 Bitcoin's technical foundation is encryption, because only encryption can guarantee its credibility. Once encryption is broken, it can't be used as a currency. That's why this type of digital document is called "encrypted currency." 技术人员对比特币感兴趣，还有一个重要原因。任何需要可靠的数字凭证的场合，也许都可以用到这种技术。 There's also an important reason why technicians are interested in bitcoin. This technology may be used in any case where reliable digital evidence is needed. 四、比特币的特点 IV. Characteristics of Bitcoin 比特币有三个特点，就是因为做到了这三点，所以它可信，能够当作钱。 Bitcoin has three characteristics: it's credible and can be used as money because it's done these three things. 首先，它不会被（轻易）偷走。或者反过来说，它使得你无法去偷别人，你只能花你自己的钱。因为必须要有别人的私钥，才能取出他的钱。正常情况下，你拿不到别人的私钥。 First, it will not be stolen. or, conversely, it will make it impossible for you to steal, and you will only spend your own money. Because someone else's private key is necessary to take out his money. Normally, you won't have someone else's private key. 其次，它无法伪造。每一个比特币都能追溯来源，而所有比特币都来源于矿工获得的奖励。矿工只有新建区块，才能获得奖励，这是很难的事情，所以无法伪造比特币。 Next, it cannot be faked. Every bitcoin can be traced, and all bitcoins come from the reward given to the miners. Miners can only get the reward if they build new blocks. It's hard, so it's not possible to falsify bitcoins. 最后，它无法大批生成。原因跟上一条一样，比特币的发行速度是稳定的，现在每10分钟新增12.5个，然后每四年减半，最终停止增长。因此不会像纸币那样，政府滥发导致通货膨胀。 Finally, it cannot be produced in large quantities. For reasons like the one that keeps pace with the distribution of Bitcoin, the speed of distribution is stable, with 12.5 new copies every 10 minutes now, then halved every four years, and eventually stopped growth. So, like banknotes, the government does not cause inflation. 五、比特币有实体吗？ V. Does Bitcoin have an entity? 由于后面要提到的原因，比特币不可能拥有实体，没法做到"从口袋里掏出一个币"这种场景，交易都必须通过互联网完成。 For the reasons to be mentioned later, Bitcoin could not have an entity and could not do the scene of "drawing out a coin from a pocket" and the transaction had to be done via the Internet. 你可能会说，钱都有实体，怎么可能存在无形的钱呢？答案正好相反，钱就应该是无形的，那些实体的钱其实是对物质材料的浪费，由于技术不够发达，不得不做成实体。 You might say that money is real, how can there be intangible money? The answer is, on the contrary, that money should be invisible, that money of those entities is a waste of material material, and that because of the lack of technology, it has to be physical. 我小时候买东西，都必须用现金，否则没法证明，自己拥有购买力。只有通过实体的钱，才能保证对方确实收到了钱。如果银行业发达，就不用现金了，可以使用银行卡。支付的时候，对方抄一下银行卡号码，查询银行"这个账户有钱吗"。银行回答有钱，OK，成交。 When I was a kid, I had to buy things in cash, or I couldn't prove that I had the purchasing power. It was only through real money that the other side actually received the money. If the banking sector was well-developed, it could use a bank card. When I paid, the other side took a copy of the bank card number and asked the bank if it had any money. The bank said it had money, OK, deal. 但是，互联网使得实体的银行卡也不需要了。如果存在一个开放的中央记账系统，任何人都可以查询，你把钱划到老板的账户，老板查询一下，发现收到了，交易自动成交，整个过程都是无形的，还需要什么银行卡呢？ The Internet, however, makes the entity’s bank card unnecessary. If there is an open central record-keeping system, anyone can access it, you transfer the money to the boss’s account, the boss checks it, finds it, the transaction is automatically done, the whole process is invisible, and what kind of bank card is needed? 这个中央记账系统已经实现了，就叫做区块链。 This central accounting system has been implemented and is known as the block chain. 六、区块链的作用 VI. The role of block chains 区块链就是一个数据库，记载了所有的交易，用作中央记账系统。 The block chain is a database that records all transactions and is used as a central accounting system. 每笔交易的核心，就是一句话，比如"张三向李四转移了1个比特币"。为了证明这句话可信，张三为它加上了数字签名。任何人都可以用张三的公钥，证明这确实是张三本人的行为。另一方面，其他人无法伪造张三的数字签名，所以不可能伪造这笔交易。 At the heart of every transaction is a sentence, like "Jan San transferred a bitcoin to Lee". To prove the credibility of this statement, Zhang San added a digital signature to it. Anyone can prove that this is really a three-person act with a three-key. On the other hand, others cannot forge a three-digit signature, so it is impossible to falsify the transaction. 矿工们收到这句话，首先验证数字签名的可信性，然后验证张三确实拥有这些比特币（每一笔交易都有上一笔交易的编号，用来查询比特币的来源）。验证通过以后，就着手把这句话写入区块链了。一旦写入区块链，所有人就都可以查询到，因此这笔比特币就被认为，从张三转移到了李四。 The miners received this statement, first to verify the credibility of the digital signature and then to verify that Zhang San did own the bitcoin (each transaction had the number of the last transaction to search for the bitcoin's origin). After the validation, the sentence was written into the block chain. Once it was written into the block chain, it was accessible to all, so the bitcoin was considered to have been transferred from Zhang San to Li Qian. 区块链的作用就是把这句话永久保存下来了，让任何人都可以查看，并且任何人（包括张三本人在内）都无法再修改了。 The effect of the block chain is to keep the phrase permanently accessible to anyone, and no one (including Zhang San) can change it. 货币是什么？其实就是这句话。这一句话就完成了一次支付。我们平时用人民币支付，其实只是用纸币表达这条信息。如果每个人都可以实时写入/读取中央记账系统（区块链），那么完全可以不携带货币。 That's what the money is? That's what it says. That's a payout. We usually pay in renminbi, but it's just a note. If everyone can write/read the central accounting system (block chain) in real time, it's completely free of money. 七、双重支出 VII. DIFFERENT EXPENDITURES 前面说过，交易不可能被伪造。但是，由于每一笔交易都是一串二进制信号，因此可能被复制。举例来说，"张三向李四转移了1个比特币"这句话，可能被其他人复制，也可能被张三自己复制，提交到区块链。 As was said earlier, transactions cannot be forged. But, since each transaction is a binary signal, it can be copied. For example, the phrase "Sang San transferred a bitcoin to Lee" may be copied by others or copied by Zhang San himself and submitted to the block chain. 如果这句话被两次写入区块链，就意味着张三可以把同一笔钱花掉两次。但是，第二次写入的时候，查询区块链可以发现张三已经把这笔钱花掉了，从而认定这是不合法的交易，不能写入区块链。因此，复制交易是不可能的。 If this sentence is written twice in a block chain, it means that Zhang San can spend the same money twice. But, when the second one is written, searching the block chain can find that Zhang San has already spent the money, thus concluding that it is an illegal transaction and cannot be written into the block chain. It is therefore impossible to duplicate the transaction. 比较麻烦的是另一种情况，就是张三把同一笔钱付给两个人。他先向区块链提交一个交易"张三向李四转移了1个比特币"，然后又提交了另一个交易"张三向王五转移了1个比特币"。这两个交易都可能被认为是真实的交易，从而进入区块链。因此，必须有办法防止出现这种情况。 The other trouble is that Zhang San paid the same money to two people. first submitted a transaction to the block chain, "Sang San transferred a bitcoin to Lee", and then another transaction, "Sang San transferred a bitcoin to Wang 5". Both transactions may be considered real and thus enter the block chain. So there must be a way to prevent this from happening. 情况一：同一个矿工收到了这两个交易。那么他会察觉到，它们不可能同时成立，因此选择其中的一笔写入区块链。 Case one: The same miner receives these two deals. Then he realizes that they cannot be established at the same time, so he chooses one of them to be written into the block chain. 情况二：矿工 A 收到了第一笔交易，矿工 B 收到了第二笔交易，他们各自都会认定这是合法的交易，分别把这两笔交易写入了两个区块，这时区块链就出现了分叉。 Case two: Miner A received the first transaction, Miner B received the second transaction, each of which was deemed to be legal and the two transactions were written into two blocks, and the chain of blocks was split. 比特币协议规定，分叉点之后最先达到6个区块的那个分支，被认定为正式的区块链，其他分支都将被放弃。由于区块的生成速度由计算能力决定，所以到底哪一笔交易最后会被写入区块链，完全由它所在的分支能吸引多少计算能力决定。隐藏的逻辑是，如果大多数人（计算能力）选择相信某一笔交易，那么它就应该是真的。 The Bitcoin agreement provides that the branch that reaches the first six blocks after the forkpoint is identified as a formal block chain, and that all the other branches will be abandoned. Since the speed at which the block is generated is determined by the ability to calculate, which transaction will eventually be written into the block chain, entirely by the ability of the branch in which it is located. The hidden logic of is that if most people (the ability to calculate) choose to believe in a particular transaction, it should be true. 综上所述，双重支出不可能发生。因为中央记账系统总有办法发现，你把同一笔钱花了两遍。但是，这也说明了比特币的一个代价，就是交易不能实时确认，必须等待至少一个小时 In summary, double spending is unlikely to happen. Because there is always a way in the central accounting system that you spend the same money twice. But, one of the costs of Bitcoin is that the transaction cannot be confirmed in real time and must wait for at least an hour.
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