北京大学肖臻老师《区块链技术与应用》公开课笔记8——BTC挖矿篇

在之前的文章，已经基本上介绍完了比特币系统的原理。本篇，将对之前内容简单总结并说明目前挖矿出现的趋势。

Previous articles & #xff0c; the principles of the Bitcoin system have been largely introduced. This & #xff0c; a brief summary of the above and a description of the current trend in mining.

之前提到，由于硬件限制，BTC系统中分为轻节点和全节点，下表阐述了全节点和轻节点的区别

xff0c; due to hardware restrictions xff0c; split into light and full nodes xff0c in the BTC system; the following table sets out the difference between full node and light node

在比特币网络中，大多数节点都是轻节点。如果只是想进行转账操作，不需要挖矿，就无需运行一个全节点。在挖矿过程中，如果监听到别人已经挖出区块延申了最长合法链，此时应该立刻放弃当前区块，在本地重新组装一个指向最后这个新合法区块的候选区块，重新开始挖矿。

In the Bitcoin network xff0c; most nodes are light nodes. If you simply want to transfer xff0c; do not need to dig xff0c; do not need to run a full node. During mining xff0c; if you hear that someone has dug out the blocks to extend the longest legal chain xff0c; then the current block xff0c should be abandoned immediately; reassemble locally a candidate block pointing to the last of the new legal block xff0c; restart mining.

1. 这样是不是有些可惜？之前花费好多资源，全部白挖了。
   实际上并不可惜。之前文章中提及，挖矿本身具有无记忆性，前面无论挖多久，对后续继续挖矿没有影响。
2. 比特币系统如何安全性？
   一是密码学的保证：别人没有自己的私钥，就无法伪造其合法签名，从而无法将其账户上BTC转走。（前提：系统中大多数算力掌握在好人手中）
   二是共识机制：保证了恶意交易不被系统承认。

目前，挖矿设备逐渐趋于专业化，其经历了三个过程，总体趋势从通用到越来越专用。
普通CPU -> GPU ->ASIC芯片（挖矿专用矿机）

At present xff0c; the gradual specialization of mining equipment xff0c; it has undergone three processes xff0c; the overall trend is more and more exclusive.
General CPU-> GPU-> ASIC chip xff08; special mine excavator xff09;

实际上，挖矿本身就是计算，对于普通计算机来说，挖矿过程中大多数内存、硬盘、CPU中大多数部件（用到指令较少）等都是闲置的，如果用普通计算机专门用于挖矿是根本不划算的。随着挖矿难度提高，用通用计算机挖矿很快变得无利可图。
所以，挖矿设备转入第二代——GPU(主要用于大规模并行计算，如：深度学习)。但是，用GPU挖矿，仍然有一定浪费(GPU为通用并行计算设计，挖矿仍然有很多部件闲置。例如：浮点数运算部件，挖矿过程只使用整数操作，该部分部件根本不会用到)。

In fact, xff0c; mining itself is a calculation xff0c; xff0c for general computers; xff0c; most of the RAM, hard disk, CPU components xff08; less command xff09; etc. are idle xff0c; if ordinary computers are used exclusively for mining, it is uneconomical. xff0c; there is still a certain amount of waste (GPU is a generic parallel calculation design xff0c; mining still has a large number of spare parts, e.g. xff1a; floating units xff0a; xff0c; mining process #0; operational components; .

GPU价格上涨，仅仅是深度学习火热导致的吗？实际上，很多GPU被用于了挖矿。

GPU price increases xff0c; is it just a result of deep learning heat? xff1f; in fact xff0c; many of the GPUs are used for mining.

当然，目前GPU挖矿也已经不划算了（目前一些新开发货币仍然用GPU挖矿）。所以，开始进入第三代设备：ASIC芯片（专门为挖矿设计的芯片），这种芯片专门为挖矿设计，只能用于特定币种的挖矿。
但ASIC芯片设计、流片流程很长，假如BTC价格剧烈变化，前期投入很可能会血本无归。所以，ASIC芯片需要提前预订。假如BTC系统中，算力突然很猛烈增加，一般是一个大的厂商生产出新的ASIC矿机。

Of course xff0c; GPU digs are not currently developed xff08; some newly developed currencies are still digging with GPU xff09; so xff0c; entering the third generation of equipment xff1a; ASIC chip xffff08; xff09; xff0c; this chip is designed specifically for mining xff0c; only for mining in specific currencies.
, but ASIC chip designs and flow processes are long xff0c; if BTC prices change dramatically xff0c; prior input is likely to be bloodless xff0c; ASIC chips need to be booked in advance.

ASIC芯片只能用于挖矿，一旦其过时，便完全作废。

ASIC chips can only be used for mining xff0c; once they are obsolete xff0c; they are completely destroyed.

思考：ASIC芯片的出现是好事吗？
很明显，ASIC芯片并不是普通人可以参与的，一定程度上提升了挖矿的门槛，违背了比特币系统去中心化的初衷。理想状态下，所有人用CPU挖矿，这样只要有一台家用计算机便可以参与挖矿。当然，后续有一些货币便考虑到了这个问题，设计了抗ASIC芯片化的解决方案，后续介绍以太坊时会对这种方案进行介绍。
但反过来想，如果大家都用ASIC矿机挖矿，如果有人想要颠覆BTC系统，必然会导致BTC价格跳水，从而导致其所购买ASIC矿机作废，投入成本血本无归。所以，很多人反倒认为ASIC芯片出现，一定程度上并不是坏事。

reflections xff1a; the emergence of the ASIC chip is a good thing xff1f;
it is clear xff0c; the ASIC chip is not an ordinary person's xff0c; xff0c; the threshold for mining has been raised to some extent xff0c; the solution for anti-ASIC chip strong is being introduced. xff0c under ideal conditions; the owner digs the CPU xff0c; so that one computer can be involved in mining. Of course xff0c; there are some currencies that take into account this issue xff0c; the solution for anti-ASIC chip xff0c; the subsequent introduction of the scheme in the too.
, but vice versa s the cost of the ASBC mine xxxx0x0xfffn; it does not necessarily result in the cost of the ICXffffX; it does not result in many.

挖矿另一个趋势便是大型矿池的出现。对于单个矿工来说，即使使用了ASIC矿机，其算力在整个系统中仍然只占据很少一部分，即使从平均收益看有利可图，但收入很不稳定。
此外，单个矿工除挖矿还要承担全节点其他责任，造成了算力的消耗。

Another trend in mining is the emergence of large ponds. xff0c for individual miners; xff0c even if the ASIC miner is used; xff0c for the whole system; xff0c for the average profit; xff0c; but income is very volatile.
and xff0c; xff0c for individual miners to assume other responsibilities for the whole node xff0c; resulting in the depletion of capacity.

因此，为了解决这些问题，便引入了矿池的概念。
矿池的架构如下图，通常是一个全节点驱动多台矿机。矿工只需要不停计算哈希值，而全节点其他职责由矿主来承担。ASIC芯片只能计算哈希值，不能实现全节点其他功能。此外，矿池出现解决了单个矿工收益不稳定的问题。当获得收益后，所有矿工对收益进行分配，从而保证了收益的稳定性。

So xff0c; to solve these problems xff0c; to introduce the concept of pond.
The structure of the pond is as follows xff0c; it is usually a full node-driven multi-mine machine. Miners only have to count Hashi xff0c; and the full node has other duties to be assumed by the mine owner. ASIC chip can only calculate the Hashi value xff0c; cannot achieve the full node other functions. xff0c; there is a problem with the unstable returns of individual miners. xff0c; all miners distribute the revenues xff0c; thus ensuring the stability of the proceeds.

所以，必须涉及如何分配的问题。如果分配不公平，挖矿的动力就会减少。

So xff0c; there's got to be a distribution problem. If the distribution is unfair xff0c; there's less incentive to dig.

矿池一般具有两种组织形式。1.类似大型数据中心（同一机构），集中成千上万矿机进行哈希计算。2.分布式。矿工与矿主不认识(不同机构)，矿工与矿主联系，自愿加入其矿池，矿主分配任务，矿工进行计算，获得收益后整个矿池中所有矿工进行利益分配。

The ponds are generally organized in two forms. 1. Similar to the large data centre xff08; the same institution xff09; xff0c; and the concentration of thousands of mining machines for Hashi calculations. 2. Distribution. Miners do not know the miners (different institutions) xff0c; miners communicate with the miners xff0c; voluntary participants in their ponds xff0c; miners assign tasks xff0c; miners compute xff0c; and all miners in the whole pond after receiving benefits are distributed benefits.

假使第二种情况，矿工来源于五湖四海（非同一机构），收益应该如何分配？

If the second scenario xff0c; miners from the four lakes xff08; non-same institution xff09; xff0c; how benefits should be distributed xff1f;

1. 思路一：平均分配，所有人平分出块奖励。
   这一点有些类似我国某段历史时期，大家一起"吃大锅饭"，会导致某些矿工懈怠，不干活（挖矿要费电，需要成本）。
   所以，这里也需要进行按劳分配，需要一个工作量证明的方案。如何证明每个矿工所作的工作量呢？
2. 思路二：降低挖矿难度（可行方案）。
   假设原本挖矿难度要求，计算所得126位的哈希值前70位都必须为0，现在降低要求，只需要前60位为0，这样挖矿会更容易挖到。当然，这个哈希是不会被区块链所承认的，我们将其称为一个share，或almost valid share。矿工每挖到一个share，将其提交给矿主，矿主对其进行记录，作为矿工工作量的证明。等到某个矿工真正挖到符合要求的的区块后，根据所有矿工提交的share数量进行分配。
   因为每个矿工尝试的nonce越多，挖到矿的可能性越大，所能得到的share也会越多，所以这种方案作为工作量证明方案是可行的。

思考一：有没有可能，某个矿工平时正常提交share，但真正挖到区块后不提交给矿主而是自己偷偷发布出去，从而避免他人分走挖矿所得到的出块奖励？
事实上，这种情况是不可能的。因为每个矿工挖矿任务是矿主分配的。矿主组装区块，交给矿工计算，而区块中铸币交易的收款人地址是矿主，如果矿工修改该地址，计算的nonce值也会作废。
思考二：如果矿工自己刚开始就自己偷偷组装一个区块，自己挖矿，这样就类似于其脱离了该矿池。因为其自己所组织的区块不会被矿主所认可，其提交的share也不会被认可，也就得不到分配的收益。
思考三：有没有可能矿工捣乱？平时提交share，等挖到后扔掉区块，不提交？
这种可能是有的，如果矿工本身仅仅想捣乱，是可以这么做的。但扔掉区块后，对其本身来说，也没有相应的奖励获得，看似是损人不利己的情况。
但是，矿池之间存在竞争关系。有可能为了打击竞争对手，会派出矿机加入竞争对手矿池挖矿，从而起到搞破坏的作用。即只参与其他矿工挖矿分红，自己挖到的区块却丢掉不给他人分。

xff1a; xff0c; xff0c for each miner; xff0c for a mine owner; xff0c for the mine owner; xff0c for the mine owner; xff0c for the mine owner; xff1f; b/xff0c; this is impossible because each miner's task is assigned to the miner. xff0c for the mine owner; xff0 for the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the miner to the mine to the miner to the miner to the miner to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to which the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to which the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to which the mine to the mine to the mine to which the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine to the mine

• 图1：矿池在各个国家分布比例图（2018年）

可见，中国所占矿池比例远远超过其他国家。

Visible xff0c; China accounts for far more than other countries.

This time xff0c; there is a pond (GHash.IO) with a power ratio of more than half of its full capacity xff0c; it caused panic (one pond can launch 51 attacks) after xff0c; the pond voluntarily reduced the capacity of the pit xff08; converted to zero xff0c; practically still has the capacity to launch 51 xff09; xff0c; avoid shaking people's confidence in bitcoin.

The surface appears to be safe xff0c; but if there is more than 50% arithmetic xff0c; if there is actually an institution, it is not bound to put it in a pond xff0c; instead, it is scattered to hide xff0c; when there is a real need to launch an attack, it concentrates on another 51 attacks xff08; xffff1a; xff09;

像不像即当裁判又当运动员？”堂下何人状告本官“？

Like an instant judge and an athlete #xff1f;” who is in the court to inform me of #xff1f;

3. 盗币（将他人账户BTC转走）
   这个是不可能的，因为其并没有他人账户私钥。如果依仗算力强，强行将没有签名的转账发布到区块链，正常节点不会认为其合法，这样，即使这条链再长，其他人也不会认为其是最长合法链。

优点：解决了矿工收入不稳定的问题，减轻了矿工的负担。
缺点：威胁到了区块链系统的安全，使得51%攻击变得容易起来。

Advantages xff1a; addressing the precarious income of miners xff0c; reducing the burden on miners.
Deficiencies xff1a; threatening the safety of block chain systems xff0c; making 51% of attacks easier.

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