Blockchain note 1: what is the significance of bitcoin?

Don't think about what will change in ten years , But to think about what will remain unchanged after ten years -- Jeff Bezos

Why? -Why？

Why bitcoin ？ Why blockchain ？

This topic , I'm a little hot , This article discusses more about the significance of blockchain . Just like every product is the answer to a question , Blockchain is a very representative answer to a question . If we want to find out “ Why blockchain ？”, Let's first ask “ Why bitcoin ？” Maybe it's a very good start . therefore , Why bitcoin ？ What problem does bitcoin solve ？

Dream return 2008

《Bitcoin: A Peer-to-Peer Electronic Cash System》 This bitcoin white paper is in 2008 year 10 month 31 Published on .2008 In addition to the Beijing Olympic Games , Also, the financial tsunami began with American real estate . Wikipedia also has a special home page, and there are many similar articles elsewhere on the network , There is also a very famous film 《 Big short 》 Also speaking 2008 Of the financial crisis in .

In conclusion , Many people with unstable jobs borrowed money from banks to buy large villas , Borrowed money, no money to pay back , Then you will default . The borrower defaulted on the lender , Borrowers in the hands of lenders default more , He defaulted on his lender , At last, the whole financial market was destroyed .

The problem here is , Why can a person with unstable job borrow so much money ？ One of the reasons for this is , There is corruption in rating agencies , For high-risk debt, it is evaluated as low-risk . We need to know , When the other party is assessing our risks , We're also evaluating each other . For an authoritative rating agency , We should trust the results issued by authoritative rating agencies . But after this incident , We have a distrust of rating agencies . There is a problem with trust , It's a very big problem .

trust

human beings , As a species , The only goal is a longer existence . So for individuals , people , The only goal will also be a longer existence . Under this goal , People live in groups , It started with family , Then the tribe grew bigger , Become a country , The ultimate goal of internationalization is the cooperation of the whole human group as a group .

For groups , No matter how big the system will be , The greatest need of people as a group is trust . If there is no trust in a group, the group will not exist .

however , How to define trust ？ Suppose your friend Zhang San says ten minutes to the place every day , But he always 15 Minutes to place . Another friend Li Si said ten minutes to the place every day , But sometimes he 4 Minutes to , sometimes 16 minute . Suppose a situation , You have a toxin ,15 You'll die in minutes , Both Zhang San and Li Si have antidotes, but your phone can only make one call , So in this case, will you call Zhang San or Li Si ？

in my opinion , I called Zhang San in fifteen minutes , Because although he must say that ten minutes is lying to me , But he'll be there in fifteen minutes . And Li Si, I'm not sure if he will be 15 Arrive at the place within minutes .

So in my opinion , The essence of trust is a kind of certainty , Your confirmation of Zhang San or Li Si's behavior in the unknown future .

So back to 2008 year , Asset rating agencies have an absolute say in the entire financial system , The whole real estate asset valuation is established around a few authoritative appraisal institutions .

When the crisis comes , We first found out , What the evaluation agency said is not necessarily right . We question the authority of the American financial system .

How do you do it? -How?

Okay , Suppose you 2008 Beginning of the year , We found a huge problem in American society , There is authority in American society , People with rights can basically call deer a horse . How to solve this problem ？ Some people say that through democracy , Someone went through a riot , But some people say , We need to set up a new financial system . This system , It's called bitcoin .

What is it? -What?

Now? , Is the most difficult problem , We need to develop a better system to replace the existing financial system . The existing financial system is a centralized system , The central node is authority , To process all information and store all information .

Take banks for example , We have to send an application for transfer to the bank , To be judged by the bank 、 Record 、 operation , Transfer money to destination account . We check our own balance , In fact, it is essentially asking the bank for our records . ad locum , determine 、 Record 、 The operation is completely in the black box state . We have no idea what's going on inside . If we want to replace the financial system , Then our system must be point-to-point transfer , And all transfer information will be made public .

Bitcoin's solution is , All nodes in the system have the authority to record and query transactions .

How to achieve ？ Suppose there is Zhang San in the system , Li Si , Wang Wu, everyone has a bookkeeping book . Zhang Sanba 2 Yuan to Li Si , For this transfer information, let everyone know , Zhang San wrote it down in the book and shouted in the group , In this way, we can update the data in our own account books .

1. Zhang San secretly wrote down what to do with the money transferred from Li Si to Zhang San ？

To solve this problem , We agree that each transfer requires the signature of the party concerned . Li Si transfers money to Zhang San , Li Si needs to sign the transaction . Implement signature on software system , We need asymmetric encryption , Everyone has their own private key , There is also a public key . Public key （PK） Can be seen by everyone , Private key （SK） For a secret key .

The information of the transaction will be based on the sponsor's PK Conduct hash, Only the sponsors use their own SK Before decoding . At this time , We agreed that only the successfully decoded standard information can be written to the system database .

2. If Zhang San doesn't have this 2 What about a hundred dollars ？

It's like playing Monopoly , At the beginning of the system , Everyone has an initial game currency , All transfers here are made in game currency . And in every transaction , The verifier needs to read the bookkeeping from beginning to end , To determine whether Zhang San has a balance transferred to Li Si .

Because it's very painful to read the bookkeeping from beginning to end , And three people can write code, so they decided to build a software system . First , At the beginning of the system, the corresponding balance will be recorded for everyone ,

 {
  "timestamp": 0, 
  "transaction": " From the system to Zhang San 、 Li Si 、 Wang Wu "
  "state":{
     " Zhang San ": 100,
     " Li Si ": 100,
     " Wang Wu ": 100
   }
 }
 Copy code 

Transactions are carried out according to time , Each transaction is chronologically arranged in the system database

 [{"timestamp": 0, "transaction":"..."},
  {
   "timestamp": 1, 
   "transaction": " Zhang San to Li Si 2 Yuan ", 
   "state":{
     " Zhang San ": 98,
     " Li Si ": 102,
     " Wang Wu ": 100
   }
 }]
 Copy code 

Every project here is a “ block ”, String together with time as signature , Namely “ Blockchain ”.

3. Who will do the audit ？

It says , Each block is connected in series according to the time arrangement .

So suppose a situation , Zhang San transfers money to Li Si 60 Yuan, so Li Si has 162 Yuan , Then Li Si transferred it to Wang Wu 160 Yuan , But because Zhang San is far away, the network speed is relatively poor , Therefore, Li Si's block is sent to the system before Zhang San's block .

that , How can we establish a mechanism to ensure that the order of blocks is arranged in time ？

Here in bitcoin's white paper , A very important mechanism is introduced “proof of work”.

First of all to see , There is time in the block we are designing now , There is transaction information . In order to connect the blocks , We also need to include the data of the block of the last time node in the block .

 [{"timestamp": 0, "transaction":"..."},
  {
   "timestamp": 1,
   "previous_block": {"timestamp": 0, "transaction":"..."},
   "transaction": " Zhang San to Li Si 2 Yuan ", 
   "state":{
     " Zhang San ": 98,
     " Li Si ": 102,
     " Wang Wu ": 100
   }
 }]
 Copy code 

In the above case , Each block is very easy to tamper with and forge , For example, Zhang San and Li Si both told everyone that my block is timestamp=1 Block of .

In a system that lacks a decisive role , Who do we listen to ？

In such a software system , The best existing model is to listen to whoever has the highest declaration cost . Zhang San pledged a gold watch when he made a statement , When Li Si made a statement, he directly took a suite up . Then let's listen to Li Si , Put Li Si's block into the system ledger .

How to implement this mechanism in software system ？ The implementation of bitcoin draws lessons from SHA256 The mechanism of . Zhang San and Li Si guess a value at the same time , Use this value hash block ,hash The result will be in several 0 start . Who finds this value first , Just listen to who . This process is called mining in Chinese , This hash The result is called... In bitcoin “nonce”.

meanwhile , Because this job can't be done in vain , So who gets this value first , Who can get a monetary reward . So it explains why mining makes money .

A little idea of yourself

I hate to describe blockchain as a product of decentralization / System .

In the question just now , We see that proof-of-work In essence, this mechanism is to recommend the person who costs more as an authority . And to hijack the system, in theory 50%（ Some chains are less ） Calculation power . From here we can actually see , Without changing this mechanism , As long as the influence of bitcoin is expanding, there will always be a very rich organization in the near future , Or individuals control the whole blockchain .

In my opinion, the essence of blockchain lies in disclosure , Decentralization is only a stage , Not the identity of this product .