What is the blockchain, how to easily introduce the blockchain? (second season)

We talked about stickers, how to ensure the accuracy of each transaction and effectiveness of it? Here comes the other features of the blockchain.

Two basic problems

After decentralization, there is no authoritative centralized agency in the whole system, and the credibility and accuracy of the information will be confronted with problems. Question 1: Class and Army Issues For the first time I heard that this issue is actually in the TCP class, which generally states that there are two far-away military forces to transmit information. The Red Army dispatched a messenger to say to the Blue Army: "You His mother took out the Italian gun! " After receiving the information, the Blues sent another messenger to the Red Army saying: "I received the order!" Then the Red Army sent a messenger to the Blue Army and said, "I know you received the order!" Then the blue army sent a messenger to the Red Army and said: "I know you know I received the order!" Then the Red Army sent a messenger to the Blue Army and said: "I know you know I know you received the order!" ... and then endless.

Figure 2: It is impossible to achieve consistency across asynchronous systems and unreliable channels in distributed computing

In this case, because of the peer-to-peer communication, it is impossible for both parties to achieve the consistency of information under such circumstances. In a nutshell, "It is not possible to attempt to achieve consistency across asynchronous systems and unreliable channels in distributed computing."

Question 2: The question of General Byzantine

Byzantine Roman Empire in the military operations, the generals vote to determine the strategy of attack or retreat, that is to say if the majority of people decided to attack, go up. However, if there are spies in the army (for example, the generals have already deliberately turned down the water or the regent revolts without modification), how can we ensure that the outcome of the final vote really reflects the will of the loyal generals?

Byzantine general problems reflected in the field of information exchange can be understood as a decentralized system, some nodes are broken, they may broadcast the wrong message to the outside world or not, how to verify in this case Data transmission accuracy.

The birth of blockchain technology

Let's start with a decentralized system. For ease of understanding, let's look at a simple decentralized lending model: If A borrows B $ 100, A shouts at the crowd at this point "I'm A, I lent B 100 dollars! ", B also shouted in the crowd," I am B, A loaned me 100 dollars! "At this time passers-by A and B both heard the news, so everyone is Heart silently note "A loan B100 dollars." You see, this time a decentralized system was set up that did not require banks or lending agreements and receipts and, strictly speaking, did not even require a long-standing relationship of trust (such as sudden B Change the mouth to say "I do not owe A money!", This time the people will stand up and say "no, my little notebook records you borrowed A100 dollars one day!").

Figure 3: Decentralized lending model

As you may have noticed, in the above model, the so-called "100 dollars" is not important anymore. In other words, anything can be exchanged in this model, and even you can invent a thing out of thin air, as long as you admit it, you can circulate what you have invented. For example: I shouted in the crowd, "I created 10 Chakra!", I do not even need to know what Chakra is or do I need to be concerned about whether the world really has Chakra, as long as everyone hears it, and then In his own notebook, write down "LaiW3n has 10 Chakra", so I really have 100 Chakra. From then on, I can claim that I gave someone a Chakra, and as long as passersby, B, and B both received and acknowledged the message, I would have completed the transaction, even if there was no Chakra in the world.

Do you now have three words in mind - bitcoin? Since the real blockchain and bitcoin are a lot more complex and detailed than my models above, so here's an example from Chakra, which is Blockchain for Babies after all.

After a long period of hypothetical time, Chakra, which I created out of thin air, has circulated in this system, and everyone is beginning to recognize Chakra. But there are only 10 Chakra in this system, so some people have a bad mood, he shouted in the crowd, "I have 10 Chakra!" What to do? We are directly in the books to note that he has 10 Chakra Mody, so that not everyone can forge Chakla it?

To prevent this from happening, I decided to tag my chakra when I created Chakra (more specifically, I was tagging "I created 10 Chakra", for example Marked as 001) so that after each transaction, I shouted, "I gave a chakra!", An extra sentence is added: "The source of this chakra Is recorded as 001 that record, my sentence is marked as 002! ". Let's take a more abstract point. The format of a person's propaganda content becomes: "The sentence number xxx, the last sentence number is yyy, and I gave a certain chakra!", Thus solving forged problem. In fact, the above model becomes a simplified version of the first block of Bitcoin blockchain agreement:

Figure 4: Comparison chart between Chakra model and Nakamoto's first blockchain protocol

This should probably understand what is the blockchain it.