Basic principles of blockchain

justry_ deng 2022-01-14 15:39:38 阅读数:640

basic principles blockchain

The basic principles of blockchain

The basic principles of blockchain

Account book

What is an account book

Tips ： The currency , Just by using Blockchain Technology Yes E-cash （ Digital currency ） System Just the realization of .

2008 year 11 month 1 Japan , Nakamoto Published papers describe a new E-cash （ Digital currency ） System —— The currency . From the perspective of technicians , To achieve a E-cash （ Digital currency ） System Is to achieve a Account book . To put it simply , Electronics cash （ Digital currency ） System It's the ledger .

Four difficulties in realizing the ledger

We know , Like RMB 、 Currencies such as the US dollar can only be accepted by the people under the endorsement of a powerful national machine , And circulating in daily production and life . Obviously , Bitcoin is not endorsed by any country or institution , Nakamoto The challenge is how to use technical means to endorse the bitcoin it releases .

Nakamoto wants to realize bitcoin , Or to say ** Implement an e-cash system （ From the perspective of technicians , namely To achieve an account book ）, We need to solve the following four problems ：**

The ledger cannot be tampered with .
The ledger cannot be lost or damaged .
Prove that you are .
The same money , Can't spend 2 Times or times （ namely ： There can be no double flower problem ）.

Double flower problem description ： For paper money , When paper money comes from A Give to the B when , The whole deal is over ; But there are some differences for digital money , hypothesis A Yes 10 Bitcoin , He chose to transfer all the money to B, When the transaction is executed on the network but has not been confirmed , He chose to give C turn 10 Bitcoin , For the system , Both transactions are legal , Can be broadcast to the network through authentication , But actually , This is obviously problematic , This is the double flower problem （ Double flower attack ）.

Distributed ledger solves the difficulties 1、 difficulty 2

In short , Distributed ledger , namely ： The ledger allows multiple people to keep accounts at the same time , That is, the ledger keeps multiple backups . So you don't have to worry about the loss or damage of the ledger , At the same time, it also makes the account book less easy to be tampered with , Because the ledger is backed up in many places , What anyone can directly modify is the local ledger , In case of disagreement of other account book depositors , Can't change the overall ledger , In other words, its modification is not recognized by others .

Cryptography solves difficult problems 3

Prove that you are , The original meaning of this sentence is A The balance of the account can only be A To manage ,A You can choose transfer or other transactions , But when making these deals ,A You must prove that this account is his . Obviously , use cryptography Knowledge , Design digital signature You can do that . There are two requirements for the details of digital signature ：

First of all ,A Signed deals A Non repudiation , Others can verify
second , Others cannot pass A The signed transaction imitates A Other signed transactions

Blockchain data structure solves difficulties 4

The blockchain technology we often refer to generally refers to digital currency technology , there Blockchain data structure It refers to the specific structure for storing data .

notes ： Because so far 2021-08-08, Blockchain technology is still the only known and relatively reliable implementation of digital currency technology , Therefore, blockchain technology is used to refer to digital currency Technology , It includes cryptography 、 The Internet 、 Data structure, etc .

Nakamoto's solution to the double flower problem is very simple , Is to design a Strong temporal data structure （ This is the blockchain structure ）. He packaged several transactions to form a block block , And impose constraints ： When there are two or more transactions in the double flower attack in the same block Time in block , The block The block will be verified as illegal , In the end, only one of the two transactions can be packaged into block block . Then the system hangs the newly generated block behind the previously generated block , In this way, a linked list structure is formed as a whole . Transactions that have been packaged in blocks are confirmed by the system , At this time, there is no problem when you receive the second transaction in the double flower attack , System （ Considering the previous transaction volume ） Confirm the balance of the current transaction , If the balance is insufficient , Then the system will recognize the current transaction as illegal .

This constant collection of transactions is packaged into pieces , Then hang it on the previous block to form a structure , Is called chain of blocks, Later, it was called blockchain（ Blockchain ）.

hash function （SHA-256）

hash Characteristics of functions

SHA-256 Algorithm hash function ：y=hash(x), For different inputs x, You can get a fixed length （256bit） It's binary y value .

hash Characteristics of functions ：

Anti collision

Not to say that hash It is absolutely anti-collision , It's just that the probability of collision is very low , So I think hash It can prevent collision .

give an example ： When hash And what you get is 22 Characters long ,300 In trillions of calculations , The probability of collision 1000 1/100000000 . With hash The increase of value space , This probability will be lower ,SHA-256 Of hash The value is actually a 64 Bit string . So we use SHA-256 Algorithm hash function , We think it is anti-collision at this level .
Information hiding

y=hash(x) in , You can go through x obtain y, But it's hard for you to pass y obtain x.

notes ： In the blockchain network , Each user will get a public key and private key when applying for an account , The private key is used to indicate your management right of this account , The public key is passed by using the private key Elliptic curve algorithm secp256k1 Encryption generated , And this algorithm is also irreversible . The bitcoin address we often see is passed by the public key 2 Time hash Get a string , This also well protects the information of the public key itself .
Easy to solve problems

hash Function in forming blockchain structure

Tips ： Mentioned in the blockchain field hash Functions refer to specific SHA-256 The algorithm supports hash function .

We mentioned earlier that the blockchain data structure is a block by block linked list , It is also mentioned that the formation is through the latter block Hang the block to the previous block Formed on a block , But I didn't mention how to hang it , actually , Hang this action through hash Functionally implemented .

For each block, you need to fill in hash value , This hash The input values include ：

Block number
data （ One or more transaction information ）
Of the previous block hash value
A random number

P2P Network profile

P2P The Internet , That is to say peer to peer The Internet .

P2P The network first came from Napster, This is a free service for users MP3 Downloaded Web Services .Napster The server does not store MP3 file , But it has an index server , To record what each user has MP3 Song list information , So when users need to download , You can directly find the corresponding host, establish a connection and download files .

When Nakamoto invented bitcoin , Also standing on the shoulders of predecessors . Every new node in the network , Through the built-in nodes DNS The seed node queries the network IP list , Some seed nodes return a set of statically reliable bitcoin nodes IP, Some seed nodes return dynamic bitcoin nodes IP Set . New node selection 8 Connect nodes , And compare each other , Synchronize blockchain data . If there is a new transaction , A node sends a transaction broadcast to all its neighboring nodes , Then continue to broadcast to lingju , Until the whole network receives the transaction information .

Consensus algorithm

What is a consensus algorithm

The blockchain system adopts decentralized design , Network nodes are scattered and independent , Therefore, systems composed of different nodes must rely on a system to maintain the data consistency of the system , And reward nodes providing blockchain services , And punish malicious nodes . The establishment of this system depends on a set of methods and rules , That is, who gets the packaging right of a block （ Or bookkeeping right ）, And get the reward of the block or how to define who is the perpetrator , How to punish him , This set of methods and rules is the consensus algorithm （ Consensus mechanism ）.

Common consensus algorithms

PoW： Proof of workload （Proof of Work） Algorithm
PoS： Proof of interest （Proof of Stake） Algorithm
DPoS： Share authorization certificate （Delegated Proof of Stake） Algorithm
PBFT： Practical Byzantine fault tolerance （Practical Byzantine Fault Tolerance） Algorithm
RAFT： Consensus algorithm

UTXO Model

UTXO namely Unspent Transaction Outpou, Transaction output not spent .

Bitcoin system doesn't really exist " Account ", And only " Address ". This address is mentioned above , Pass through with a public key 2 Time hash Calculated address . Only those who master the private key can master the address , You can use the... In this address " balance ".

A person's bitcoin balance actually depends on how many bitcoins are contained in his address , The way to calculate the number of bitcoins or its data structure is called UTXO.

^_^ Collated from 《Go Language blockchain application development from entry to mastery 》 Takano Huang,

^_^ This article has been included in 《 Programmer growth notes 》 , The author JustryDeng

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