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1. What is blockchain? A cartoon to help you understand (a must-read for beginners)

The word "blockchain" was actually used in the early cryptography circles Here, the underlying technology of Bitcoin is called "Bitcoin". In English, Bitcoin starting with a capital B refers to the network system or network protocol of Bitcoin.

However, due to public confusion, people are now very resistant when talking about Bitcoin, thinking that Bitcoin is synonymous with illegality, scams, pyramid schemes, and another phenomenal bubble in Internet finance! As a result, people had to merge all the underlying technologies (timestamps, proof-of-work mechanisms, etc.). In order to distinguish them from Bitcoin, they renamed them Blockchain, which translated into "blockchain". This is how the term “blockchain” appeared.

Blockchain is not a single technology, but a collection of a series of technologies.

How should we understand blockchain? Let’s first use the love story that everyone loves to talk about as a simple example. Establish a simple blockchain model, then the following situation will occur when falling in love in this blockchain model:

In the future, all men and women of the right age will fall in love and the entire process of marriage commitment will be blocked by all other men and women of the right age. Consensus, all the stories that happen between two people will form a block.

All other men and women are a chain. If a third party intervenes or you violate your partner, others can see it, and you will never find a partner in the future.

To be precise, the blockchain is a "full center" system, that is, every node on the chain is the center.

Trial marriages for men and women to fall in love, post on friends, show affection, promise to love each other for a lifetime and be known by all other marriageable men and women are the applications of blockchain. If one day one party breaks their promise, don't think that deleting the photos will be useful, because every piece of it has been recorded by all marriageable men and women.

Cannot be deleted or changed, this is blockchain technology.

2. An easy-to-understand explanation of blockchain

The popular explanation of blockchain technology is as follows:

To put it simply: blockchain is the use of a package of Some network technologies have formed a new generation of network systems. This network system has a new structure, a new mechanism, and unprecedented new value. Five major technologies or innovations are specifically used: encryption technology, P2P network technology, distributed storage technology, consensus mechanism, and smart contracts.

Essentially: it is a shared database, and the data or information stored in it is "unforgeable", "full-process traces", "traceable", "open and transparent" and "collectively maintained" ” and other characteristics. Based on these characteristics, blockchain technology has laid a solid foundation for "trust-based sales" and created a reliable "cooperation" mechanism. Yunchun has broad application prospects.

2. Openness.

In addition to the encryption of private information of all parties to the transaction, the blockchain data is open to everyone and provides a flexible script code system. The entire system information is highly transparent and within the rules specified by the system. Nodes cannot deceive each other.

3. Autonomy.

Consensus technology, smart contracts.

3. What is blockchain? A popular explanation of a new accounting method (you will understand after reading it carefully)

In the past two years, a new method of accounting has been circulated on the Internet. The financial model is "blockchain". I think many people still don't understand the meaning of this. After all, "blockchain" is still "advanced" to ordinary people in the past, so what is blockchain? What is the popular explanation? In fact, it is not as complicated as we imagined, so let me tell you what "blockchain" is and see what is special about this model!

The most popular explanation of blockchain:

What exactly is the "blockchain" that people often talk about? I believe that many people don’t know much about it, and most of the information they view on the Internet is “unclear”. In fact, it is easy to understand. So what is the popular explanation of blockchain? Fundamentally speaking, this model is a "decentralized" accounting method. So what is "decentralization"? All our current exchanges and communications on the Internet will actually be stored in a "centralized" server on a browser or APP. The other party can check our browsing information at will, and "decentralization" is convenient. This can be completely avoided.

Once information is written into the "blockchain", it cannot be tampered with, ensuring its authenticity and confidentiality. It can also avoid third-party platforms in transactions on the virtual market. Intervention, the transaction is directly completed by both parties, which saves a lot of procedures and time, and also ensures that information is not leaked, transparent and other security issues, and there is no possibility of data loss!

After reading the above introduction, do you have a new understanding of the "blockchain" model? can't read? Let’s take a look at it through a comic below!

Fields of application of blockchain

The "blockchain" model can be applied in many fields, the first of which must be finance. The earliest blockchain is from Born in Bitcoin. There are also areas such as education, e-commerce, film and television, etc.Using this new technology, all walks of life are now exploring this new field, hoping to have a foothold in the development of the future era!

4. Comic illustration: What is blockchain

Comic illustration: What is blockchain

What is blockchain?
Blockchain, English Blockchain, is essentially a decentralized distributed database. Anyone can become a node of this huge network as long as they set up their own server and connect to the blockchain network.
Since the blockchain is essentially a database, what exactly is stored in it? Let’s take a look at the basic unit of blockchain: Block.
A block is divided into two parts:
1. Block header
The block header stores the header information of the block, including the hash value (PreHash) of the previous block. The hash value of the block body (Hash), the timestamp (TimeStamp), etc.
2. Block body
The block body stores the detailed data (Data) of this block. This data contains several rows of records, which can be transaction information or some other information.
What does the hash value just mentioned mean?
Everyone must have heard of MD5. MD5 is a typical hash algorithm that can convert a string of plaintext of any length into a string of fixed length (128 bits). This string is the hash value.
In our blockchain, a more complex hash algorithm called SHA256 is used. After a series of complex calculations, the latest data information (such as transaction records) will eventually be converted into a 256-bit hash value string through this hash algorithm, which is the Hash in the block header. The format is as follows:

Blocks and Hash have a one-to-one correspondence, and Hash can be regarded as the unique identifier of the block.
How are different blocks related to each other? Rely on Hash and PreHash to associate. The PreHash value of each block is equal to the Hash value of the previous block.
Why do we need to calculate the hash value of the block?
Since the blockchain is a chain structure, there must be a head node (the first block) and a tail node (the last block) of the chain. Once someone calculates the hash value of the latest data in the blockchain, which is equivalent to packaging the latest transaction records, a new block will be created and connected to the end of the blockchain.
The Hash of the new block header is the hash value just calculated, and the PreHash is equal to the Hash of the previous block. The data in the block body stores the transaction records before packaging, and this part of the data information has become unmodifiable.
This process of calculating Hash values ​​and creating new blocks is called mining.
Used to enterServers that perform massive calculations are called mining machines.
The workers who operate calculations are called miners.
What is so difficult about calculating hash values? Let’s give the most superficial explanation. The formula for calculating the hash value is as follows:
Hash = SHA-256 (Hash of the last block + basic information of the new block + transaction record information + random number)
Among them, the transaction record information is also a string of hash values, and its calculation involves a data structure Merkle Tree. Interested friends can check the relevant information, we will not introduce it for now.
The key computational difficulty here lies in the generation of random numbers. In order to increase the difficulty of Hash calculation, the wretched inventor of the blockchain requires that the first 72 bits of the Hash result must be 0. This probability is too small.
Since (the Hash of the last block + the basic information of the new block + the transaction record information) is fixed, whether the Hash that meets the requirements can be obtained depends entirely on the value of the random number. Miners must go through massive calculations and repeatedly generate random numbers in a general attempt to "get lucky" before they can get the correct Hash and successfully mine.
At the same time, the block header also contains a dynamic difficulty coefficient. When the world's hardware computing power becomes faster and faster, the difficulty coefficient of the blockchain will also increase, making the entire network capable of completing the task every 10 minutes on average. A new block is generated.
Friends, do you understand how difficult mining is? It should be added that different blockchain applications are different in details. The mining rules described here take Bitcoin as an example.
Applications of Blockchain

The concept of Bitcoin (BitCoin) was first proposed by Satoshi Nakamoto in 2008, and then based on this idea, open source software and P2P built on it were designed and released. network. Bitcoin is a P2P form of digital currency. Peer-to-peer transmission means a decentralized payment system.
What is a P2P network?
Traditional currencies are uniformly issued by the central bank, and all personal savings are uniformly managed by banks. This is a typical centralized system.
Bitcoin is deployed on a decentralized network composed of many peer nodes around the world. Every node is qualified to record and issue this digital currency.
As for the underlying data storage of Bitcoin, it is based on blockchain technology. Each transaction in Bitcoin corresponds to a row in the block data. A simple diagram is as follows:
Each row of the transaction record contains a timestamp, transaction details, and digital signature.
The table is only for ease of understanding. The actual stored transaction details are anonymous, and only the wallet addresses of the payer and payee are recorded.
As for digital signatures, they can be understood as anti-counterfeiting marks for each single transaction, generated by an asymmetric encryption algorithm..
Next let’s talk about the rewards of Bitcoin miners:
The Bitcoin protocol stipulates that miners who mine new blocks will receive rewards. Starting from 2008, it is 50 Bitcoins, and then halved every 4 years. , currently 12.5 Bitcoin in 2018. The new Bitcoins in circulation are all born in this way. No wonder everyone is so eager to mine Bitcoins!
Advantages and Disadvantages of Blockchain
Advantages of Blockchain:
1. Decentralization
Blockchain does not rely on a central node. The data of the entire system is All peer nodes in the entire network are jointly maintained and can store and verify data. In this way, unless the attacker hacks more than half of the nodes in the entire network, the entire system will not be destroyed.
2. Information cannot be tampered
The data in the block cannot be tampered with. Once the data is tampered with even a little bit, the hash value corresponding to the entire block will change accordingly, and it will no longer be a valid hash value, and the subsequent linked blocks will also be broken.
Disadvantages of blockchain:
1. Excessive consumption of energy
To generate a new block, a large amount of server resources must be used to perform a large number of unnecessary trial calculations, which seriously consumes electricity.
2. Network delay of information
Take Bitcoin as an example. Any transaction data needs to be synchronized to all other nodes. The synchronization process will inevitably be affected by network transmission delay, resulting in a long time consuming.
A few additional points:
1. Part of the content of this comic refers to Ruan Yifeng’s blog post "Blockchain Introductory Tutorial". I would like to thank this great master for his popular science.
2. Due to limited space, the knowledge about Merkle Tree and asymmetric encryption has not been discussed in detail for the time being. Interested friends can check the information for further study.

5. Popular explanation of what is blockchain

Popular explanation of what is blockchain

Popular explanation of what is blockchain, blockchain is the present A hot topic, the development speed in China is getting faster and faster, but many people still don’t know what blockchain is? Now I will give you an easy-to-understand explanation of what blockchain is!

Popular explanation of what blockchain is 1

Generally speaking, blockchain is a decentralized distributed ledger database. The advantage of this distributed ledger is that buyers and sellers can trade directly. There is no need for any intermediary, everyone has a backup, even if your copy is lost, it will not be affected.

Suppose you have a ledger at home, and your parents give you your salary and ask you to record it in the ledger. You misappropriated more than ten yuan privately because of your greed, and no one else knew about it. But the way to solve the problem with blockchain is to keep accounts with the whole family. Not only you are keeping accounts, but your father, mother, brother, sister, younger brother, sister, etc. are all keeping accounts, and they can all see it.The general ledger, you can't change it, and no one else can change it.

Blockchain is a new application model of computer technology such as distributed data storage, point-to-point transmission, consensus mechanism, and encryption algorithm. Blockchain technology has been widely used in different industries. Such as product traceability, copyright protection and transactions, payment and settlement, Internet of Things, digital marketing, medical care, etc.

Popular explanation of what blockchain is 2

Common questions in blockchain engineer interviews

What do you think the block in blockchain technology means?

The blockchain consists of information about all financial transactions. A block is nothing more than a list of records. When these lists are combined together, they are called a blockchain. For example, if an organization has 100 ledgers, their combination is called a blockchain, and a single ledger will be considered a single block.

Why is blockchain a trustworthy approach?

There are many reasons to trust blockchain. The first reason is that it is compatible with other business applications because it is open source. Secondly, it is secure because it was developed for online transactions, so the developers pay special attention to its data synchronization while keeping it safe. Because the type of business it holds is unrelated, it is easy to consider distinguishing chains when choosing.

How much do you know about blockchain?

This is a technology that was actually designed for Bitcoin and later heavily promoted for the multiple benefits of monitoring and recording all financial transactions on the network. This is a trusted method that is currently being used by many organizations. Since everything is secure and open source, it is easy to gain trust in the long run.

Utilizing blockchain in an organization, if there are specific technical requirements for that network?

No specific conditions of use. However, the network must be a peer-to-peer network under the relevant protocol. It literally just validates new blocks and helps organizations stay in sync without having to invest in third-party applications.

What is encryption? What is its role in blockchain?

Data security is always very important. Encryption is basically a way to help organizations keep their data secure. In this technique, data is encoded or altered to some extent by the sender before being sent to the network. Only the receiver can know how to decode it. This practice is very useful in blockchain because it increases the overall security and authenticity of the block and helps ensure that the block is secure.

What types of records can be saved on the blockchain? Are there any restrictions?

There are no restrictions on any type of records in the blockchain approach. Currently, many organizations around the world are using this approach and the fact is that medical transaction records, organization related events, administrative activities, transaction processing, identity management, file records are all common record types that can use blockchain. And record keeping is not limited to these applications..

What is double spending?

This is one of the main issues related to digital currencies. In practice, this is a condition of passing a digital certificate, since the card can be used multiple times through a digital file that is often easily cloned. It only leads to inflation and the organization has to bear huge losses. A major technical goal of blockchain is to eliminate this approach as much as possible.

Explain the importance of blind signatures and how they are useful?

It is actually a form of digital signature, an important part of cryptography, where all information is blinded until it is actually considered or signed. This is a proven method often considered in different privacy-related agreements between the author and the signatory. Digital currency design is one of the most common examples.

What is key sharing? Are there any benefits to blockchain technology?

As we all know, security issues in digital transactions are very important. Key sharing is a similar approach. In blockchain technology, this is a method of dividing keys or personal information into different units and sending them to network users. The original information can only be merged if the participant who distributed the key agrees to be merged with other participants. It can provide various security-related benefits in blockchain technology.

What organizations can use blockchain technology?

This method can be considered as commercial class without strict upper limit. In fact, almost all businesses are doing or online financial transactions that require them to successfully complete the implementation process. Large enterprises, financial institutions, private enterprises, government departments, and even defense agencies can easily trust this technology.

What is the difference between a blockchain ledger and a general ledger?

First of all, the main difference is that blockchain is a digital ledger that can be easily decentralized. This method is far less likely to go wrong than a regular ledger. Normal books are written by hand or by hand, blockchain does all the tasks automatically. You just need to configure it the right way and follow all the guidelines.

What is a soft fork?

Blocks in the ledger are included in a way that builds the longest chain, i.e. the chain with the greatest cumulative difficulty. A fork is a situation where there are two candidate blocks competing to form the longest blockchain, and two miners discover a working problem and fail to synchronize with each other within a short period of time. Causes network fragmentation because some nodes get blocks from miner #1 and others get blocks from miner #2. Forks are usually resolved in one block because the probability of this happening again becomes very low as the next block comes out so soon there is a new longest chain that will be considered primary.

6. Illustration of what is blockchain

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Blockchain is so popular that it has begun to affect my life. I don’t even want to know about it. Today I will take a look at what blockchain is.

Structure of this article:

As its name suggests,
A blockchain is a chain composed of a set of blocks.
A block is a block of information that contains information. , the chain also contains information.

Blockchain technology was first developed by a group of researchers in 1991 to time-stamp digital documents so that these documents cannot be tampered with. It essentially played no other role after that, until 2009, when Satoshi Nakamoto used blockchain technology to create the digital cryptocurrency Bitcoin.

A blockchain is a distributed ledger that is completely open to everyone. It has a very interesting property: once certain data is recorded in a blockchain, the data is very It is difficult to change.

Let’s take a look at the composition of a block:

Each block contains some data, the hash value of this block, and the hash value of the previous block. Hope value.

The data saved in the block is related to the type of blockchain. For example, the blocks in the Bitcoin blockchain save relevant transaction information, including sellers, buyers, and transaction Bitcoins. quantity.

Each block contains a hash value. The hash value is used to identify a block and all the content it contains, and it is unique, like a fingerprint. Once a block is created, its hash value is calculated accordingly. If you change something in the block, the hash value will change. If the fingerprint of a block changes, it will no longer be the previous block.

The third element contained in the block is the hash value of the previous block. This element allows links to be formed between blocks and makes the blockchain very secure.

Suppose we have a blockchain containing 3 blocks
Each block contains its own hash value and the hash value of the previous block
No. 3 Block points to block No. 2, and block No. 2 points to block No. 1
Block No. 1 is a bit special, it cannot point to the previous block because it is the first
We put 1 The block number is called the genesis block.

Now suppose we tamper with the second block
This will result in the hash of the second blockChange
This will then cause block No. 3 and all subsequent blocks connected to block No. 3 to become illegal
because now the previous block number they store becomes illegal< br />So changing a block alone will cause all subsequent content to become invalid.

But to prevent tampering, hashing is not enough
Because today’s computer computing speed is powerful enough and can calculate thousands of hash values ​​per second
This way You can tamper with a block and recalculate the hashes of other blocks, making your block legal again.

So in order to reduce this risk, the blockchain also uses a technology called proof of work
This is a mechanism that slows down the creation process of new blocks
In the Bitcoin area In the blockchain, it takes about 10 minutes to complete the required proof of work and add a new block to the blockchain
This mechanism makes the tampering of the blockchain more difficult
because once it is tampered Once a block is obtained, the proof of work of all subsequent blocks needs to be recalculated.

Therefore, the security of blockchain technology mainly comes from hash value and workload proof mechanism.

Blockchain also has a mechanism to protect its own security, which is distributed
Compared to using a centralized entity to manage the blockchain network, blockchain uses A peer-to-peer network that anyone can join
When someone joins this network, he will get a copy of the entire blockchain
This person can use this to verify that all The blocks are still legal and untampered, that is, different nodes can use this to verify each other.

When someone creates a new block,
the new block is sent to everyone on the network.
Everyone then verifies the block to ensure that it has not been tampered with.
If everything is verified correct, then everyone can add the new block to their own area. On the blockchain
We can call it that everyone on the network has reached a "consensus".

All nodes in the blockchain network reach a consensus
They agree on which blocks in the network are legal and which are illegal
Those blocks that have been tampered with will Will be rejected by other users on the network
Therefore, to successfully tamper with a blockchain, you need to tamper with all blocks on the blockchain
Re-complete the proof of work of each block and control more than 50% of the users in the blockchain network
/> Only in this way will the block you tamper with be recognized by everyone
It can be said that this is basically impossible to do!

Blockchain technology itself is also constantly developing
For example, a later technological improvement is called smart contracts
Smart contracts are simple programs stored on the blockchain
br /> It can automatically execute based on the conditions recorded in the contract. As long as the conditions are met, transactions will be automatically completed in accordance with the contract
For example, automated Bitcoin transactions can be realized under specific conditions.

Learning materials:
https://www.youtube.com/watch?v=SSo_EIwHSd4

7. A simple explanation of what blockchain is, with a picture Understand the blockchain

What is the popular explanation of the blockchain? Understand the blockchain with one picture

Blockchain is a hot topic recently, and many people are talking about it. Discussing the issue of blockchain, recently some domestic companies have begun to develop some products using blockchain technology. Blockchain is an underlying technology used in Bitcoin. This is officially because of the popularity of Bitcoin, which has attracted the attention of many people. Bitcoin, but many people still don’t understand what blockchain is. Let me explain blockchain to me.

Bitcoin is a digital currency that many people are paying close attention to, and the underlying technology of Bitcoin is blockchain. Blockchain is a computer technology and a new application model. The blockchain is like a large database ledger, in which all transactions are recorded. The person who records this ledger is very different from traditional bookkeepers. Traditional bookkeepers are usually led by specialized bookkeepers. The accounting party performs the operations. For example, Taobao and Tmall are accounted for by Alibaba, and WeChat transactions are accounted for by Tencent. In the blockchain, all people participate in accounting. Everyone who participates in accounting has a ledger. .

Let me give you an example. For example, A wants to borrow 10,000 yuan from B. B wants to lend the money to A, but is worried that A will default on the debt after borrowing the money, so he will ask for a loan when borrowing money. A third-party notary helps B write down the account. This is the traditional accounting method, which relies on a third party to gain trust. The accounting books are in the hands of the third party. This kind of accounting There is the possibility of a third party tampering with the ledger, and decentralization means that there is no need for a notary when borrowing money, and there is no need to rely on a third party to gain trust. The decentralized situation is like when B lends money to A., B shouted with a loudspeaker, "A asked me to borrow 10,000 yuan, please help me write down the account." At this time, everyone will record the account with their own account books. Everyone has one The ledger can avoid the possibility of tampering with the ledger.