Blockchain buffer pool

1. Introction to seven core technologies of blockchain operation on January 15, 2018
1. Blockchain links
as the name suggests, blockchain is a chain composed of blocks. Each block is divided into block head and block body (including transaction data). The block head includes the prevhash value (also known as hash value) of the previous block used to realize the block link and the random number (nonce) used to calculate the mining difficulty. The hash value of the previous block is actually the hash value of the head of the previous block, and the random number calculation rule determines which miner can obtain the right to record the block
2. Consensus mechanism
blockchain is accompanied by the birth of bitcoin, which is the basic technology architecture of bitcoin. Blockchain can be understood as an Internet-based decentralized accounting system. A decentralized digital currency system like bitcoin requires the consistency of accounting of honest nodes without a central node, which needs blockchain to complete. Therefore, the core of blockchain technology is a consensus mechanism to reach a consensus on the legitimacy of transactions between indivials without mutual trust without central control
there are four main types of consensus mechanisms in blockchain: pow, POS, dpos and distributed consistency algorithm
3. Unlocking script
script is an important technology to realize automatic verification and contract execution on blockchain. Every output of every transaction does not point to an address in the strict sense, but to a script. A script is like a set of rules that constrain how the receiver can spend the asset locked on the output
the validation of transactions also depends on scripts. At present, it depends on two kinds of scripts: Lock script and unlock script. Locking script is a condition added to the output transaction, which is realized by a script language and located in the output of the transaction. The unlocking script corresponds to the locking script. Only when the conditions required by the locking script are met can the assets corresponding to the script be spent, which is located in the input of the transaction. Many flexible conditions can be expressed by script language. Interpretation script is similar to the "virtual machine" in our programming field, which runs in every node of the blockchain network in a distributed way
4. Transaction rules
blockchain transaction is not only the basic unit of a block, but also the actual effective content recorded by the blockchain. A blockchain transaction can be a transfer, or the deployment of smart contracts and other transactions
as far as bitcoin is concerned, a transaction refers to a single payment transfer. The transaction rules are as follows:
1) the input and output of the transaction cannot be empty
2) for each input of a transaction, if its corresponding utxo output can be found in the current transaction pool, the transaction will be rejected. Because the current transaction pool is the transaction not recorded in the blockchain, and each input of the transaction should come from the confirmed utxo. If it is found in the current trading pool, it is Shuanghua trading
3) for each input in a transaction, the corresponding output must be utxo
4) each input unlocking script must verify the compliance of the transaction together with the corresponding output locking script
5. Transaction priority
the priority of blockchain transaction is determined by the blockchain protocol rules. For bitcoin, the priority of a transaction to be included in a block is determined by the time when the transaction is broadcast to the network and the amount of the transaction. With the increase of transaction broadcast time on the network and the increase of transaction chain age, the priority of transaction will be improved and eventually be included by the block. For Ethereum, the priority of the transaction is also related to the transaction fee that the publisher is willing to pay. The higher the transaction fee that the publisher is willing to pay, the higher the priority that the transaction is included in the block
6. Merkle proof
the original application of Merkle proof is bitcoin, which was described and created by Satoshi Nakamoto in 2009. Bitcoin blockchain uses Merkle proof to store transactions in each block. So that the transaction can not be tampered with, but also easy to verify whether the transaction is included in a specific block
7. RLP
RLP (recursive length prefix) is one of the main encoding methods of object serialization in Ethereum. Its purpose is to encode the sequence of arbitrary nested binary data.

2.

Blockchain technology is widely used. Under the integration of new technologies, the main application scenarios of blockchain include finance and insurance, intelligent manufacturing, intelligent environmental protection, energy and power, health care, ecation, culture and innovation, smart city, social welfare, agriculture and many other fields

1. blockchain + finance

   blockchain can help financial institutions solve problems such as trust and data sharing

3. blockchain + right art

   Tianhe Guoyun's blockchain right system

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3. Blockchain + government

in statistics, voting, budget management and other aspects, blockchain can rece costs, improve efficiency, and increase transparency, so as to prevent the risk of failure of centralized system

4. Blockchain + insurance

fraud identification and risk prevention: by placing insurance claims under an unchangeable general ledger, blockchain helps to eliminate the common sources of fraud in the insurance instry

property insurance and accidental injury insurance: policies and shared ledgers recorded in the form of smart contracts can improve the efficiency of property insurance and accidental injury insurance

Health Insurance: blockchain technology enables medical records to be encrypted and shared among health service providers, thus improving the interoperability of the health insurance ecosystem

Reinsurance: the information security of reinsurance contracts on the blockchain platform can be ensured through the form of smart contracts, which can rece the amount of information and simplify the payment process between insurers and reinsurers

3. At present, there are four main types of consensus mechanisms: pow, POS, dpos, pool
1. POW workload proof, which is familiar with mining, calculates a random number that meets the rules through and or operation, that is, obtains the bookkeeping right, sends out the data that needs to be recorded in this round, and stores it together with other nodes in the whole network after verification
advantages: complete decentralization, free access of nodes
disadvantages: bitcoin has attracted most of the computing power in the world, and other blockchain applications using POW consensus mechanism are difficult to obtain the same computing power to ensure their own security; Mining causes a lot of waste of resources; The period of reaching consensus is long, which is not suitable for commercial application.

2. Proof of rights and interests of POS, a mechanism of upgrading consensus of pow; According to the token proportion and time of each node; It can rece the difficulty of mining in equal proportion, so as to speed up the speed of finding random numbers< Advantages: to a certain extent, it shortens the time to reach a consensus
disadvantages: mining is still needed, which does not solve the pain point of commercial application in essence

3. Dpos share authorization certification mechanism is similar to the voting of the board of directors, in which the coin holders cast a certain number of nodes to verify and account on their behalf
advantages: greatly rece the number of participating verification and accounting nodes, which can achieve second level consensus verification
disadvantages: the whole consensus mechanism still depends on token, and many commercial applications do not need token to exist

4. Pool verification pool, which is based on traditional distributed consistency technology and data verification mechanism; It is a consensus mechanism widely used in the instry chain at present.
advantages: it can work without token, and realizes second level consensus verification on the basis of mature distributed consistency algorithms (pasox and raft)
disadvantages: the degree of decentralization is not as good as that of bictin; The multi center business model is more suitable for multi-party participation

it has great advantages in using consensus mechanism to ensure data consistency (the consensus mechanism is first proposed by ripple, and the network transaction synchronization mechanism with data correctness priority. In the consensus network, no matter how the software code changes, if you can't reach a consensus, you can't enter the network, let alone fork)
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PS: a little black, although the consensus mechanism can absolutely ensure that there will be no hard bifurcation at any time. However, the disadvantage of this mechanism is obvious, that is, it is much longer than the current bitcoin network to reach a consensus with other nodes. In extreme cases, the consequences of disconnection in ripple consensus mechanism network are also very terrible

it is possible that one day after the power failure in your home, the whole system will no longer be able to reach a consensus with other rippled nodes (in fact, the consensus mechanism requires more than 80% of the nodes to acknowledge your data before your submission will be accepted by other nodes, otherwise it will be rejected by exclusive nodes), Even you can only empty all your 500 GB data and resynchronize to connect to other ripple nodes

so at present, the existing rippled end is not suitable for civil use (if it is commercial, the impact is relatively small. For example, RL's own rippled node is hosted in Amazon cloud data center. If it has no response for a long time, it can make high claims, and there is almost no break in that place except for large disasters). This is one of the aspects RL has always wanted to improve.

4.

In the traditional supply chain finance, financing difficulty, high financing cost and cumbersome financing process have always been one of the bottlenecks restricting small and medium-sized enterprises to become bigger and stronger. Banks rely on the ability of core enterprises to control goods and regulate sales. For the sake of risk control, banks are only willing to provide factoring services to upstream suppliers (limited to first tier suppliers) with direct accounts payable obligations of core enterprises, or provide prepayment or inventory financing to their downstream distributors (first tier suppliers). As a result, the demand of secondary and tertiary suppliers / distributors with huge financing demand can not be met, the business volume of supply chain finance is limited, and the small and medium-sized enterprises can not get timely financing, which will easily lead to proct quality problems and damage the whole supply chain system

to solve these problems, we can make use of the characteristics of decentralized, tamper proof and distributed ledger of blockchain technology to build a blockchain supply chain financial platform

The core enterprise issues a / R certificate to the distributor. After the distributor signs the receipt, it indicates that it has signed the purchase and sales contract and the core enterprise delivers the goods

Because of the shortage of funds, distributors need to borrow money from finance

3. After the financial institutions have approved, the amount of loans will be sent to the core enterprises

The distributor will repay the loan and interest after selling the goods

5.

The most important reason why blockchain is questioned is that there is no practical application scenario, and ordinary people can't see the possible value. In the eyes of these experts, where are the most likely application scenarios of blockchain

Shuai Chu, the founder of quantum chain, said: at present, the evolution of the whole blockchain technology is still at an early stage, just like the Internet era 20 years ago. At that time, we could not imagine that there would be applications like Uber on the Internet. The development of technology would give you more diversity. The possibility is the future

According to the technical characteristics of blockchain, Zeng Ming, Dean of Hupan University, gave several possible answers:

1. The most important advantage of blockchain is transparent, unchangeable and distributed ledger. Some areas have never been covered by the Internet, such as acceptance bills

2. Another big advantage of blockchain is that from the perspective of smart contract, it is possible to form more efficient network collaboration at the point-to-point level. Like crowdfunding

3. In the field of innovation, blockchain will definitely be closely combined with the development of Internet of things, artificial intelligence and other fields, including cloud computing, edge computing and so on

6. At present, the exchange rate between vnd and RMB is about 2600:1. You can exchange the money for 7 yuan and 23 cents. The price of a bowl of beef powder is not enough in some places..

7. Blockchain is a kind of account book recording technology. It can record every bitcoin from generation to circulation through the network, showing how many financial contracts can be digitized, identified and stored safely, and transmitted instantaneously. A bitcoin corresponds to a solution. Only after getting a correct solution through the miner can we get the bitcoin corresponding to that solution, and a bitcoin corresponds to a special solution. Therefore, blockchain is not the solution, but the ledger recording the flow of bitcoin. For more information, pay attention to Weibo: digital assets and business value-added points training