Distributed consensus method in Ethereum
Publish: 2021-04-23 10:59:33
1.
what is Ethereum:
Ethereum is an innovation based on the application of technologies and concepts in bitcoin to computers. Ethereum itself imitates a lot of bitcoin technology to maintain the computer platform. blockchain technology is one of them
Ethereum platform can safely run any program users want
advantages of Ethereum over other competitive currencies before Ethereum appeared, some digital currencies imitated bitcoin. However, these projects have their own shortcomings, they can only support one or several specific applications at the same time< However, the reason why Ethereum can surpass the limitations of these projects in the past is because of the core idea of Ethereum
what Ethereum wants to implement is a blockchain protocol with built-in programming language. Since it supports programming language, in theory, any blockchain application can be defined with this language, and then run on Ethereum's blockchain protocol as an application
The design of Ethereum is very flexible and adaptable
Ethereum target sets the advantages of blockchain technology, in order to add the advantages of blockchain, such as decentralization, openness and security, to almost all computing fields
blockchain applications of Ethereum
Ethereum has many blockchain applications, such as digital applications of gold and stocks, financial derivatives applications, DNS and digital authentication, etc
Ethereum has achieved more than 100 blockchain applications by many start-ups
Ethereum has also been closely watched by some financial institutions, banking consortia (such as R3), as well as large companies like Samsung, Deloitte, RWE and IBM. As a result, a number of blockchain applications such as simplified and automated financial transactions, merchant loyalty index tracking, and gift cards designed to achieve decentralization of electronic transactions have emerged
the relationship between Ethereum and blockchain:
Ethereum is a programmable blockchain
Ethereum does not give users a series of preset operations (such as bitcoin transaction), but allows users to create complex operations according to their own wishes
in this way, Ethereum can be used as a platform for various types of decentralized blockchain applications, including but not limited to cryptocurrency
like other blockchains, Ethereum also has a peer-to-peer network protocol. Ethereum blockchain database is maintained and updated by many nodes connected to the network. Each network node runs the Ethereum simulator and executes the same instructions. Therefore, people sometimes call Ethereum "world computer"
2. Ethereum blockchain has exposed three major problems, and its founder vitalik buterin has been unable to interpret them for a long time. The first is the low performance and TPS of Ethereum blockchain as a whole; The second is that resources are not isolated. The event of cryptokitties virtual cat once occupied 20% of the traffic of the whole Ethereum, which directly caused Ethereum network users unable to carry out timely transactions, which is the biggest pain point of resources not isolated; The third problem lies in the embodiment of Ethereum's governance structure. As a decentralized distributed ledger, the founder team of Ethereum has dominated its network development in the past. The over centralized governance mode has led to the bifurcation of eth, etc and ETF in Ethereum, and the Ethereum community is now in a state of fragmented governance. In the view of Ma Haobo, founder and CEO of "aelf", all kinds of disadvantages of Ethereum are unacceptable. Therefore, the positioning of "aelf" is born for the next generation of decentralized underlying computing platform of Ethereum, which focuses on solving the problems of insufficient performance, non isolation of resources and governance structure of Ethereum.
3. At the top of Ethereum is DAPP. It exchanges with the smart contract layer through Web3. JS. All smart contracts run on EVM (Ethereum virtual machine) and use RPC calls. Below EVM and RPC are the four core contents of Ethereum, including: blockchain, consensus algorithm, mining and network layer. Except DAPP, all other parts are in the Ethereum client. The most popular Ethereum client is geth (go Ethereum)
4. 1. What is the ether classic<
etc (Ethereum Classic) is a bifurcated currency that Ethereum hard bifurcates after 1920000 blocks, and its function is very similar to Ethereum. Etc adheres to the concept of decentralization and supports the consensus mechanism of blockchain guarantee. Etc firmly believes that once the blockchain starts to run, its development direction will not be controlled by any central team, but will be determined by the consensus of the people participating in the whole network and the consensus of the computing power of the whole network
the Ethereum blockchain hard branching in July 2016 aims to transfer the Dao funds stolen by hackers to an account controlled by investors, and let the old transaction records be forgotten by history. Most Ethereum developers are involved in the reversal, as are exchanges, startups and other members of the ecosystem. A few days later, the project returned to normal. But not everyone wants to forget the old record. As a result, a small number of miners continued to use the original blockchain as a protest. They described the hard fork as a capital withdrawal for the abandoned project of the Dao. So Ethereum classic (etc) was born
2. Detailed parameters
Chinese Name: Ethereum classic English Name: Ethereum classic English abbreviation: etc
developer: Ethereum Classic team core algorithm: ethash consensus proof: POW
release date: 2016 / 7 / 20 block time: About 15-17 seconds / block
total currency: fixed at 210 million, up to 230 million, Every 5 million blocks decelerate by 20%, and the first proction rection is expected to be in December 2017
main features: independent cryptocurrency
etc (Ethereum Classic) is a bifurcated currency that Ethereum hard bifurcates after 1920000 blocks, and its function is very similar to Ethereum. Etc adheres to the concept of decentralization and supports the consensus mechanism of blockchain guarantee. Etc firmly believes that once the blockchain starts to run, its development direction will not be controlled by any central team, but will be determined by the consensus of the people participating in the whole network and the consensus of the computing power of the whole network
the Ethereum blockchain hard branching in July 2016 aims to transfer the Dao funds stolen by hackers to an account controlled by investors, and let the old transaction records be forgotten by history. Most Ethereum developers are involved in the reversal, as are exchanges, startups and other members of the ecosystem. A few days later, the project returned to normal. But not everyone wants to forget the old record. As a result, a small number of miners continued to use the original blockchain as a protest. They described the hard fork as a capital withdrawal for the abandoned project of the Dao. So Ethereum classic (etc) was born
2. Detailed parameters
Chinese Name: Ethereum classic English Name: Ethereum classic English abbreviation: etc
developer: Ethereum Classic team core algorithm: ethash consensus proof: POW
release date: 2016 / 7 / 20 block time: About 15-17 seconds / block
total currency: fixed at 210 million, up to 230 million, Every 5 million blocks decelerate by 20%, and the first proction rection is expected to be in December 2017
main features: independent cryptocurrency
5. The token of Ethereum is proced in the process of mining, with a mining rate of 5 Ethereum coins per piece. The mining process of Ethereum is almost the same as that of bitcoin. For each transaction, miners can use the computer to run the unique title metadata of the block through hash function, and guess the answer repeatedly and quickly until one of them wins
many new users believe that the sole purpose of mining is to generate ether in a way that does not require a central issuer (see our guide "what is ether?"). It's true. The token of Ethereum is proced in the process of mining, with a mining rate of 5 Ethereum coins per piece. But mining is at least as important. Usually, banks are responsible for keeping accurate records of transactions. They make sure that money is not created out of thin air and that users don't cheat and spend money many times. However, blockchain introces a new way to keep records, the whole network instead of intermediary, to verify transactions and add them to the public ledger
Ethereum mining
although "no trust" or "trust minimization" monetary system is the goal, there are still people who need to ensure the security of financial records and ensure that no one cheats. Mining is one of the innovations that makes decentralized records possible. Miners have reached a consensus on the history of transactions in terms of preventing fraud (especially double spending on ether) - an interesting issue that hasn't been addressed before the decentralized currency works on the blockchain. While Ethereum is looking at other ways to reach a consensus on the effectiveness of the deal, mining currently keeps the platform together
how mining works
today, the mining process of Ethereum is almost the same as that of bitcoin. For each transaction, the miner can use the computer to guess the answer repeatedly and quickly until one of them wins. More specifically, the miner will run the unique header metadata (including time stamp and software version) of the block through the hash function (which will return a fixed length, unordered string of numbers and letters, which appears to be random), changing only the 'nonce value', which will affect the hash value of the result
if the miner finds a hash that matches the current target, the miner will be granted ether and broadcast the block across the network for each node to verify and add to their own ledger . If miner B finds the hash, miner a stops working on the current block and repeats the process for the next block. It's hard for miners to cheat in this game. There is no way to fake the work and come up with the right answer to the puzzle. That's why solving puzzles is called "proof of work."
on the other hand, others have little time to verify whether the hash value is correct, which is exactly what each node does. About every 12-15 seconds, a miner finds a stone. If the miner starts to solve the puzzle faster or slower than this, the algorithm will automatically re adjust the difficulty of the problem so that the miner can rebound to about 12 seconds of solution time
miners earn these ethers randomly, and their profitability depends on their luck and the computing power they put in. The specific workload verification algorithm used by Ethereum is called "ethash", which aims to require more memory, making it difficult to mine with expensive ASIC. Special mining chips are now the only profitable way to mine bitcoin
in a sense, ethash may have achieved this goal successfully, because dedicated ASIC is not available for Ethereum (at least not yet). In addition, as Ethereum aims to shift from proof of work mining to "proof of equity" (which we will discuss below), buying ASIC may not be a wise choice because it may not prove useful for a long time< However, Ethereum may never need miners. Developers plan to abandon proof of work, the algorithm currently used by the network to determine which transactions are valid and protect them from tampering to support proof of equity, which is guaranteed by token owners. If and when the algorithm is launched, proof of equity can become a means to achieve distributed consensus, and the consensus uses less resources.
many new users believe that the sole purpose of mining is to generate ether in a way that does not require a central issuer (see our guide "what is ether?"). It's true. The token of Ethereum is proced in the process of mining, with a mining rate of 5 Ethereum coins per piece. But mining is at least as important. Usually, banks are responsible for keeping accurate records of transactions. They make sure that money is not created out of thin air and that users don't cheat and spend money many times. However, blockchain introces a new way to keep records, the whole network instead of intermediary, to verify transactions and add them to the public ledger
Ethereum mining
although "no trust" or "trust minimization" monetary system is the goal, there are still people who need to ensure the security of financial records and ensure that no one cheats. Mining is one of the innovations that makes decentralized records possible. Miners have reached a consensus on the history of transactions in terms of preventing fraud (especially double spending on ether) - an interesting issue that hasn't been addressed before the decentralized currency works on the blockchain. While Ethereum is looking at other ways to reach a consensus on the effectiveness of the deal, mining currently keeps the platform together
how mining works
today, the mining process of Ethereum is almost the same as that of bitcoin. For each transaction, the miner can use the computer to guess the answer repeatedly and quickly until one of them wins. More specifically, the miner will run the unique header metadata (including time stamp and software version) of the block through the hash function (which will return a fixed length, unordered string of numbers and letters, which appears to be random), changing only the 'nonce value', which will affect the hash value of the result
if the miner finds a hash that matches the current target, the miner will be granted ether and broadcast the block across the network for each node to verify and add to their own ledger . If miner B finds the hash, miner a stops working on the current block and repeats the process for the next block. It's hard for miners to cheat in this game. There is no way to fake the work and come up with the right answer to the puzzle. That's why solving puzzles is called "proof of work."
on the other hand, others have little time to verify whether the hash value is correct, which is exactly what each node does. About every 12-15 seconds, a miner finds a stone. If the miner starts to solve the puzzle faster or slower than this, the algorithm will automatically re adjust the difficulty of the problem so that the miner can rebound to about 12 seconds of solution time
miners earn these ethers randomly, and their profitability depends on their luck and the computing power they put in. The specific workload verification algorithm used by Ethereum is called "ethash", which aims to require more memory, making it difficult to mine with expensive ASIC. Special mining chips are now the only profitable way to mine bitcoin
in a sense, ethash may have achieved this goal successfully, because dedicated ASIC is not available for Ethereum (at least not yet). In addition, as Ethereum aims to shift from proof of work mining to "proof of equity" (which we will discuss below), buying ASIC may not be a wise choice because it may not prove useful for a long time< However, Ethereum may never need miners. Developers plan to abandon proof of work, the algorithm currently used by the network to determine which transactions are valid and protect them from tampering to support proof of equity, which is guaranteed by token owners. If and when the algorithm is launched, proof of equity can become a means to achieve distributed consensus, and the consensus uses less resources.
6. Ethereum is a distributed computing platform. It generates an cryptocurrency called ether. Programmers can write "smart contracts" on the Ethereum blockchain, and these Ethereum smart contracts will be executed automatically according to the code
what is Ethereum
Ethereum is often compared with bitcoin, but the situation is different. Bitcoin is a kind of cryptocurrency and distributed payment network, which allows bitcoin to be transferred between users
related: what is bitcoin? How does it work
Ethereum has a bigger goal. As Ethereum says, "Ethereum is a distributed platform running smart contracts.". These smart contracts run on "Ethereum virtual machine", a distributed computing network composed of all devices running Ethernet nodes
"distributed platform" means that anyone can set up and run an Ethereum node just as anyone can run a bitcoin node. Anyone who wants to run "smart contracts" on nodes must pay the operators of these nodes in ether, which is a cryptocurrency related to Ethereum. Therefore, the person running the Ethernet node provides computing power and gets paid in the Ethernet, which is similar to the way that the person running the bitcoin node provides hash power and pays in bitcoin
in other words, although bitcoin is only a blockchain and payment network, Ethereum is a distributed computing network, and its blockchain can be used for many other things. Details are provided in the Ethereum white paper
what is ether
Ethernet is a digital token (or cryptocurrency) related to Ethereum blockchain. In other words, Ethereum is the token and Ethereum is the platform. But now people often use these terms alternately. For example, coinbase allows you to buy Ethereum, which stands for Ethereum
this is technically "altcoin", which actually means a non bitcoin cryptocurrency. Like bitcoin, ether is supported by distributed blockchain - in this case, Ethereum blockchain
developers who want to create applications or Ethereum smart contracts on Ethereum blockchain need Ethernet token to pay for nodes to host it, while users of Ethereum based applications may need Ethernet to pay for services in these applications. People can also sell services outside the Ethereum network and accept Ethernet payments, or they can sell Ethernet tokens in cash - just like bitcoin
what is Ethereum
Ethereum is often compared with bitcoin, but the situation is different. Bitcoin is a kind of cryptocurrency and distributed payment network, which allows bitcoin to be transferred between users
related: what is bitcoin? How does it work
Ethereum has a bigger goal. As Ethereum says, "Ethereum is a distributed platform running smart contracts.". These smart contracts run on "Ethereum virtual machine", a distributed computing network composed of all devices running Ethernet nodes
"distributed platform" means that anyone can set up and run an Ethereum node just as anyone can run a bitcoin node. Anyone who wants to run "smart contracts" on nodes must pay the operators of these nodes in ether, which is a cryptocurrency related to Ethereum. Therefore, the person running the Ethernet node provides computing power and gets paid in the Ethernet, which is similar to the way that the person running the bitcoin node provides hash power and pays in bitcoin
in other words, although bitcoin is only a blockchain and payment network, Ethereum is a distributed computing network, and its blockchain can be used for many other things. Details are provided in the Ethereum white paper
what is ether
Ethernet is a digital token (or cryptocurrency) related to Ethereum blockchain. In other words, Ethereum is the token and Ethereum is the platform. But now people often use these terms alternately. For example, coinbase allows you to buy Ethereum, which stands for Ethereum
this is technically "altcoin", which actually means a non bitcoin cryptocurrency. Like bitcoin, ether is supported by distributed blockchain - in this case, Ethereum blockchain
developers who want to create applications or Ethereum smart contracts on Ethereum blockchain need Ethernet token to pay for nodes to host it, while users of Ethereum based applications may need Ethernet to pay for services in these applications. People can also sell services outside the Ethereum network and accept Ethernet payments, or they can sell Ethernet tokens in cash - just like bitcoin
7. The bifurcation of Ethereum Constantinople is about to begin. Many people are curious about this bifurcation and are not sure whether they need to be prepared in advance
to put it simply: if you are only the holder of eth, you don't need to make any preparation for this upgrade.
to put it simply: if you are only the holder of eth, you don't need to make any preparation for this upgrade.
9. Casper is a consensus mechanism of the next generation of Ethereum, which belongs to POS. Casper's consensus was reached by blocks, not by chains, as pos did. Currency exchange of digital currency
10. What do pow, POS and dpow mean
when it comes to blockchain, we must talk about its consensus mechanism. If we don't understand the consensus mechanism of blockchain, we can't understand the real meaning of blockchain. So, what about the consensus mechanism of today's blockchain
what is the consensus mechanism
what is consensus? Take its literal meaning, that is & quot; Common understanding & quot
people are different, not only in stature, appearance and ability, but also in culture, views, ideas, interests and so on
consensus, in short, is the consensus reached by members of a group in a certain aspect
we have learned that trust is a major pain point in the operation of society. Banks have their own credit system. In the past, the financial system only served a few entrepreneurs, because the establishment of credit system cost a lot. Later, Alipay had sesame credit. Credit has already been related to many aspects of life, credit card size, spending amount of flowers, sesame credit and high going abroad can be avoided. We are enjoying the convenience of credit
the essence of blockchain is decentralization, and the core of decentralization is consensus mechanism. The consensus mechanism on blockchain mainly solves the problems of who constructs the block and how to maintain the unity of blockchain
the goal of the blockchain consensus mechanism is to make all honest nodes save consistent blockchain views, while meeting two properties:
1) consistency: the prefix part of the blockchain saved by all honest nodes is exactly the same
2) effectiveness: the information released by an honest node will be recorded in its own blockchain by all other honest nodes
the confidence of blockchain is mainly reflected in the fact that users distributed in the blockchain do not need to trust the other party of the transaction or a centralized organization, and only need to trust the software system under the blockchain protocol to realize the transaction
what is the consensus mechanism? What do pow, POS and dpow mean
the necessity of consensus mechanism
in a distributed system, multiple hosts form a network cluster through asynchronous communication. In such an asynchronous system, state replication between hosts is needed to ensure that each host can reach a consensus. Error messages may appear in asynchronous systems and propagate continuously, so it is necessary to define fault-tolerant protocols in default unreliable asynchronous networks to ensure that all hosts reach a safe and reliable state consensus, which is the necessity of consensus mechanism
the premise of such self-confidence is the consensus mechanism of the blockchain, that is, in a market of mutual distrust, the sufficient and necessary condition for each node to reach an agreement is that each node will spontaneously and honestly abide by the pre-set rules in the agreement to judge the authenticity of each record for the sake of maximizing its own interests, Finally, the records judged to be true are recorded in the blockchain. Attachments-2018-08-9yy7vrha5b738e3d96021. JPG
in other words, if each node has its own independent interests and competes with each other, it is almost impossible for these nodes to conspire to cheat you, especially when they have public reputation in the network. Blockchain technology is the use of a set of mathematical algorithms based on consensus to establish & quot; Trust & quot; Network, so as to create new credit through technical endorsement rather than centralized credit institutions
Introction to several consensus mechanisms in today's blockchain
there are many consensus mechanisms in blockchain, but none of them is perfect, or suitable for all application scenarios
POW workload proof
each node in the whole system provides computing power (referred to as computing power) for the whole system. Through a competitive mechanism, the node with the best computing work can be rewarded by the system, that is, to complete the allocation of newly generated currency. It is simply understood that more work pays more. Currency blockchains such as bitcoin and LTC apply POW mechanism
advantages
completely decentralize the nodes to get in and out freely, the algorithm is simple, easy to realize, and the cost of destroying the system is huge. As long as the computing power of the network destroyer does not exceed 50% of the total computing power of the network, the transaction status of the network can reach an agreement
disadvantages
waste energy, which is the biggest disadvantage. It is difficult to shorten the block confirmation time, for example, bitcoin can only do 7 transactions per second, It is not suitable for commercial application. A new blockchain must find a different hash algorithm, or it will face bitcoin's computing power attack. It has high requirements on the performance of the nodes, and the network environment is prone to bifurcation. It needs to wait for multiple confirmations, and can not reach the final agreement
POS proof of equity
also known as proof of equity, which is similar to you deposit your property in the bank, This model will allocate interest to you according to the amount and time of cryptocurrency you hold< Advantages
low requirements for node performance and short consensus time
disadvantages
there is no final consistency, so checkpoint mechanism is needed to make up for the finality
dpow is an evolutionary scheme of pos. in conventional POW and POS, any newly added block needs to be confirmed by all nodes of the whole network, which greatly affects the efficiency
dpos is similar to the voting mechanism of modern board of directors, which elects representatives to vote and make decisions. The N selected accounting nodes are used for the creation, verification, signature and mutual supervision of new blocks, which greatly reces the time and computational cost of block creation and confirmation
advantages
greatly rece the number of nodes participating in verification and accounting, which can achieve second level consensus verification
disadvantages
sacrifice the concept of decentralization, which is not suitable for public chain
pbft practical Byzantine fault tolerance
practical Byzantine fault tolerance mechanism is a kind of adoption & quot; Permission to vote, minority subject to majority & quot; The consensus mechanism allows Byzantine fault tolerance, allows strong supervision nodes to participate, has the ability of authority classification, higher performance and lower energy consumption, and each round of bookkeeping will be jointly elected by the whole network nodes, allowing 33% of nodes to do evil, and the fault tolerance rate is 33%. Practical Byzantine fault tolerance is especially suitable for the application scenario of alliance chain<
advantages
will deviate from centralization, the existence of cryptocurrency and reward mechanism will proce Matthew effect, making the poor poorer and the rich richer in the community, achieving high consensus efficiency and realizing high-frequency trading
disadvantages
when only 33% of the nodes in the system are running, the system will stop running
dbft authorizes Byzantine fault tolerance
this mechanism is to use rights to select bookkeeper, Then bookkeepers reach a consensus through Byzantine fault-tolerant algorithm. The core of Byzantine fault tolerance mechanism is to ensure the system's finality to the maximum extent, so that the blockchain can be applied to real financial application scenarios
advantages
Professional bookkeeper can tolerate any type of error, bookkeeping is completed by multiple people, each block has finality, no bifurcation, the reliability of the algorithm has strict mathematical proof
disadvantages
when one-third or more bookkeepers stop working, the system will not be able to provide services, when one-third or more bookkeepers jointly commit crimes, The system may be bifurcated
pool verification pool
based on traditional distributed consistency technology and data verification mechanism
advantages
it can work without cryptocurrency. Based on the mature distributed consistency algorithms (pasox, raft), it realizes second level consensus verification
disadvantages
the degree of decentralization is not as good as bitcoin, which is more suitable for the multi center business model with multi participation
Paxos
this is a traditional distributed consensus algorithm, which is a consensus mechanism based on election leaders. The leader node has absolute authority, and allows strong supervision node to participate, which has high performance and low resource consumption. Generally, all nodes have wired access mechanism, but there is no malicious node in the election process, which is not fault-tolerant< In Paxos algorithm, nodes are divided into three types:
proposer: put forward a proposal and wait for everyone's approval. The client often plays the role
acceptor: responsible for voting on the proposal. Usually, the server plays this role
learner: is informed of the result of the case settlement, and unifies with it, and does not participate in the voting process. Maybe the client or server
Paxos can ensure that the system can reach a consensus when more than 50% of the normal nodes exist
REBO consensus mechanism
REBO consensus algorithm enables a group of nodes to form a consensus based on the special node list. The initial special node list is like a club. To accept a new member, it must be voted by 51% of the members of the club. Consensus follows the & quot; 51% rights;, Outsiders have no influence. Since the club starts with centralization, it will always be, and if it starts to corrupt, shareholders can do nothing. Like bitcoin and peercoin, the reborn system separates shareholders from their voting rights, so it is more centralized than other systems
peercoin
peercoin (PPC) is a combination of proof of pow workload and proof of POS equity. POW is mainly used to issue currency. In the future, with the increase of mining difficulty, the output will decrease, and the system security will be mainly maintained by POS
in the blockchain network, e to different application scenarios, different goals are designed, and different blockchain systems adopt different consensus algorithms. Each consensus algorithm is not perfect and has its own advantages and limitations
blockchain solves the problems of transmitting trusted information and value transfer on untrusted channels, while consensus mechanism solves the problem of how blockchain achieves consistency in distributed scenarios
although the blockchain is still in the early stage of development, and the instry development is still facing some obstacles, the society has recognized the value of the blockchain enough, the pace of blockchain development will never stop, and the instry development will certainly find a way to break through the obstacles.
when it comes to blockchain, we must talk about its consensus mechanism. If we don't understand the consensus mechanism of blockchain, we can't understand the real meaning of blockchain. So, what about the consensus mechanism of today's blockchain
what is the consensus mechanism
what is consensus? Take its literal meaning, that is & quot; Common understanding & quot
people are different, not only in stature, appearance and ability, but also in culture, views, ideas, interests and so on
consensus, in short, is the consensus reached by members of a group in a certain aspect
we have learned that trust is a major pain point in the operation of society. Banks have their own credit system. In the past, the financial system only served a few entrepreneurs, because the establishment of credit system cost a lot. Later, Alipay had sesame credit. Credit has already been related to many aspects of life, credit card size, spending amount of flowers, sesame credit and high going abroad can be avoided. We are enjoying the convenience of credit
the essence of blockchain is decentralization, and the core of decentralization is consensus mechanism. The consensus mechanism on blockchain mainly solves the problems of who constructs the block and how to maintain the unity of blockchain
the goal of the blockchain consensus mechanism is to make all honest nodes save consistent blockchain views, while meeting two properties:
1) consistency: the prefix part of the blockchain saved by all honest nodes is exactly the same
2) effectiveness: the information released by an honest node will be recorded in its own blockchain by all other honest nodes
the confidence of blockchain is mainly reflected in the fact that users distributed in the blockchain do not need to trust the other party of the transaction or a centralized organization, and only need to trust the software system under the blockchain protocol to realize the transaction
what is the consensus mechanism? What do pow, POS and dpow mean
the necessity of consensus mechanism
in a distributed system, multiple hosts form a network cluster through asynchronous communication. In such an asynchronous system, state replication between hosts is needed to ensure that each host can reach a consensus. Error messages may appear in asynchronous systems and propagate continuously, so it is necessary to define fault-tolerant protocols in default unreliable asynchronous networks to ensure that all hosts reach a safe and reliable state consensus, which is the necessity of consensus mechanism
the premise of such self-confidence is the consensus mechanism of the blockchain, that is, in a market of mutual distrust, the sufficient and necessary condition for each node to reach an agreement is that each node will spontaneously and honestly abide by the pre-set rules in the agreement to judge the authenticity of each record for the sake of maximizing its own interests, Finally, the records judged to be true are recorded in the blockchain. Attachments-2018-08-9yy7vrha5b738e3d96021. JPG
in other words, if each node has its own independent interests and competes with each other, it is almost impossible for these nodes to conspire to cheat you, especially when they have public reputation in the network. Blockchain technology is the use of a set of mathematical algorithms based on consensus to establish & quot; Trust & quot; Network, so as to create new credit through technical endorsement rather than centralized credit institutions
Introction to several consensus mechanisms in today's blockchain
there are many consensus mechanisms in blockchain, but none of them is perfect, or suitable for all application scenarios
POW workload proof
each node in the whole system provides computing power (referred to as computing power) for the whole system. Through a competitive mechanism, the node with the best computing work can be rewarded by the system, that is, to complete the allocation of newly generated currency. It is simply understood that more work pays more. Currency blockchains such as bitcoin and LTC apply POW mechanism
advantages
completely decentralize the nodes to get in and out freely, the algorithm is simple, easy to realize, and the cost of destroying the system is huge. As long as the computing power of the network destroyer does not exceed 50% of the total computing power of the network, the transaction status of the network can reach an agreement
disadvantages
waste energy, which is the biggest disadvantage. It is difficult to shorten the block confirmation time, for example, bitcoin can only do 7 transactions per second, It is not suitable for commercial application. A new blockchain must find a different hash algorithm, or it will face bitcoin's computing power attack. It has high requirements on the performance of the nodes, and the network environment is prone to bifurcation. It needs to wait for multiple confirmations, and can not reach the final agreement
POS proof of equity
also known as proof of equity, which is similar to you deposit your property in the bank, This model will allocate interest to you according to the amount and time of cryptocurrency you hold< Advantages
low requirements for node performance and short consensus time
disadvantages
there is no final consistency, so checkpoint mechanism is needed to make up for the finality
dpow is an evolutionary scheme of pos. in conventional POW and POS, any newly added block needs to be confirmed by all nodes of the whole network, which greatly affects the efficiency
dpos is similar to the voting mechanism of modern board of directors, which elects representatives to vote and make decisions. The N selected accounting nodes are used for the creation, verification, signature and mutual supervision of new blocks, which greatly reces the time and computational cost of block creation and confirmation
advantages
greatly rece the number of nodes participating in verification and accounting, which can achieve second level consensus verification
disadvantages
sacrifice the concept of decentralization, which is not suitable for public chain
pbft practical Byzantine fault tolerance
practical Byzantine fault tolerance mechanism is a kind of adoption & quot; Permission to vote, minority subject to majority & quot; The consensus mechanism allows Byzantine fault tolerance, allows strong supervision nodes to participate, has the ability of authority classification, higher performance and lower energy consumption, and each round of bookkeeping will be jointly elected by the whole network nodes, allowing 33% of nodes to do evil, and the fault tolerance rate is 33%. Practical Byzantine fault tolerance is especially suitable for the application scenario of alliance chain<
advantages
will deviate from centralization, the existence of cryptocurrency and reward mechanism will proce Matthew effect, making the poor poorer and the rich richer in the community, achieving high consensus efficiency and realizing high-frequency trading
disadvantages
when only 33% of the nodes in the system are running, the system will stop running
dbft authorizes Byzantine fault tolerance
this mechanism is to use rights to select bookkeeper, Then bookkeepers reach a consensus through Byzantine fault-tolerant algorithm. The core of Byzantine fault tolerance mechanism is to ensure the system's finality to the maximum extent, so that the blockchain can be applied to real financial application scenarios
advantages
Professional bookkeeper can tolerate any type of error, bookkeeping is completed by multiple people, each block has finality, no bifurcation, the reliability of the algorithm has strict mathematical proof
disadvantages
when one-third or more bookkeepers stop working, the system will not be able to provide services, when one-third or more bookkeepers jointly commit crimes, The system may be bifurcated
pool verification pool
based on traditional distributed consistency technology and data verification mechanism
advantages
it can work without cryptocurrency. Based on the mature distributed consistency algorithms (pasox, raft), it realizes second level consensus verification
disadvantages
the degree of decentralization is not as good as bitcoin, which is more suitable for the multi center business model with multi participation
Paxos
this is a traditional distributed consensus algorithm, which is a consensus mechanism based on election leaders. The leader node has absolute authority, and allows strong supervision node to participate, which has high performance and low resource consumption. Generally, all nodes have wired access mechanism, but there is no malicious node in the election process, which is not fault-tolerant< In Paxos algorithm, nodes are divided into three types:
proposer: put forward a proposal and wait for everyone's approval. The client often plays the role
acceptor: responsible for voting on the proposal. Usually, the server plays this role
learner: is informed of the result of the case settlement, and unifies with it, and does not participate in the voting process. Maybe the client or server
Paxos can ensure that the system can reach a consensus when more than 50% of the normal nodes exist
REBO consensus mechanism
REBO consensus algorithm enables a group of nodes to form a consensus based on the special node list. The initial special node list is like a club. To accept a new member, it must be voted by 51% of the members of the club. Consensus follows the & quot; 51% rights;, Outsiders have no influence. Since the club starts with centralization, it will always be, and if it starts to corrupt, shareholders can do nothing. Like bitcoin and peercoin, the reborn system separates shareholders from their voting rights, so it is more centralized than other systems
peercoin
peercoin (PPC) is a combination of proof of pow workload and proof of POS equity. POW is mainly used to issue currency. In the future, with the increase of mining difficulty, the output will decrease, and the system security will be mainly maintained by POS
in the blockchain network, e to different application scenarios, different goals are designed, and different blockchain systems adopt different consensus algorithms. Each consensus algorithm is not perfect and has its own advantages and limitations
blockchain solves the problems of transmitting trusted information and value transfer on untrusted channels, while consensus mechanism solves the problem of how blockchain achieves consistency in distributed scenarios
although the blockchain is still in the early stage of development, and the instry development is still facing some obstacles, the society has recognized the value of the blockchain enough, the pace of blockchain development will never stop, and the instry development will certainly find a way to break through the obstacles.
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