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Blockchain raft
Publish: 2021-05-14 13:32:22
1. What is "decentralization"
"decentralization" is translated from the English word decentralization, which is composed of the prefix de -, stem central and suffix ization. Among them, the stem central means "center", the suffix - ization means "... Hua", and the prefix de - has the meanings of leaving, removing, canceling and opposite. Therefore, it is very accurate to translate it into decentralization
what is the meaning of decentralization
vitalik buterin, founder of Ethereum, published the article "the meaning of decentralization" in February 2017, elaborating the meaning of decentralization. He thinks that we should distinguish the centralization and decentralization of computer software from three perspectives: architecture, governance and logic
Architecture centralization refers to the number of nodes that the system can tolerate and continue to run; Governance centralization refers to how many indivials and organizations are needed to control the system; Logic centralization refers to whether the interface and data presented by the system are like a single whole
blockchain is a unified account book of the whole network, so it is logically centralized, which is beyond doubt. From the perspective of architecture, blockchain is based on peer-to-peer network, so it is decentralized. From the perspective of governance, blockchain makes it difficult for a few people to control the whole system through consensus algorithm, so it is decentralized. The decentralization of architecture and governance brings three benefits to blockchain: fault tolerance, anti attack and anti collusion
five differences between blockchain and traditional distributed system
as a new kind of distributed system, blockchain is often mistakenly regarded as a distributed database or log system. In fact, there is a fundamental difference between blockchain and traditional distributed system, namely decentralization. Now let's look at the main differences between blockchain and traditional distributed systems:
(1) consistency algorithm: what blockchain needs to solve is the Byzantine general problem, that is, there are one or more fraulent nodes in the network, which may deliberately violate the protocol or transmit wrong data, Therefore, Byzantine fault-tolerant consensus algorithms, such as BFT, pow, POS, are often used in blockchain; The traditional distributed system only needs to consider the node failure and communication errors, and often uses consistency algorithms such as Paxos and raft, which can not resist the fraulent nodes
(2) central controller: there is no central controller in the blockchain network, and no node can control or coordinate the generation of ledger data. All nodes coordinate through consensus algorithm to generate consistent ledger. However, the traditional publishing system is often controlled by one organization, which uniformly dispatches all nodes to participate in the calculation
(3) rule making: the rule of blockchain is consensus protocol, also known as consensus mechanism, and consensus algorithm is a part of it. Consensus mechanism is generally designed and developed by a person or a team, and the corresponding proceres are developed for the community to use. This seems to be the same as the traditional distributed system, but the change and upgrading of the consensus mechanism of the blockchain requires the community to have a consensus on it. If no consensus can be reached, anyone can implement hard bifurcation and build another community and chain. This is the decentralization process of consensus mechanism.
"decentralization" is translated from the English word decentralization, which is composed of the prefix de -, stem central and suffix ization. Among them, the stem central means "center", the suffix - ization means "... Hua", and the prefix de - has the meanings of leaving, removing, canceling and opposite. Therefore, it is very accurate to translate it into decentralization
what is the meaning of decentralization
vitalik buterin, founder of Ethereum, published the article "the meaning of decentralization" in February 2017, elaborating the meaning of decentralization. He thinks that we should distinguish the centralization and decentralization of computer software from three perspectives: architecture, governance and logic
Architecture centralization refers to the number of nodes that the system can tolerate and continue to run; Governance centralization refers to how many indivials and organizations are needed to control the system; Logic centralization refers to whether the interface and data presented by the system are like a single whole
blockchain is a unified account book of the whole network, so it is logically centralized, which is beyond doubt. From the perspective of architecture, blockchain is based on peer-to-peer network, so it is decentralized. From the perspective of governance, blockchain makes it difficult for a few people to control the whole system through consensus algorithm, so it is decentralized. The decentralization of architecture and governance brings three benefits to blockchain: fault tolerance, anti attack and anti collusion
five differences between blockchain and traditional distributed system
as a new kind of distributed system, blockchain is often mistakenly regarded as a distributed database or log system. In fact, there is a fundamental difference between blockchain and traditional distributed system, namely decentralization. Now let's look at the main differences between blockchain and traditional distributed systems:
(1) consistency algorithm: what blockchain needs to solve is the Byzantine general problem, that is, there are one or more fraulent nodes in the network, which may deliberately violate the protocol or transmit wrong data, Therefore, Byzantine fault-tolerant consensus algorithms, such as BFT, pow, POS, are often used in blockchain; The traditional distributed system only needs to consider the node failure and communication errors, and often uses consistency algorithms such as Paxos and raft, which can not resist the fraulent nodes
(2) central controller: there is no central controller in the blockchain network, and no node can control or coordinate the generation of ledger data. All nodes coordinate through consensus algorithm to generate consistent ledger. However, the traditional publishing system is often controlled by one organization, which uniformly dispatches all nodes to participate in the calculation
(3) rule making: the rule of blockchain is consensus protocol, also known as consensus mechanism, and consensus algorithm is a part of it. Consensus mechanism is generally designed and developed by a person or a team, and the corresponding proceres are developed for the community to use. This seems to be the same as the traditional distributed system, but the change and upgrading of the consensus mechanism of the blockchain requires the community to have a consensus on it. If no consensus can be reached, anyone can implement hard bifurcation and build another community and chain. This is the decentralization process of consensus mechanism.
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3. Blockchain is a decentralized distributed ledger system, which can be used to register and issue digital assets, property rights certificates, points, etc., and transfer, pay and trade in a point-to-point manner. Compared with the traditional centralized ledger system, blockchain system has the advantages of complete disclosure, tamper proof, multiple payment prevention, and does not rely on any trusted third party
e to the high network delay in peer-to-peer network, the transaction order observed by each node can not be completely consistent. Therefore, the blockchain system needs to design a mechanism to reach a consensus on the sequence of transactions that occur in the same time. This algorithm to reach consensus on the order of transactions in a time window is called consensus mechanism
-- chainknow
e to the high network delay in peer-to-peer network, the transaction order observed by each node can not be completely consistent. Therefore, the blockchain system needs to design a mechanism to reach a consensus on the sequence of transactions that occur in the same time. This algorithm to reach consensus on the order of transactions in a time window is called consensus mechanism
-- chainknow
4. 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)
- - - - - - - -
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.
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)
- - - - - - - -
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.
5. 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.
6. First of all, no consensus mechanism is perfect. Each consensus mechanism has its own advantages and disadvantages. Some consensus mechanisms are created to solve some specific problems
1. Pow (proof of work) workload proof
in a word: the more you do, the more you get
it relies on machines to perform mathematical operations to obtain accounting rights. Compared with other consensus mechanisms, the resource consumption is high and the supervision is weak. At the same time, the whole network needs to participate in the operation to reach a consensus every time, so the performance efficiency is relatively low. In terms of fault tolerance, 50% of nodes in the whole network are allowed to make mistakes< Advantages:
1) the algorithm is simple and easy to implement
2) there is no need to exchange additional information between nodes to reach a consensus
3) the cost of destroying the system is huge< Disadvantages:
1) waste of energy
2) it is difficult to shorten the block confirmation time
3) the new blockchain must find a different hash algorithm, otherwise it will face bitcoin attack
4) it is easy to generate bifurcation and needs to wait for multiple confirmations
5) there is no finality, and checkpoint mechanism is needed to make up for it
2. POS proof of stake
in a word: the more you hold, the more you get
the main idea is that the difficulty of obtaining the node's accounting right is inversely proportional to the equity held by the node. Compared with pow, the resource consumption brought by mathematical operation is reced to a certain extent, and the performance has also been improved correspondingly. However, it is still a way to obtain the accounting right based on hash operation competition, which is weak in supervision. The fault tolerance of the consensus mechanism is the same as pow. It is an upgrade consensus mechanism of pow, according to the proportion and time of token 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 can shorten the time of reaching consensus; No longer need to consume a lot of energy mining
disadvantages: mining is still needed, which does not solve the pain point of commercial application in essence; All the confirmations are just a probability expression, not a certainty. Theoretically, there may be other attack effects. For example, Ethereum's Dao attack event caused Ethereum's hard fork, and etc's appearance of this event actually proved the failure of this hard fork
the principle of dpos is the same as that of POS, except that some "deputies to the National People's Congress" are selected
bitshares community first proposed dpos mechanism
the main difference from POS is that the node elects several agents, which are verified and recorded by the agents. Its compliance, performance, resource consumption and fault tolerance are similar to POS. Similar to board voting, coin holders cast a certain number of nodes to verify and account on their behalf
the working principle of dpos is:
decentralization means that each shareholder has influence according to its shareholding ratio, and the voting result of 51% shareholders will be irreversible and binding. The challenge is to achieve 51% approval in a timely and efficient way. To achieve this goal, each shareholder can delegate his voting right to a representative. The top 100 representatives with the largest number of votes will take turns to proce blocks according to the established schele. Each delegate is assigned a time period to proce the block. All representatives will receive 10% of the transaction fee equivalent to an average block. If an average block contains 100 shares as a transaction fee, a representative will receive 1 share as a reward
network delay may make some representatives fail to broadcast their blocks in time, which will lead to the bifurcation of the blockchain. However, this is unlikely to happen because the representative of the manufacturing block can establish a direct connection with the representative of the block before and after manufacturing. This direct connection to your next representative (and perhaps the next) is to make sure you get paid
this mode can generate a new block every 30 seconds, and under normal network conditions, the possibility of blockchain bifurcation is extremely small, even if it occurs, it can be solved in a few minutes
to be a delegate:
to be a delegate, you must register your public key on the network and assign it to a 32-bit unique identifier. The identifier is then referenced by the "header" of each transaction data
authorized ballot:
each wallet has a parameter setting window, in which users can select one or more representatives and grade them. Once set, each transaction made by the user will transfer the vote from "input representative" to "output representative". In general, users will not create transactions specifically for voting purposes, because that will cost them a transaction fee. But in an emergency, some users may find it worthwhile to change their vote in a more positive way by paying fees
keep representatives honest:
each wallet will display a status indicator to let users know how their representatives are doing. If they miss too many blocks, the system will recommend users to replace them with a new representative. If any representative is found to have issued an invalid block, all standard wallets will ask for a new representative to be selected before each wallet makes more transactions
resist attack:
in resisting attack, because the top 100 representatives have the same power, and each representative has an equal vote. As a result, power cannot be concentrated on a single representative by winning more than 1% of the vote. Since there are only 100 representatives, we can imagine an attacker carrying out a denial of service attack on each representative in turn. Fortunately, the threat of this particular attack can be easily mitigated by the fact that each delegate's identity is his public key rather than his IP address. This will make it more difficult to target DDoS attacks. The potential direct connection between representatives will make it more difficult to block their proction
advantages: the number of nodes participating in verification and bookkeeping is greatly reced, which can achieve second level consensus verification
disadvantages: the whole consensus mechanism still relies on token, and many commercial applications do not need token< Pbft: practical Byzantine fault tolerance
3. Pbft: practical Byzantine fault tolerance
Introction: it provides (n-1) / 3 fault tolerance on the premise of ensuring the activity and safety
in distributed computing, different computers try to reach a consensus through message exchange; But sometimes, the coordinator / commander or member / client may exchange wrong messages e to system errors, which may affect the final system consistency
the Byzantine general problem is based on the number of wrong computers to find possible solutions, which can not find an absolute answer, but can only be used to verify the effectiveness of a mechanism
the possible solutions to Byzantine problems are:
consistency is possible when n ≥ 3F + 1. Where n is the total number of computers and F is the total number of computers with problems. After the information is exchanged among computers, each computer lists all the information obtained and takes most of the results as the solution
1) the operation of the system can be separated from the existence of currency, pbft algorithm consensus that each node is composed of business participants or regulators, and the security and stability are guaranteed by business stakeholders
2) the consensus delay is about 2-5 seconds, which basically meets the requirements of commercial real-time processing
3) consensus efficiency is high, which can meet the demand of high frequency trading volume
disadvantages:
1) when 1 / 3 or more bookkeepers stop working, the system will not be able to provide services
2) when 1 / 3 or more bookkeepers work together, and all other bookkeepers are just divided into two network islands, malicious bookkeepers can make the system bifurcate, but will leave cryptographic evidence
let's talk about two domestic ones ~
4. Dbft: delegated BFT authorization Byzantine fault tolerance algorithm
Introction: dbft mechanism adopted by ant, The bookkeeper is selected by the rights and interests, and then the bookkeeper reaches a consensus through Byzantine fault-tolerant algorithm
based on pbft, this algorithm has the following improvements:
the request response mode of C / S architecture is improved to a peer-to-peer mode suitable for P2P network
the static consensus participation node is improved to a dynamic consensus participation node that can enter and exit dynamically
for the generation of consensus participation nodes, a voting mechanism based on the proportion of holding equity is designed, and the consensus participation nodes (Accounting nodes) are determined by voting
digital certificate is introced into the blockchain to solve the authentication problem of the real identity of the accounting node in voting< Advantages:
1) professional bookkeeper
2) it can tolerate any kind of errors
3) bookkeeping is completed by multiple people, and each block is final and will not be forked
4) the reliability of the algorithm has strict mathematical proof
disadvantages:
1) when 1 / 3 or more bookkeepers stop working, the system will not be able to provide services
2) when 1 / 3 or more bookkeepers commit crimes together and all other bookkeepers are divided into two network islands, malicious bookkeepers can make the system bifurcate, but leave behind cryptographic evidence
to sum up, the core of dbft mechanism is to ensure the system's finality to the maximum extent, so that the blockchain can be applied to real financial application scenarios
5. Pool verification pool
is based on traditional distributed consistency technology and data verification mechanism
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; It is more suitable for multi center business model.
1. Pow (proof of work) workload proof
in a word: the more you do, the more you get
it relies on machines to perform mathematical operations to obtain accounting rights. Compared with other consensus mechanisms, the resource consumption is high and the supervision is weak. At the same time, the whole network needs to participate in the operation to reach a consensus every time, so the performance efficiency is relatively low. In terms of fault tolerance, 50% of nodes in the whole network are allowed to make mistakes< Advantages:
1) the algorithm is simple and easy to implement
2) there is no need to exchange additional information between nodes to reach a consensus
3) the cost of destroying the system is huge< Disadvantages:
1) waste of energy
2) it is difficult to shorten the block confirmation time
3) the new blockchain must find a different hash algorithm, otherwise it will face bitcoin attack
4) it is easy to generate bifurcation and needs to wait for multiple confirmations
5) there is no finality, and checkpoint mechanism is needed to make up for it
2. POS proof of stake
in a word: the more you hold, the more you get
the main idea is that the difficulty of obtaining the node's accounting right is inversely proportional to the equity held by the node. Compared with pow, the resource consumption brought by mathematical operation is reced to a certain extent, and the performance has also been improved correspondingly. However, it is still a way to obtain the accounting right based on hash operation competition, which is weak in supervision. The fault tolerance of the consensus mechanism is the same as pow. It is an upgrade consensus mechanism of pow, according to the proportion and time of token 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 can shorten the time of reaching consensus; No longer need to consume a lot of energy mining
disadvantages: mining is still needed, which does not solve the pain point of commercial application in essence; All the confirmations are just a probability expression, not a certainty. Theoretically, there may be other attack effects. For example, Ethereum's Dao attack event caused Ethereum's hard fork, and etc's appearance of this event actually proved the failure of this hard fork
the principle of dpos is the same as that of POS, except that some "deputies to the National People's Congress" are selected
bitshares community first proposed dpos mechanism
the main difference from POS is that the node elects several agents, which are verified and recorded by the agents. Its compliance, performance, resource consumption and fault tolerance are similar to POS. Similar to board voting, coin holders cast a certain number of nodes to verify and account on their behalf
the working principle of dpos is:
decentralization means that each shareholder has influence according to its shareholding ratio, and the voting result of 51% shareholders will be irreversible and binding. The challenge is to achieve 51% approval in a timely and efficient way. To achieve this goal, each shareholder can delegate his voting right to a representative. The top 100 representatives with the largest number of votes will take turns to proce blocks according to the established schele. Each delegate is assigned a time period to proce the block. All representatives will receive 10% of the transaction fee equivalent to an average block. If an average block contains 100 shares as a transaction fee, a representative will receive 1 share as a reward
network delay may make some representatives fail to broadcast their blocks in time, which will lead to the bifurcation of the blockchain. However, this is unlikely to happen because the representative of the manufacturing block can establish a direct connection with the representative of the block before and after manufacturing. This direct connection to your next representative (and perhaps the next) is to make sure you get paid
this mode can generate a new block every 30 seconds, and under normal network conditions, the possibility of blockchain bifurcation is extremely small, even if it occurs, it can be solved in a few minutes
to be a delegate:
to be a delegate, you must register your public key on the network and assign it to a 32-bit unique identifier. The identifier is then referenced by the "header" of each transaction data
authorized ballot:
each wallet has a parameter setting window, in which users can select one or more representatives and grade them. Once set, each transaction made by the user will transfer the vote from "input representative" to "output representative". In general, users will not create transactions specifically for voting purposes, because that will cost them a transaction fee. But in an emergency, some users may find it worthwhile to change their vote in a more positive way by paying fees
keep representatives honest:
each wallet will display a status indicator to let users know how their representatives are doing. If they miss too many blocks, the system will recommend users to replace them with a new representative. If any representative is found to have issued an invalid block, all standard wallets will ask for a new representative to be selected before each wallet makes more transactions
resist attack:
in resisting attack, because the top 100 representatives have the same power, and each representative has an equal vote. As a result, power cannot be concentrated on a single representative by winning more than 1% of the vote. Since there are only 100 representatives, we can imagine an attacker carrying out a denial of service attack on each representative in turn. Fortunately, the threat of this particular attack can be easily mitigated by the fact that each delegate's identity is his public key rather than his IP address. This will make it more difficult to target DDoS attacks. The potential direct connection between representatives will make it more difficult to block their proction
advantages: the number of nodes participating in verification and bookkeeping is greatly reced, which can achieve second level consensus verification
disadvantages: the whole consensus mechanism still relies on token, and many commercial applications do not need token< Pbft: practical Byzantine fault tolerance
3. Pbft: practical Byzantine fault tolerance
Introction: it provides (n-1) / 3 fault tolerance on the premise of ensuring the activity and safety
in distributed computing, different computers try to reach a consensus through message exchange; But sometimes, the coordinator / commander or member / client may exchange wrong messages e to system errors, which may affect the final system consistency
the Byzantine general problem is based on the number of wrong computers to find possible solutions, which can not find an absolute answer, but can only be used to verify the effectiveness of a mechanism
the possible solutions to Byzantine problems are:
consistency is possible when n ≥ 3F + 1. Where n is the total number of computers and F is the total number of computers with problems. After the information is exchanged among computers, each computer lists all the information obtained and takes most of the results as the solution
1) the operation of the system can be separated from the existence of currency, pbft algorithm consensus that each node is composed of business participants or regulators, and the security and stability are guaranteed by business stakeholders
2) the consensus delay is about 2-5 seconds, which basically meets the requirements of commercial real-time processing
3) consensus efficiency is high, which can meet the demand of high frequency trading volume
disadvantages:
1) when 1 / 3 or more bookkeepers stop working, the system will not be able to provide services
2) when 1 / 3 or more bookkeepers work together, and all other bookkeepers are just divided into two network islands, malicious bookkeepers can make the system bifurcate, but will leave cryptographic evidence
let's talk about two domestic ones ~
4. Dbft: delegated BFT authorization Byzantine fault tolerance algorithm
Introction: dbft mechanism adopted by ant, The bookkeeper is selected by the rights and interests, and then the bookkeeper reaches a consensus through Byzantine fault-tolerant algorithm
based on pbft, this algorithm has the following improvements:
the request response mode of C / S architecture is improved to a peer-to-peer mode suitable for P2P network
the static consensus participation node is improved to a dynamic consensus participation node that can enter and exit dynamically
for the generation of consensus participation nodes, a voting mechanism based on the proportion of holding equity is designed, and the consensus participation nodes (Accounting nodes) are determined by voting
digital certificate is introced into the blockchain to solve the authentication problem of the real identity of the accounting node in voting< Advantages:
1) professional bookkeeper
2) it can tolerate any kind of errors
3) bookkeeping is completed by multiple people, and each block is final and will not be forked
4) the reliability of the algorithm has strict mathematical proof
disadvantages:
1) when 1 / 3 or more bookkeepers stop working, the system will not be able to provide services
2) when 1 / 3 or more bookkeepers commit crimes together and all other bookkeepers are divided into two network islands, malicious bookkeepers can make the system bifurcate, but leave behind cryptographic evidence
to sum up, the core of dbft mechanism is to ensure the system's finality to the maximum extent, so that the blockchain can be applied to real financial application scenarios
5. Pool verification pool
is based on traditional distributed consistency technology and data verification mechanism
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; It is more suitable for multi center business model.
7.
reprint the reply of Dr. Tan Yiyong, founder of Fanrong Technology:
consensus is the core algorithm of blockchain technology, which also basically determines the efficiency of the chain. Blocks are what machines need to agree on. At the account level, through the Merkle verification tree of OLOG (n), the tampered data can be quickly located, the user balance can be safely obtained by traversing statetree, and the occurrence of double flowers can be prevented
through consensus algorithm, blockchain is the foundation of trust between machines, which is to solve the Byzantine general problem in practice. In BFT, 3F + 1 & lt; N can be said to be an important consensus theory. In practice, BFT has a variety of variants: pbft, rbft, Q / u, HQ, zyzzyva, abstracts, aardvark, adapt, a2m-pbft-eaandminbft, etc. These algorithms, according to different scenarios, optimize the efficiency from the aspects of message broadcast mode, node network topology, hardware configuration and so on. The goal of consensus is to reach consensus, and the final solution is to vote, whether it's BFT, pow, POS, dpos... Voting is a bit like the proction mode of human beings. In the blockchain, it's machine voting. BFT is similar to 4pc (four stage) submission, which consists of four stages: prepare, prepare, commit and reply. In each stage, messages are broadcast to all nodes in the network to participate in the voting of the next stage
The biggest problem ofBFT is the broadcast of messages between nodes, which will be especially large. And the node base of this message voting must be determined in advance. Considering the poor voting performance of BFT, we propose a scheme that allows BFT to participate in only a few voting processes, such as the base number of nodes. Suppose there are 100 candidate nodes, how to select 21? How many blocks are recorded in each node? Can these 100 nodes reach the current highest level, and can the network delay and other performance meet the standard? This information actually has nothing to do with our transaction. But it will affect the performance of the whole chain. We use pbft to solve the problem of node base, which provides a higher and more efficient infrastructure for subsequent transaction broadcast and block voting. At this level, everyone is equal and has no right to participate
next, raft is a leader follow algorithm. In each round of term, a leader will be randomly selected to collect and broadcast the transaction, and other nodes will follow the information of the master node. In the application of vertical blockchain 3.0, the performance of VM on the chain is required to be higher than that of EVM. For example, if every node in the main server of the game participates in the VM calculation, it will cause a lot of waste of resources. In the big data processing system, raft can solve the problem of division of labor, be a scheler of work, and distribute tasks to different node machines fairly and safely. The advantage is that we can build a super machine through several machines. Raft consensus: in our chain, it is responsible for the verification and broadcast distribution of transactions, which is the basis of blocking. If all transactions are wrong, there is no need to enter the block
finally, we combine the dpos consensus algorithm to randomly generate the current rotation node, package the verified transactions and broadcast the block header. The block is just a header verification information, which can reach each machine quickly. As for the node of rotation, we think that a node records a block every time. The block speed is determined by the better nodes in the network, which constitute the super node accounting mode
8. At present, many enterprises are extremely concerned about sac application ecology, because they hope to ensure the data security of enterprises through it and create an indestructible data security model for enterprises. The traditional data application technology can be said to have certain loopholes, as long as the enterprise information and network connection will be received by the central organization, and the central organization in order to earn higher interests will sell the enterprise information, and then damage the interests of the enterprise. Sac application ecosystem is divided into two systems: application chain and data chain. The application chain adopts docker deployment, which can effectively rece the difficulty of enterprise application deployment. Based on SDK, interface, smart contract, it can quickly develop various business applications. It will support multiple languages to write smart contract, making the business development process more in line with enterprise software development practices. The consensus adopts pluggable mole mechanism, supports pow, POS, and more efficient pbft, raft consensus algorithms, which can realize different consensus mechanisms to meet different business needs. It supports grouping multiple copies to store files, and saves the hash value and related addressing information of files in the blockchain, so as to improve the efficiency of blockchain storage and network synchronization. Regulatory nodes are introced to better ensure the compliance and auditability, and support a variety of encryption moles. The data link of sac application ecological interface layer can interact with the application chain, and also provide some interface support such as baas of storage and verification. Users can develop their own data link and data link applications. In a word, the preciseness of this world leading computer technology is extremely high, not to mention scientific, so it is absolutely worth the experience of the majority of users.
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