Blockchain 100 Talk: The Soul of the Blockchain - Consensus Algorithm
This article was sourced from: Pippin Investments, Haipai Tribe, Supertrader
Collated by Cynthia
In explaining the issue of Byzantine generals mentioned“ consensual mechanism”， current period《 blockchain100 lecture》 Let's talk about what has been called the soul of the blockchain“ consensual algorithm”。
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consensual mechanism
consensual mechanism， The explanation on Baidu's encyclopedia is this：
Doesn't it look confusing?？ So I'll give you a more understandable explanation here： so-called consensual mechanism， It's as if everyone was having a“ sessions”， A final agreement was reached， But there are many ways to reach agreement， This is where the main chain of the subsequent blockchain has a variety of consensual mechanism。 So this time.“ sessions” What's the consensus?？ Let's say someone does a good deed， We all know.； Someone's done something bad.， And we all know it.。 So this is consensual mechanism The biggest benefit of the， It's the solution to the mutual distrust of people who don't know each other； at the same time， In this“ sessions” I don't care who's doing what.， We all know that.。
So one might ask, if most of the people at this "meeting" defect, won't that lead to the destruction of the "meeting" and therefore the entire blockchain? This is certainly a possibility, but it is difficult to control the people who are attending this "conference" because they are from all over the world and do not know each other. Theoretically, if you control 51% of the people attending the "meeting", you can disrupt the entire network, but if you have the power to control 51% of the people, would you still want to disrupt the entire blockchain? I think normal people should be desperate to maintain it, so that's one reason why the blockchain is so hard to attack.
So with that said， We put consensual mechanism analogize to open“ sessions”， So we know.， If the meeting is crowded， It takes longer to reach a final result， Fewer people in meetings， The time to reach the final result is faster； Put it in the blockchain， It's actually the same thing.。 Higher number of participants， People will be less likely to be controlled， Then the more decentralized it gets， Then it takes a long time to reach agreement； for the same reason， Fewer participants。 People are easy to control.， The less decentralized it gets， But the time to reach an agreement may become faster。
One will find that the strength of the decentralization of the consensus mechanism is inversely related to the speed of the blockchain: the weaker the decentralization, the lower the security and the faster the blockchain; the stronger the decentralization, the higher the security and the slower the blockchain will be. Of course there are other factors that affect blockchain speed, which we'll talk more about later. However, the fact that many media outlets take the slow speed to bash Bitcoin shows that many media outlets and project parties are unskilled. There are various consensus mechanisms on the blockchain, but none of them is perfect, only that the scenarios for which each is applicable are different.
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Mainstream consensus algorithms
1. Pow workload certification
It is the familiar mining, through the operation, calculate a random number that satisfies the rules, that is, get the right to this bookkeeping, send out the data that needs to be recorded in this round, other nodes across the network to verify and store together.
Pros. Fully decentralized， Free access to nodes。
Disadvantages: currently bitcoin has attracted most of the world's computing power, other blockchain applications that use Pow consensus mechanism again is difficult to obtain the same computing power to secure itself; mining causes a lot of wasted resources; the cycle of consensus reached is long, not suitable for commercial applications.
2. Pos proof of interest
Depending on the proportion of tokens and time taken by each node; the mining difficulty is reduced in equal proportion, thus speeding up the search for random numbers.
Pros. Shortens the time to consensus to some extent。
Disadvantages. Contrary to the decentralization of blockchain。
3. DPos share authorization certification mechanism
Similar to a board vote, coin holders vote for a certain number of nodes, which are verified and booked by proxy.
Benefit: Dramatically reduces the number of nodes involved in verification and bookkeeping, allowing for second-level consensus verification.
Disadvantages. total consensual mechanism Still dependent on tokens， Tends to be centralized to some extent。
4、Pool validation pool
Based on traditional distributed consistency techniques， Plus data validation mechanisms； is currently in use by the industry chain on a large scale consensual mechanism。
Pros: works without tokens, second-level consensus verification based on proven distributed consistency algorithms (Pasox, Raft).
Cons: Not as decentralized as bictoin; better suited for multi-participant polycentric business models.
5. Proof of Authority PoA (Proof of Authority)
Proof of Authority (PoA) is the use of a set of so-called "permissions" to allow people to create new nodes on the blockchain and secure the blockchain.
Pros: fast out of block time, easy to land high speed concurrent applications, can assign different nodes based on participant roles, rich open source systems.
Cons: Not as decentralized as bictoin; better suited for multi-participant polycentric business models.
6、PBFT : Practical Byzantine Fault Tolerance, Practical Byzantine Fault Tolerance
In guaranteeing activity and safety（liveness & safety） The premise of the(n-1)/3 Fault-tolerance of。
On distributed computing, different computers try to reach consensus through message exchange.
However, sometimes the coordinator (Coordinator / commander) or member (Member / Lieutanent) computer on the system may have a system error and exchange the wrong messages, which can affect the final system consistency.
Disadvantages.
When 1/3 or more of the bookkeepers stop working, the system will not be available.
When 1/3 or more bookkeepers are jointly evil and all other bookkeepers are split into exactly two network silos, the malicious bookkeeper can cause the system to bifurcate, but leave cryptographic evidence.
7.dBFT: delegated BFT Authorized Byzantine Fault Tolerance Algorithm
Introduction: the dBFT mechanism used by Little Ant is to select the bookkeepers by equity, and then the bookkeepers reach consensus among themselves through a Byzantine fault-tolerant algorithm.
This algorithm improves on the PBFT as follows.
Improving the request response model of the C/S architecture to a peer-to-peer node model suitable for P2P networks.
Improving static consensus participation nodes into dynamic consensus participation nodes that can be dynamically entered and exited.
A voting mechanism based on the percentage of interests held is designed for the generation of consensus participation nodes, which are determined by voting (bookkeeping nodes).
The introduction of digital certificates in the blockchain solves the problem of authenticating the true identity of the bookkeeping nodes in voting.
Pros.
Professionalized bookkeepers.
Tolerate any type of error.
Bookkeeping is done collaboratively by multiple people, with finality in each block and no forking.
There is a rigorous mathematical proof of the reliability of the algorithm.
Disadvantages.
When 1/3 or more of the bookkeepers stop working, the system will not be available.
When 1/3 or more bookkeepers are jointly evil and all other bookkeepers are split into exactly two network silos, the malicious bookkeeper can cause the system to bifurcate, but leave cryptographic evidence.
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A variety of existing consensual mechanism existing problems
A. Wasted computing power
In the proof-of-work mechanism POW, the fastest number guesser is usually the one with the best computer computational power. The super computational power level is a waste to use only for guessing numbers.
B. Concentration of interests to the top
In the proof-of-stake mechanism POS, the higher the balance of the token the higher the probability of getting the public information, and the public will get a certain amount of token as a reward, so that those who hold more token will get more and more, and those who hold less and less will get less and less.
C. Low cost of doing evil
In a model where the right to public information is based on the amount of power and equity, it is easy for a few people to do something against the rules when the power and equity is concentrated in a few people; in PBFT, with everyone voting, if someone without any token balance wants to mess up, he has almost nothing to lose.
D. poses a threat to true decentralization
In the proof of workload mechanism, the more computational power is available, the higher the probability of obtaining the right to record. If someone pools a lot of people together to guess numbers and adds up the computing power of many computers to use, it will be easier for these groupings to gain the right to public information, and it may grow to the point where the right to public information is directly in the hands of these people.
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