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Consensus Algorithm-a complete List/comparation (Pros&Cos) of all Consensus Algorithm 6 to 10 (total of 30)  


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May 20, 2019 10:17 am  
Consensus algorithms are the basis of all the blockchains/DAGs. They are the most important part of the blockchain/DAG platforms.
Without them(consensus algorithms) we will be left with just a dumb, immutable database.
Here we list all the major consensus algorithms and will evaluate their pros and cons. 
Here is a list of 5 consensus algorithms.
6. Proof-of-Weight
Energy efficient.
Highly Customisable and scalable.
Incentivization can be hard.
Used by: Algorand
Explanation: Proof-of-Weight is a broad classification of consensus algorithms based around the Algorand consensus model. The general idea is that where in PoS, your percentage of tokens owned in the network represents your probability of “discovering” the next block, in a PoWeight system, some other relatively weighted value is used. Some of it’s implementations are Proof of Reputation and Proof of Space.
7. Proof of Reputation
Good for private, permissoned networks.
Only used in private, permissioned blockchains.
Used by: GoChain
Type: Collaborative consensus
Explanation: Similar to Proof of Authority. As mentioned by GoChain:
Proof of Reputation (PoR) consensus model depends on the reputation of the participants to keep the network secure. A participant (a block signer) must have a reputation important enough that they would face significant financial and brand consequences if they were to attempt to cheat the system. This is a relative concept as almost all businesses would suffer significantly if they were caught attempting to be deceitful, but larger companies will typically have more to lose and thus are chosen over companies with less to use (smaller businesses).
Once a company proves reputation and passes verification, they may be voted into the network as an authoritative node and at this point, it operates like a Proof of Authority network (PoA), where only authoritative nodes can sign and validate blocks.
You can find more about Proof of Reputation in Further Reading.
8. Proof of Elapsed Time
Low cost of participation.Thus more people can participate easily, thus decentralized.
It is simple for all participants to verify that the leader was legitimately selected.
The cost of controlling the leader election process is proportional to the value gained from it.
Even though it’s cheap, you have to use specialized hardware. Thus cannot be mass-adopted.
Not suited for public blockchains.
Used by: Hyperledger Sawtooth
Type: Competitive consensus
Explanation: PoET is a consensus mechanism algorithm that is often used on the permissioned blockchain networks to decide the mining rights or the block winners on the network. Permissioned blockchain networks are those which require any prospective participant to identify themselves before they are allowed to join. Based on the principle of a fair lottery system where every single node is equally likely to be a winner, the PoET mechanism is based on spreading the chances of a winning fairly across the largest possible number of network participants.
The working of the PoET algorithm is as follows. Each participating node in the network is required to wait for a randomly chosen time period, and the first one to complete the designated waiting time wins the new block. Each node in the blockchain network generates a random wait time and goes to sleep for that specified duration. The one to wake up first — that is, the one with the shortest wait time — wakes up and commits a new block to the blockchain, broadcasting the necessary information to the whole peer network The same process then repeats for the discovery of the next block.
The PoET network consensus mechanism needs to ensure two important factors. First, that the participating nodes genuinely select a time that is indeed random and not a shorter duration chosen purposely by the participants in order to win, and two, the winner has indeed completed the waiting time.
The PoET concept was invented during early 2016 by Intel, the famous chip manufacturing giant. It offers a readymade high tech tool to solve the computing problem of “random leader election.”
The ingrained mechanism allows applications to execute trusted code in a protected environment, and this ensures that both requirements — for randomly selecting the waiting time for all participating nodes and genuine completion of waiting time by the winning participant — are fulfilled.
The mechanism of running trusted code within a secure environment also takes care of many other necessities of the network. It ensures that the trusted code indeed runs within the secure environment and is not alterable by any external participant. It also ensures that the results are verifiable by external participants and entities, thereby enhancing transparency of the network consensus.
PoET controls the cost of the consensus process and keeps it nimble so that the cost remains proportional to the value derived from the process, a key requirement for the cryptocurrency economy to continue flourishing.
9. Proof of Capacity aka Proof of Space
Similar to PoW but uses space instead of computation. Thus much environmental friendly.
Can be used for malware detection, by determining whether the L1 cache of a processor is empty (e.g., has enough space to evaluate the PoSpace routine without cache misses) or contains a routine that resisted being evicted.
Can be used for anti-spam measures and denial of service attack prevention.
Incentivization can be an issue.
Used by: Burstcoin, Chia, SpacesMint
Type: Collaborative Consensus
Explanation: Proof-of-space(PoSpace), also called proof-of-capacity (PoC), is a means of showing that one has a legitimate interest in a service (such as sending an email) by allocating a non-trivial amount of memory or disk space to solve a challenge presented by the service provider. The concept was formulated by Dziembowski et al. in 2015. (Ateniese et al.’s paper, while also titled Proof-of-space, is in fact a memory-hard proof-of-work protocol.)
Proofs of space are very similar to proofs of works, except that instead of computation, storage is used. Proof-of-space is related to, but also considerably different from, memory-hard functions and proofs of retrievability.
A proof-of-space is a piece of data that a prover sends to a verifier to prove that the prover has reserved a certain amount of space. For practicality, the verification process needs to be efficient, namely, consumes a small amount of space and time. For soundness, it should be hard for the prover to pass the verification if it does not actually reserve the claimed amount of space. One way of implementing PoSpace is by using hard -to-pebble graphs. The verifier asks the prover to build a labeling of a hard-to-pebble graph. The prover commits to the labeling. The verifier then asks the prover to open several random locations in the commitment.
Proofs of space are seen as a fairer and greener alternative due to the general-purpose nature of storage and the lower energy cost required by storage.
10. Proof of History
Used by: Solana
Explanation: The basic idea here is that instead of trusting the timestamp on the transaction, you could prove that the transaction occurred sometime before and after an event.
When you take a photograph with the cover of New York Times, you are creating a proof that your photograph was taken after that newspaper was published, or you have some way to influence what New York Times publishes. With Proof of History, you can create a historical record that proves that an event has occurred at a specific moment in time.
The Proof of History is a high frequency Verifiable Delay Function. A Verifiable Delay Function requires a specific number of sequential steps to evaluate, yet produces a unique output that can be efficiently and publicly verified.
This specific implementation uses a sequential pre-image resistant hash that runs over itself continuously with the previous output used as the next input. Periodically the count and the current output are recorded.
For a SHA256 hash function, this process is impossible to parallelize without a brute force attack using 2¹²⁸ cores.
We can then be certain that real time has passed between each counter as it was generated, and that the recorded order each counter is the same as it was in real time.
You can find all the details in Further Reading.
This topic was modified 1 year ago 2 times by alberdioni8406