A consensus mechanism is an algorithm that participants in a blockchain network use to reach an agreement on the state of the blockchain ledger, including the order of transactions. Popular consensus algorithms include Proof-of-Work (PoW), Proof-of-Stake (PoS), and Delegated Proof-of-Stake (DPoS).
Here is a list of all the consensus mechanisms:
Proof of Access (PoA)
PoA is the consensus mechanism of the Arweave Protocol. In order to mine or verify a new block, miners must provide cryptographic proof that they have access to a recall block, which is a block from earlier in the blockweave’s history. For this reason, Arweave’s consensus algorithm is called Proof of Access (PoA), and is a variation of a Proof-of-Work (PoW) algorithm. PoA is intended to incentivize long-term data storage because miners must access older, random blocks from the blockweave’s history in order to mine new blocks and receive mining rewards.
Proof of Authority (PoA)
Proof of Authority (PoA) is a consensus mechanism utilized by many blockchain networks. PoA was originally created by Gavin Wood, co-founder of Ethereum and former Chief Technology Officer (CTO) of Ethereum. PoA is a consensus mechanism that leverages the value of identity and reputation instead of cryptographic assets or computational power. PoA relies on a limited number of nodes to verify transactions and is often criticized for being too centralized. This trade-off is offset by remarkable scalability and transaction speeds.
Proof of Burn (PoB)
Through the Proof-of-Burn (PoB) consensus mechanism, miners intentionally destroy, or “burn”, tokens to obtain a proportional right to mine new blocks and verify transactions. The more tokens a miner burns, the higher the chance that the miner will be selected as the next block validator. By demonstrating their dedication to the network via intentional token destruction rather than expending computational resources and leveraging powerful mining hardware, miners within a PoB setup are able to operate using far less energy than classic PoW systems. The PoB consensus mechanism is utilized by Counterparty, Slimcoin, Factom, and several other blockchain systems.
Proof of Capacity (PoC)
Proof of Capacity (PoC) is a consensus mechanism that makes use of the available hard drive space in a miner’s device to decide its mining rights and validate transactions rather than expending computational power. Through the PoC mechanism, a list of possible cryptographic mining solutions is stored in the mining device’s hard drive even before the mining activity begins, with larger hard drives being capable of storing more potential solution values. PoC was designed in order to mitigate both the energy inefficiencies of classic Proof-of-Work (PoW) mechanisms and the token-hoarding that can sometimes arise from implementing many Proof-of-Stake (PoS) configurations.
Proof of Contribution (PoC/PoCo)
Proof of Contribution (PoC) is a consensus mechanism that is based on user contributions to the network. This process works by using specialized algorithms that monitor the contributions of all the network’s nodes during each consensus round. The node that has the highest contribution value in each round is given the right to generate the next block. Proof of Contribution is considered to be a quite decentralized consensus model. Proponents maintain that it is extremely resistant to hard forks and can enhance the security and transparency of networks that implement it.
Proof of Coverage (PoC)
Proof of Coverage (PoC) is a consensus mechanism employed by the Helium Network. As a variation of Proof of Work (PoW), PoC relies on mining to achieve network consensus. However, miners on the Helium Network — known as Hotspots — double as wireless internet access points for Internet of Things (IoT) devices. As such, PoC incorporates nuanced mechanisms to track the participation of nodes — or Hotspots — and their continued provision of services.
Proof of Goods and Services Delivered
In Crypto.com blockchain network architecture, Proof of Goods and Services Delivered is a status that is cryptographically verified to prove that a payment was sent and received correctly via its Visa card and mobile wallet products into merchant accounts. This mechanism is used by payment merchants and customers to confirm the legitimacy of the payment process and ensure transparency.
Proof of History (PoH)
Proof of History (PoH) is a consensus methodology on the Solana blockchain that incorporates the measurement of time into a blockchain ledger with the intent of scaling and streamlining transactional throughput. While most blockchains operate without a timestamp, PoH functions like a decentralized clock that enables nodes on the Solana network to process transactions without devoting processing power to solving discrepancies in minuscule differentiations in time and order.
Proof of Importance (PoI)
Proof of Importance is an innovative consensus algorithm developed by the NEM blockchain protocol and is a variation of Proof of Stake. The system allows a wide pool of users to participate in the addition of new blocks in exchange for receiving tokenized rewards. The rewards are determined in proportion to a score that quantifies the user's contribution to the network. Additionally, PoI encourages healthy activity in the ecosystem by preventing users from hoarding the XEM asset.
Proof of Replication (PoRep)
Proof of Replication (PoRep) is one of the consensus mechanisms used by the Filecoin network. Specifically, it is a process through which a storage miner proves to the blockchain protocol that it has created a distinct copy of a specific piece of data on the network’s behalf. This process is verified by the network through zk-SNARK cryptographic proof technology.
Proof of Service (Holochain)
Proof of Service is a relatively rare consensus mechanism that is used on certain blockchain protocols such as Holochain. In the case of Holochain, Proof of Service does not function like a traditional blockchain consensus mechanism, because the distributed hash table (DHT) plays the primary role in achieving network consensus. In this scenario, the Proof-of-Service protocol is merely designed to ensure that once a peer-to-peer transaction is completed, then the agent providing the service automatically issues an invoice and receives payment.
Proof of Service (PoSe)
The DASH blockchain features a master node system referred to as Proof of Service (PoSe) on account of the critical services that master nodes provide to the DASH network. Proof of Service is the mechanism on the DASH blockchain network used to determine if a stake-bearing master node is providing the correct services in good faith to users who have contributed coins to it.
Proof of Spacetime (PoSpacetime)
Proof of Spacetime (PoSpacetime) is a consensus mechanism utilized by the Filecoin network. It allows the blockchain to prove its capacity, and in doing so, it can cryptographically verify that the entire file is being stored in an unaltered fashion for an agreed-upon time frame. Proof of Spacetime is made up of two distinct subsets: 1.) Window Proof of Spacetime (WindowPoSpacetime) and 2.) Winning Proof of Spacetime (WinningPoSpacetime).
Proof of Stake (PoS)
Proof of Stake (PoS) is emerging as one of the most widely used blockchain consensus mechanisms in existence. PoS networks incentivize participants to stake native coins in a network of validator nodes. Upon the close of a transaction block, validator nodes are eligible to be randomly chosen to validate block data, thus generating the subsequent block, and earning native coins as a reward. A robust nodal network offers increased network security, resiliency, and computational power. Proof-of-Stake systems also generally enable validator nodes to contribute democratically in decentralized platform governance through voting on key updates and decisions. While still a recent innovation, PoS networks are already proving they can be faster and more scalable than Proof-of-Work (PoW) blockchains, in addition to being more energy efficient.
Proof of Storage (PoStorage)
Proof of Storage (PoStorage) is a consensus algorithm used by the Filecoin network to prove that network participants are indeed providing the specified amount of storage that they claim to be. This storage space is verified by the network through zk-SNARK cryptographic proof technology.
Proof of Validation (PoV)
Proof of Validation (PoV) is a unique Proof-of-Stake consensus mechanism that works to achieve consensus by evaluating the stake of validator nodes. Typically, each node within the system keeps a copy of the sequence of transactions in blocks that are integrated into the blockchain as well as a copy of user accounts that are identifiable by a specific user’s public key or address. Accounts within the protocol bond or hold coins inside validator nodes. The number of coins bonded with the validator is proportional to the number of votes that a specific validator possesses, and can only be reduced when the coins are unlocked at a later date.
Proof of Work (PoW)
Proof of Work (PoW) is a blockchain consensus mechanism first popularized by the Bitcoin blockchain network. Proof-of-Work systems rely on a process of mining to maintain the network. Miners provide computer hardware that competes to solve the complex cryptographic puzzles required to confirm data transacted on the network, and are rewarded for doing so with the network's underlying cryptographic token for doing so. Proof-of-Work blockchain systems are decentralized and secure as compared to other network consensus methodologies but typically struggle to achieve the network scalability needed for widespread global enterprise adoption. Proof of Work is also criticized for its high energy intensivity.
Pure Proof of Stake (PPoS) (Algorand)
Pure Proof of Stake (PPoS) is Algorand’s variation on the traditional Proof-of-Stake (PoS) consensus mechanism. It is a decentralized Byzantine Agreement protocol that is characterized by a low barrier to entry, requiring as little as 1 ALGO to become a participating node. PPoS strives for quick transaction processing and finality. It leverages a verifiable random function to coordinate its participation nodes.
Secure Proof of Stake (SPoS)
Secure Proof of Stake (SPoS) is Elrond Network’s enhanced version of Proof of Stake (PoS). It enables advanced security and distributed fairness while eliminating computational waste that Proof-of-Work (PoW) systems typically struggle with. The SPoS consensus system achieves high security through a Byzantine Fault Tolerant (BFT)-like consensus methodology that utilizes instantaneous randomized validator selection through the reshuffling of nodes into other shards. To accomplish this, SPoS makes use of Boneh–Lynn–Shacham (BLS) multi-signature technology to randomly select nodes within each shard to achieve validator selection finalization in 100 milliseconds or 0.1 seconds.
Shard chains are created by partitioning a blockchain into smaller, more manageable pieces. This process decreases the workload on validator nodes, which are only required to store and manage one shard instead of the entire blockchain system. Alongside other optimizations, shard chains are expected to drastically increase network throughput and speed as opposed to monolithic consensus mechanisms. The Ethereum 2.0 blockchain will be separated into 64 shards that will operate as smaller blockchains tied to a main Beacon Chain. Ethereum 1.0 is intended to make up just one of those shards.
The Cardano blockchain utilizes a protocol called the Ouroboros Praos protocol. This unique consensus mechanism functions by breaking down time into epochs that last approximately 5 days, which are then broken down into 432,000 slots. Nodes are selected at random to be slot leaders, which in turn are selected to produce blocks.
Snowball Consensus Mechanism (Avalanche)
Snowball is Avalanche’s proprietary Proof-of-Stake (PoS) consensus mechanism. Snowball requires validator nodes within a subnet to repeatedly query each other to determine the validity of network transactions until they reach a consensus. Snowball is the most advanced portion of Avalanche's consensus mechanism which is a combination of Avalanche’s Directed Acyclic Graph (DAG) architecture, the system’s Slush consensus (single-decree consensus), and Snowflake (Byzantine Fault Tolerance-based) mechanisms.
Tendermint Core Byzantine Fault Tolerance (BFT)
Tendermint Core Byzantine Fault Tolerance (BFT) consensus is a language-agnostic consensus method designed by the Tendermint team to be a more scalable, secure, and decentralized version of the Practical Byzantine Fault Tolerance (pBFT), State Machine Replication (SMR), and Depth Limit Search (DLS) algorithms. As a result, Tendermint Core supports state machines written in any programming language, enables fast finality rates, and can tolerate up to a third of its constituent nodes failing arbitrarily before the network's performance is significantly affected. This consensus engine was used to construct numerous noteworthy blockchains, including the Crypto.com blockchain platform and the protocol for the Binance decentralized exchange (DEX).
Asynchronous Byzantine Fault Tolerance (aBFT)
Asynchronous Byzantine Fault Tolerance (aBFT) is a consensus mechanism that improves on typical Byzantine Fault Tolerance (BFT) consensus by solving the Byzantine General’s Fault problem in a unique way. Through aBFT, nodes are able to reach consensus independently by making use of a two-stage block confirmation process using a two-thirds supermajority. The first stage proposes a last irreversible block (LIB), while the second stage finalizes the proposed LIB to make the block irreversible. ABFT consensus is considered leaderless, with no independent leading node responsible for block creation and finalization, resulting in a faster and more secure network. The Fantom and Hedera Hashgraph protocols and other networks employ different variations of aBFT.
BABE Consensus Mechanism (Polkadot)
The Blind Assignment for Blockchain Extension (BABE) is one of the two central components of the hybrid consensus mechanism that Polkadot utilizes to secure and maintain its network. BABE is a mechanism for producing blocks, while its counterpart, GHOST-based Recursive Ancestor Deriving Prefix Agreement (GRANDPA), is a mechanism for finalizing the state of the blockchain.
Byzantine Fault Tolerance Delegated Proof of Stake (BFT-DPoS)
Byzantine Fault Tolerance Delegated Proof of Stake (BFT-DPoS) is the primary consensus mechanism that runs the EOS and ICON blockchain ecosystems. BFT-DPoS is a highly-performant consensus mechanism that makes use of data passing between parties without an intermediary. It is composed of two main layers that work together: Asynchronous Byzantine Fault Tolerance (aBFT) to propagate and validate block production, and Delegated Proof of Stake (DPoS) for block producer voting and scheduling.
Casper Correct by Construction (CBC)
Casper Correct by Construction (CBC) is the consensus mechanism employed by the Casper Network. Casper CBC was initially developed by Vlad Zamfir, a well-known software engineer and technologist who helped create Ethereum. The Casper Network’s current consensus protocol, the Highway Protocol, is based on the original Casper CBC specification, with several improvements relating to block finality and network flexibility.
Delegated Byzantine Fault Tolerance (dBFT)
Delegated Byzantine Fault Tolerance (dBFT) is the consensus method that was created by Neo to be a more advanced version of Proof of Stake. The consensus mechanism is similar to regular Byzantine Fault Tolerance (BFT) except it employs a methodology whereby anyone can become a delegate that meets specific requirements. In this case, delegates are allowed to share and compare the proposals from other potential delegates. The system possesses extremely fast finality times and transaction speeds, but some argue that it is highly centralized because Neo only employs 7 main Consensus Nodes to maintain network consensus.
Delegated Proof of Contribution (DPoC) (ICON Network)
Delegated Proof of Contribution (DPoC) is a unique economic governance protocol implemented on the ICON Network that leverages the ICON Incentives Scoring System (IISS). DPoC is a variant of Delegated Proof of Stake (PoS) in that stakers delegate votes towards block validation privileges, but DPoC sees ICX holders delegating tokens towards individuals who have exercised positive participation on the network rather than for particular nodes. The elected entity then validates blocks on a delegate's behalf and earns token rewards accordingly.
Delegated Proof of Stake (DPoS)
Much like the more widespread Proof-of-Stake (PoS) system, Delegated Proof of Stake (or DPoS) incentivizes users to confirm network data and ensure system security by staking collateral. However, the distinctive characteristic of DPos is its voting and delegation structure. In contrast to PoS, where nodes are usually awarded the ability to process new blocks based solely on the total amount each node stakes, the DPoS system allows users to delegate their own stake to a node of their choosing — known as a delegate — and vote for the nodes to earn block validation access. Elected validators receive block rewards after verifying the transactions in a block, and those rewards are then shared with users who delegated them as validators.
It is named after Reliable, Replicated, Redundant, And Fault-Tolerant. Raft is not a Byzantine fault-tolerant algorithm: the nodes trust the elected leader. It is the basis of Hyperledger 2.X. Consensus helps to determine whether to commit it or not, and it is the responsibility of the Orderer Service Node to establish this Consensus.