The consensus in the Blockchain is a vital concept which basically supports consensus algorithms on their own. Consensus algorithm blockchain is a protocol that makes sure all nodes are synchronized with each other. Furthermore, it decides which transactions are valid and are added to the Blockchain. Consensus algorithms make sure every participant in the Blockchain network uses the same Blockchain. Furthermore, the consensus in Blockchain ensures whether the Blockchain is functioning correctly. Besides, it constantly checks the transactions, audits the nodes as whole consensus mechanisms facilitate the decision-making processes. To be more precise – consensus in blockchain objectives of consensus mechanisms are:

Seeking Agreement – As mentioned earlier, the consensus is an agreement between Blockchain network members. Hence, seeking agreement is the primary objective of a consensus mechanism that brings about most members’ agreement.

Collaboration – The secondary objective of a consensus protocol is the collaboration between the intermediaries who participated in the agreement.

Egalitarianism – It should be called consensus only when votes of individual members of a group should hold equal weight. No one would be considered more critical or get less priority in this regard.

Inclusiveness – The voting process on a Blockchain must be unbiased for all the members and open to as many entrants as possible.

However, it is important to choose the right consensus protocol to make the fault tolerance and security of blockchain networks easier. With the right consensus protocol, a blockchain network maintains exactly the same distributed ledger. Though it is not tough to arrive at a consensus in a centralized system easily, for a blockchain network, since it is a decentralized network with each host acting as a server, information exchange is necessary to reach a consensus. Moreover, if some of the nodes remain offline, it becomes extremely challenging for consensus. So, it is important to choose the right consensus protocol that can tolerate such adverse conditions.

Related read – Top 10 Blockchain platforms you should know about

How do you choose the right Blockchain consensus?

To choose a consensus protocol, it is important first to analyze the type of blockchain network used in the system. 

There are mainly four types of Blockchain networks: 

• Consortium or Federated Blockchain
• permissioned Blockchain
• private-permissioned Blockchain
• Permission-less Blockchain

Each type of Blockchain is used in different application scenarios. So, a consensus protocol must be chosen based on this application scenario.

To assess whether a consensus protocol is suitable for your network or not, the below conditions must be considered:

•  Safe: All the nodes should produce results following the rules of the protocol.
• Participation: All the nodes should participate and contribute to the database modifications happening in the network.
• Inclusive: The algorithm must ensure that every node must be inclusive in the voting process.
• Equal Opportunities: Each vote that is acquired from a node should be given equal weightage by the consensus algorithm

These are some of the factors that must be considered before selecting a consensus protocol:

• resiliency against node failures
• network partitioning
• node behavior
• corrupt or out-of-order inputs
• network latency

What may happen if you choose the wrong consensus protocol?

Blockchain Forks

Choosing a bad consensus algorithm makes the chains vulnerable, which leads to blockchain forks. Blockchain fork happens when a single chain diverges into two or more. If a blockchain fork occurs, it leads the application to behave unpredictably, creating two or more diverged nodes ahead.

Low Performance

If you choose a bad consensus mechanism, either the node will malfunction or suffer from network partition. As a result, the message exchanging process gets delayed, and latency increases, ultimately lowering the performance level.

Consensus Failure

Another effect of incorporating a bad consensus mechanism into your business model is consensus failure. In this situation, a fraction of nodes fails to participate in any process, and thus, in the absence of their votes, the consensus fails to deliver accurately and desired outcomes.

Some of the Blockchain protocols that you can implement

Proof of Work (PoW)

Proof of Work is the most widely used consensus in the Blockchain. The bitcoin creator, Satoshi Nakamoto, developed it. Proof of Work consensus protocols relies on computing hardware to solve complex but superfluous mathematical equations. This way, it finds a hash. The first miner who can solve the hash can produce the next block, which records a transaction set. No doubt, the Proof of Work consensus algorithm unveils the power of the hash function.

Example: Bitcoin

 Proof of Stake (PoS)

Proof of Work consensus algorithm raises the growing use of power-intensive equipment, which generates a potentially negative environment. To answer this concern, the Proof of Stake consensus algorithm comes into the picture. It does not depend on computer power. Instead, it relies on the coin numbers that a user stakes. The more coins a user stakes, the higher the likelihood he can process the next block. Here the reward for the miner is the transaction fees. PoS consumes less power than PoW. However, to some extent, it encounters the same problem as PoW.

Example: Cardano, QTUM, Ethereum 

Delegated Proof of Stake (DPoS)

Delegated Proof of Stake relies on the Proof of Stake (PoS) system, where a user’s stake determines voting power. However, DPoS adds new blocks to the network with the stake of their coin holdings to select nodes.

Example: Lisk, Steem, BitShares

 Directed Acyclic Graph (DAG)

This is the third evolution of Blockchain technology, and, according to graph theory, it is a finite directed graph. Though it does not have directed cycles, DAG allows numerous transactions on multiple chains at a time. This, in turn, unlocks the potential for Blockchain to perform transactions instantly and at minimum cost.

Example: IOTA

Practical Byzantine Fault Tolerance (PBFT)

The PBFT consensus mechanism with having participants confirm messages sent to them by running a computation. This determines it’s a decision about the message’s validity. The party then broadcasts the decision to other nodes, which then process a decision on it. The final decision depends on the decisions returned by the other nodes.

PBFT is a lightweight consensus algorithm, as it depends on the number of nodes as opposes to a high hash rate to reach consensus.

Example: Ripple, Stellar, Hyperledger

Proof of Elapsed Time (PoET)

Proof of Elapsed Time solves the user commission issues caused by Proof of Stake consensus algorithms. This effectively ensures every participant has an equal opportunity to produce a block. This is mostly used in permissioned Blockchains and allows each node to produce blocks for a specified amount of time. After that, it rests for a certain amount of time. At the same time, other nodes add blocks to the network.