Consensus

Consensus is the backbone of a blockchain and, as a result, it provides decentralization of control through an optional process known as mining. The choice of the consensus algorithm is also governed by the type of blockchain in use; that is, not all consensus mechanisms are suitable for all types of blockchains. For example, in public permissionless blockchains, it would make sense to use PoW instead of a simple agreement mechanism that is perhaps based on proof of authority. Therefore, it is essential to choose an appropriate consensus algorithm for a particular blockchain project.

Consensus is a process of agreement between distrusting nodes on the final state of data. To achieve consensus, different algorithms are used. It is easy to reach an agreement between two nodes (in client-server systems, for example), but when multiple nodes are participating in a distributed system and they need to agree on a single value, it becomes quite a challenge to achieve consensus. This process of attaining agreement common state or value among multiple nodes despite the failure of some nodes is known as distributed consensus.