Before a new block can be added to a blockchain, all nodes on the network must first reach an agreement, or consensus, that the data held within their local copy of the database is consistent with that stored by all other nodes on the network.

This is achieved using a consensus algorithm, consensus algorithms are a technique by which decentralised systems i.e. those without a central governing body, achieve overall consistency and reliability.

They work by requiring all nodes on a network to validate each other's transactions before committing data to the blockchain.

So as per our previous video, even if someone was somehow able to alter records within their own copy of the database, this doctored data would be rejected by all other nodes on the network during the consensus algorithm process

 

Popular Consensus Algorithms

There are a number of Consensus Algorithms being used today, some being more popular than others

Four well-known consensus algorithms include:

  • Proof-of-Work
  • Proof-of-Stake
  • Proof of Elapsed Time
  • And, Proof of Burn

Let’s take a deeper look at Proof-of-Work, the widely known consensus algorithm used by Bitcoin