The following three consensus algorithms or protocols are used in the majority of blockchain platforms:

• PoW
• PoS
• PoET

We will also do a quick comparison of these three, in the later sections. Before we look at these different consensus algorithms, let's take a look at the reasons behind the variety of algorithms. The following are some of the reasons for that variety:

• Business need: Business demands drive which algorithm to use.
• Use case: The use case for using a public or private blockchain influences which algorithm will be used.
• Token need: Not every business case needs to use tokens or cryptocurrencies, and may just want to use the underlying blockchain with a consensus.
• Security and privacy: Security requirements may vary, and the same goes for privacy. Some may want a public blockchain, while others may prefer private ones.

• Performance: Public blockchains may need more time to arrive at a consensus, while private ones may do it faster.
• Robustness: Banking use cases may demand extremely high cryptography and consensus algorithms, as compared to others.