Casper: Ethereum’s Proof-of-Stake Algorithm

Casper is the proposed name for Ethereum’s PoS consensus algorithm. It is still under active research and development and is not implemented on the Ethereum blockchain at the time of publication of this book. Casper is being developed in two competing “flavors”:

• Casper FFG: “The Friendly Finality Gadget”

• Casper CBC: “The Friendly GHOST/Correct-by-Construction”

Initially, Casper FFG was proposed as a hybrid PoW/PoS algorithm to be implemented as a transition to a more permanent “pure PoS” algorithm. But in June 2018, Vitalik Buterin, who was leading the research work on Casper FFG, decided to “scrap” the hybrid model in favor of a pure PoS algorithm. Now, Casper FFG and Casper CBC are both being developed in parallel. As Vitalik explains:

The main tradeoff between FFG and CBC is that CBC seems to have nicer theoretical properties, but FFG seems to be easier to implement.

More information about Casper’s history, ongoing research and future plans can be found at the following links:

• Ethereum Casper (Proof of Stake)

• History of Casper, Part 1

• History of Casper, Part 2

• History of Casper, Part 3

• History of Casper, Part 4

• History of Casper, Part 5