Casper the Friendly Finality Gadget (FFG)

Friendly Finality Gadget (FFG), hybrid PoW/PoS. FFG is a Proof of Stake algorithm implementing stake slashing for bad behavior like chain halts and censorship. Foreseen for Ethereum 2.0

Algorithm

• validators stake a portion of their Ethers as stake.

• validators start validating the blocks. when they discover a block which they think can be added to the chain, they will validate it by placing a bet on it.

• If the block gets appended, he validators will get a reward proportionate to their bets.

• Malicious validator acts trying to do a “nothing at stake”, the will immediately be punished, and all of their stake is going to get slashed.

Pros

• all Pros of Proof of stake

• punish validator trying to do a “nothing at stake” attack,

• punishing miners who go offline, unintentionally or not,

Used in

• Casper the Friendly Finality Gadget (FFG), hybrid PoW/PoS that will be implmented first and ease transtion to full PoS. blocks are mined using POW, every 50th block a POS checkpoint where finality is assessed by a network of validators will be used. Read Vitalik’s note on hybrid PoW/FFG, his medium post on minimal slashing conditions and the FFG paper.

• Casper the Friendly GHOST: Correct-by-Construction (CBC): full PoS

Resources

• https://hackernoon.com/what-to-expect-when-eths-expecting-80cb4951afcd