Ethereum: Proof of stake (PoS)

Proof-of-stake is a type of consensus mechanism used by blockchains to achieve distributed consensus. Within that, validator is then responsible for checking that new blocks propagated over the network are valid and occasionally creating and propagating new blocks themselves.

👉 VALIDATORS

• Must deposit 32 ETH into the deposit contract 
• Run three separate pieces of software: an execution client, a consensus client, and a validator.
• Validators receive new blocks from peers on the Ethereum network --> The transactions delivered in the block are re-executed, and the block signature is checked to ensure the block is valid --->  sends a vote (called an attestation) in favor of that block across the network.
• Time in proof-of-stake Ethereum is divided into slots (12 seconds) and epochs (32 slots). 
• Randomly selected to be a block proposer in every slot.

👉 FINALITY

• Using "checkpoint" blocks which first block in each epoch.

👉 CRYPTO-ECONOMIC SECURITY

• Validator is paid in ether (their staked balance increases).
• Receive minor attestation penalties every day because they are present on the network but not submitting votes.
• Ejection from the network on Day 36th of penalty.

👉 FORK CHOICE

• The algorithm used called LMD-GHOST to identify the fork that has the greatest weight of attestations in its history.

👉 PROOF-OF-STAKE AND SECURITY

• POS have community has flexibility in mounting a counter-attack.
• Attacker would need 51% of the staked ETH (about $15,000,000,000 USD). These are strong economic defenses against a 51% attack

👉 PROS AND CONS of POS

Pros	Cons
Staking makes it easier for individuals to participate in securing the network, promoting decentralization. validator node can be run on a normal laptop. Staking pools allow users to stake without having 32 ETH.	Proof-of-stake is younger and less battle-tested compared to proof-of-work
Staking is more decentralized. Economies of scale do not apply in the same way that they do for PoW mining.	Proof-of-stake is more complex to implement than proof-of-work
Proof-of-stake offers greater crypto-economic security than proof-of-work	Users need to run three pieces of software to participate in Ethereum's proof-of-stake compared to one for proof-of-work.