Post by @harfang • Hey

Did you know that Proof of Stake was not the consensus protocol of Ethereum ? Instead it is a little cute ghost called Casper ! A thread 🧵 #Thread #cryp

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Casper initially started in 2014 and is a descendant of the PBFT (Practical Byzantine fault tolerance) protocol and involves computer science, economics and cryptography. But PBFT has a default it does not punish incompetent validators, this is why slashing was introduced. The first slashing proposition by Vitalik Buterin was the following (explained later): 1. A validator must not publish two distinct votes for the same target height. 2. A validator must not vote within the span of its other votes. How Casper FFG works? First of all Casper is not responsible for the blockchain itself it is independent of the block proposing mechanism. It is only responsible for consensus. On Ethereum, a slot is filled every 12 seconds by a block. An epoch is 32 slots (6.4 min). On Casper when we will talk about a checkpoint we are referring to the first slot of an epoch. PoS is based on validators voting. A vote is a link between two checkpoints of different epochs. A source checkpoint and a target checkpoint. When a validator votes, it collects other votes and when a specific vote is more than 2/3 total votes it is called the supermajority link. Starting from the first checkpoint (root), when a checkpoint is a source checkpoint it is considered as finalized and if it is a target checkpoint it is considered as justified / proposed.