Thread by @cemozer_

1/ Here comes a thread to give a high-level overview of Ethereum 2.0, and its first phase, the Beacon Chain.
#ethereum #eth2 #beaconchain

2/ Ethereum 2.0 is the result of years of research on how to scale Ethereum to deliver thousands of transactions per second and to implement Proof of Stake, addressing environmental and centralization concerns due to Proof of Work.

3/ From a high level, Eth 2.0 will have a hub and spoke model. The hub, called the Beacon Chain, will be the root security of the whole system and provide services such as finality, randomness, and management of validators for all the spoke chains, i.e. the shard chains.

4/ Eth 2.0 is being researched & developed in three phases. The first phase is the Beacon Chain. The research is mostly complete, and the development is hoped to be finalized during 2019. So how will the Beacon Chain work?

5/ There will be a Validator Registration Contract that lives on Ethereum 1.0. People that want to become Validators, i.e. actors incentivized to secure the network, will deposit 32 ETH to this contract.

6/ Beacon Chain clients will be listening to this contract. Once there is enough number of Validators registered, Beacon Chain will come alive.
In Eth 2.0, time is going to be divided into slots of 6 seconds. At each slot, a randomly chosen Validator will propose a new block.

7/ 3 seconds after the block proposal, randomly chosen group of validators will publish attestations that attest to what they see as the head of the chain (ideally, this should be the latest proposed block) and to a shard block in a shard chain, creating what we call a crosslink

8/ Crosslinks will allow the beacon chain to learn the state of each shard, and through finalized beacon blocks shards will get to learn the state of other shards. This is how cross-shard communication will occur. So how will beacon chain blocks get finalized?

9/ Beacon Chain will run Proof of Stake and provide finality through Casper FFG, a consensus algorithm authored by Vitalik and others. However, there are some discussions on switching to Casper CBC.

10/ Regardless of the specific algorithm, Beacon Chain will provide finality, which means that unless more than 1/3 of the validators act nefariously, it will be impossible to revert blocks.

11/ Also, in the case that more than 1/3 of validators do attack the chain, honest validators will be able to provide fraud proofs and slash attackers deposits. All in all, through Casper, validators will be rewarded for being active, and penalized for being offline.

12/ The second phase will add the shard chains, although there will be no state or accounts, meaning that you won’t be able to do meaningful computation on them. The research for this phase is hoped to be finalized in 2019, and development around 2020.

13/ The third phase will implement a sharded VM on top of the shard chains, bringing the good old Turing Complete Smart Contracts on Ethereum, this time with 1000x scalability.

14/ However, with unresolved research problems such as load-balancing across shards, and slow communication between contracts that live in different shards. The development of this phase is hoped to be finalized in 2021.