# The Merge

###### tags: `thread`

### Merge (PoW → PoS) does not have much impact on EVM and zkEVM

The essence of “the merge” is to replace the PoW consensus mechanism of Ethereum with PoS (PoS is a type of consensus mechanism, and Ethereum uses [Gasper](https://ethereum.org/en/developers/docs/consensus-mechanisms/pos/gasper/), which is Casper FFG + LMD-GHOST)

Compared to the previous monolithic structure, Ethereum now has two parallel chains handling the logic of the consensus layer and the execution layer at the same time


While merge only affects the consensus layer and has almost no effect on the execution layer (EVM), the only change is to replace the DIFFICULTY opcode with PREVRANDAO (refer to [EIP-4399](https://eips.ethereum.org/EIPS/eip-4399))

After the merge, all DIFFICULTY will always return 0, so this field is discarded. Therefore, the merge is actually backward compatible. If there are smart contracts that contain PoW logic, it may be affected to a certain extent

Except for the DIFFICULTY opcode, the EVM continues to process transactions and execute smart contract code, nothing has changed

Since what zkEVM does is to verify the correctness of layer2 EVM execution results (i.e. trace data) through zk-proof system and circuits, it won't change much too

### Track the evolution of Ethereum PoS and the merge

The Ethereum white paper was released in 2013, but theoretical research on PoS has been around since 2014. If you read the articles on the Ethereum blog carefully, you will find that the first article is "Bootstrapping A Decentralized Autonomous Corporation"

And [the second article](https://blog.ethereum.org/2014/01/15/slasher-a-punitive-proof-of-stake-algorithm) is about a PoS algorithm "Slasher: A Punitive Proof-of-Stake Algorithm”

As for the engineering implementation of Ethereum PoS (i.e. Beacon Chain), it will start in 2018, and the spec of phase 0 will be initially determined in September 2020 ([EIP-2982](https://eips.ethereum.org/EIPS/eip-2982)), and it was launched in December 2020

After the launch of Beacon Chain, there are still two important EIPs
It is [EIP-3675](https://eips.ethereum.org/EIPS/eip-3675), which defines when and how the merge occurs

And [EIP-4895](https://eips.ethereum.org/EIPS/eip-4895), to determine how the validator can withdraw funds from the Beacon Chain (it is still in the draft stage, it is expected to deploy in the next Shanghai upgrade)

If you want to go deeper, [consensus-spec](https://github.com/ethereum/execution-specs) and execution-spec you won't miss

### PoS could theoretically have more nodes, but still needs some improvements

Validators are more decentralized relative to ASICs (many disagree, it's worth writing an article to debate), and since validators don't need to compete with each other, it's easier for regular users to run a node on their own laptops

But becoming a validator is easy to be limited by capital and technology
Without 32ETH, you cannot become a validator. And if you don't have enough technical knowledge, you may give up being a validator to avoid being slashed (or trust center staking pool, that's another story)

In fact, most users choose to use the center staking pool, and the sum of the top few centralized staking pools has already more than 50%


Therefore, although the validator is theoretically more decentralized, there are still many directions worthy of efforts to improve decentralization

- For example, is it possible to build a decentralized staking pool
- And whether it is technically convenient for more ordinary users to become validators
- Discussion on strong vs weak censorship, how to design the censorship resistance mechanism of Ethereum

### Conclusion

Previously, my attention was more on zkp, zkevm, zk-Rollup, but when I found so many interesting things in ethereum roadmap, I chose to step out of my comfort zone and study new things

[Thread](https://twitter.com/LuozhuZhang/status/1572911221992726528?s=20&t=hf32T6kwnUQiTjAV1MfiLA)