Comparing Scroll and Hermez, understanding zkVM and zkEVM
Original author: Luozhu
Original compilation: Leo, BlockBeats
I haven't delved into Hermez's zkevm solution yet, but it's interesting to compare Scroll and Polygon Hermez's zkevm is A good perspective can help you better understand zkVM and zkEVM.
Basically, Scroll's zkEVM solution implements EVM etc. by "reimplementing" the entire EVM However, all operations of EVM are defined in zkevm-circuits (zk circuits), which requires many steps (constraints) to prove.
Hermez's zkEVM solution is different, instead of reimplementing an EVM, they implement A specific zkVM, and map EVM operations to their own zkVM. Therefore, proving the operation of EVM is equivalent to proving the corresponding operation in Hermez's zkVM, and zkVM has a very large degree of freedom, they can avoid the zk-unfriendly part of EVM.
There are different ways to define whether Hermez is zkEVM or zkVM:
- As long as you can prove that all operations from the EVM are correct, be satisfied - Hermez is zkEVM;
- Had to re-implement full EVM, not satisfied - Hermez is zkVM
Hence, Scroll and PSE The zkEVM is very complex (and miraculously implements the zk-unfriendly part). Our zkEVM has 34469 lines of code, but Hermez's zkEVM has less than 3000 lines of code, Click to learn
The original zkEVM trade-off Scroll/PSE is Difficult to implement, but post-processing EVM updates are easy, Hermez's zkEVM is easy to implement initially, but subsequent updates are difficult (may require redesign of zkVM), and the PSE scheme is more suitable for Layer 1, and subsequent upgrades are also easy, and because Scroll works directly with PSE (and even contributes to the same repo), and subsequent upgrades to Scroll's zkEVM are easy.
A promising future is that we optimize the proof generation time to 12 seconds (exactly in When a slot is proposed), zkEVM can be directly used in the production environment of Layer 1 at this time, and the limit of running a node will also be reduced.
If zkEVM can be directly used in Layer 1, then the main network will have its own prover, if Prove that the generation time can be optimized to 12s, I think a prover network that can help accelerate (hardware acceleration, community participation, etc.) will be considered.
Scroll will have its own Prover network in the future, and its roadmap is as follows:
p>
-Pre-alpha Testnet Upgrade
-Alpha Testnet
-Decentralized roller network
-Mainnet launch
So if Scroll’s roller network works well (there may be a new consensus mechanism), it will have a direct impact on Layer 1, and the Ethereum mainnet is likely to learn from Scroll Based on the experience, try to use the roller-network method to speed up your own zkEVM (up to 12s).
Rollup is an innovative testing area for layer 1 that involves not only novel applications but also Involves these underlying infrastructures. There are currently multiple zkEVM implementations led by different rollup teams, this is good for both rollup and Layer 1 in the long run, for rollup we can use other zkEVM implementations to check if our own zkEVM misses constraints or exists bugs etc.
One zkEVM generates the proof, the other zkEVM verifies its process.
If multi-zkEVM can form a cooperative mechanism , there is no reason for Layer 1 not to learn this way directly, and of course, not that many layer 2 teams will implement the consensus layer zkEVM (but still learn how they were designed).
In any case, in the future we will still see very active discussions about zkEVM, there will be More designs, more innovations, more bugs, and finally an upgrade of EVM on layer 1 -> zkEVM. We will also see rollup innovations learned on layer 1, helping Ethereum itself get better (not just lower gas transactions).
Finally, Hermez has a great team with outstanding contributions in the field of zkEVM and zkp, I think different L2 teams should be more Communicate/collaborate as much as we are all on the same page, we are all allies in Ethereum, we are here to scale Ethereum and get the blockchain ready for the next phase and the next billion users.
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