TL；DR

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2. The difference between zkEVM and zkVM mainly lies in the compatibility of EVM and the support for zero-knowledge proof.

3. In terms of developers and development resources, Ethereum has the most developers, the most complete and rich development resources and infrastructure, and the developers and development resources of Ethereum are more convenient to transfer to zkEVM. The developers and development resources of zkVM such as StarkNet and zkSync are far behind Ethereum.

4. In terms of application ecology, Ethereum has the largest number of DApps and a 58% share of DeFi. The existing applications on Ethereum will be the development dividend of zkEVM. Due to the poor compatibility of EVM, it will be difficult for zkVM to transplant these existing applications; but zkVM Being more compatible with zero-knowledge proofs makes zkVM more likely to emerge application innovations.

This article belongs to the third article in the series of "understanding zkEVM in one article".first timeIntroduced the basic principles and subdivision levels of zkEVM,part twoAfter taking stock of the mainstream zkEVM projects in the industry, this article will explain the basic differences between two different ZKR projects, zkEVM and zkVM.

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Why you should know the difference between zkEVM and zkVM

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basic introduction

basic introduction

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Compared

Compared

The two schemes of zkEVM and zkVM represent the two directions of ZKR development.We will compare the differences between zkEVM and zkVM ZKR solutions in terms of developers and development resources, application ecology, and technical prospects.

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Developers and Development Resources

In terms of developers, the data in the "Developer Report 2021" compiled by Electric Capital shows that the monthly active developers of Ethereum will reach 4011 in 2021, ranking first among all blockchains and far ahead of other blockchains.

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"Developer Report 2021" report

According to the data of popular code warehouses of Ethereum, StarkNet, zkSync and other zkVM projects on Github, it can be seen that Ethereum has a very large developer group and code resources, and StarkNet and zkSync are far behind Ethereum.

Although the development resources of StarkNet are relatively complete, the number is relatively small, and it is not as mature as Ethereum.

To sum up, Ethereum has the most developers and the most abundant development resources, which will be the development dividend of zkEVM in the future. zkVM ZKRs such as StarkNet and zkSync face a huge disadvantage of latecomers.

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Application ecologyIn terms of application ecology, we will start fromApplication Migration and Application Innovation

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Data Sources:https://www.stateofthedapps.com/zh/stats

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Data Sources:https://defillama.com/chains

Ethereum's DApp and DeFi have a very large market, and zkEVM has very good development prospects in application porting.

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Applied Innovation

In terms of application innovation, zkVM lacks a lot of EVM compatibility compared with zkEVM, making it difficult for zkVM to undertake the application dividend of Ethereum. However, because the zkVM project tailors a virtual machine for zero-knowledge proofs, zkVM has emerged many innovations that zkEVM ZKR cannot achieve.

For example, StarkNet's team Topology claims to have realized the full-chain game Issac.

Issac's asset transactions, state storage, and logic execution are all on the chain.

The full chain also means that the game conforms to the basic attributes of the blockchain, which are decentralized, license-free, and combinable. No entity can change the basic rules of the game. Players and players can participate in the game and create in it without permission. Developers can create the front end of the game and the facilities and assets in the game by themselves according to the contract.The Topology team'sFocuses on Isaac's design philosophy.

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technology prospectIn terms of technical outlook, we will beAlgorithmic, language, architectural aspects

To compare the pros and cons of zkEVM and zkVM.

In terms of algorithms, most zkEVM ZKRs use the SNARKs algorithm, while StarkNet, as the most extreme zkVMist, uses the STARKS algorithm. It should be noted that SNARKs is a general term for a series of algorithms including Groth16, Halo, Fractal, and Sonic. STARKs is a An emerging specific SNARKs algorithm, we will compare the advantages and disadvantages between the two.

Compared with SNARKs, STARKs have higher security and scalability, and have better performance potential. However, at present, STARKs have a larger proof scale, longer verification time, and are in the initial stage. The infrastructure and code base are not as complete as SNARKs.。

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On the one hand, due to the imperfect compatibility between opcodes and bytecodes, unknown vulnerabilities will appear in the process of transplanting and converting Solidity codes. For example, Polygon Hermez directly converts EVM bytecodes into virtual machine bytecodes.

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Image from: https://blog.hermez.io/introducing-hermez-zkevm/

On the other hand, with the maturity of zero-knowledge proof technology, zkEVM will inevitably appear as a demand for custom circuits, and languages ​​such as Solidity are not friendly to zero-knowledge proof, which will cause huge technical obstacles.

And zkVM such as StarkNet and zkSync are designed to be compatible with zero-knowledge proof languages ​​such as Cairo and Zinc. Developers can directly generate zero-knowledge proofs for their own programs through these languages, without the need to learn professional zero-knowledge proof knowledge to write a set of polynomial equations and convert them into circuits.

To sum up, zkEVM may have unknown vulnerabilities in the writing process of Solidity language due to immature compatibility technology in the short term, and the programming language of zkVM is more suitable for zero-knowledge proof than zkEVM.In terms of architecture, according toEthereum Yellow Paper

According to the specification, EVM is a stack-based, serial state machine. Simply put, EVM is inherently incompatible with zero-knowledge proofs. The zkVM is a virtual machine tailored for zero-knowledge proofs, and is more suitable for zero-knowledge proofs in the underlying architecture.Hardware Acceleration for Zero Knowledge Proofs》

The Cairo language invented by zkVM extremist StarkNet is a CPU-friendly high-level language adapted to zero-knowledge proofs, making StarkNet more adaptable to zero-knowledge proofs at the CPU level, and can even customize zero-knowledge proof hardware for this purpose. Paradium, an investment institution, also noticed the hardware opportunities in zero-knowledge proofs, and wrote a paper for this purpose, "Cairo – a Turing-complete STARK-friendly CPU architecture》。

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future outlook

future outlook

Scroll founder Ye Zhang suggested on Twitter that StarkWare verify the proof program written in Cairo language on StarkNet through zkEVM, simply speaking, it is to build another L2 on one L2. Such a proposal is technically feasible, and certainly describes a more imaginative, inclusive L2 world.