Foresight Ventures: Starting from Polygon zkEVM, understanding zkEVM Rollup

特邀专栏作者

2022-09-05 07:24

This article is about 12768 words, reading the full article takes about 19 minutes

The core of a truly final zkEVM Rollup will not be technical architecture or technological advancement, but Social Consensus and who will be the first to touch ecological DApp developers.

Original Author: msfew@Foresight Ventures

Original Author: msfew@Foresight Ventures

The future route of Ethereum can be said to be tailor-made for Rollup, and currently the most highly anticipated solution is zk Rollup using zero-knowledge proof technology.Generally speaking, in everyone's perception,,zk Rollup needs years of engineering development before it can really landThis is becauseThe development difficulty of building zkEVM is huge

. In order for developers to seamlessly transplant and deploy Ethereum smart contracts to zk Rollup, the development team needs to develop and optimize the performance of zkEVM compatible with EVM.The implementation of zkEVM has always been the key task of other zk Rollup teams such as the Ethereum Foundation and Polygon. In the long-term perspective, the implementation of zkEVM can not only solve:

Aspects of Ethereum Mainnet Consensus Bottlenecks
I/O: via stateless and enshrined zkEVMs
Storage: via stateless and enshrined zkEVMs

Computation: via enshrined zkEVMs

At the same time, with zkEVM as the core component, a truly perfect general-purpose Rollup network can be built.Polygon recently brought such a zkEVM with,alpha version zk Rollup

0. zkEVM

Compared with Scroll, StarkNet, zkSync, Sin7Y and other solutions, each has its advantages and disadvantages. The existence of these zkEVMs is a huge leap for Polygon and the Ethereum ecosystem, and it also means that a new and better Rollup user experience is coming.

a) Introduction to zkEVMBefore understanding how zkEVM Rollup subverts the user experience of Ethereum, we need to understand the concept of zkEVM. If you want to know more about zk, zkVM and zkEVM, welcome to read.

Our previous research articles

The concept of zkEVM can be broken down into two parts:
zk: Zero-knowledge proof technology, which can prove the validity of a batch of tx through a simplified proof, achieve computational credibility, and achieve expansion.EVM: The smart contract executor of Ethereum ecology. It is the existence of EVM that makes Ethereum have the ability to run smart contracts and become a global computing network (in contrast, the function of Bitcoin may only be a calculator), and EVM is also Derived fromEVM compatible, EVM equivalent, EVM superset

Then zkEVM is a zk virtual machine compatible with EVM at least at the programming language level. After the smart contract runs in zkEVM, it will generate a zk proof, which can prove the validity of the running state transition and ensure the credibility of the calculation. The verifier only needs to verify the Prove that verification is enough (low overhead), no need to re-execute (large redundancy).

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b) The meaning of zkEVM

zkEVM is significant at every level:
For Rollup expansion: zkEVM can generate proofs for batch tx to quickly verify on the main network, and achieve computational credibility with the help of main network security in a completely credible and multi-round complicated consensus manner.
For DApp developers: Developers don’t need to learn any zk-related hard-core knowledge or new languages other than Solidity and Vyper, they can use zkEVM to give any smart contract superpowers of zk.
For zkEVM developers: Instead of writing different circuits for the functionality of smart contracts on the network, just maintain the zkEVM.
For Layer3 builders: You can try to build a Layer3 Verifier in zkEVM, so Layer3 batch transactions can be further proved at the same time and batched into a tx for verification on the main network (L3: 1000 tx → L2: 10 tx → L1: 1 tx), implement App-rollup.

For Ethereum: The existence of multiple zkEVM solutions will eventually become important Public Goods, helping Ethereum realize the next stage of Enshrined zkEVM and zk everything Roadmap.

c) zkEVM plan and progress comparison

The zk Rollup project is very active recently. StarkNet announced that it will issue coins in the future, Aztec released private DeFi, zkSync released the countdown to the mainnet launch, Scroll released the Pre-Alpha version of zkEVM, Polygon open sourced the full set of codes of the zkEVM project...The Ethereum ecology can be described as an arms race between zk and zkEVM. And as we arePrevious zkVM and zkEVM articles

As mentioned in , the zkEVM solutions have their own advantages and disadvantages.

The first is the difference in the general direction of technology, which is basically divided into two directions:

There are different players in both directions:
Based on native: Polygon, AppliedZKP, Scroll, Taiko. Of course, the latter three are all developed in the same Repo, which can basically be regarded as the same solution.

Based on compilation: StarkNet, zkSync, OlaVM, etc. This track has the most players, but the differences between different projects are actually quite large.according toVitalik's classification comparison method

, are divided into the following types:
Type 1: fully adapted to the enshrined zkEVM of Ethereum L1. Such as AppliedZKP.
Type 2: zkEVM with the same EVM, but with a slightly different internal structure. Such as the future Scroll and Hermez.
Type 2.5: EVM is the same, only the gas cost is different (may cause subtle compatibility differences). Such as Scroll and Hermez after adding complex operation precompiles.
Type 3: zkEVM that is almost equivalent to EVM. Such as Scroll and Hermez at this stage.

Type 4: zkEVM compatible with EVM at the language level, the features and developer facilities will be different, and developers cannot directly write EVM Bytecode. Such as zkSync and StarkNet.

In the choice of the plan, there are actually a lot of variables. Just like adding points to the initial character of the game, only a certain amount of talent points can be allocated to each variable, which can be said to be another trilemma:
Performance (zk Prover, Verifier, overhead, hardware acceleration)
Adaptability (DApp developers, infrastructure, development tools, miners)

Development difficulty (maintenance difficulty, development progress, system complexity, engineering implementation complexity)Among the typical schemesthe difference

StarkNet: Completely implement a brand new zkVM (CairoVM), with good performance and low development difficulty, but insufficient adaptability (Warp translator is required to realize EVM). The biggest highlight is that it has formed an ecology and hasstorage proofandfractal scalingand
Wait for innovation.zkSync: zkEVM at the IR level (LLVM-IR part). Good adaptability (adaptation at the language level), moderate performance and development difficulty,,more flexible
The biggest highlight is that it can support languages other than Solidity through LLVM during the iteration process of the compiler.

1. Polygon zkEVM Rollup

Hermez and Scroll: Both can be regarded as zkEVM at the Bytecode level (it does not mean that the EVM Bytecode is fully reused, but the difference between the two is very subtle). The adaptability is excellent, and the performance is sacrificed (the original EVM is not zk-friendly, after circuitization There are many performance challenges to overcome), the development is very difficult, and the biggest highlight is the security of the architecture and the most native.

The core component of Polygon Hermez's open-source zkEVM Rollup network is zkEVM. The comparison of its overall technical solution with other solutions is basically the same as what we described above.

a) Polygon zkEVM Rollup architecture

The overall architecture of Polygon zkEVM Rollup is as follows:

The core of the architecture is zkEVM itself. zkEVM will execute L2 tx, and the off-chain proof network will generate validity proofs for the execution of tx in zkEVM, and the final state changes and proofs will be submitted to the Ethereum mainnet.

The key components of Polygon zkEVM Rollup are: PoE consensus algorithm, zkNode, zkProver, STARK and SNARK Proof Builder, Rollup cross-chain bridge:PoE consensus algorithm

: In order to improve security, efficiency, and decentralization, the PoE algorithm replaces the PoD algorithm of Hermez 1.0. PoE can be combined with PoS to ensure the decentralization and high efficiency of Polygon zkEVM Rollup blocks. Any miner running zkNode can Can become a Sequencer, and any miner running zkNode and zkProver can become an Aggregator. The gas fee of the miner's block production rights will be traded using $MATIC.
zkNode: zkNode is the software that any miner who wants to participate in the Polygon zkEVM Rollup network needs to run. zkNode will perform tx synchronization, sorting, and verification. In addition, if you just want to understand the operating status of the network instead of participating, You only need to run a read-only node, no need to run zkNode.

zkProver: zkProver is the software that any miner who wants to participate in the Polygon zkEVM Rollup network as an Aggregator needs to run. As the name implies, zkProver is a prover that generates zk proofs. Essentially, zkEVM is a state transition under polynomial representation, and zkProver contains a Main SM Executor and multiple Secondary State Machines to achieve the proof of state transition.

STARK and SNARK Proof Builder: The two Proof Builders will generate STARK and SNARK two different types of proofs. STARK (PIL STARK) generates proofs for the polynomial constraints of state transition batches, while SNARK (SnarkJS) generates STARK proofs The proof of constant size can be published on the chain at a lower cost.

Rollup cross-chain bridge: In addition to being a traditional Burn/Mint cross-chain bridge, Polygon zkEVM Rollup can also be used as a cross-chain bridge with other L2.

b) Polygon zkEVM Rollup design

The core design idea of Polygon zkEVM Rollup is:
Decentralization (anyone can rebuild the state of the entire Rollup through DA, without any Censorship and centralized control)
No admission required (anyone can participate in the network, as a Sequencer or Aggregator)

Performance and efficiency (through PoE, off-chain calculation, UTXO mode settlement of cross-chain bridge contracts, and various cryptography optimization schemes for performance improvement)

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c) Features of Polygon zkEVM Rollup

There are many advantages that really make the Polygon solution stand out.First of all, the collaboration between the Polygon development teams naturally formed a joint force. Polygon's zk universe includes Polygon Hermez (that is, what we call the main development team of Polygon zkEVM), Polygon Zero, Polygon Miden, and Polygon Nightfall, modular The plan also includes many other teams. Although the directions of the three zk teams are slightly different, they are all top teams in the zkVM field, and they can directly collaborate and help each other in terms of technical solutions and architecture..

For example, Polygon Hermez chooses 64-bit small field to generate STARK certificates, which is the proposal of Polygon Zero.In addition, Polygon zkEVM Rollup has many innovations in zk technology. For example, the creation of two DSLs, zkASM and PIL, can be used to explain EVM bytecode and encode polynomial promises; the combination of STARK and SNARK has played a role in the Scalable of STARK and the SNARK of SNARK. Succinct, which makes the proof faster overall and consumes less space on the final chain;,optimizationAdoptedVery efficient Goldilocks

As a base field, the parallel computing of Keccek circuit is realized, and the Poseidon-hash Merkle tree is used as the data structure for system storage.Both Polygon Hermez and Scroll have made great efforts in their own ways to prove the equivalence of decentralization and EVM. To achieve EVM equivalence, the EVM opcode must be written in the form of a zk circuit , Polygon through (zkASM to explain, and then execute in zkExecutor),Geth is essentially the same as interpretingAnd Scroll can directlyexplainexplainoror), Translation has no effect on adaptability,In contrastPolygon's solution is more friendly and efficient for proof nodes in terms of EVM equivalence. In contrast, Scroll focuses on fully reusing the security foundation of Geth..

Easier to audit

I think Polygon Hermez's zkEVM solution hits the sweet spot between native EVM support and performance. It not only explains EVM through zkASM, avoids the problem of extremely high complexity in the underlying development of EVM, but also through different angles of innovation and Optimization makes performance no longer the fatal problem of zkEVM.

2. Advantages of the zkEVM Rollup solution

a) Layer 1 and RollupThe user has been suffering from Layer 1 gas for a long time, inOur previous research on MEV

In , the shape of an ideal network is discussed.in aideal network

inside:
Anyone can send transactions (no censorship)
No spam (no spam)

Very low rates (low fees)

low fees with no spam
decentralized with no permission and no censorship
scalable with general computation

At the same time, in the context of Crypto and blockchain, the network needs to be decentralized and scalable. This is the trilemma of an ideal blockchain network:

It is impossible for a Layer 1 single blockchain to achieve the above points at the same time, and Rollup achieves a high-performance, decentralized, and low-rate finality through centralized block generation and decentralized verification.this is where we areRollup Articles

conclusions drawn from.

b) Optimistic Rollup and zk RollupIn the long-term perspective and the actual theoretical performance upper limit, zk Rollup compared to OP Rollup, more scalable.

Stronger security assumptions

The challenge period of Optimistic Rollup makes it take a long time for a tx to be truly finalized, and once the proof of zk Rollup is generated and verified, it can directly make tx fully finalized.

Rollup's OP is like Layer 1's PoW and the longest chain principle, zk is like PoS and its related consensus. For Layer 1, both PoW and PoS mechanisms are acceptable, but Rollup, which pursues performance, needs to be stronger in the final game Guaranteed (by pledge or cryptography) zk mechanism to achieve.this is where we areModular Blockchain Articles

conclusions drawn from.

c) zk Rollup and zkEVM Rollup

Since zk Rollup, why is Optimistic Rollup so popular now?

Because the currently running zk Rollup does not have general computing capabilities, such as Loopring, etc., it only stays at the stage of a single operation, and developers cannot deploy and transplant smart contracts into Rollup.

The zk proof is mainly used to prove the correctness of the operation. The emergence of a zkEVM Rollup can cultivate a smart contract ecology like Optimistic Rollup, which is far more flexible than ordinary zk Rollup transfer expansion network, and it is more secure than Optimistic Rollup. Users The experience is better.

3. User experience of zkEVM Rollup

a) The right time, place and people

The emergence of zkEVM Rollup is at the right time and place:
Time: Layer 1 expansion has encountered a bottleneck, and Optimistic Rollup has explored the path of Rollup.
Geographical advantage: The security and social consensus provided by Ethereum provide the perfect soil for the establishment of zkEVM Rollup.

Renhe: The EVM ecology occupies a dominant position in blockchain development, and countless zk development teams have contributed to the zkEVM solution.

So what kind of experience improvement does zkEVM Rollup bring to users?

First of all, we need to define users. In my opinion, users include developers and ordinary users:

b) User experience for developers
zkEVM ⇒ No need to learn new languages or even write new contracts to develop DApps: Solidity, as the first language in the blockchain contract world, has countless resources and ecology, and is the most suitable language for blockchain scenarios. The combination of these two advantages Up, far better than Move or Rust etc.

Rollup ⇒ Unlock more application scenarios: It is not suitable to use the Ethereum main network for payment or game applications due to performance and overhead issues. zkEVM Rollup allows more Apps to be realized in the form of DApps.

c) User experience for users
zk ⇒ Stronger security than PoS networks and faster finality than OP Rollup: some PoS networks rely on token pledges to ensure security, and their funds are small, and the security guarantee created is not strong, The cryptography of zk guarantees absolute security through mathematics. The challenge period of OP Rollup makes a tx unconfirmable within a certain period of time, and zk Rollup confirms tx once the proof of tx is generated.
EVM ⇒ Completely consistent usage process and infrastructure: Except for the need to switch networks in wallets and applications, all user usage processes will be exactly the same as on the main network, without additional learning costs, and only need to use the application as before.

Rollup ⇒ OP and zk Rollup can both provide L2 instant finality: From the perspective of user experience, the transaction has already been executed before it reacts. Therefore, users do not need to wait for more than ten seconds or ten minutes to continue sending The next transaction. In terms of application use, users can carry out activities on the chain more without burden, conduct high-frequency transactions or games on the chain, etc.

d) Polygon zkEVM Rollup user experience

In the future, the experience of users and developers on zkEVM Rollup will be infinitely close to that of the Ethereum mainnet, and the experience will be faster and smoother with the advantages of low gas and fast confirmation.In the plan of Polygon zkEVM Rollup,,ETH will always be used as the pricing unit of Rollup's gas fee, and MATIC will be used as the token required for pledge

This is a very good decision:
Better value capture: Polygon's experience in operating a PoS network has concluded that the value capture brought by staking is better than directly using tokens as gas.
Better user experience: ETH as a Rollup token can save L1 users or cross-chain bridge projects from the extra Swap step in the process (most people will directly cross ETH). At the same time, ETH is more orthodox as gas.

More significant differences: Polygon zkEVM Rollup will have more obvious differences from Polygon PoS, and the difference in mechanism does require such differences to allow users to choose a more suitable solution.

At the same time, what Polygon brings to zkEVM Rollup is:

Familiar "environment": Users don't need to care about the underlying technology changes, everything will be very similar to Polygon PoS, but zkEVM Rollup will be faster, safer and more usable in all aspects. Developers can also participate in familiar hackathons , enjoying the rich development ecology and community accumulated by Polygon.

4. The future of zkEVM Rollup

Regarding the future of the zkEVM Rollup scheme, we will analyze the technical future and what is the final form of this scheme.

a) zkEVM technology

Vitalik has very deep insights on this topic. Of the four zkEVM classifications he outlines, there is no real good or bad, just different technical trade-offs: closer to the bottom but slower, less compatible but faster.

In the long run, the engineering implementation and optimization of zkEVM is only a matter of time. All solutions have their own value. Vitalik also said that these different solutions may slowly transform over time until they find the one that suits their positioning .

The best future is that we have a lot of different flavors of zkEVM, so that developers can choose the one they like, and the Ethereum mainnet can also improve itself through their innovations. The more innovations, the better future.

b) Rollup technology

The end of Rollup technology will be zkEVM Rollup, and Optimistic Rollup will continue to have its own place, and there will even be a Rollup that combines zkEVM and Optimistic (personally think that one mechanism is actually sufficient).

zkEVM Rollup is better than Optimistic Rollup in many aspects. But the biggest advantage of Optimistic Rollup is that it is easier to build. The difference between Optimism Bedrock and Geth is only 500 lines of code. Any engineer who knows Geth can easily build an Optimistic Rollup. Or use Optimint and other engines on Celestia in the future. The path of OP Rollup has been fully explored. However, zkEVM Rollup is more complex, has a higher learning threshold, and has no real experience and solutions that have been fully implemented.

c) Technology...isn't the most important thing

We talked a lot about technology, but technology is definitely not the most important. The bottleneck of zkEVM Rollup, Rollup, Ethereum, and even the blockchain is never the technical bottleneck of project implementation or DA or consensus, but the user.

Give an example of Web2 (thanks to Nelson): Apple's App Store. All developers will give priority to publishing applications on the App Store, but the App Store's review is very unstable, and often randomly rejects the upload of applications. In contrast , Android’s application market, or Amazon’s application market review is much friendlier. But why does everyone want to publish to the App Store? Because the App Store has a mature and stable user group! Regardless of the developer experience of the Android or Amazon application market No matter how extravagant the hype is, developers will still flock to platforms with users.

The goal of software development is not an elegant API, 100% Test Coverage, or the best programming language, but: to solve more problems and provide more value. This means that it needs to be oriented to more users.

d) Final form

So in our imagination, what would a truly final zkEVM Rollup look like?
Fundamentals of Endgame: Technologyproving overheadzkEVM level: All solutions are good as long as they can be implemented, but they don’t have to be too fundamentalist. Ethereum’s EVM is a very legacy system (of course it is still a top-notch solution), although more improvements and improvements to zkEVM Innovation. In addition, zkEVM needs more optimization, reducing
Come catch up with the Optimistic solution.
Rollup level: Ensure that the core values of the blockchain (decentralization, security) are satisfied first, rather than blindly conducting an arms race on TPS.
Heart of Endgame: Social Consensus
Ecological level: Ideally, all Ethereum mainnet applications are migrated to a Rollup. If this zkEVM Rollup itself has a good ecological foundation, then there will be a lot of other solutions at launch. In this On the other hand, it has to be said that Polygon has a huge advantage.
Developer level: EVM compatibility is not the decisive factor, but which zkEVM Rollup can reach developers the fastest, allowing developers to use it as a network for development. It is never the network that adapts to the developers, but the developers to choose An overall fastest or best network, and then slowly adapt to the development of this network.

About Foresight Ventures

Foresight Ventures bets on the innovation of cryptocurrency in the next few decades. It manages multiple funds: VC fund, secondary active management fund, multi-strategy FOF, special purpose S fund "Foresight Secondary Fund l", with a total asset management scale of more than 4 One hundred million U.S. dollars. Foresight Ventures adheres to the concept of "Unique, Independent, Aggressive, Long-term" and provides extensive support for projects through strong ecological forces. Its team comes from senior personnel from top financial and technology companies including Sequoia China, CICC, Google, Bitmain, etc.

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The core of a truly final zkEVM Rollup will not be technical architecture or technological advancement, but Social Consensus and who will be the first to touch ecological DApp developers.

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Foresight Ventures: Starting from Polygon zkEVM, understanding zkEVM Rollup

0. zkEVM

Compared with Scroll, StarkNet, zkSync, Sin7Y and other solutions, each has its advantages and disadvantages. The existence of these zkEVMs is a huge leap for Polygon and the Ethereum ecosystem, and it also means that a new and better Rollup user experience is coming.

secondary title

For Ethereum: The existence of multiple zkEVM solutions will eventually become important Public Goods, helping Ethereum realize the next stage of Enshrined zkEVM and zk everything Roadmap.

1. Polygon zkEVM Rollup

The core component of Polygon Hermez's open-source zkEVM Rollup network is zkEVM. The comparison of its overall technical solution with other solutions is basically the same as what we described above.

Rollup cross-chain bridge: In addition to being a traditional Burn/Mint cross-chain bridge, Polygon zkEVM Rollup can also be used as a cross-chain bridge with other L2.

secondary title

2. Advantages of the zkEVM Rollup solution

conclusions drawn from.

conclusions drawn from.

3. User experience of zkEVM Rollup

First of all, we need to define users. In my opinion, users include developers and ordinary users:

Rollup ⇒ Unlock more application scenarios: It is not suitable to use the Ethereum main network for payment or game applications due to performance and overhead issues. zkEVM Rollup allows more Apps to be realized in the form of DApps.

Regarding the future of the zkEVM Rollup scheme, we will analyze the technical future and what is the final form of this scheme.

The best future is that we have a lot of different flavors of zkEVM, so that developers can choose the one they like, and the Ethereum mainnet can also improve itself through their innovations. The more innovations, the better future.

The goal of software development is not an elegant API, 100% Test Coverage, or the best programming language, but: to solve more problems and provide more value. This means that it needs to be oriented to more users.

About Foresight Ventures

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