There are currently countless Layer-1 projects in the blockchain industry, including Bitcoin, Ethereum, BNB Chain, Polygon, Solana, Avalanche, Near, Fantom, and Tron. Even in this era of fierce competition, new L1 public chains with different characteristics and advantages are emerging one after another, and their technologies are constantly iterating. The author believes that in the future, almost all Layer1s, including Aptos, will eventually embrace zkEVM-based zkRollup, and Omnichain zkRollup will eventually appear in the future.

Source: PANews, Author: Kang Shuiyue

Edited by: Aptos Global

New public chain Aptos and Move smart contract language

As of 2022, the most popular among the many emerging industrial chains is the so-called Diem L1 public chain, including Aptos, which features the Move smart contract language. Aptos was initiated by engineers who developed Diem (formerly Libra) at Meta (formerly Facebook). Diem is the name of Meta's proprietary blockchain and its stablecoin. The project inherits many of Diem's ​​features, while having different characteristics from existing L1 public chains in terms of performance, programming language, and mechanism.

The feature of the programming language Move used by Aptos is that it completely redefines the "module structure", allowing tokens, NFTs, smart contracts and other assets to be concisely defined in a modular manner using a single data module. This is something that Ethereum's EVM cannot match - anyone who has developed using EVM will know how difficult it is to use module structures (and nested structures) in Solidity. Consider the classic re-entrancy attack. This has plagued EVM-based projects for a long time, often causing millions or tens of millions of dollars in losses. Since the Move language uses a resource-based approach, re-entrancy attacks are impossible in Move.

Whether Aptos can stand out as a mainstream public chain in the future is not only related to the language used, but also depends on the imagination of future projects on the chain. If ETH is a 4-lane road, although the lanes are not wide, there is a constant flow of people coming and going, and occasionally there are complaints about congested roads, then Aptos is like an 8-lane highway, using the best asphalt and the most advanced and safe traffic lights, but it seems that there is not much traffic. For public chains, on the one hand, there is technological innovation, and on the other hand, the projects on the public chain feed back the traffic of the public chain itself. A public chain without applications will hardly stand out even if the technology is good.

In order to obtain the huge traffic of the EVM system, Aptos will eventually embrace the EVM system and Layer2 network, especially the most advanced zkEVM-Based zkRollup.

How to build a zkEVM-based zkRollup on Aptos?

In the long run, zkRollup will become the most concise, highly secure and efficient expansion solution. In principle, a zkRollup can be deployed on any network (as long as the network can verify the proof sent by the zkRollup), so we can definitely build a zkEVM zkRollup on Aptos. So, what are the benefits of doing this?

The first is to attract developers and users from EVM. For developers, deploying products on a highly compatible zkEVM-based zkRollup on Aptos is just like deploying products on Ethereum or other EVM-compatible chains. They don't need to modify too much code and design. This means that with zkRollup, developers in the EVM ecosystem can migrate their applications to the Aptos ecosystem at almost zero cost. At this point, as long as there is a small incentive, it can attract a large number of successful projects in the EVM system to migrate and deploy, bringing a large number of ecosystems and scenarios to Aptos.

On the other hand, for users, zkRollup allows them to further enjoy lower (or even imperceptible) transaction fees, and have the opportunity to obtain a user experience close to traditional applications in terms of interaction speed and payment mode. Such a vision is undoubtedly exciting, so how do we build a zkEVM-based zkRollup on Aptos? Let's take a look at the general zkEVM-based zkRollup model designed by Fox Tech.

Figure 1: General purpose zkEVM-based zkRollup

First, we need a Sequencer, which is responsible for receiving transactions on zkRollup and executing transactions through a node with EVM to ensure EVM compatibility. During this process, the Sequencer will also generate an easy-to-proven execution process record (Trace) and send it to the proof packager zkProver.

zkProver is a proof producer with zk-EVM. zk-EVM finally has a complete zero-knowledge proof circuit designed according to EVM, which can verify whether the execution record process is correct (that is, whether it is consistent with the execution rules of EVM). Finally, a set of zero-knowledge proof algorithms are used to generate zero-knowledge proofs and send the proofs to Aptos. Finally, we need to deploy several contracts on Aptos: We need a contract to escrow zkRollup assets, which will manage the flow of assets between Aptos and zkRollup. We also need a verification contract to verify the proof sent by zkProver and a governance contract to manage authority issues (such as recording Prover and registering asset types in zkRollup).

Omnichain zkRollup will eventually appear on Web3 network

In the future, the ecology of Web3 network will not be dominated by Ethereum alone, but multiple public chains will coexist and compete with each other. Therefore, cross-chain asset and cross-chain interaction will become important needs. If we consider the traditional cross-chain bridge, if we put aside the security, then if there are only 3 chains, only 3 cross-chain bridges are needed, but if there are 5 chains, 10 cross-chain bridges are needed, and if there are 20 chains, nearly 200 cross-chain bridges are needed to realize direct communication between these chains.

Therefore, an Omnichain zkRollup will eventually become the final destination for cross-chain or even full-chain applications. Based on the above-mentioned general zkEVM-based zkRollup, another Ominichain Interoperation Protocol (this is a very important track in the next five years, with players such as LayerZero, HyperLane, Way Network, etc.) is connected to form the so-called Omnichain zkRollup. It will bring together asset liquidity from all chains and play the role of the full-chain execution layer. It ensures the correctness of transactions through zero-knowledge proofs and enjoys security equivalent to the sum of the entire chain. We envision that an Omnichain zkRollup will realize fully programmable interactivity of assets and information from all chains. Users can initiate such interactions by sending transactions on it. These interactions will change the status of accounts from various chains. Omnichain zkRollup will calculate and update the status on each chain in blocks and submit proof of status update.

The vision of Omnichain zkRollup contains infinite possibilities. People can deploy decentralized exchanges that bring together all chains on it; they can create GameFi and SocialFi that bring together users from all chains; even more diverse, varied, and borderless applications will become possible.