From the perspective of public chain scalability, what technical dilemmas does Rollup face?

Written by: Bing Ventures

Rollup, as a scalability solution, has significant potential in the expansion of public chains. However, it still faces several challenges, such as security, decentralization, user experience, and cost-effectiveness. By addressing these challenges and establishing a robust ecosystem and standardized support, Rollup is expected to achieve broader applications and development, providing lasting support for the scalability of public chains.

Hybrid Rollup is a beneficial exploration to achieve this goal. Hybrid Rollup is an innovative concept that combines different architectures to leverage their advantages. By doing so, Hybrid Rollup can better address the scalability and performance issues of public chains while providing higher security and better user privacy protection.

This article from Bing Ventures will consider the challenges faced by Rollup as a scalability solution from the perspective of public chain expansion, exploring issues such as security, decentralization, user experience, and cost-effectiveness, and discussing possible solutions and the prospects for Rollup.

Challenges of Single Rollup

Zero-knowledge Rollup and Optimistic Rollup are currently the two mainstream Rollup architectures, but each has its own obvious limitations. Optimistic Rollup requires the submission of fraud proofs, leading to a finality time of up to one week, while Zero-knowledge Rollup faces high costs due to the need to verify validity proofs on-chain. The former has a poor user experience, while the latter has suboptimal cost-effectiveness and sustainability. Both also have different trade-offs in terms of security and decentralization. For example, Optimistic Rollup has the risk of operator fraud leading to exit scams, while most Zero-knowledge Rollups are centralized, with only a few operators able to submit transactions and validity proofs to L1, increasing the risk of censorship.

A hybrid model that combines Optimistic Rollup and Zero-knowledge Rollup is expected to provide a better trade-off in terms of security and decentralization, enhancing overall system security while maintaining a certain degree of decentralization. This hybrid model also aims to provide the best possible experience for users and developers.

Furthermore, the large-scale generalization of Rollup requires a healthy ecosystem that provides better tools and documentation for developers to support them in building and deploying Rollup solutions. At the same time, establishing unified standards and specifications is necessary to ensure the interoperability and compatibility of different Rollup solutions. Source: 0XJIM

Potential Advantages of Hybrid Rollup

As an emerging scalability solution, Hybrid Rollup is expected to bring improvements in the following areas:

First, Hybrid Rollup offers greater flexibility and scalability. By constructing ZK circuits suitable for simple machines on L2, Hybrid Rollup can publish validity proofs based on Optimistic Rollup while avoiding the frequent updating of circuits, as the target machine architecture is fixed. This flexibility allows Hybrid Rollup to adapt to different application scenarios and needs, effectively scaling to handle large volumes of transactions.

Second, Hybrid Rollup combines the advantages of Optimistic and Zero-knowledge proofs, providing higher security. Optimistic Rollup offers high performance and low-cost transaction processing but carries certain risks since verification occurs after transaction submission. Zero-knowledge proofs ensure the validity and privacy of transactions, making it difficult for attackers to tamper with or steal user assets. By combining these two mechanisms, Hybrid Rollup can provide stronger security guarantees.

Additionally, Hybrid Rollup can reduce the need for trust. By using zero-knowledge proofs to demonstrate the correct execution of transactions, Hybrid Rollup can lessen users' reliance on the honesty of verification nodes. Users only need to trust the correctness of the ZK circuit without needing to trust the honesty of verification nodes, thereby lowering the trust requirements for users. Source: Bing Ventures

Technical Implementation Challenges of Hybrid Rollup

As an emerging scalability solution, the Hybrid Rollup model faces several technical implementation challenges. Here are two main challenges:

First, the process of compiling the execution layer to a simplified virtual machine may require complex engineering and research. This process needs to ensure that the compiled code can execute correctly on the simplified virtual machine and remains consistent with the original execution layer. To address this challenge, a series of technical issues related to compiler optimization, virtual machine architecture, and compatibility must be tackled. Only when these issues are properly resolved can the Hybrid Rollup model realize its advantages in flexibility and scalability.

Second, the implementation of traceable zero-knowledge proofs may need to handle large amounts of data and computation, which poses performance and scalability challenges. The Hybrid Rollup model uses zero-knowledge proofs to verify the correctness of execution traces, which requires generating and verifying a large amount of proof data. To ensure real-time generation and verification of these traceable proofs in actual networks, the proof generation and verification algorithms need to be optimized to improve their efficiency and scalability.

Given these difficulties, the Hybrid Rollup model is more suitable for specific application scenarios and needs at the current stage of technological development. Here are two main application scenarios that I believe are quite suitable:

• First is large-scale transaction processing. The Hybrid Rollup model provides higher flexibility and scalability through the method of compiling the execution layer to a simplified virtual machine, making it more suitable for handling large-scale transactions. It can effectively batch process a large number of transactions and achieve low-latency transaction confirmations, thereby meeting the demands of large-scale transaction processing.
• Second is applications with a high focus on privacy. The Hybrid Rollup model uses zero-knowledge proofs to verify execution traces, thereby protecting transaction privacy. The detailed contents of transactions can be proven to be correct, but the actual transaction data can remain confidential, accessible only to the nodes involved in the verification. This privacy protection mechanism makes the Hybrid Rollup model more suitable for applications with high privacy protection needs, such as financial transactions or personal identity verification.

In summary, the Hybrid Rollup model faces technical implementation challenges such as compiling the execution layer to a simplified virtual machine and traceable zero-knowledge proofs. However, it demonstrates its advantages and applicability in large-scale transaction processing and applications with a high focus on privacy. By addressing technical challenges and meeting specific needs, Hybrid Rollup is expected to play an important role in the field of scalability.

Future Development Directions for Rollup

Hybrid Rollup is considered the future direction of Rollup development, but its further maturity must be built on the premise of further advancements in single Rollup technologies:

First is the Optimistic Rollup model. Optimistic Rollup can provide higher transaction throughput and lower costs by further optimizing and improving the mechanism of optimistic confirmation (finality). This may involve innovations in more effective state management, transaction submission, and dispute resolution mechanisms. The Optimistic Rollup model has the potential to surpass Hybrid Rollup in terms of performance and cost.

Second is the Zero-knowledge proof Rollup model. With the development of zero-knowledge proof technology, more efficient and faster verification processes will emerge, thereby improving the performance and scalability of Zero-knowledge proof Rollup, including innovations in more efficient proof construction, more compact proof sizes, and faster verification algorithms. The Zero-knowledge proof Rollup model is expected to surpass Hybrid Rollup in terms of verification efficiency and performance. Source: Bing Ventures

We believe that the introduction of Hybrid Rollup will encourage more projects and developers to participate in building the Rollup ecosystem. By providing flexibility and scalability, Hybrid Rollup offers more opportunities for various application scenarios and industries. For example, the DeFi sector can leverage the high performance and low-cost advantages of Hybrid Rollup to build more complex financial protocols and smart contracts. Here are several directions I see as promising:

1. Cross-chain Interoperability: Hybrid Rollup can provide cross-chain interoperability solutions for different public chains. By using Hybrid Rollup as a bridging layer, various public chains can achieve secure and efficient asset transfers and information exchanges. This will promote collaboration and value flow between multiple chains, breaking down existing barriers between chains. Interoperability between Ethereum and other public chains is a potential opportunity, enabling larger-scale seamless interactions and combinations of on-chain assets through Hybrid Rollup.
2. Industry Compliance and Privacy Protection: The combined features of Hybrid Rollup can provide solutions for industry compliance and privacy protection. By adopting zero-knowledge proof technology, Hybrid Rollup can ensure transaction privacy and provide verifiable transaction execution. This is particularly important for areas such as RWA and institutional users that have high demands for privacy protection.
3. Community Governance and Consensus Mechanism Innovation: The development of Hybrid Rollup will encourage more community governance and consensus mechanism innovations. By introducing Hybrid Rollup, public chain communities can achieve higher transaction throughput and lower costs while maintaining a high degree of decentralization and security. This may lead to experiments and improvements in public chain governance and consensus mechanisms to meet the needs of different DAOs.
4. Infrastructure and Development Tool Support: With the development of Hybrid Rollup, it is expected that more infrastructure and development tool support will emerge. Developers can build tools and platforms for deploying and managing Hybrid Rollup, simplifying the development process and providing a better user experience. This will further promote the adoption of Hybrid Rollup and provide developers with more opportunities and resources.

In summary, Hybrid Rollup is expected to bring positive trends in ecosystem expansion, cross-chain interoperability, industry compliance and privacy protection, community governance and consensus mechanism innovation, as well as infrastructure and development tool support. As technology and applications continue to evolve, Hybrid Rollup will drive further improvements in the scalability and practicality of L1 and L2.