As blockchain technology evolves, there is a need for increased scalability and security. One solution to this problem is Rollup technologies, which are ways to process transactions outside the main blockchain (L1) and then validate the data at the main level. The best known of these are Optimistic Rollups (OP Rollups) and Zero-Knowledge Rollups (ZK-Rollups).
In this paper, we will discuss the concept of Hybrid Rollup, which contains the advantages of both approaches, and the integration of a zkVM (Zero-Knowledge Virtual Machine) into the Optimistic Rollup architecture, such as zkMIPS from the ZKM project.
Optimistic Rollups, such as Optimism, offer high compatibility with Ethereum (EVM) and provide efficient transaction execution. However, they take a long time to confirm withdrawals due to the fraud verification mechanism, thereby reducing usability for users who would not mind making quick transfers.
ZK-rollups, on the other hand, offer instant proofs using Zero-Knowledge Proofs (ZKP), but face high computational cost of SNARK proof generation and implementation complexity.
But there’s a new player with a hybrid approach, seeking to eliminate current limitations and compromises, thereby unlocking the full potential of Layer 2 (L2).
The hybrid approach starts by creating an architecture similar to Optimism's Bedrock that is as Ethereum-compatible as possible. In this architecture, transactional data is collected and processed at L2 and then validated at L1. The main challenge is to provide evidence that transactions are correctly executed.
The next step is the integration of zkVM, which allows the creation of proofs of correctness of L2 program execution using a simple and static architecture such as MIPS. This significantly reduces the circuit complexity and size, and improves the flexibility and adaptability of the system. Unlike zkEVM, zkMIPS does not require frequent updates when changes are made to the EVM, which reduces the cost of auditing and maintaining the system.
The ZKM project has revealed to the world a general-purpose zkVM called zkMIPS, the essence of which is seamless integration with existing L2 solutions, including the Optimism architecture.
One of the outstanding features of zkMIPS is its ability to generate compact proofs, which play a key role in supporting ZK Rollup and facilitating the implementation of Hybrid Rollup.
This means that second-tier solutions based on optimistic models can take advantage of zkMIPS to create proofs of their calculations. As a result, this could reduce the current seven-day withdrawal period to much shorter intervals.
Imagine two coasts, now to get to the other shore, users won't have to take a detour because there is a kind of bridge between them that will speed up transactions, making them much more efficient.
The major components of system integration include:
The main benefit of upgrading is the ability to provide faster transaction validation and eliminate the need for long withdrawal delays, as in the case of pure Optimistic Rollup. In addition, this approach can optimize transaction validation costs and improve the user experience through shorter wait times.
Thanks to zkMIPS, Hybrid Rollup can offer users different withdrawal options depending on their needs: a cheaper but longer withdrawal using Optimistic Rollup or a faster but potentially more costly withdrawal via ZK Rollup.
Integrating zkMIPS into Optimistic Rollup requires significant effort to optimize computation and reduce verification time. However, using a fixed architecture such as MIPS allows you to focus on performance optimisation without having to consider changes to the EVM.
The prospects for hybrid Rollup systems lie in their widespread application in various fields such as finance, identification and other areas requiring high privacy and security. In the long term, the development of hardware solutions such as ASICs and FPGAs can significantly speed up the verification process and make hybrid Rollup more attractive for mass use.
Using the example of the ZKM project, the goal of its design is to cover the greatest number of use cases.
Hybrid Rollup, which combines the advantages of Optimistic and ZK solutions, represents a promising direction for blockchain technology. The zkVM integration allows for a more flexible and performant system that can meet scalability and security needs. The zkMIPS technology from the ZKM project plays a key role in the creation of these Hybrid Rollups, making them an important element of future highly efficient and secure blockchain platforms.
