Modular Proof Verification


Modular proof verification is a process where confirming the validity and correctness of a ZK Proof is offloaded to a dedicated service.

What Is Modular Proof Verification?

Modular proof verification is a process whereby confirming the validity and correctness of a ZK Proof, one of the most expensive parts of running ZK rollups and ZK apps, is offloaded to a dedicated service. This helps reduce costs and time for L2 scalability solutions and applications that make use of ZK technology.

The Rise of Modularity

Blockchain scalability is a multi-faceted problem, and base-layer networks like Ethereum have started to solve it by shifting from a monolithic approach to a modular approach. For example, Ethereum has recently pivoted to a “rollup-centric” roadmap.

This means many blockchain networks are now focusing on solving specific problems while delegating other solutions to different parts of the web3 stack. These solutions are external but remain decentralized and composable. 

In the case of L1 chains, it means that they can solve the blockchain trilemma by focusing on getting the security and decentralization parts of the triangle right while leaving the third component, scalability, to L2 solutions like zero-knowledge rollup (ZK rollup) chains. 

However, when we move on to ZK rollups, we find a new set of challenges.

Refreshing ZK Rollups

Let’s revisit what ZK rollups are before diving into their current impasse:

“Simply put, zero-knowledge rollups or zk-rollups are a layer-2 scalability solution that allows blockchains to validate transactions faster while also ensuring that gas fees remain minimal. ZK rollups manage to perform better than traditional layer-1 blockchains because they combine on-chain and off-chain processes.”

To achieve these scalability advantages, ZK rollup L2 chains use zero knowledge proofs — hence the name — where transactions on the L2 chain are batched and sent to the L1 chain as a single, short transaction. The validity of the single batched transaction is verified using the zero-knowledge technique.

The Problem with ZK Rollups

ZK rollups are the second most popular solution to blockchain scalability via L2s as of 2024. They have long been regarded as the optimal and most secure way to scale L1 chains, but they have faced some adoption challenges when compared to the more popular solution: optimistic rollups.

The main problem with ZK rollups is that they rely on proof verification, which is a very computationally expensive process. This extra step, required for settling transactions on an L1 chain, consumes significant resources, adding complexity and affecting transaction costs and speed.

Extending Modularity to ZK Rollups

The solution lies in applying the same modular approach that has benefited L1 chains to ZK rollups. Modularity doesn’t need to stop at the base layer.

Modular proof verification offloads the computational costs of proof verification to a separate service, which then settles transactions in batches on the L1 chain. The result of this modular approach is that the proof verification process no longer burdens the execution or settlement layers. Modular proof verification uses a specialized proof verification layer dedicated to only verifying the validity of transaction proofs.

In other words, by using a modular proof verification provider, L2 chains can simply take care of the scalability part of the blockchain trilemma. They just focus on executing the transactions that enhance user experience, while L1s only have to worry about security and decentralization during settlement.

Modular proof verification is estimated to bring over 90% savings in the cost of transactions for L2 chains such as ZK rollups. It also allows these chains to focus on optimizing the execution of transactions without dedicating additional resources to proof verification. Moreover, modular proof verification can optimize applications that use ZK technology as well, known as ZK apps.

Author: Rob Viglione, co-founder and CEO of Horizen Labs

Rob Viglione is the co-founder and CEO of Horizen Labs, the development studio behind several leading Web3 projects, including zkVerify, Horizen, and ApeChain. 

Rob served in the U.S. Air Force for several years and was deployed to Afghanistan, where he supported Special Operations Task Force intelligence efforts. During this time, he developed an early interest in Bitcoin, recognizing its potential benefits for countries with unstable economies.

Rob is deeply interested in Web3 scalability, blockchain efficiency, and zero-knowledge proofs. His work focuses on developing innovative solutions for zk-rollups to enhance scalability, create cost savings, and drive efficiency. He holds a Ph.D. in Finance, an MBA in Finance and Marketing, and a Bachelor's degree in Physics and Applied Mathematics.  Rob currently serves on the Board of Directors for the Puerto Rico Blockchain Trade Association.