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The confrontation and debate between ZKR and OR: Is EVM equivalence a lower bound rather than an upper bound?

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This confrontation appeared lively and prosperous at the beginning of the year.

Original Title: "The First Debate between ZKR and OR in 2023: Is EVM Equivalence a Lower Bound Rather Than an Upper Bound?"

Original Author: Nian Qing, ChainCatcher

Since the second half of last year, the zk-Rollup expansion project has been intensively launched, constantly catching up with the progress, and related plans and projects have also emerged, gaining more funding and attention. When everyone praises the bright future of zk, Optimistic Rollup, as a competitor, cannot sit still. Therefore, ZKR (zk-Rollup) and OR (Optimistic Rollup) have ushered in the first positive confrontation (in public opinion) at the beginning of 2023.

A few days ago, Steven Goldfeder, co-founder of Offchain Labs, the development team behind Arbitrum, once again poured cold water on ZK Rollup and zkEVM in a tweet.

Steven Goldfeder states that he does not agree with the common belief that "ZK Rollup can better replace Optimistic Rollup". Currently, zkEVM has not yet been implemented in a production environment, and at this stage, zk-Rollup is more expensive and less compatible than op-Rollup.

Additionally, Goldfeder mentioned that "EVM equivalence is a lower bound, not an upper bound". In this view, Arbitrum has a long-term advantage as the first Rollup to fully implement EVM equivalence in a production environment. Building on this foundation, Arbitrum is now developing higher-level EVM+ to open up to a wider range of developers and users (such as supporting Rust or Move). Nitro's design based on WASM has significant structural advantages in EVM+ innovation, while the zk team finds it "almost impossible" to achieve EVM+ in the short term.

Finally, Goldfeder boldly predicts that before any fully functional zkEVM is available, Arbitrum will already support Solidity and Rust contracts!

ZKR 和 OR 的交锋和论战：EVM 等效是下限，而不是上限？

Steven Goldfeder's somewhat arrogant and indiscriminate criticism of zk-Rollup projects sparked a "spectacular debate (flame war)".

Polygon zkEVM, a zero-knowledge proof development company, engineer Brendan responded point by point to Goldfeder's views: Goldfeder does not fully understand the architecture of Polygon zkEVM. First of all, in terms of time, Polygon has already released a production-ready zkEVM testnet and generated over 80,000 block proofs, which will be launched on the mainnet in about 3 months. In terms of cost, the proof cost of Polygon zkEVM is not that high. For example, the cost of a Uniswap transaction is $0.0019, and this cost will be reduced to 1/100 of the current cost in the future. Moreover, unloading expensive calculations to ZKP is better than forcing each full node to re-execute the model.

In addition, Brendan believes that a bigger issue should be whether compatibility with EVM can be ensured after introducing new opcodes. He also made a "targeted" prediction: a fully functional zkEVM will be put into production before Optimistic Rollup supporting EVM with permissionless fraud proof.

Scroll co-founder Ye Zhang refuted Goldfeder's underestimation of zkEVM, stating that Goldfeder should take a closer look at Scroll's blog from 8 months ago, where Scroll's zkEVM was built in a highly modular way. Moreover, adding features too aggressively can increase security risks, and based on real needs, there is no need to add new features.

In addition, he also raised several further questions for exploration: How many people truly care about writing Rust contracts together with Solidity? How much additional tool support is needed? Is composability supported? What are the security assumptions?

And zkSync co-founder Alex G. partially affirmed Goldfeder's view, and he also agrees that EVM+ > EVM, and the synchronization interoperability with Rust/Move code is much stronger than with Solidity alone. But this kind of development is not only possible with Optimistic Rollup, our zkSync is currently compiling Solidity through LLVM and adding Rust and Move. In comparison, zk-Rollup wins easily.

Starkware did not participate in this debate due to the unique nature of CairoVM.

ZKR 和 OR 的交锋和论战：EVM 等效是下限，而不是上限？

In fact, with the rise of zk-Rollup, the confrontation and debate between ZKR and OR have been ongoing.

When Polygon happily announced the open source zkEVM code in July last year, Goldfeder poured cold water on it by pointing out that "zkEVM is still far from running normally". Goldfeder's observation that zkEVM still has certain centralization issues and has not been open sourced on the verifier is indeed a fact.

But even more exciting was during last year's Devcon in Bogota.

With the launch of zkSync 2.0, zkSync has begun promoting itself as "the world's first fully functional open-source zkEVM network." Similarly, Polygon zkEVM also claimed to be "the first and only decentralized zkEVM testnet" during Devcon.

However, while these two are debating the "first zkEVM", they have also attracted a lot of skepticism. Among them, Steven Goldfeder believes that the zkEVM testnet of zkSync did not use zk-proofs and did not undergo security audits. Polygon, on the other hand, has been criticized for not having an open source license for its zkEVM prover source code, although it is available on Github. Although it claims to be "completely equivalent", its Github code repository shows that it has only tested 97% compatibility coverage so far. In response, the Polygon team stated that "there is no deliberate concealment, and some content is being written for better documentation."

Steven Goldfeder has a fairly accurate saying: "Although many teams are steadily advancing zkEVM, it is far from the 'golden age', and any team promoting this narrative is harming the community."

The debate between ZKR and OPR can be traced back to the end of 2021. Offchain Labs has published an article titled "Why Optimistic Rollup Represents the Future of Ethereum Scaling Better Than ZK Rollup?" comparing the two scaling technologies of ZK Rollups and Optimistic Rollup. Since then, Offchain Labs has been emphasizing the scalability and cost advantages of the Optimistic Rollup system, which is fully compatible with EVM and existing tools.

Later, Polygon's zero-knowledge proof engineer Brendan Farmer (the same person mentioned earlier) published "Polygon Rebuts Offchain Labs: ZK Rollup is the Future of Ethereum Scaling," stating that compared to Optimistic Rollup, zk can provide the same level of security and higher capital efficiency. Additionally, OR is limited by L1 because fraud proofs must be able to be executed on Ethereum, while ZK does not have this limitation.

You will find that the two factions have been debating until this year, and the things they discuss have not fundamentally changed. But these discussions are meaningful, if there can be more extension on the topic.

Despite the first-mover advantage and the current market share of over 80% held by Optimistic Rollup, opinion leaders including Vitalik generally have a more positive long-term outlook on ZKR. Since the second half of last year, a large number of capital and developers have flooded into the zk field, and related projects have continued to emerge, with the development progress of zk-Rollup gradually accelerating. While OR does have arrogant capital at present, facing the gradually stronger competitors, Arbitrum, who sits firmly on the throne, may also feel somewhat restless, so frequent dissing is understandable and is also a good encouragement for zk-Rollup.

Overall, the L2 track in the encryption industry has been slightly less affected by the bear market compared to other areas. At the beginning of 2023, this competition appears to be lively and prosperous. However, compared to seizing public opinion, we are more looking forward to the real battle between OR and ZKR.