zkEVM: When Zero Knowledge and Ethereum Virtual Machine Become One

Zero-knowledge proofs, considered to be the ultimate solution for scaling Ethereum, are finally here. There are many ZK-based projects, but how to distinguish one from another?

It’s easy to get dazzled by the exitoic tech around prover systems, arithmetization methods and network architectures. Teams will also talk about their proof and verification times, proof size and cryptographic assumptions. But by far the most important characteristic is the design choices around the virtual machine. 

A VM is an emulation of a physical computer system rendered in software that can run programs. On Ethereum, the Ethereum Virtual (EVM) is a virtual computer that executes smart contracts. The EVM powers most of what we know as Web3, from DeFi applications to non-fungible tokens and DAOs.

Ethereum is a distributed state machine, or a device that keeps track of something, like ETH accounts and balances. The EVM then is what computes how that state changes from block to block. When the EVM executes smart contracts written in Solidity language, it compiles them into much simpler bytecodes and every node on the Ethereum network runs a copy of these bytecodes. Once run successfully, the initial state of the blockchain is changed to a final state.

One problem with the EVM is that it was not designed with zero knowledge proofs in mind and that’s a major roadblock for getting Ethereum to accommodate the next billion users. While projects have found ways around it, the holy grail is a zero-knowledge EVM, or zkEVM. 

For a primer on ZK, check out A Gentle Introduction to Zero Knowledge Proofs

Until recently, building one has been considered impossible or at least decades away. Now Polygon Hermez is about to make history with a launch of a zkEVM that is fully-compatible with Solidity code written for the original EVM. The Hermez team achieved this by coming up with the concept of tailor-made micro opcodes, or instructions the EVM uses to manipulate inputs. 

Parsing claims and Reddit discussions of the various competing projects can be a real challenge. But one fact is beyond dispute -- none offer the complete EVM compatibility that the Hermez team is building with its zkEVM. What may seem like a small difference, which is often obscured by confusing terminology, translates into major contrast in practice. Using different VM architectures breaks existing tooling and infrastructure and requires projects to build these things from scratch.

Complete compatibility means that any application built for the EVM can seamlessly  run on the zkEVM without the need to account for all of the zero-knowledge complexities under the hood. In practice, this will allow more dApps to take advantage of throughput and low fees offered by Layer 2 scaling. Most importantly, the zkEVM unleashed network effects of Ethereum’s rich ecosystem of applications.

For DeFi applications, this means enjoying high security and censorship resistance without the waiting period for deposits and withdrawals that comes with Optimistic rollups. NFT projects and games can take advantage of low gas costs and high transaction speeds, while payment service can allow users to transact with each other in near real-time.

Read more: ZK and the Future of Ethereum Scaling

Polygon is so bullish on the future of ZK, the core development team made it a centerpiece of its strategic vision in the Zero Knowledge Thesis published in August 2021. As part of that mission, the team has committed $1 billion, a significant portion of the treasury, to ZK-related efforts.

Polygon Hermez is close to a testnet release of its zkEVM. In the meantime, check the documentation, track their work on Github and tune in to the Polygon Blog to keep up with the most exciting experiments in this space.

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