What is a zkEVM and how does it work?

A zkEVM is a virtual machine that is able to support Ethereum applications in a very native way, while making use of complex zero-knowledge proof scaling technology.

In order to truly grasp what a zkEVM is or what it does, it's worth understanding how developers got to the point of creating one.

The road to a zkEVM

It started with the need to scale cryptocurrency protocols. This has been an issue for years and is tricky because it's hard to scale blockchains without making them more centralized.

Building Layer 2 networks on top of Ethereum has been a key focus on solving this. The idea is that transactions are processed and batched on a secondary network and then the result of these transactions are output to the Ethereum blockchain in one go. This is beneficial because it results in lower transaction fees overall and puts less bloat on the Ethereum blockchain.

However, one key risk is how the network knows that these transactions are genuine. Well, a key method has been to create a cryptographic proof of the transactions, one that mathematically verifies that they were all legitimate. This uses zero-knowledge proof technology, known as zk-proofs.

So by this point, you had Layer 2 networks that could support the processing of transactions using zk-proofs. But projects building this kind of thing became even more ambitious.

A key element of Ethereum is the computer at the heart of its network known as the Ethereum Virtual Machine. This is the technology that supports smart contracts and all manner of complex decentralized applications. For a Layer 2 network to be successful, it really needs to be EVM-compatible and to support these kinds of apps.

So the next step for Layer 2 networks that use zk-proofs was to make them EVM-compatible. This would allow them to not only support transactions and decentralized applications, but all interactions would be mathematically secure. Plus, depending on the level of compatibility, it can become very straightforward for developers to port applications from Ethereum straight to the network.

These EVM-compatible Layer 2 networks that use zk-proofs are what we call zkEVMs.

Popular zkEVM projects

Several blockchain projects, including Polygon, zkSync, and Scroll, have competed over the past year to develop a functional ZK-based Layer 2 solution capable of natively supporting Ethereum apps. Here's a quick primer on some of the main projects working on zkEVMs:

1. zkSync: zkSync is a Layer 2 scaling solution for Ethereum that utilizes zk-proofs to enable fast and low-cost transactions while maintaining high security and privacy. It allows users to conduct transactions off-chain while still benefiting from the security guarantees of the Ethereum blockchain. zkSync supports token transfers, decentralized exchanges and other smart contract interactions.
2. Scroll: Scroll is an Ethereum scaling project established in 2021, designed to enhance Ethereum's performance and scalability. Scroll's technology is particularly focused on maintaining compatibility with existing Ethereum applications, enabling these applications to migrate onto the Scroll platform without any modifications. This transition is made possible through bytecode-level compatibility with Ethereum, ensuring that developers can easily scale their applications without the need to rewrite or significantly alter their existing smart contracts.
3. Polygon zkEVM: Polygon zkEVM is an advanced scaling solution developed by Polygon, a platform known for providing Ethereum scaling and infrastructure development. The zkEVM is designed to leverage zk-proof technology to enhance Ethereum's scalability and efficiency without compromising security or decentralization.
4. Taiko: Taiko is also working on a zkEVM that it intends to launch soon on mainnet. Its goal is to get to a very high level of compatibility with Ethereum.
5. Loopring: Loopring is a DEX protocol built on Ethereum that uses zkRollups, a type of zk-proof technology, to significantly increase transaction throughput and reduce gas fees. Loopring is also working on a zkEVM implementation.