Scroll: EVM-Equivalent zkEVM

The race between zkEVM teams is heating up. While a lot of the attention has gone to zkSync and Polygon, there is one project that is making large strides in development and research and making different tradeoffs worth exploring: Scroll. They are working directly with the Ethereum Foundation and are looking to create a zkEVM system that is more EVM-Equivalent than their counterparts, with an emphasis on decentralization and open-source building.

zkEVM

Given the prevalence of the EVM for developers, there has been a large desire to marry the immense scalability of zk rollup technology with the developer experience of the EVM. This has led to a race to create zkEVM systems, where the major players have been Scroll, zkSync, and Polygon. While zkSync has officially gone live on mainnet with their baby alpha at the end of October, there is still a question of whether or not they are truly “first” in the space. In addition, it’s important to understand the nuances between zkEVM system design because they are certainly not created equal.

zkEVMs are immensely challenging to build from a technical level due to the fact that the EVM design was not created with the demand of zero knowledge proofs in mind. This includes the lack of support for elliptic curves necessary for recursive proofs, the requirement of special opcodes and error types, and the overhead required for the necessary storage and proof generation. Beyond these issues, zkEVMs were finally able to be built due to the immense acceleration of hardware to deal with these constraints, as well as technological breakthroughs such as polynomial commitments, lookup tables, and the reduction in cost of recursive proofs.

Types of zkEVMs

Given the constraints of the EVM, zkEVMs face a necessary tradeoff between compatibility/equivalency and performance. Vitalik Buterin laid out a scale from type 1 to 4 in an effort to clarify the difference between various zkEVM design choices: