Why a VM Instead of a Fixed Circuit

In this episode of the lean Ethereum miniseries, Nico Mohnblatt speaks with Thomas Coratger and Emile from the Ethereum Foundation about the design and implementation of LeanVM, a minimal zkVM created to support post-quantum signature aggregation on Ethereum’s consensus layer. They explain why the team chose a VM architecture over fixed circuits and how LeanVM takes inspiration from Cairo with just 4 opcodes and 2 precompiles to keep the instruction set extremely small and make formal verification easier.

The conversation also covers LeanVM implementation choices like using Plonky3 and WHIR for efficient proving on CPUs, benchmarks for aggregation speed, and the role of Python specs in testing client interop. They share ongoing efforts to optimize low-level primitives and invite community input on the project.

Related Links

• lean Ethereum Part 1: Introduction with Justin Drake
• lean Ethereum Part 2: PQ Signatures and Poseidon with Dmitry and Benedikt
• lean Ethereum Part 3: Security of PQ SNARKs and an update about the Proximity Prize
• lean Ethereum
• Lean Consensus R&D Progress
• Cairo zkVM
• WHIR: Reed–Solomon Proximity Testing with Super-Fast Verification
• Minimal zkVM for Lean Ethereum by Emile

Repos

• leanEthereum github organization
• leanSig repo (optimized Rust implementation of XMSS for Ethereum usage)
• leanSpec repo (the Python spec of the lean consensus)
• WHIR repo
• Plonky3 repo
• leanVM