lean Ethereum Part 4: leanVM, a Custom VM for Signature Aggregation

March 11, 2026·33 min·2 clips

Emil explains why LeanVM's signature aggregation speed dropped from 1,000 to 500 XMSS per second — implementing recursion required removing the fancy optimization tricks that made the prover fast.

The technical center is Lean VM. Nico uses the Lean Ethereum miniseries frame to ask why post-quantum signature aggregation needs a custom virtual machine in consensus. The answer stays close to the engineering work. The guests describe a system that is still changing quickly, getting simpler in pieces instead of showing up as a finished design. That matters because Lean VM is tied to Ethereum consensus, post-quantum signature aggregation, and implementation choices that are still being tested. Cairo is the nearest comparison. When Nico asks whether that comparison is fair, the answer is yes, which gives listeners a useful handle on the VM's shape. The episode also points people toward the dedicated PQ Telegram channel, weekly post-quantum interrupt calls, and the Lean Ethereum GitHub organization. The work is spread across repos. Lean Seek carries the XMSA signature scheme in Rust and has performance work to do. Lean Multisig is another active place to help. The discussion also reaches lower in the stack, into Plonky 3 and Weir, where contributors can work on performance and proof machinery. Nico keeps the stack from turning into fog. Short questions about tools, comparisons, and contribution paths give the guests room to explain without sanding off the technical detail. One guest says the system had changed even the previous week, so this feels like live engineering notes, not settled documentation. The close points listeners toward client implementation calls and the next Lean Ethereum episode, with Lean VM still very much in motion around Ethereum consensus and Ethereum Foundation researchers.

As heard by us

A focused look at why Lean VM is being shaped for a narrow post-quantum role on Ethereum.

Zero Knowledge keeps Part 4 of its Lean Ethereum series on the technical side of the room. The discussion stays on Lean VM, the smallest ZKVM in the project, and on the tradeoffs behind choosing a VM instead of a fixed circuit.

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Why you'd press play

If you want the design logic behind Ethereum's minimal ZKVM, start here.

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