Ethereum co-founder Vitalik Buterin published a technical proposal Monday called “The Extremely Lean Chain,” outlining a two-phase redesign of Ethereum’s consensus layer that would shrink each validator’s onchain data from 114 bytes to 6, a 95% reduction, using zero-knowledge proofs.

The first phase eliminates the need for the Beacon chain to process every validator’s balance at the end of each epoch. Instead, validators would track their own state and submit a single daily ZK-STARK proof covering their participation and balance changes since the previous day. A validator’s pubkey would also be replaced onchain with a 5-byte index pointing into the deposit tree, rather than storing the full 48-byte key. Buterin estimated the proofs are feasible within an hour even on weak hardware.

This story is an excerpt from the Unchained Daily newsletter.

Buterin said the changes could allow the network to scale to millions of validators.

A second phase layers in privacy: validator identities would be re-anonymized daily, with fresh keys issued each day and deposits shielded through hiding commitments, making it far harder to link a validator’s entry, staking activity, and eventual withdrawal. Slashing, the mechanism that punishes misbehaving validators, stays outside the zero-knowledge system so violations can still be caught and penalized in real time rather than with a delay.

The proposal extends the “Lean Ethereum” roadmap the network has been exploring since mid-2025, which also includes single-slot finality, quantum-resistant signatures, and a separate near-term privacy plan covering transaction unlinking and metadata shielding. Buterin has called the effort the network’s third major upgrade, comparable in ambition to the 2022 Merge that shifted Ethereum to proof-of-stake.

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