zkEVM for L1 block verification

zkEVM is a technology that uses zero-knowledge proofs to verify Ethereum block execution. Instead of requiring every to re-execute all transactions in a block, a single specialized actor (called a "prover") executes the block and generates a cryptographic proof that the execution was correct. Any node can then verify this proof—a process that is orders of magnitude cheaper than re-executing all the transactions.

The re-execution problem

Today, Ethereum uses an "N-of-N" verification model: every validator must independently re-execute every transaction in every block to verify that the proposed state changes are correct. While this approach is maximally trustless, it creates a fundamental bottleneck.

The problem is that Ethereum's throughput is limited by what the average validator can process. Raising the would allow more transactions per block, but it would also raise the hardware requirements for validators. This threatens decentralization—if running a validator requires expensive hardware, fewer people can participate in securing the network.

zkEVM offers a way out of this tradeoff. By shifting from "everyone re-executes" to "one proves, everyone verifies," Ethereum can safely increase the gas limit without raising validator hardware requirements.

How zkEVM L1 verification works

zkEVM verification transforms block validation into a "1-of-N" model:

1. Execution: A prover executes all transactions in a block, tracking every state change
2. Proving: The prover generates a cryptographic proof (a SNARK or STARK) that attests to the correctness of the execution
3. Verification: Validators verify the proof instead of re-executing transactions—this is dramatically cheaper than full re-execution

The security guarantee remains the same: if the execution was incorrect, no valid proof can be generated. But now, instead of every node doing expensive computation, only the prover does—and verification is cheap enough that it doesn't constrain the gas limit.

Type 1 zkEVMs

zkEVMs are classified into types based on their compatibility with Ethereum:

• Type 1: Fully Ethereum-equivalent. No modifications to the EVM, so any Ethereum block can be proven exactly as-is
• Type 2-4: Make various tradeoffs, modifying EVM behavior to make proving easier

For L1 verification, Type 1 is essential. The zkEVM must be able to prove any valid Ethereum block, including edge cases and historical blocks. Any deviation from Ethereum's exact behavior would create consensus issues.

The Ethereum Foundation's zkEVM research focuses on Type 1 implementations that are fully compatible with existing Ethereum execution.

Benefits for Ethereum

Higher throughput

When verification is cheap, the gas limit can safely increase. This expands network capacity and helps stabilize fees during high-demand periods. The current gas limit is partly constrained by validator hardware—zkEVM removes this constraint.

Stronger decentralization

With zkEVM verification, validators only need to verify proofs rather than execute transactions. This dramatically lowers the hardware requirements for running a validator, enabling more people to participate in securing the network. Greater validator diversity strengthens Ethereum's censorship resistance and resilience.

Note that proving itself requires significant computational resources, greater than that of current validator hardware. However, unlike validation, proving does not need to be decentralized in the same way: only one correct proof is needed per block, and anyone can verify it quickly. Research into prover markets, proof aggregation, and hardware acceleration aims to ensure that proving remains competitive and accessible rather than concentrated among a few large operators.

Predictable finality

Proof verification operates in constant time regardless of block complexity. This makes attestation timing more predictable and reduces missed attestations that can occur when validators struggle to process complex blocks in time.

Real-time proving challenges

The main challenge for zkEVM L1 verification is speed. Ethereum blocks are produced every 12 seconds, meaning proofs need to be generated within a similar timeframe to be useful for consensus.

Current zkEVM implementations can take minutes to hours to prove a single block. Research focuses on closing this gap through:

• Parallelization: Distributing proving work across multiple machines
• Specialized hardware: Designing circuits and hardware optimized for ZK proving
• Algorithmic improvements: More efficient proof systems and circuit designs
• Incremental proving: Generating proofs as transactions execute, rather than after

Current research and implementations

The Ethereum Foundation funds zkEVM research through the Privacy Stewards of Ethereum (PSE) (opens in a new tab) team. Key research tracks include:

• Real-time proving: Generating full block proofs within 12-second slots
• Client integration: Standardizing interfaces between execution clients and provers
• Economic incentives: Designing sustainable prover markets and fee structures

Implementation status

Several zkVM implementations are being developed and tested for Ethereum block proving:

These use RISC-V based virtual machines to execute EVM bytecode, then generate ZK proofs of correct execution. Up-to-date test results and progress are tracked at the Ethereum Foundation's zkVM tracker (opens in a new tab).

How zkEVM fits with other upgrades

zkEVM L1 verification connects with several other Ethereum roadmap items:

• Verkle Trees: Enable smaller witnesses for stateless verification, reducing the data provers need to work with
• Statelessness: zkEVM is a key enabler—with ZK proofs of execution, nodes don't need full state to verify blocks
• PBS: Block builders could potentially integrate proof generation, or a separate prover market could emerge
• Single Slot Finality: Faster proof generation could enable single-slot finality with cryptographic guarantees

Further reading

• zkEVM Foundation (opens in a new tab) - Official Ethereum Foundation zkEVM research hub
• Ethproofs (opens in a new tab) - Track the race to prove Ethereum in real-time
• zkevm.fyi (opens in a new tab) - Technical book on zkEVM for L1
• PSE zkEVM Specs (opens in a new tab) - Technical specifications
• The Verge (opens in a new tab) - Vitalik's overview of verification improvements
• EF zkEVM Blog (opens in a new tab) - Performance analysis from the EF team