Ethereum Foundation launches evm.fast challenge to verify block limits

The foundation has set up the evm.fast challenge to determine a certified upper bound on execution steps for a 64-bit RISC-V model. The current best score is infinity, and the goal is to prove a uniform ceiling that holds across all inputs.

Contestants must use a Lean 4 proof assistant and a verified Flapjack compiler to run through a baseline program. Startup steps count toward the total, so warm-up periods cannot be skipped to artificially lower the score.

The challenge is open to contributors, though no monetary prizes, deadlines, or submission platforms have been announced. The first valid entry, backed by a machine-checked proof, will win by default, even with a loose bound.

Why worst-case bounds matter for zk proving

This effort fits into the foundation’s broader zero-knowledge proof agenda. A zero-knowledge proof allows one party to show a computation was done correctly without the checker redoing all of it. Systems that generate these proofs for general programs are called zkVMs.

The foundation’s 2025 to 2026 objectives include provable security, recursion soundness, and predictable proving costs. Recursion soundness refers to proofs that verify other proofs, which need to stay correct as they stack up. Predictable proving costs is where this challenge plugs in most directly.

Speed has already improved sharply in this area. Latency has fallen from roughly 16 minutes to under 10 seconds for 99% of mainnet blocks on target hardware, in the context of real-time proofs of full Ethereum blocks.

Security and denial-of-service implications

Real-time proving of full blocks only works if provers can budget for the hardest possible block, not just the typical one. A proven K gives that budget a mathematical foundation instead of an empirical guess.

There is also a denial-of-service angle. If an attacker could craft a block that takes vastly more steps to verify than expected, provers could fall behind. A certified ceiling makes that kind of surprise much harder to engineer, because the worst case is already known and documented.

The challenge sits alongside other ongoing foundation work on security estimation, guest-program verification, and RISC-V semantics in Ethereum execution. A guest program is the code a zkVM runs and proves, in this case the logic that checks an Ethereum block.