Vyper releases public, machine-checked formal semantics in HOL4, building on Verifereum’s EVM proofs

Vyper, the security-focused smart contract language for the Ethereum Virtual Machine (EVM), has released a public, machine-checked formal semantics of Vyper in the HOL4 theorem prover, marking a significant step toward fully verified Vyper smart contracts. This work builds on the Verifereum project’s existing formally verified EVM model in HOL4, which has been validated against the Ethereum Execution Spec Tests, creating a unified, mathematically precise description that connects Vyper source code to low-level EVM behavior. Contributors describe it as the first complete, precise, executable definition of the meaning of every Vyper program in HOL4. Formal semantics specify, in mathematical logic, exactly what each construct in the language does, and being machine-checked in HOL4 means the definition and associated proofs are mechanically verified by an interactive theorem prover rather than relying on informal reasoning. This semantic foundation enables deep verification: developers and researchers can prove properties directly about Vyper source programs, and, once the ongoing compiler-correctness work is finished, have those guarantees carry through to the deployed EVM bytecode. It also leverages Verifereum’s formally modeled EVM, narrowing the gap between high-level security proofs and real-world Ethereum execution. For the broader ecosystem, this aligns Vyper with rigorous formal-methods efforts (such as KEVM and other EVM models) and responds to past concerns about compiler bugs and security by providing a route to end-to-end, mathematically backed assurances for production smart contracts.

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More coverage

• Vyper (vyperlang.org)
• Formal Verification of Software-Defined Network ... - Diva-Portal.org (diva-portal.org)
• verifereum/vyper-hol: Formal specification and verification ... - GitHub (github.com)
• [PDF] A Formal Semantics for Viper (ethz.ch)
• [PDF] KEVM: A Complete Formal Semantics of the Ethereum Virtual Machine (fsl.cs.illinois.edu)

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• EVM
• Vyper