Definition
Formal verification evaluates a program or protocol against a formal specification. Rather than only executing selected examples, it can reason about all behaviors represented by a model or prove particular invariants. In smart contracts, a property might state that only an authorized role can perform an action or that a defined accounting relationship always holds. The strength of the result depends on what was specified and what the model includes.
How It Works
Engineers define the relevant semantics and desired properties, then use techniques such as theorem proving or model checking. The analysis may concern source code, compiled code, or a simplified model, and the distinction matters. A counterexample can reveal a flaw in either the implementation or the proposed specification. A successful proof applies to the stated version and assumptions, not automatically to every upgrade or surrounding service.
Key Considerations
Formal verification complements testing and manual review rather than eliminating them. An incomplete specification can omit the very risk that users care about, and assumptions about oracles, external contracts, compilers, or privileged actors may fail in practice. A proof of accounting consistency does not demonstrate that market inputs are honest or an investment is profitable. Read which properties were established, what remains unproven, and whether the deployed system matches the analyzed artifact. The phrase formally verified should never be interpreted as a blanket guarantee of security.