A proof assistant is software that helps a user build a formal proof while automatically checking every step against precise logical rules. Unlike a normal editor, it only accepts arguments that satisfy the underlying logic, so mistakes in definitions, inference, or assumptions are caught early.
In cyber security, proof assistants matter because many defenses depend on properties that must be exact: cryptographic protocols, access-control rules, operating-system kernels, and safety-critical code. Security teams use them to prove that a protocol resists certain attacks, that an implementation matches its specification, or that a bug cannot violate a trust boundary. Attackers benefit when systems rely on informal reasoning, but a proof assistant can reduce that risk by turning security claims into machine-checked guarantees. They are especially useful for high-assurance software where “looks correct” is not enough.