Reasoning with Past to Prove PKCS#11 Keys Secure

PKCS#11 is a widely adopted standard that defines a security API for accessing devices such as smartcards and hardware security modules. Motivated by experiments on several devices we develop an approach that allows us to formally establish security properties of keys stored on such devices. We use first-order linear time logic extended by past operators. The expressiveness of a first-order language allows us to model the security API and its features close to how it is specified while the past operators enable proof by backwards analysis. We apply this approach to prove that keys that initially have the attribute extractable set to false are secure.