A Modal Deconstruction of Access Control Logics

We present a translation from a logic of access control with a “says” operator to the classical modal logic S4. We prove that the translation is sound and complete. We also show that it extends to logics with boolean combinations of principals and with a “speaks for” relation. While a straightforward definition of this relation requires second-order quantifiers, we use our translation for obtaining alternative, quantifier-free presentations. We also derive decidability and complexity results for the logics of access control.