Secrecy by typing and file-access control

Secrecy properties can he guaranteed through a combination of static and dynamic checks. The static checks may include the application of special type systems with notions of secrecy. The dynamic checks can be of many different kinds; in practice, the most important are access-control checks, often ones based on ACLs (access-control lists). In this paper, we explore the interplay of static and dynamic checks in the setting of a file system. For this purpose, we study a pi calculus with file-system constructs. The calculus supports both access-control checks and a form of static scoping that limits the knowledge of terms - including file names and contents - to groups of clients. We design a system with secrecy types for the calculus: using this system, we can prove secrecy properties by static typing of programs in the presence of file-system access-control checks.