Channel Dependent Types for Higher-Order Mobile Processes (Part I)

We introduce a new expressive theory of types for the higher-order π-calculus which significantly improves our previous work presented in [65] by the use of channel dependent/existential types. New dependent types control dynamic change of process accessibility via channel passing, while existential types guarantee safe scope-extrusion in higher-order process passing. This solves an open issue in [65], leading to significant enlargement of original typability and offering a general basis for analysing and verifying higher-order mobile computation. This paper establishes a basic theory of dependent and existential types for the higher-order πcalculus, and coherently integrates the resulting formalism with the linear/affine typing disciplines as well as state, concurrency and distribution [6, 27, 63, 66], which allow precise embedding of major language constructs in the calculus. The type discipline can guarantee unique accessibility of resources, termination of migrating code, a response property from a remote server and encapsulation of higher-order code by hidden names. The technical development in this paper gives a firm basis for the applications discussed in its sequels. Part II presents uniform type-based static analyses of two basic security concerns for higher-order mobility, secrecy for data confidentiality and access controls for authorised resources. Part III uses this framework for developing and justifying a type discipline for a simple multi-threaded class-based language with distributed code mobility which enforces secrecy and safe access controls.