The Security Picalculus and Non-interference

The security p-calculus is a typed version of the asynchronous p-calculus in which the types, in addition to constraining the input/output behaviour of processes, have security levels associated with them. This enables us to introduce a range of typing disciplines which allow input or output behaviour, or both, to be bounded above or below by a given security level. We define typed versions of may and must equivalences for the security p-calculus, where the tests are parameterised relative to a security level. We provide alternative characterisations of these equivalences in terms of actions in context; these describe the actions a process may perform in a given typing environment, assuming the observer is constrained by a related, but possibly different, environment. The paper also contains non-interference results with respect to may and must testing. These show that certain form of non-interference can be enforced using our typing systems.