Abstract. Recently, opacity has proved to be a promising technique for describing security properties. Much of the work has been couched in terms of Petri nets. Here, we extend the notion of opacity to the model of labelled transition systems and generalise opacity in order to better represent concepts from the work on information flow. In particular, we establish links between opacity and the information flow concepts of anonymity and non-interference such as non-inference. We also investigate ways of verifying opacity when working with Petri nets. Our work is illustrated by an example modelling requirements upon a simple voting system.

We consider opacity as a property of the local states of the secure (or high-level) part of the system, based on the observation of the local states of a low-level part of the system as well as actions. We propose a Petri net modelling technique which allows one to specify different information flow properties, using suitably defined observations of system behaviour. We then discuss expressiveness of the resulting framework and the decidability of the associated verification problems.

Abstract. Recently, opacity has proved to be a promising technique for describing security properties. Much of the work has been couched in terms of Petri nets. Here, we extend the notion of opacity to the model of labelled transition systems and generalise opacity in order to better represent concepts from the work on information flow. In particular, we establish links between opacity and the information flow concepts of anonymity and non-interference such as non-inference. We also investigate ways of verifying opacity when working with Petri nets. Our work is illustrated by an example modelling requirements upon a simple voting system.

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Abstract-This paper proposes and demonstrates an architectural pattern for the contractual specification of interfaces between constituent systems within a System of Systems (SoS). We take a structured approach to the development of the pattern, which we call the Contract Pattern. It is developed and demonstrated in SysML using a case study from the Audio/Video domain. We also identify some of the obstacles in the way of checking the conformance of a constituent system to a contract, and discuss how these may be overcome.

In this work we explore the use of process algebra in formalising and analysing access control policies. We do this by considering a standard access control language (XACML) and show how the core concepts in the language can be represented in CSP. We then show how properties of these policies may also be described in CSP, and how model checking may be used to verify that a policy meets the property.We further consider how we may introduce a notion of workflow into this framework, and show that a simple appreciation of the workflow context may limit the things we need to verify about a policy.