Expressive Policy Analysis with Enhanced System Dynamicity

Despite several research studies, the effective analysis of policy based systems remains a significant challenge. Policy analysis should at least (i) be expressive (ii) take account of obligations and authorizations, (iii) include a dynamic system model, and (iv) give useful diagnostic information. We present a logic-based policy analysis framework which satisfies these requirements, showing how many significant policy-related properties can be analysed, and we give details of a prototype implementation. Copyright 2009 ACM

Design and semantics of a decentralized authorization language

We present a declarative authorization language that strikes a careful balance between syntactic and semantic simplicity, policy expressiveness, and execution efficiency. The syntax is close to natural language, and the semantics consists of just three deduction rules. The language can express many common policy idioms using constraints, controlled delegation, recursive predicates, and negated queries. We describe an execution strategy based on translation to Datalog with Constraints, and table-based resolution. We show that this execution strategy is sound, complete, and always terminates, despite recursion and negation, as long as simple syntactic conditions are met

Formal Specification and Validation of Security Policies

International audienceWe propose a formal framework for the specification and validation of security policies. To model a secured system, the evolution of security information in the system is described by transitions triggered by authorization requests and the policy is given by a set of rules describing the way the corresponding decisions are taken. Policy rules are constrained rewrite rules whose constraints are first-order formulas on finite domains, which provides enhanced expressive power compared to classical security policy specification approaches like the ones using Datalog, for example. Our specifications have an operational semantics based on transition and rewriting systems and are thus executable. This framework also provides a common formalism to define, compare and compose security systems and policies. We define transformations over secured systems in order to perform validation of classical security properties

Semi-Automatic Synthesis of Security Policies by Invariant-Guided Abduction - Full version

We present a specification approach of secured systems as transition systems and security policies as constraints that guard the transitions. In this context, security properties are expressed as invariants. Then we propose an abduction algorithm to generate possible security policies for a given transition-based system. Because abduction is guided by invariants, the generated security policies enforce security properties specified by these invariants. In this framework we are able to tune abduction in two ways in order to: (i) filter out bad security policies and (ii) generate additional possible security policies. Invariant-guided abduction helps designing policies and thus allows using formal methods much earlier in the process of building secured systems. This approach is illustrated on role-based access control systems

PlexC: A Policy Language for Exposure Control

With the widespread use of online social networks and mobile devices, it is not uncommon for people to continuously broadcast contextual information such as their current location or activity. These technologies present both new opportunities for social engagement and new risks to privacy, and traditional static ‘write once’ disclosure policies are not well suited for controlling aggregate exposure risks in the current technological landscape. Therefore, we present PlexC, a new policy language designed for exposure control. We take advantage of several recent user studies to identify a set of language requirements and features, providing the expressive power to accommodate information sharing in dynamic environments. In our evaluation we show that PlexC can concisely express common policy idioms drawn from survey responses, in addition to more complex information sharing scenarios