Predicting global usages of resources endowed with local policies

The effective usages of computational resources are a primary concern of up-to-date distributed applications. In this paper, we present a methodology to reason about resource usages (acquisition, release, revision, ...), and therefore the proposed approach enables to predict bad usages of resources. Keeping in mind the interplay between local and global information occurring in the application-resource interactions, we model resources as entities with local policies and global properties governing the overall interactions. Formally, our model takes the shape of an extension of pi-calculus with primitives to manage resources. We develop a Control Flow Analysis computing a static approximation of process behaviour and therefore of the resource usages.Comment: In Proceedings FOCLASA 2011, arXiv:1107.584

A Language-based Approach to Distributed Resources

Modern computing paradigms for distributed applications advocate a strong control on shared resources available on demand in order to guarantee their correct usages. An illustrative example of such paradigms is Cloud Computing. In this dissertation, we study formal models for distributed applications, paying particular attention to resource usage analysis. Formal methods for specifying and analysing different aspects of resource management could play an important role for the widespread usages of distributed resources. They provide not only the theoretical framework to understand the stages underlying the design and implementation issues, but also the mathematically-based techniques for the specification and verifications of properties of such systems. In this dissertation, we introduce two models, called lambda clouds and G-Local pi calculus, which are extensions of the lambda calculus and pi calculus respectively. The lambda clouds is an extension of concurrent lambda calculus enriched with suitable mechanisms to express and enforce application-level security policies governing usages of resources available on demand in the clouds. We focus on the server side of cloud systems, by adopting a pro-active approach, where explicit security policies, which are expressed as a set of execution traces, regulate server's behaviour. By providing an abstract cloud semantics, we ensure that enforcing security policies embedded in cloud applications is sound. The G-Local pi calculus is built on top of the standard pi calculus by introducing new primitives to manage resources. Unlike the previous model, where resources are highly abstract, resources in this approach are modelled as stateful entities with local states and global policies. A high degree of loose coupling among applications and resources is achieved through the publish/subscribe model. Furthermore, we develop two static, language-based techniques, namely Control Flow Analysis (CFA) and Type and Effect Systems, to reason about resource usages and therefore able to predict \textit{bad} usages of resources. The CFA mainly focuses on reachability properties related to resource usages. It computes an over-approximation of resource usages of applications. As a result, if the approximation does not contain bad usages, then it guarantees that applications correctly use resources. The type and effect system provides a closer view of resource behaviour. Resource behaviour is extracted in the form of side effect of the type system. We exploit side effect to verify regular linear time properties, expressed by Linear Time Logic formulas, of resource usages

Uniqueness Typing for Resource Management in Message-Passing Concurrency

We view channels as the main form of resources in a message-passing programming paradigm. These channels need to be carefully managed in settings where resources are scarce. To study this problem, we extend the pi-calculus with primitives for channel allocation and deallocation and allow channels to be reused to communicate values of different types. Inevitably, the added expressiveness increases the possibilities for runtime errors. We define a substructural type system which combines uniqueness typing and affine typing to reject these ill-behaved programs

A Typed Model for Dynamic Authorizations

Security requirements in distributed software systems are inherently dynamic. In the case of authorization policies, resources are meant to be accessed only by authorized parties, but the authorization to access a resource may be dynamically granted/yielded. We describe ongoing work on a model for specifying communication and dynamic authorization handling. We build upon the pi-calculus so as to enrich communication-based systems with authorization specification and delegation; here authorizations regard channel usage and delegation refers to the act of yielding an authorization to another party. Our model includes: (i) a novel scoping construct for authorization, which allows to specify authorization boundaries, and (ii) communication primitives for authorizations, which allow to pass around authorizations to act on a given channel. An authorization error may consist in, e.g., performing an action along a name which is not under an appropriate authorization scope. We introduce a typing discipline that ensures that processes never reduce to authorization errors, even when authorizations are dynamically delegated.Comment: In Proceedings PLACES 2015, arXiv:1602.0325

Name-passing calculi and crypto-primitives: A survey

The paper surveys the literature on high-level name-passing process calculi, and their extensions with cryptographic primitives. The survey is by no means exhaustive, for essentially two reasons. First, in trying to provide a coherent presentation of different ideas and techniques, one inevitably ends up leaving out the approaches that do not fit the intended roadmap. Secondly, the literature on the subject has been growing at very high rate over the years. As a consequence, we decided to concentrate on few papers that introduce the main ideas, in the hope that discussing them in some detail will provide sufficient insight for further reading

Cirquent calculus deepened

Cirquent calculus is a new proof-theoretic and semantic framework, whose main distinguishing feature is being based on circuits, as opposed to the more traditional approaches that deal with tree-like objects such as formulas or sequents. Among its advantages are greater efficiency, flexibility and expressiveness. This paper presents a detailed elaboration of a deep-inference cirquent logic, which is naturally and inherently resource conscious. It shows that classical logic, both syntactically and semantically, is just a special, conservative fragment of this more general and, in a sense, more basic logic -- the logic of resources in the form of cirquent calculus. The reader will find various arguments in favor of switching to the new framework, such as arguments showing the insufficiency of the expressive power of linear logic or other formula-based approaches to developing resource logics, exponential improvements over the traditional approaches in both representational and proof complexities offered by cirquent calculus, and more. Among the main purposes of this paper is to provide an introductory-style starting point for what, as the author wishes to hope, might have a chance to become a new line of research in proof theory -- a proof theory based on circuits instead of formulas.Comment: Significant improvements over the previous version