Advances in internet of things (IoT) and cloud computing technologies have led to the emergence of new applications such as in e-health domain bringing convenience for both physicians and patients. However, the development of these new technologies makes users' privacy vulnerable. The threats on private data may arise from service providers themselves voluntarily or by inadvertence. As a result, the data owner would like to ensure that the collected data are securely stored and accessed only by authorised users. In this paper, we propose a novel data-owner centric privacy model in IoT/cloud environment. Our model combines two promising paradigms for data privacy, which are attribute-based encryption (ABE) and blockchain, to strengthen the data-owner privacy protection. We propose a new scheme of ABE that is, in one hand, suitable to resource-constrained devices by externalising the computing capabilities, thanks to fog computing paradigm and, in the other hand, combined with a blockchain-based protocol to overcome a single point of trust and to enhance data-owner access control.

Information technology (IT) service providers are nowadays moving toward cloud computing. Software-as-a-service (SaaS) refers to cloud service-oriented web applications. As a result of computation outsourcing, a customer (tenant) can subscribe to a self-service SaaS and use it on a pay-per-use basis. To reduce resource costs, a single instance of SaaS serves multiple tenants (multi-tenancy). However, outsourcing and multi-tenancy bring about new security issues. Indeed, tenants lose control over the source code, databases and infrastructure and cannot deploy their own intrusion detection system (IDS). In this context, the provider must not only integrate their preferred IDS into a public cloud, but also protect the tenants according to their individual security requirements. We put forth a multi-tenant intrusion detection framework as a service for SaaS (MTIDaaS) to allow the provider to undertake such integration. Our MTIDaaS has been integrated and tested in a real public cloud environment. It provides security-as-a-service (SecaaS) for both provider and tenant with high levels of portability, flexibility and cost-effectiveness. The experimental results demonstrate that our MTIDaaS offers easy integration of IDS with little virtualization overhead and insignificant impact on HTTP response time.

Recently, we are attending to the proliferation of Cloud Computing (CC) as the new trending internet-based-Platform. Thanks to the outsourcing paradigm, CC is enabling many services. Software as a Service (SaaS) is one of those cloud-based-services. Indeed, SaaS model allows providers to reduce the cost of maintenance and management by transferring traditional on premise deployment to public Cloud. Clients can subscribe, in self-service, to SaaS services based on a pay-per-use model. However, since user data are outsourced to the Cloud, serious security breaches are rising and could harm the reputation of providers and slow down the subscription of clients. SQL injection attack (SQLIA) is one of the most critical SaaS vulnerabilities that allows attackers to violate the availability, confidentiality and integrity of user data. In this paper, we propose SQL injection intrusion detection framework as a service for SaaS providers, SQLIIDaaS, which allows a SaaS provider to detect SQLIAs targeting several SaaS applications without reading, analyzing or modifying the source code. To achieve SQL query/HTTP request mapping, we propose an event correlation based on the similarity between literals in SQL queries and parameters in HTTP requests. SQLIIDaaS is integrated and validated in Amazon Web Services (AWS). A SaaS provider can subscribe to this framework and launch its own set of virtual machines, which holds on-demand self-service, resource pooling, rapid elasticity, and measured service properties.

Cloud computing is an attractive business model offering cost-efficiency and business agility. Recently, the trend is that small and large businesses are moving their services to cloud environments. The quality of service is always negotiated between the cloud users and the cloud providers and documented in the service level agreement (SLA). Yet assuring -- or even measuring -- the quality of the provided service can be challenging. This paper proposes a formal approach for quantifying the quality of service in the cloud systems as promised in the SLA. The proposed approach uses controller synthesis to find a system configuration that meets the SLA requirement. The formal approach suggested in this paper is based on, but not limited to, %the controller synthesis of Time Petri Nets (TPN). As a case study, we focus on service availability as a key performance indicator in the SLA and for a sample set of resources providing a service, we determine the system configuration satisfying the SLA.

The operational transformation (OT) approach, used in many collaborative editors, allows a group of users to concurrently update replicas of a shared object and exchange their updates in any order. The basic idea is to transform any received update operation before its execution on a replica of the object. Concretely, OT consists of a centralized/decentralized integration procedure and a transformation function. In the context of decentralized integration, designing transformation functions for achieving convergence of object replicas is a critical and challenging issue. Indeed, the transformation functions proposed in the literature are all revealed inefficient. In this paper, we investigate the existence of transformation functions. From the theoretical point of view, two properties, named TP1 and TP2, are necessary and sufficient to ensure convergence. Using controller synthesis technique, we show that there are some transformation functions, which satisfy TP1 for the basic signatures of insert and delete operations. But, there is no transformation function, which satisfies both TP1 and TP2. Consequently, a transformation function which satisfies both TP1 and TP2 must necessarily have additional parameters in the signatures of some update operations. We propose, in this paper, a new transformation function and show formally that it ensures convergence.

The main limitation of the verification approaches based on state enumeration is the state explosion problem. The partial order reduction techniques aim at attenuating this problem by reducing the number of transitions to be fired from each state while preserving properties of interest. Among the reduction techniques proposed in the literature, this article considers the stubborn set method of Petri nets and investigates its extension to time Petri nets. It establishes some useful sufficient conditions for stubborn sets, which preserve deadlocks and k-boundedness of places.

The main problem of firewall configuration is to ensure the filtering rules consistency w.r.t. a global security policy. However, the overall firewalls configuration on a network, which requires a human intervention, is often an error-prone process. Therefore, automated solutions are needed in order to detect firewall configuration inconsistencies and to check the inter-firewalls consistency. In this paper, we propose a formal modeling and verification framework based on model checking. It allows to verify automatically the end-to-end security behavior of a set of firewalls w.r.t. a global security policy. To deal with state explosion problem, two abstractions are proposed and evaluated in term of space and time complexity, according to the network size and connectivity rate.

The main problem of verification techniques based on exploration of (reachable) state space is the state explosion problem. In timed models, abstract states reached by different interleavings of the same set of transitions are, in general, different and their union is not necessarily an abstract state. To attenuate this state explosion, it would be interesting to reduce the redundancy caused by the interleaving semantics by agglomerating all these abstract states whenever their union is an abstract state. This article considers the time Petri net model and establishes some sufficient conditions that ensure that this union is an abstract state. In addition, it proposes a procedure to compute this union without computing beforehand intermediate abstract states. Finally, it shows how to use this result to improve the reachability analysis.

In this paper, we propose an attribute based access control (ABAC) approach for safely sharing knowledge in a collaborative environment. Indeed, existing similar systems facilitate collaboration at the risk to convey doubtful information and sometimes serve as a gate to vandalism. Our system called

We propose in this paper some efficient approaches, based on the state class graph method, to construct abstractions for the Time Petri Net (TPN) model, suitable to verify its linear or reachability properties. Experimental results have shown that these abstractions are very appropriate as both time and size are considerably reduced. For some tested models, abstractions that preserve reachability properties can be as many as 2,051 times smaller and more than 592 times faster to compute. For abstractions, which are overapproximations (useful to prove that certain states are not reachable), gains can overpass 10,000 for both time and size.

We consider Time Petri Nets (TPN) for which a firing time interval is associated with each transition. State space abstractions for TPN preserving various classes of properties (LTL, CTL and CTL∗) can be computed, in terms of so called state classes. Some methods were proposed to check quantitative timed properties but are not suitable for effective verification of properties of real-life systems. In this article, we consider subscript TCTL for TPN (TPN-TCTL) for which temporal operators are extended with a time interval, specifying a time constraint on the firing sequences. We prove the decidability of TPN-TCTL on bounded TPN and give its theoretical complexity. We propose a zone-based state space abstraction that preserves marking reachability and traces of the TPN. As for Timed Automata (TA), the abstraction may use an over-approximation operator on zones to enforce the termination. A coarser (and efficient) abstraction is then provided and proved exact w.r.t. marking reachability and traces (LTL properties). Finally, we consider a subset of TPN-TCTL properties (TPN-TCTLS) for which it is possible to propose efficient on-the-fly model-checking algorithms. Our approach consists in computing and exploring the zone-based state space abstraction. On a practical point of view, the method is integrated in Romeo [Gardey et al. (2005, Proceedings of 17th International Conference on CAV’05, Vol. 3576 of Lecture Notes in Computer Science, 418–423)], a tool for TPN edition and analysis. In addition to the old features it is now possible to effectively verify a subset of TCTL directly on TPN.

Traditional modelling and analysis of workflow aims at verifying the correctness of its control flow. When dealing with workflow security, the compliance of information flow with the adopted security policies needs also to be analyzed. In this paper, we propose a two-steps verification approach. While the first step is concerned by soundness of the workflow, the second one is concerned by the data consistency with respect to a multilevel security policy where the granting of access rights to objects by the workflow system is done according to information flow rules of Bell-LaPadula model. Our approach is based on the ECATNet formalism. It offers means to incorporate the security constraints on information flow into an initial WF net modeling the control flow of a workflow specification. We then show how to analyze the impact of the security rules on the whole Workflow through the model checker of the MAUDE environment and how to relax them before producing the correct specification and submitting it to the workflow system.

Continuous and discrete components can be integrated in diverse systems including defense, medical, electronic, communication, and automotive applications. Given the heterogeneity of concepts that have to be taken into consideration, their design involves overcoming specific global modeling and validation challenges. This paper presents semantics for model-based validation of continuous/discrete systems. It focuses on the simulation interfaces semantics, representation and verification. The proposed approach is applied for the validation of a continuous/discrete medical system, an automatic glycemia level regulator.

Abstract We consider here the interval timed coloured Petri net model (ITCPN). This model associates with each created token a time interval specifying when the token will become available and forces enabled transitions to occur as soon as possible. This model can simulate other timed Petri nets and allows to describe large and complex real-time systems. We propose a much more efficient contraction for its generally infinite state space than those developed in the literature. Our contraction approach captures all linear properties of the model and produces finite graphs for all bounded models.