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The increasing popularity of Cloud computing as an attractive alternative to classic information processing systems has increased the importance of its correct and continuous operation even in the presence of faulty components. In this paper, we introduce an innovative, system-level, modular perspective on creating and managing fault tolerance in Clouds. We(More)
Secure and reliable authentication is an essential prerequisite for many online systems, yet achieving this in a way which is acceptable to customers remains a challenge. GrIDsure, a one-time PIN scheme using random grids and personal patterns, has been proposed as a way to overcome some of these challenges. We present an analytical study which demonstrates(More)
We present a reliability certification scheme in which services are modeled as discrete-time Markov chains. A machine-readable certificate is issued to the service after validating its reliability properties, and validity of the certificate is verified using constant run-time monitoring. In addition, we present a solution that allows users to search and(More)
We provide the first formal foundation of SAND attack trees which are a popular extension of the well-known attack trees. The SAND attack tree formalism increases the expressivity of attack trees by introducing the sequential conjunctive operator SAND. This operator enables the modeling of ordered events. We give a semantics to SAND attack trees by(More)
We address the problem of guaranteeing security, with additional consideration on reliability and availability issues, in the management of resources in Cloud environments. We investigate and formulate different requirements that users or service providers may wish to specify. Our framework allows providers to impose restrictions on the allocations to be(More)
Fault tolerance, reliability and availability in Cloud computing are critical to ensure correct and continuous system operation also in the presence of failures. In this paper, we present an approach to evaluate fault tolerance mechanisms that use the virtualization technology to transparently increase the reliability and availability of applications(More)
Fault tolerance, reliability and resilience in Cloud Computing are of paramount importance to ensure continuous operation and correct results, even in the presence of a given maximum amount of faulty components. Most existing research and implementations focus on architecture-specific solutions to introduce fault tolerance. This implies that users must(More)
In this tool demonstration paper we present the ADTool2.0: an open-source software for design, manipulation and analysis of attack trees. The tool supports ranking of attack scenarios based on quantitative attributes entered by the user; it is scriptable; and it incorporates attack trees with sequential conjunctive refinement.
Security, availability and performance are critical to meet service level agreements in most Cloud computing services. In this paper, we build on the virtual machine technology that allows software components to be cheaply moved, replicated, and allocated on the hardware infrastructure to devise a solution that ensures users availability and performance(More)