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This work analyzes a new and very subtle kind of security threat that can affect large-scale cloud-based IT service infrastructures, by exploiting the computational resources of their component data center to waste as much energy as possible. The consequence of these threats ranges from increased costs in the energy bill, to penalization for exceeding the agreed quantity of greenhouse gases (GHG) emissions, up to complete denial of service caused by electrical outages due to power budget exhaustion. We analyzed different types of such attacks with their potential impacts on the energy consumption, modeled their behavior and quantified how current energy-proportional technologies may provide attackers with great opportunities for raising the target facility emissions and costs. These efforts resulted in a simple model with some parametric reference values that can be used to estimate the impact of such attacks also in presence of very large infrastructures containing thousands or millions of servers. [ABSTRACT FROM AUTHOR]

Distributed cryptographic file systems enable file sharing among their users and need the adoption of a key management scheme for the distribution of the cryptographic keys to authorized users according to their specific degree of trust. In this paper we describe the architecture of a basic secure file sharing facility relying on a multi-party threshold-based key-sharing scheme that can be overlaid on top of the existing stackable networked file systems, and discuss its application to the implementation of distributed cryptographic file systems. It provides flexible access control policies supporting multiple combination of roles and trust profiles. A proof of concept prototype implementation within the Linux operating system framework demonstrated its effectiveness in terms of performance and security robustness. [ABSTRACT FROM AUTHOR]