Towards Trustworthy Cloud Storage

The success of cloud computing is driven by the tremendous economic benefit offered to companies, private citizens and public administration to deploy, provision and use cloud services in a cost effective manner. The cloud is gaining increasing importance and applicability in numerous application domains. By shaping the way we access, store, and compute on data, the cloud offers a largely profitable business. Forrester projected that providing access to emails, and social networks will solely contribute towards a multi-billion dollar business by 2020. Clearly, the larger are the utility and extent of the cloud and its services, the greater is the advantage in exploiting, abusing and attacking its components. As a matter of fact, Dropbox claims improper access to accounts using stolen passwords led to a spam attack, and Amazon and Gmail outages have left behind millions of disappointed customers not only because of access to their services but also those services (even third party) that depended on their cloud infrastructure. The literature contains a number of similar incidents that threaten the availability of cloud services, the security of the underlying cloud infrastructure, and the privacy of the cloud customers and users. As a matter of fact, a very recent study by the Centre for European Policy Studies concludes that security is not sufficiently addressed by current cloud technology and strongly underlines that “the challenge of privacy in a cloud context is underestimated, if not ignored.” In this paper, we explore the solution space for enhancing the robustness and security of existing clouds. More specifically, we categorize a multitude of cutting edge techniques according to realistic cloud attacker models. Finally, we portray a “service image” that depicts the integration of these various technologies into one single multi-purpose cloud service. The remainder of this paper is organized as follows. In Section 2, we classify the various attacker models. In Section 3, we outline a taxonomy of solutions that enhance the security and dependability of data stored in the cloud. In Section 4, we present a novel service image that combines the described technologies in a single framework.