Sara Foresti

Combining fragmentation and encryption to protect privacy in data storage

The impact of privacy requirements in the development of modern applications is increasing very quickly. Many commercial and legal regulations are driving the need to develop reliable solutions for protecting sensitive information whenever it is stored, processed, or communicated to external parties. To this purpose, encryption techniques are currently used in many scenarios where data protection is required since they provide a layer of protection against the disclosure of personal information, which safeguards companies from the costs that may arise from exposing their data to privacy breaches. However, dealing with encrypted data may make query processing more expensive. In this article, we address these issues by proposing a solution to enforce the privacy of data collections that combines data fragmentation with encryption. We model privacy requirements as confidentiality constraints expressing the sensitivity of attributes and their associations. We then use encryption as an underlying (conveniently available) measure for making data unintelligible while exploiting fragmentation as a way to break sensitive associations among attributes. We formalize the problem of minimizing the impact of fragmentation in terms of number of fragments and their affinity and present two heuristic algorithms for solving such problems. We also discuss experimental results, comparing the solutions returned by our heuristics with respect to optimal solutions, which show that the heuristics, while guaranteeing a polynomial-time computation cost are able to retrieve solutions close to optimum.

Encryption policies for regulating access to outsourced data

Current access control models typically assume that resources are under the strict custody of a trusted party which monitors each access request to verify if it is compliant with the specified access control policy. There are many scenarios where this approach is becoming no longer adequate. Many clear trends in Web technology are creating a need for owners of sensitive information to manage access to it by legitimate users using the services of honest but curious third parties, that is, parties trusted with providing the required service but not authorized to read the actual data content. In this scenario, the data owner encrypts the data before outsourcing and stores them at the server. Only the data owner and users with knowledge of the key will be able to decrypt the data. Possible access authorizations are to be enforced by the owner. In this article, we address the problem of enforcing selective access on outsourced data without need of involving the owner in the access control process. The solution puts forward a novel approach that combines cryptography with authorizations, thus enforcing access control via selective encryption. The article presents a formal model for access control management and illustrates how an authorization policy can be translated into an equivalent encryption policy while minimizing the amount of keys and cryptographic tokens to be managed. The article also introduces a two-layer encryption approach that allows the data owner to outsource, besides the data, the complete management of the authorization policy itself, thus providing efficiency and scalability in dealing with policy updates. We also discuss experimental results showing that our approach is able to efficiently manage complex scenarios.

A data outsourcing architecture combining cryptography and access control

Data outsourcing is becoming today a successful solution that allows users and organizations to exploit external servers for the distribution of resources. Some of the most challenging issues in such a scenario are the enforcement of authorization policies and the support of policy updates. Since a common approach for protecting the outsourced data consists in encrypting the data themselves, a promising approach for solving these issues is based on the combination of access control with cryptography. This idea is in itself not new, but the problem of applying it in an outsourced architecture introduces several challenges. In this paper, we first illustrate the basic principles on which an architecture for combining access control and cryptography can be built. We then illustrate an approach for enforcing authorization policies and supporting dynamic authorizations, allowing policy changes and data updates at a limited cost in terms of bandwidth and computational power.

Key management for multi-user encrypted databases

Database outsourcing is becoming increasingly popular introducing a new paradigm, called database-as-a-service (DAS), where an organizations database is stored at an external service provider. In such a scenario, access control is a very important issue, especially if the data owner wishes to publish her data for external use.In this paper, we first present our approach for the implementation of access control through selective encryption. The focus of the paper is then the presentation of the experimental results, which demonstrate the applicability of our proposal.

Keep a few: outsourcing data while maintaining confidentiality

We put forward a novel paradigm for preserving privacy in data outsourcing which departs from encryption. The basic idea behind our proposal is to involve the owner in storing a limited portion of the data, and maintaining all data (either at the owner or at external servers) in the clear. We assume a relational context, where the data to be outsourced is contained in a relational table. We then analyze how the relational table can be fragmented, minimizing the load for the data owner. We propose several metrics and present a general framework capturing all of them, with a corresponding algorithm finding a heuristic solution to a family of NP-hard problems.

Fragmentation and encryption to enforce privacy in data storage

Privacy requirements have an increasing impact on the realization of modern applications. Technical considerations and many significant commercial and legal regulations demand today that privacy guarantees be provided whenever sensitive information is stored, processed, or communicated to external parties. It is therefore crucial to design solutions able to respond to this demand with a clear integration strategy for existing applications and a consideration of the performance impact of the protection measures. In this paper we address this problem and propose a solution to enforce privacy over data collections by combining data fragmentation with encryption. The idea behind our approach is to use encryption as an underlying (conveniently available) measure for making data unintelligible, while exploiting fragmentation as a way to break sensitive associations between information.

Efficient and Private Access to Outsourced Data

As the use of external storage and data processing services for storing and managing sensitive data becomes more and more common, there is an increasing need for novel techniques that support not only data confidentiality, but also confidentiality of the accesses that users make on such data. In this paper, we propose a technique for guaranteeing content, access, and pattern confidentiality in the data outsourcing scenario. The proposed technique introduces a shuffle index structure, which adapts traditional B+-trees. We show that our solution exhibits a limited performance cost, thus resulting effectively usable in practice.

Computer Security – ESORICS 2012

ion-Based Malware Analysis Using Rewriting and Model Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 806 Philippe Beaucamps, Isabelle Gnaedig, and Jean-Yves Marion Detecting Phishing Emails the Natural Language Way . . . . . . . . . . . . . . . . 824 Rakesh Verma, Narasimha Shashidhar, and Nabil Hossain

Managing and accessing data in the cloud: Privacy risks and approaches

Ensuring proper privacy and protection of the information stored, communicated, processed, and disseminated in the cloud as well as of the users accessing such an information is one of the grand challenges of our modern society. As a matter of fact, the advancements in the Information Technology and the diffusion of novel paradigms such as data outsourcing and cloud computing, while allowing users and companies to easily access high quality applications and services, introduce novel privacy risks of improper information disclosure and dissemination. In this paper, we will characterize different aspects of the privacy problem in emerging scenarios. We will illustrate risks, solutions, and open problems related to ensuring privacy of users accessing services or resources in the cloud, sensitive information stored at external parties, and accesses to such an information.

J wave, QRS slurring, and ST elevation in athletes with cardiac arrest in the absence of heart disease marker of risk or innocent bystander?

Background—QRS-ST changes in the inferior and lateral ECG leads are frequently observed in athletes. Recent studies have suggested a potential arrhythmogenic significance of these findings in the general population. The aim of our study was to investigate whether QRS-ST changes are markers of cardiac arrest (CA) of unexplained cause or sudden death in athletes. Methods and Results—In 21 athletes (mean age, 27 years; 5 women) with cardiac arrest or sudden death, the ECG recorded before or immediately after the clinical event was compared with the ECG of 365 healthy athletes eligible for competitive sport activity. We measured the height of the J wave and ST elevation and searched for the presence of QRS slurring in the terminal portion of QRS. QRS slurring in any lead was present in 28.6% of cases and in 7.6% of control athletes (P=0.006). A J wave and/or QRS slurring without ST elevation in the inferior (II, III, and aVF) and lateral leads (V4 to V6) were more frequently recorded in cases than in control athletes (28.6% versus 7.9%, P=0.007). Among those with cardiac arrest, arrhythmia recurrences did not differ between the subgroups with and without J wave or QRS slurring during a median 36-month follow-up of sport discontinuation. Conclusions—J wave and/or QRS slurring was found more frequently among athletes with cardiac arrest/sudden death than in control athletes. Nevertheless, the presence of this ECG pattern appears not to confer a higher risk for recurrent malignant ventricular arrhythmias.