A Definitional Framework for Functional Encryption

Functional encryption (FE) is a powerful generalization of various types of encryption. We investigate how FE can be used by a trusted authority to enforce access-control policies to data stored in an untrusted repository. Intuitively, if (functionally) encrypted data items are put in a publicly-readable repository, the effect of the encryption should be that every user has access to exactly (and only) those functions of the data items for which he has previously received the corresponding decryption key. That is, in an ideal-world view, the key authority can flexibly manage read access of users to the repository. This appears to be exactly what FE is supposed to achieve, and most natural applications of FE can be understood as specific uses of such a repository with access control. However, quite surprisingly, it is unclear whether known security definitions actually achieve this goal and hence whether known FE schemes can be used in such an application. In fact, there seems to be agreement in the cryptographic community that identifying the right security definitions for FE remains open. To resolve this problem, we treat FE in the constructive cryptography framework and propose a new conventional security definition, called composable functional encryption security (CFE-security), which exactly matches the described ideal-world interpretation. This definition (and hence the described application) is shown to be unachievable in the standard model but achievable in the random oracle model. Moreover, somewhat weaker definitions, which are achievable in the standard model, can be obtained by certain operational restrictions of the ideal-world repository, making explicit how schemes satisfying such a definition can (and cannot) meaningfully be used. Finally, adequate security definitions for generalizations of FE (such as multi-input, randomized functions, malicious ciphertext generation, etc.) can be obtained by straight-forward operational extensions of the repository and extracting the corresponding security definitions. This leads towards a unified treatment of the security of FE

On the semantic security of functional encryption schemes

Functional encryption (FE) is a powerful cryptographic primitive that generalizes many asymmetric encryption systems proposed in recent years. Syntax and security definitions for FE were proposed by Boneh, Sahai, and Waters (BSW) (TCC 2011) and independently by O’Neill (ePrint 2010/556). In this paper we revisit these definitions, identify several shortcomings in them, and propose a new definitional approach that overcomes these limitations. Our definitions display good compositionality properties and allow us to obtain new feasibility and impossibility results for adaptive token-extraction attack scenarios that shed further light on the potential reach of general FE for practical applications.ENIAC Joint UndertakingFundação para a Ciência e a Tecnologia (FCT

Finding an Unlikely Combatant in the War Against Ransomware: Opportunities for Providers to Utilize Off-Site Data Backup Within the HIPAA Omnibus and Hitech Amendments

Each day the health care sector is subjected to an onslaught of thousands of ransomware virus attacks which attempt to capture a provider’s IT operations until a ransom is paid to the hacker. Apart from monetary, functional, and civil liability considerations, compromised health systems that contain electronic patient health information could expose a provider to legal liability under multiple HIPAA laws. This article will explore how recent amendments made to HIPAA, particularly under the Omnibus and HITECH Acts, incentivize providers to obtain legal, functional, and policy-based benefits by utilizing off-site data backup business associates as part of their cybersecurity defense strategy in the escalating war against ransomware

Equivalence-based Security for Querying Encrypted Databases: Theory and Application to Privacy Policy Audits

Motivated by the problem of simultaneously preserving confidentiality and usability of data outsourced to third-party clouds, we present two different database encryption schemes that largely hide data but reveal enough information to support a wide-range of relational queries. We provide a security definition for database encryption that captures confidentiality based on a notion of equivalence of databases from the adversary's perspective. As a specific application, we adapt an existing algorithm for finding violations of privacy policies to run on logs encrypted under our schemes and observe low to moderate overheads.Comment: CCS 2015 paper technical report, in progres

International copyright and the challenges of digital technology

PhDDigital technology is challenging traditional copyright principles. Despite suggestions from a number of commentators that copyright cannot survive the challenge, this thesis aims to demonstrate that copyright can evolve and adapt rather than face elimination. This hypothesis is tested and illustrated by means of an examination of law in conjunction with technology, and by means of concrete examples. Analysis of the author's position in the face of digital technology requires firstly, an investigation of the way in which the existence and exercise of the author's copyright itself is affected by such technology, and secondly, an examination of how the author's standing in relation to dissemination of works generally is concerned (e.g. as regards freedom of speech). It is with the first of these aspects that this thesis is mainly concerned, although, for the sake of a more comprehensive view, some considerations on the second aspect are also advanced. This thesis examines challenges raised in the copyright field by digital technology and the consequential problems in relation to classification of subject matter, identification of authors, fixation and reproduction, the criterion of originality, the meaning of publication, recognition of moral rights, recognition of economic rights, exceptions and limitations, liability of service providers, authenticity of works, infringement, feasibility of enforcement and conflict of laws. Broader issues relating to Government and private control of access to the new media are also analysed. The analysis is focused on copyright subsistence as well as infringement. Furthermore, both the legal and the technological aspects are considered (with the aid of a comprehensive glossary of technological terms). The approach is one of law and technology in equal measure. In the context of these problems there follows a critical examination and comparison of the main national systems, the main international instruments, and the main regional instruments. This systematic survey seeks to encapsulate the work of learned authors in a concise manner, leading to certain proposals. The approach is one of criticism and selection of feasible and practical solutions. Nearly all elements of the proposed solutions exist already, albeit in a fragmented way. These solutions are based on law and on technology, and are formulated to apply in both the analogue and digital worlds. The thesis concludes that for an effective solution of the problems raised by digital technology, an international standard for copyright protection must be adopted, one apposite for the digital world. The thesis puts forward detailed suggestions towards the adoption of an International Digital Copyright Protection System, in the form of definitional, obligational, conflict of laws and technological proposals, whose common denominator is the will to find new answers for the digital challenges. The definitional proposals will clarify conceptual questions arising from the digital revolution. The obligational proposals will regulate the issue of exemptions from liability and duties of Internet service providers. The conflict of laws proposals will address the problems arising in connection with jurisdiction and applicable law on the Internet. The technological proposals will give practical effect to the system by focusing on deterrence and tracing of copyright infringement