270 research outputs found
An evaluation of relationships between fatigue and depression in patients with chronic obstructive pulmonary disease
Longitude : a privacy-preserving location sharing protocol for mobile applications
Location sharing services are becoming increasingly popular. Although many location sharing services allow users to set up privacy policies to control who can access their location, the use made by service providers remains a source of concern. Ideally, location sharing providers and middleware should not be able to access usersā location data without their consent. In this paper, we propose a new location sharing protocol called Longitude that eases privacy concerns by making it possible to share a userās location data blindly and allowing the user to control who can access her location, when and to what degree of precision. The underlying cryptographic algorithms are designed for GPS-enabled mobile phones. We describe and evaluate our implementation for the Nexus One Android mobile phone
Bilinear Entropy Expansion from the Decisional Linear Assumption
We develop a technique inspired by pseudorandom functions that allows us to increase the entropy available for proving the security of dual system encryption schemes under the Decisional Linear Assumption. We show an application of the tool to Attribute-Based Encryption by presenting a Key-Policy ABE scheme that is fully-secure under DLIN with short public parameters
Special Libraries, June 1921
Volume 12, Issue 6https://scholarworks.sjsu.edu/sla_sl_1921/1005/thumbnail.jp
Attribute-Based Encryption Optimized for Cloud Computing
Abstract. In this work, we aim to make attribute-based encryption (ABE) more suitable for access control to data stored in the cloud. For this purpose, we concentrate on giving to the encryptor full control over the access rights, providing feasible key management even in case of multiple independent authorities, and enabling viable user revocation, which is essential in practice. Our main result is an extension of the decentralized CP-ABE scheme of Lewko and Waters [LW11] with identity-based user revocation. Our revocation system is made feasible by removing the computational burden of a revocation event from the cloud service provider, at the expense of some permanent, yet acceptable overhead of the encryption and decryption algorithms run by the users. Thus, the computation overhead is distributed over a potentially large number of users, instead of putting it on a single party (e.g., a proxy server), which would easily lead to a performance bottleneck. Besides describing our scheme, we also give a formal proof of its security in the generic bilinear group and random oracle models.
Delegatable homomorphic encryption with applications to secure outsourcing of computation
In this work we propose a new cryptographic primitive called Delegatable Homomorphic Encryption (DHE). This allows a Trusted Authority to control/delegate the capability to evaluate circuits over encrypted data to untrusted workers/evaluators by issuing tokens. This primitive can be both seen as a public-key counterpart to Verifiable Computation, where input generation and output verification are performed by different entities, or as a generalisation of Fully Homomorphic Encryption enabling control over computations on encrypted data.
Our primitive comes with a series of extra features as follows: 1) there is a one-time setup procedure for all circuits; 2) senders do not need to be aware of the functions which will be evaluated on the encrypted data, nor do they need to register keys; 3) tokens are independent of senders and receiver; and 4) receivers are able to verify the correctness of computation given short auxiliary information on the input data and the function, independently of the complexity of the computed circuit.
We give a modular construction of such a DHE scheme from three components: Fully Homomorphic Encryption (FHE), Functional Encryption (FE), and a (customised) MAC. As a stepping stone, we first define Verifiable Functional Encryption (VFE), and then show how one can build a secure DHE scheme from a VFE and an FHE scheme. We also show how to build the required VFE from a standard FE together with a MAC scheme. All our results hold in the standard model.Finally, we show how one can build a verifiable computation (VC) scheme generically from a DHE. As a corollary, we get
the first VC scheme which remains verifiable even if the attacker can observe verification result
DĆ©jĆ Q all over again: Tighter and broader reductions of q-type assumptions
In this paper, we demonstrate that various cryptographic constructionsāincluding ones for broadcast, attribute-based, and hierarchical identity-based encryptionācan rely for security on only the static subgroup hiding assumption when instantiated in composite-order bilinear groups, as opposed to the dynamic q-type assumptions on which their security previously was based. This specific goal is accomplished by more generally extending the recent DĆ©jĆ Q framework (Chase and Meiklejohn, Eurocrypt 2014) in two main directions. First, by teasing out common properties of existing reductions, we expand the q-type assumptions that can be covered by the framework; i.e., we demonstrate broader classes of assumptions that can be reduced to subgroup hiding. Second, while the original framework applied only to asymmetric composite-order bilinear groups, we provide a reduction to subgroup hiding that works in symmetric (as well as asymmetric) composite-order groups. As a bonus, our new reduction achieves a tightness of log(q) rather than q
Unbounded Dynamic Predicate Compositions in Attribute-Based Encryption
We present several transformations that combine a set of attribute-based encryption (ABE) schemes for simpler predicates into a new ABE scheme for more expressive composed predicates. Previous proposals for predicate compositions of this kind, the most recent one being that of Ambrona et.al. at Crypto\u2717, can be considered static (or partially dynamic), meaning that the policy (or its structure) that specifies a composition must be fixed at the setup. Contrastingly, our transformations are dynamic and unbounded: they allow a user to specify an arbitrary and unbounded-size composition policy right into his/her own key or ciphertext. We propose transformations for three classes of composition policies, namely, the classes of any monotone span programs, any branching programs, and any deterministic finite automata. These generalized policies are defined over arbitrary predicates, hence admitting modular compositions. One application from modularity is a new kind of ABE for which policies can be ``nested\u27\u27 over ciphertext and key policies. As another application, we achieve the first fully secure completely unbounded key-policy ABE for non-monotone span programs, in a modular and clean manner, under the q-ratio assumption. Our transformations work inside a generic framework for ABE called symbolic pair encoding, proposed by Agrawal and Chase at Eurocrypt\u2717. At the core of our transformations, we observe and exploit an unbounded nature of the symbolic property so as to achieve unbounded-size policy compositions
Recommended from our members
Prevalence, severity, and risk factors of disability among adults living with HIV accessing routine outpatient HIV care in London, United Kingdom (UK): A cross-sectional self-report study.
BACKGROUND: The study objectives were to measure disability prevalence and severity, and examine disability risk factors, among adults living with HIV in London, United Kingdom (UK). METHODS: Self-reported questionnaires were administered: World Health Organization Disability Assessment Schedule 2.0 (WHODAS), HIV Disability Questionnaire (HDQ), Equality Act disability definition (EADD), and demographic questionnaire. We calculated proportion (95% Confidence Interval; CI) of "severe" and "moderate" disability measured using EADD and WHODAS scores ā„2 respectively. We measured disability severity with HDQ domain severity scores. We used demographic questionnaire responses to assess risk factors of "severe" and "moderate" disability using logistic regression analysis, and HDQ severity domain scores using linear regression analysis. RESULTS: Of 201 participants, 176 (87.6%) identified as men, median age 47 years, and 194 (96.5%) virologically suppressed. Severe disability prevalence was 39.5% (n = 79/201), 95% CI [32.5%, 46.4%]. Moderate disability prevalence was 70.5% (n = 141/200), 95% CI [64.2%, 76.8%]. Uncertainty was the most severe HDQ disability domain. Late HIV diagnosis was a risk factor for severe disability [Odds Ratio (OR) 2.71; CI 1.25, 5.87]. Social determinants of health, economic inactivity [OR 2.79; CI 1.08, 7.21] and receiving benefits [OR 2.87; CI 1.05, 7.83], were risk factors for "severe" disability. Economic inactivity [OR 3.14; CI 1.00, 9.98] was a risk factor for "moderate" disability. Economic inactivity, receiving benefits, and having no fixed abode were risk factors (Pā¤0.05) for higher HDQ severity scores in physical, mental and emotional, difficulty with day-to-day activities, and challenges to social participation domains. Personal factors, identifying as a woman and being aged <50 years, were risk factors (Pā¤0.05) for higher HDQ severity scores in mental and emotional, uncertainty, and challenges with social participation domains. CONCLUSIONS: People living with well-controlled HIV in London UK experienced multi-dimensional and episodic disability. Results help to better understand the prevalence, severity, and risk factors of disability experienced by adults living with HIV, identify areas to target interventions, and optimise health and functioning
- ā¦