Towards an Information Theoretic Analysis of Searchable Encryption (Extended Version)

Searchable encryption is a technique that allows a client to store data in encrypted form on a curious server, such that data can be retrieved while leaking a minimal amount of information to the server. Many searchable encryption schemes have been proposed and proved secure in their own computational model. In this paper we propose a generic model for the analysis of searchable encryptions. We then identify the security parameters of searchable encryption schemes and prove information theoretical bounds on the security of the parameters. We argue that perfectly secure searchable encryption schemes cannot be efficient. We classify the seminal schemes in two categories: the schemes that leak information upfront during the storage phase, and schemes that leak some information at every search. This helps designers to choose the right scheme for an application

Adaptively Secure Computationally Efficient Searchable Symmetric Encryption

Searchable encryption is a technique that allows a client to store documents on a server in encrypted form. Stored documents can be retrieved selectively while revealing as little information as\ud possible to the server. In the symmetric searchable encryption domain, the storage and the retrieval are performed by the same client. Most conventional searchable encryption schemes suffer\ud from two disadvantages.\ud First, searching the stored documents takes time linear in the size of the database, and/or uses heavy arithmetic operations.\ud Secondly, the existing schemes do not consider adaptive attackers;\ud a search-query will reveal information even about documents stored\ud in the future. If they do consider this, it is at a significant\ud cost to updates.\ud In this paper we propose a novel symmetric searchable encryption\ud scheme that offers searching at constant time in the number of\ud unique keywords stored on the server. We present two variants of\ud the basic scheme which differ in the efficiency of search and\ud update. We show how each scheme could be used in a personal health\ud record system

Influence of Salicylic Acid on the Antimicrobial Potential of Stevia (Stevia rebaudiana Bertoni, Asteraceae) Leaf Extracts against Soybean Seed-Borne Pathogens

Purpose: To investigate the effect of salicylic acid (SA) on the antimicrobial profile of Stevia leaf extracts against soybean seed-borne pathogens.Methods: Stevia seeds were planted in a greenhouse and SA foliar applied after six weeks on the whole plant at concentrations of 0 and 0.1 g L-1. The extracts of the plant leaf were separately obtained using four different solvents (water, acetone, ethanol and chloroform), and the oil composition of the extracts determined by gas chromatography-mass spectrophotometry (GC-MS). The antibacterial and antifungal potentials of each of the extracts were examined against 11 selected pathogens responsible for soybean seed and seedling diseases.Results: Chloroform extracts had the highest amount of α-cadinol, spathulenol, caryophyllene oxide, methyl salicylate and safranal in the SA-treated plants, and were 8, 10, 18, 14 and 11 %, respectively, higher than the non-SA treated control. In the anti-microbial tests, chloroform extract exhibited the highest diameter of inhibition zone (max 18 mm) against all the tested microorganisms while water extract showed the least effect (max 9 mm), with no effect at all on two fungi (Phomopsis spp and Cercospora kikuchii) and two bacteria (Pseudomonas syringae and Xanthomonas campestris). All extracts with or without SA had no effect on Xanthomonas campestris. SA treatment enhanced the antimicrobial potential of all extracts in the pathogenicity test compared with untreated plant extracts.Conclusion: Stevia leaf extract has antimicrobial effect against soybean seed-borne disease if applied on the seed before planting. Application of SA on the Stevia plant substantially enhances the antimicrobial activity of the leaf extract thus affording the seeds greater protection.Keywords: Stevia, Antimicrobial, Salicylic acid, Soybean, Pathogens

Ranking Iranian biomedical research centers according to Hvariants (G, M, A, R) in Scopus and Web of Science

Background: We conducted a comprehensive bibliometrics analysis to calculate the H, G, M, A and R indicators for all Iranian biomedical research centers (IBRCs) from the output of ISI Web of Science (WoS) and Scopus between 1991 and 2010. We compared the research performance of the research centers according to these indicators. Methods: This was a cross-sectional and descriptive-analytical study, conducted on 104 Iranian biomedical research centers between August and September 2011. We collected our data through Scopus and WoS. Pearson correlation coefficient between the scientometrics indicators was calculated using SPSS, version 16. Results: The mean values of all indicators were higher in Scopus than in WoS. Drug Applied Research Center of Tabriz University of Medical Sciences had the highest number of publications in both WoS and Scopus databases. This research center along with Royan Institute received the highest number of citations in both Scopus and WoS, respectively. The highest correlation was seen between G and R (.998) in WoS and between G and R (.990) in Scopus. Furthermore, the highest overlap of the 10 top IBRCs was between G and H in WoS (100) and between G-R (90) and H-R (90) in Scopus. Conclusion: Research centers affiliated to the top ranked Iranian medical universities obtained a better position with respect to the studied scientometrics indicators. All aforementioned indicators are important for ranking bibliometrics studies as they refer to different attributes of scientific output and citation aspects

Barrier tuning of atomic layer deposited Ta2O5 and Al2O3 in resonant tunnelling diodes for terahertz applications

The performance of double dielectric (MIIM) resonant tunneling diodes using atomic layer deposited oxides of low (Al2O3) and high (Ta2O5) electron affinity (χ) is investigated. Varying the individual layer thickness of Ta2O5 with a 1 nm thick Al2O3, evidence for resonant tunneling is observed and related to the bound states in the quantum well established between the oxide layers. The results show good rectifying capability of resonant tunneling diodes at low turn-on voltage enabling their potential use for terahertz applications

Privacy Enhanced Access Control by Means of Policy Blinding

Traditional techniques of enforcing an access control policy\ud rely on an honest reference monitor to enforce the policy. However, for\ud applications where the resources are sensitive, the access control policy\ud might also be sensitive. As a result, an honest-but-curious reference monitor would glean some interesting information from the requests that it\ud processes. For example if a requestor in a role psychiatrist is granted access to a document, the patient associated with that document probably\ud has a psychiatric problem. The patient would consider this sensitive in-\ud formation, and she might prefer the honest-but-curious reference monitor\ud to remain oblivious of her mental problem.\ud We present a high level framework for querying and enforcing a role\ud based access control policy that identifies where sensitive information\ud might be disclosed. We then propose a construction which enforces a\ud role based access control policy cryptographically, in such a way that the\ud reference monitor learns as little as possible about the policy. (The reference monitor only learns something from repeated queries). We prove\ud the security of our scheme showing that it works in theory, but that it\ud has a practical drawback. However, the practical drawback is common\ud to all cryptographically enforced access policy schemes. We identify several approaches to mitigate the drawback and conclude by arguing that\ud there is an underlying fundamental problem that cannot be solved. We\ud also show why attribute based encryption techniques do not not solve the\ud problem of enforcing policy by an honest but curious reference monitor