On Improving Communication Complexity in Cryptography

Cryptography grew to be much more than "the study of secret writing". Modern cryptography is concerned with establishing properties such as privacy, integrity and authenticity in protocols for secure communication and computation. This comes at a price: Cryptographic tools usually introduce an overhead, both in terms of communication complexity (that is, number and size of messages transmitted) and computational efficiency (that is, time and memory required). As in many settings communication between the parties involved is the bottleneck, this thesis is concerned with improving communication complexity in cryptographic protocols. One direction towards this goal is scalable cryptography: In many cryptographic schemes currently deployed, the security degrades linearly with the number of instances (e.g. encrypted messages) in the system. As this number can be huge in contexts like cloud computing, the parameters of the scheme have to be chosen considerably larger - and in particular depending on the expected number of instances in the system - to maintain security guarantees. We advance the state-of-the-art regarding scalable cryptography by constructing schemes where the security guarantees are independent of the number of instances. This allows to choose smaller parameters, even when the expected number of instances is immense. - We construct the first scalable encryption scheme with security against active adversaries which has both compact public keys and ciphertexts. In particular, we significantly reduce the size of the public key to only about 3% of the key-size of the previously most efficient scalable encryption scheme. (Gay,Hofheinz, and Kohl, CRYPTO, 2017) - We present a scalable structure-preserving signature scheme which improves both in terms of public-key and signature size compared to the previously best construction to about 40% and 56% of the sizes, respectively. (Gay, Hofheinz, Kohl, and Pan, EUROCRYPT, 2018) Another important area of cryptography is secure multi-party computation, where the goal is to jointly evaluate some function while keeping each party’s input private. In traditional approaches towards secure multi-party computation either the communication complexity scales linearly in the size of the function, or the computational efficiency is poor. To overcome this issue, Boyle, Gilboa, and Ishai (CRYPTO, 2016) introduced the notion of homomorphic secret sharing. Here, inputs are shared between parties such that each party does not learn anything about the input, and such that the parties can locally evaluate functions on the shares. Homomorphic secret sharing implies secure computation where the communication complexity only depends on the size of the inputs, which is typically much smaller than the size of the function. A different approach towards efficient secure computation is to split the protocol into an input-independent preprocessing phase, where long correlated strings are generated, and a very efficient online phase. One example for a useful correlation are authenticated Beaver triples, which allow to perform efficient multiplications in the online phase such that privacy of the inputs is preserved and parties deviating the protocol can be detected. The currently most efficient protocols implementing the preprocessing phase require communication linear in the number of triples to be generated. This results typically in high communication costs, as the online phase requires at least one authenticated Beaver triple per multiplication. We advance the state-of-the art regarding efficient protocols for secure computation with low communication complexity as follows. - We construct the first homomorphic secret sharing scheme for computing arbitrary functions in NC 1 (that is, functions that are computably by circuits with logarithmic depth) which supports message spaces of arbitrary size, has only negligible correctness error, and does not require expensive multiplication on ciphertexts. (Boyle, Kohl, and Scholl, EUROCRYPT, 2019) - We introduce the notion of a pseudorandom correlation generator for general correlations. Pseudorandom correlation generators allow to locally extend short correlated seeds into long pseudorandom correlated strings. We show that pseudorandom correlation generators can replace the preprocessing phase in many protocols, leading to a preprocessing phase with sublinear communication complexity. We show connections to homomorphic secret sharing schemes and give the first instantiation of pseudorandom correlation generators for authenticated Beaver triples at reasonable computational efficiency. (Boyle, Couteau, Gilboa, Ishai, Kohl, and Scholl, CRYPTO, 2019

Die Schätzung von nichtlinearen Interaktionen in der Cox-Regression mittels Fraktionaler Polynome

Für die Analyse von Überlebensdaten ist das proportionale Hazard-Modell (PH) nach Cox (1972) das am Häufigsten verwendete Regressionsmodell. Im PH-Modell wird für einen kontinuierlichen Faktor standardmäßig eine lineare Beziehung mit dem Log Hazard angenommen. Nichtlineare Effekte von kontinuierlichen Faktoren können zum Beispiel mit Hilfe von Fraktionalen Polynomen (FP) oder Restricted Cubic Splines (RCS) berechnet werden. Bei der Analyse wird aus einem vordefinierten Set von sogenannten 'Powers' jene Kombination von Transformationen (mit diesen 'Powers') der originalen Variable ausgewählt, welche den besten Fit liefert. Konfidenzintervalle für den Log Relative Hazard werden mit der Bootstrap-Methode geschätzt, wobei der Selektionsprozess bei jedem Boostrapdatensatz wiederholt werden muss. In dieser Magisterarbeit sollen im Speziellen Interaktionen von kontinuierlichen Faktoren, wie Hämatokrit-Level, mit binären Faktoren, wie Geschlecht, untersucht werden. Dabei wird davon ausgegangen, dass der kontinuierliche Faktor unterschiedliche nichtlineare Effekte für die Ausprägungen des binären Faktors annehmen kann. Für die Schätzung der Modelle wird neben der Maximum-Likelihood-Methode (ML) die ML-Methode mit der Firth-Korrektur (FC; Firth, 1993) verwendet. Bei der FC wird von der Likelihood ein Strafterm abgezogen. Die Bestrafung der Likelihood nach Firth ermöglicht, dass keine unendlichen Parameterschätzer im Form von Monotoner Likelihood auftreten und eine geringere Verzerrung der Schätzer in kleinen und mittleren Datensätzen, in denen keine Monotone Likelihood auftritt (Heinze u. Schemper, 2001). Für die Analyse wurde ein neues R Package, das FPs und die Firth-Korrektur kombiniert, verwendet. In einer Simulationsstudie wurden sechs verschiedene Szenarien, die sich durch den Zensierungsanteil, die Stichprobengröße und die Form des nichtlinearen Effekts unterscheiden, generiert. Von diesen Szenarien wurde das Auftreten von Monotoner Likelihood, das Schätzverhalten der Punktschätzer und die Abweichungen der Schätzer mittels medianen Bias und dem Median der absoluten Abweichungen (MAD) untersucht. Dabei war ersichtlich, dass die ML-Methode bessere Ergebnisse beim medianen Bias lieferte, während bei der zusätzlichen Verwendung der Firth-Korrektur bessere Ergebnisse beim MAD erzielt werden konnten. Bei steigendem Zensierungsanteil und kleiner werdenden Stichproben nahm die Häufigkeit von Monotoner Likelihood zu, während die Abweichungen der Schätzer größer wurden. Zusätzlich wurde der nichtlineare geschlechterspezifische Effekt von Hämatokrit in einer Fallstudie über Venenthrombosen aufgedeckt. Dabei wurde besonderes Augenmerk auf den Vergleich der Konfidenzintervalle von FP und RCS gelegt. Dabei war erkennbar, dass die Schätzung der Konfidenzintervalle von nichtlinearen Interaktionen durch die Verwendung der Firth-Korrektur verbessert werden kann.Cox's proportional hazards (PH) model is frequently used in medical biostatistics to analyze survival outcomes (Cox, 1972). For continuous prognostic factors, the standard definition of the PH model assumes a linear relationship with the log hazard. Nonlinear effects of continuous prognostic factors could be accommodated, e. g., by the use of fractional polynomials (FP) or restricted cubic splines (RCS). The FP method selects so-called 'powers' to create nonlinear transformations of the original variable, which lead to the best fit in a subsequent Cox regression. Due to the optimal selection, confidence intervals of log hazard ratios have to be estimated by the bootstrap, repeating the selection process in resampled data sets. Here, we consider estimating the interaction of a binary prognostic factor, such as type of treatment or sex, with a continuous prognostic factor, such as haematocrit level. We further assume, as is often seen in practice, that the continuous factor could exhibit different types of nonlinear effects on survival time in both levels of the binary factor. In this context, we explored Firth´s bias corrective (FC) approach for estimating the parameters of the Cox model (Firth, 1993). The likelihood penalization imposed by FC not only prevents the occurrence of infinite parameter estimates in case of monotone likelihood, but it also provides more accurate estimates in small- or moderately-sized samples without monotone likelihood (Heinze and Schemper, 2001). Using a newly developed R package for PH regression combining the FC and FP approaches, we performed a comparative analysis of a medical study inferring the gender-specific effect of haematocrit levels on the risk of recurrence of deep vein thrombosis. We were mainly interested in the comparison of confidence intervals from FPs and RCS. We conclude that confidence interval estimation for nonlinear interaction effects can be improved by using FC. We also report on a simulation study investigating properties of FC/FP point estimates of nonlinear interaction effects. The error in the point estimates were expressed by the median bias and the median absolute deviation (MAD). In the simulation study as well as in the case study we monitored the occurrence of monotone likelihood. It was distinctly and visibly that the proportion of censoring and the sample size have an influence on the error and on monotone likelihood. We also could see that the FC leads to better results by the MAD whereas the maximum likelihood method leads to better results by the median bias

Acquiring Articles through Unmediated, User-Initiated Pay-Per-View Transactions: An Assessment of Current Practices

Depressed economic times often lead libraries to consider new practices, including alternatives to the traditional subscription model. This column discusses a pay-per-view (PPV) model for acquiring journal articles whereby a library creates an account with a content provider through which authenticated users can purchase articles at the library’s expense. To gain insight into the current use of this model, the paper draws on both a literature review and the results of a survey assessing the practices of academic libraries with experience acquiring articles through unmediated, user-initiated pay-per-view transactions. The future of the PPV model as well as issues and challenges that it raises are also considered

Proposed criteria for the evaluation of the scientific quality of mandatory rat and mouse feeding trials with whole food/feed derived from genetically modified plants

In recent years, animal feeding trials conducted with whole food/feed have been a focal issue in the controversy on the safety assessment of genetically modified (GM) plants and derived food/feed. Within the scientific community and among stakeholders, quite different views have been expressed on how these studies should be conducted, analysed and interpreted, what they might add in terms of information relevant to safety and whether 90-day rodent feeding trials should be mandatory. Despite the fact that the Commission Implementing Regulation (EU) No. 503/2013 (specifying the requirements for the risk assessment of GM food/feed) requests mandatory 90-day feeding trials for GM plants with single transformation events, the controversy continues. This is due to the fact that in 2016 the European Commission will have to review this particular provision in the legislation (ibid, Article 12), and because of questions raised by long-term feeding studies with GM maize

Hepato(Geno)toxicity assessment of nanoparticles in a HepG2 liver spheroid model

(1) In compliance with the 3Rs policy to reduce, refine and replace animal experiments, the development of advanced in vitro models is needed for nanotoxicity assessment. Cells cultivated in 3D resemble organ structures better than 2D cultures. This study aims to compare cytotoxic and genotoxic responses induced by titanium dioxide (TiO), silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) in 2D monolayer and 3D spheroid cultures of HepG2 human liver cells. (2) NPs were characterized by electron microscopy, dynamic light scattering, laser Doppler anemometry, UV-vis spectroscopy and mass spectrometry. Cytotoxicity was investigated by the alamarBlue assay and confocal microscopy in HepG2 monolayer and spheroid cultures after 24 h of NP exposure. DNA damage (strand breaks and oxidized base lesions) was measured by the comet assay. (3) Ag-NPs were aggregated at 24 h, and a substantial part of the ZnO-NPs was dissolved in culture medium. Ag-NPs induced stronger cytotoxicity in 2D cultures (EC 3.8 µg/cm 2) than in 3D cultures (EC > 30 µg/cm 2), and ZnO-NPs induced cytotoxicity to a similar extent in both models (EC 10.1-16.2 µg/cm 2). Ag- and ZnO-NPs showed a concentration-dependent genotoxic effect, but the effect was not statistically significant. TiO-NPs showed no toxicity (EC > 75 µg/cm 2). (4) This study shows that the HepG2 spheroid model is a promising advanced in vitro model for toxicity assessment of NPs

PARQUE DE EXPOSIÇÕES: ANTEPROJETO PARA A CIDADE DE SÃO DOMINGOS/ SC.

O estudo refere-se ao embasamento teórico e elaboração de anteprojeto para um parque de exposições na cidade de São Domingos, Oeste de Santa Catarina. As pesquisas bibliográficas, estudos de caso e analise total do terreno escolhido serviram de base para conceituar os primeiros traços e pré-dimensionamentos. O município não possui espaço adequado para realização das festividades, principalmente a FAIC (Feira Agropecuária, Industrial, Comercial e Artesanal), principal evento do calendário municipal. A feira acontece a cada dois anos, está na sua 4ª edição e demonstrou um crescimento de 700% em relação ao público e 347% de expositores entre 2010 (1ª edição) e 2014 (última edição) de acordo com dados da prefeitura municipal. Atualmente a feira acontece na Praça Germano Griss e ruas circundantes. Em função do seu crescimento, o espaço tornou-se pequeno para a realização da feira. A cada edição a FAIC demanda da montagem de uma estrutura grande gerando custos e transtornos à população próxima a praça e ausência de estacionamento apropriado para o público. Contudo, o objetivo deste trabalho foi elaborar um anteprojeto adequado à realização da FAIC com infraestrutura arrojada, com uso posterior para os demais eventos que ocorrem no município, suprindo a necessidade por espaço físico adequado. Palavras-chave: Parque de exposições. Capital Catarinense das Araucárias. FAIC

Transcriptome-pathology correlation identifies interplay between TDP-43 and the expression of its kinase CK1E in sporadic ALS.

Sporadic amyotrophic lateral sclerosis (sALS) is the most common form of ALS, however, the molecular mechanisms underlying cellular damage and motor neuron degeneration remain elusive. To identify molecular signatures of sALS we performed genome-wide expression profiling in laser capture microdissection-enriched surviving motor neurons (MNs) from lumbar spinal cords of sALS patients with rostral onset and caudal progression. After correcting for immunological background, we discover a highly specific gene expression signature for sALS that is associated with phosphorylated TDP-43 (pTDP-43) pathology. Transcriptome-pathology correlation identified casein kinase 1ε (CSNK1E) mRNA as tightly correlated to levels of pTDP-43 in sALS patients. Enhanced crosslinking and immunoprecipitation in human sALS patient- and healthy control-derived frontal cortex, revealed that TDP-43 binds directly to and regulates the expression of CSNK1E mRNA. Additionally, we were able to show that pTDP-43 itself binds RNA. CK1E, the protein product of CSNK1E, in turn interacts with TDP-43 and promotes cytoplasmic accumulation of pTDP-43 in human stem-cell-derived MNs. Pathological TDP-43 phosphorylation is therefore, reciprocally regulated by CK1E activity and TDP-43 RNA binding. Our framework of transcriptome-pathology correlations identifies candidate genes with relevance to novel mechanisms of neurodegeneration

Population-Attributable Fractions of Modifiable Lifestyle Factors for CKD and Mortality in Individuals With Type 2 Diabetes: A Cohort Study

BackgroundWe quantified the impact of lifestyle and dietary modifications on chronic kidney disease (CKD) by estimating population-attributable fractions (PAFs).Study DesignObservational cohort study.Setting & ParticipantsMiddle-aged adults with type 2 diabetes but without severe albuminuria from the Ongoing Telmisartan Alone and in Combination With Ramipril Global Endpoint Trial (ONTARGET; n=6,916).FactorsModifiable lifestyle/dietary risk factors, such as physical activity, size of social network, alcohol intake, tobacco use, diet, and intake of various food items.OutcomesThe primary outcome was CKD, ascertained as moderate to severe albuminuria or ≥5% annual decline in estimated glomerular filtration rate (eGFR) after 5.5 years. The competing risk for death was considered. PAF was defined as the proportional reduction in CKD or mortality (within 5.5 years) that would occur if exposure to a risk factor was changed to an optimal level.ResultsAt baseline, median urinary albumin-creatinine ratio and eGFR were 6.6 (IQR, 2.9-25.0) mg/mmol and 71.5 (IQR, 58.1-85.9) mL/min/1.73m2, respectively. After 5.5 years, 704 (32.5%) participants developed albuminuria, 1,194 (55.2%) had a ≥5% annual eGFR decline, 267 (12.3%) had both, and 1,022 (14.8%) had died. Being physically active every day has PAFs of 5.1% (95% CI, 0.5%-9.6%) for CKD and 12.3% (95% CI, 4.9%-19.1%) for death. Among food items, increasing vegetable intake would have the largest impact on population health. Considering diet, weight, physical activity, tobacco use, and size of social network, exposure to less than optimum levels gives PAFs of 13.3% (95% CI, 5.5%-20.9%) for CKD and 37.5% (95% CI, 27.8%-46.7%) for death. For the 17.8 million middle-aged Americans with diabetes, improving 1 of these lifestyle behaviors to the optimal range could reduce the incidence or progression of CKD after 5.5 years by 274,000 and the number of deaths within 5.5 years by 405,000.LimitationsAscertainment of changes in kidney measures does not precisely match the definitions for incidence or progression of CKD.ConclusionsHealthy lifestyle and diet are associated with less CKD and mortality and may have a substantial impact on population kidney health

In vivo ligamentogenesis in embroidered poly(lactic-co-ε-caprolactone) / polylactic acid scaffolds functionalized by fluorination and hexamethylene diisocyanate cross-linked collagen foams

Although autografts represent the gold standard for anterior cruciate ligament (ACL) reconstruction, tissue-engineered ACLs provide a prospect to minimize donor site morbidity and limited graft availability. This study characterizes the ligamentogenesis in embroidered poly(L-lactide-co-epsilon-caprolactone) (P(LA-CL)) / polylactic acid (PLA) constructs using a dynamic nude mice xenograft model. (P(LA-CL))/PLA scaffolds remained either untreated (co) or were functionalized by gas fluorination (F), collagen foam cross-linked with hexamethylene diisocyanate (HMDI) (coll), or F combined with the foam (F+coll). Cell-free constructs or those seeded for 1 week with lapine ACL ligamentocytes were implanted into nude mice for 12 weeks. Following explantation, cell vitality and content, histo(patho)logy of scaffolds (including organs: liver, kidney, spleen), sulphated glycosaminoglycan (sGAG) contents and biomechanical properties were assessed. Scaffolds did not affect mice weight development and organs, indicating no organ toxicity. Moreover, scaffolds maintained their size and shape and reflected a high cell viability prior to and following implantation. Coll or F+coll scaffolds seeded with cells yielded superior macroscopic properties compared to the controls. Mild signs of inflammation (foreign-body giant cells and hyperemia) were limited to scaffolds without collagen. Microscopical score values and sGAG content did not differ significantly. Although remaining stable after explantation, elastic modulus, maximum force, tensile strength and strain at F-max were significantly lower in explanted scaffolds compared to those before implantation, with no significant differences between scaffold subtypes, except for a higher maximum force in F+coll compared with F samples (in vivo). Scaffold functionalization with fluorinated collagen foam provides a promising approach for ACL tissue engineering

Examining associations Between School-Level Determinants and the Implementation of Physical activity Opportunities

School-based physical activity (PA) opportunities can help students engage in greater amounts of daily PA, meet PA guidelines, and lead to improved health and educational outcomes. However, we do not completely understand the organizational challenges to implementing these opportunities successfully. This exploratory study examined associations between school-level determinants and the implementation of school-based PA opportunities. We analyzed cross-sectional survey data from schools (n = 46) participating in the Healthy Zone School Program (HZSP) (Dallas, Texas, USA) during 2019-2020. Respondents completed an electronic survey that included measures of school-level determinants (e.g. culture, leadership, priority) and the implementation of school-based PA opportunities. We used linear regression models to examine associations between determinants and implementation outcomes (number of PA opportunities delivered, perceived overall success of each PA program/activity used). After adjusting for campus type (i.e. elementary, middle, high, K-12), student race/ethnicity, and percentage of economically disadvantaged students, no constructs were associated with the number of PA opportunities implemented. Linear regression models suggest access to knowledge and information (β = 0.39, P = .012, 95% CI = 0.24-1.44) and implementation climate (β = 0.34, P = .045, 95% CI = 0.02-1.59) were positively associated with the success of school-based PA opportunities. Our findings provide suggestive evidence that access to knowledge and information and a supportive school climate may improve the overall success of PA opportunities provided to students. Future research should examine additional school-level determinants to understand their importance to implementation and inform the development of strategies to improve schools\u27 capacity for implementing PA opportunities successfully