How to Build an Ideal Cipher: The Indifferentiability of the Feistel Construction

This paper provides the first provably secure construction of an invertible random permutation (and of an ideal cipher) from a public random function that can be evaluated by all parties in the system, including the adversary. The associated security goal was formalized via the notion of indifferentiability by Maurer et al. (TCC 2004). The problem is the natural extension of that of building (invertible) random permutations from (private) random functions, first solved by Luby and Rackoff (SIAM J Comput 17(2):373–386, 1988) via the four-round Feistel construction. As our main result, we prove that the Feistel construction with fourteen rounds is indifferentiable from an invertible random permutation. We also provide a new lower bound showing that five rounds are not sufficient to achieve indifferentiability. A major corollary of our result is the equivalence (in a well-defined sense) of the random oracle model and the ideal cipher model.     

Perceptions of success in virtual cross-disciplinary design teams in large multinational corporations

The nature of design problems facing industry today often requires the use of cross-disciplinary teams in order to maximise innovation. Three case studies were used to answer the research question: What factors contribute to the success of virtual cross-disciplinary design teams in large multinational engineering corporations? Results indicate that factors that contribute to success include the context in which teams work, the method by which teams do their work, and the media by which teams communicate. In addition, this study also found that technology facilitates, but does not take the place of, well-defined and shared processes.     

The influence of the nitriding parameters on the microstructure and strength of the open-cell reaction bonded silicon nitride foams fabricated via wet processing

In this study, the parameters which influence strength of the open-cell reaction bonded silicon nitride foams were investigated. These parameters include the monomer content in the suspension, the porosity level of the foam, the nitriding atmosphere including N₂ and N₂–4 %H₂, and the nitriding temperature ranging from 1350 to 1425 °C. The nitriding mechanisms dominating under different nitriding conditions were also studied based on the phase and microstructural analysis. It was observed that there is a minimum monomer concentration of 25 wt% required in the premix solution to obtain a defect-free and homogeneous RBSN foam. Increasing the monomer content only from 15 to 20 wt% resulted in a threefold increase in the foam strength. The high porosity level of the foam which is above 70 vol% significantly affects the nitriding mechanisms and microstructures compared to those of dense RBSN ceramics. The maximum strength was obtained for the foams nitrided under N₂–H₂ atmospheres, and the nitriding temperature had a negligible effect on the foam strength when H₂ is present in the atmosphere. α-Si₃N₄ is also the dominant phase in the microstructure in the presence of H₂ regardless of the nitriding temperature. It was observed that β-Si₃N₄ can also be present in high quantities when N₂ atmospheres are used. β-Si₃N₄ is present in the microstructures in two different morphologies including interlocking rods and angular grains. Each morphology forms based on a specific nitriding mechanism.     

Probabilistic causes in Markov chains

Innovations in Systems and Software Engineering - By combining two of the central paradigms of causality, namely counterfactual reasoning and probability-raising, we introduce a probabilistic...     

Attending to structural programming features predicts differences in learning and motivation

Educational robotics programs offer an engaging opportunity to potentially teach core computer science concepts and practices in K–12 classrooms. Here, we test the effects of units with different programming content within a virtual robotics context on both learning gains and motivational changes in middle school (6th–8th grade) robotics classrooms. Significant learning gains were found overall, particularly for groups introduced to content involving program flow, the structural logic of program execution. Relative gains for these groups were particularly high on items that require the transfer of knowledge to dissimilar contexts. Reaching units that included program flow content was also associated with greater maintenance of programming interest when compared with other units. Therefore, our results suggest that explicit instruction in the structural logic of programming may develop deeper transferrable programming knowledge and prevent declines in some motivational factors.     

Colorectal Cancer and Nonfermented Milk,Solid Cheese,and Fermented Milk Consumption: A Systematic Review and Meta-Analysis of Prospective Studies

Colorectal cancer is the second most prevalent cancer worldwide. A systematic review and meta-analysis of prospective studies was conducted to examine the association between intake of different types of dairy foods during adulthood and the development of colorectal cancer, specifically comparing nonfermented milk, solid cheese, and fermented milk. Seven databases were systematically searched and 15 cohort studies selected for inclusion, involving over 900,000 subjects and over 5200 colorectal cancer cases. Meta-analysis resulted in an overall relative risk of colon cancer of 0.74 (95% confidence interval 0.60–0.91) in men consuming nonfermented milk (highest intake category averaging 525 g/day). No association was found between consumption of nonfermented milk and rectal cancer in men or nonfermented milk and colon or rectal cancer in women. No protective association was found between consumption of solid cheese or fermented milk and colorectal cancer. Reasons for the differences in the impact of nonfermented milk, solid cheese, and fermented milk in the colon are discussed. This meta-analysis supports the inverse association between nonfermented milk consumption and risk of colon cancer in men, and provides an evidence base to assist in the formulation of dietary guidelines involving dairy foods.     

Effect of zinc oxide nanoparticles on the in vitro degradation of electrospun polycaprolactone membranes in simulated body fluid

Even though the biodegradability of polycaprolactone (PCL) is well established, few studies have carried out on the effect of nanofillers on the in vitro degradability of electrospun PCL membranes. Thus, the authors incorporated common nanofiller zinc oxide (ZnO) nanoparticles in electrospun PCL membranes. From the study of morphological schanges as well as the changes in crystallinity, it is clear that the ZnO nanoparticles accelerated the degradation of PCL. The FTIR results ascertain that the hydrolysis of the PCL nanofibers generates free hydroxyl and carbonyl groups in the bulk of the polymer. The tensile property of the PCL/ZnO nanocomposite membranes decreased with an increase in filler loading during degradation.