4,390 research outputs found
Discrete Logarithms in Generalized Jacobians
D\'ech\`ene has proposed generalized Jacobians as a source of groups for
public-key cryptosystems based on the hardness of the Discrete Logarithm
Problem (DLP). Her specific proposal gives rise to a group isomorphic to the
semidirect product of an elliptic curve and a multiplicative group of a finite
field. We explain why her proposal has no advantages over simply taking the
direct product of groups. We then argue that generalized Jacobians offer poorer
security and efficiency than standard Jacobians
Efficient algorithms for pairing-based cryptosystems
We describe fast new algorithms to implement recent cryptosystems based on the Tate pairing. In particular, our techniques improve pairing evaluation speed by a factor of about 55 compared to previously known methods in characteristic 3, and attain performance comparable
to that of RSA in larger characteristics.We also propose faster algorithms for scalar multiplication in characteristic 3 and square root extraction
over Fpm, the latter technique being also useful in contexts other than that of pairing-based cryptography
More Discriminants with the Brezing-Weng Method
The Brezing-Weng method is a general framework to generate families of
pairing-friendly elliptic curves. Here, we introduce an improvement which can
be used to generate more curves with larger discriminants. Apart from the
number of curves this yields, it provides an easy way to avoid endomorphism
rings with small class number
Carbon burial in deep-sea sediment and implications for oceanic inventories of carbon and alkalinity over the last glacial cycle
Although it has long been assumed that the glacialâinterglacial cycles of
atmospheric CO2 occurred due to increased storage of CO2
in the ocean, with no change in the size of the active carbon inventory,
there are signs that the geological CO2 supply rate to the active
pool varied significantly. The resulting changes of the carbon inventory cannot be
assessed without constraining the rate of carbon removal from the system,
which largely occurs in marine sediments. The oceanic supply of alkalinity is
also removed by the burial of calcium carbonate in marine sediments, which
plays a major role in airâsea partitioning of the active carbon inventory. Here, we
present the first global reconstruction of carbon and alkalinity burial in
deep-sea sediments over the last glacial cycle. Although subject to large
uncertainties, the reconstruction provides a first-order constraint on the
effects of changes in deep-sea burial fluxes on global carbon and alkalinity
inventories over the last glacial cycle. The results suggest that reduced
burial of carbonate in the Atlantic Ocean was not entirely compensated by the
increased burial in the Pacific basin during the last glacial period, which
would have caused a gradual buildup of alkalinity in the ocean. We also
consider the magnitude of possible changes in the larger but
poorly constrained rates of burial on continental shelves, and show that
these could have been significantly larger than the deep-sea burial changes. The
burial-driven inventory variations are sufficiently large to have
significantly altered the ÎŽ13C of the oceanâatmosphere carbon
and changed the average dissolved
inorganic carbon (DIC) and alkalinity concentrations of the
ocean by more than 100 ”M, confirming that carbon burial fluxes
were a dynamic, interactive component of the glacial cycles that
significantly modified the size of the active carbon pool. Our results also
suggest that geological sources and sinks were significantly unbalanced
during the late Holocene, leading to a slow net removal flux on the order of
0.1 PgC yrâ1 prior to the rapid input of carbon during the industrial
period.</p
The Unlock Project: A Python-based framework for practical brain-computer interface communication âappâ development
In this paper we present a framework for reducing the development time needed for creating applications for use in non-invasive brain-computer interfaces (BCI). Our framework is primarily focused on facilitating rapid software âappâ development akin to current efforts in consumer portable computing (e.g. smart phones and tablets). This is accomplished by handling intermodule communication without direct user or developer implementation, instead relying on a core subsystem for communication of standard, internal data formats. We also provide a library of hardware interfaces for common mobile EEG platforms for immediate use in BCI applications. A use-case example is described in which a user with amyotrophic lateral sclerosis participated in an electroencephalography-based BCI protocol developed using the proposed framework. We show that our software environment is capable of running in real-time with updates occurring 50â60 times per second with limited computational overhead (5 ms system lag) while providing accurate data acquisition and signal analysis
Reaction physics and mission capabilities of the magnetically insulated inertial confinement fusion reactor
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76048/1/AIAA-25451-882.pd
Increasing human dominance of tropical forests
Tropical forests house over half of Earthâs biodiversity and are an important influence on the climate system. These forests are experiencing escalating human influence, altering their health and the provision of important ecosystem functions and services. Impacts started with hunting and millennia-old megafaunal extinctions (Phase I), continuing via low-intensity shifting cultivation (Phase II), to todayâs global integration (Phase III), dominated by intensive permanent agriculture, industrial logging, and attendant fires and fragmentation. Such ongoing pressures together with an intensification of global environmental change may severely degrade forests in the future (Phase IV, global simplification) unless new âdevelopment without destructionâ pathways are established alongside climate change resilient landscape designs
Antimatter-driven fusion propulsion scheme for solar system exploration
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76531/1/AIAA-23527-891.pd
Pasture Land Management System Decision Support Software
Controlled or rotational grazing provides benefits to producers and society through profitable and sound management of grazing land and livestock. Pasture land management system (PLMS) is a decision support system developed to help university, government, and professionals provide technical pasture management assistance to beef and dairy producers. The PLMS focuses on the balance between seasonal forage supply and nutrient demand in a dairy or beef cattle operation. It allows users to explore and compare alternatives (dividing fields into multiple paddocks, changing stocking rates, and forage species) through a visual display and embedded simulation. Users enter a description of the farm by drawing a map. Maps can be drawn freehand, traced over a scanned image, or GIS data may be incorporated. Once map and field data are entered the grazing options are specified via input screens. Grazing systems can be easily compared without economic risk and with almost immediate feedback on how these alternative systems affect variables like milk production and pounds of beef sold. PLMS serves as both an educational tool and a strategic planning tool for evaluating alternative grazing operations and management related investments (website: http://clic.cses.vt.edu/PLMS/)
Converting Pairing-Based Cryptosystems from Composite-Order Groups to Prime-Order Groups
We develop an abstract framework that encompasses the key properties of bilinear groups of composite order that are required to construct secure pairing-based cryptosystems, and we show how to use prime-order elliptic curve groups to construct bilinear groups with the same properties. In particular, we define a generalized version of the subgroup decision problem and give explicit constructions of bilinear groups in which the generalized subgroup decision assumption follows from the decision Diffie-Hellman assumption, the decision linear assumption, and/or related assumptions in prime-order groups.
We apply our framework and our prime-order group constructions to create more efficient versions of cryptosystems that originally required composite-order groups. Specifically, we consider the Boneh-Goh-Nissim encryption scheme, the Boneh-Sahai-Waters traitor tracing system, and the Katz-Sahai-Waters attribute-based encryption scheme. We give a security theorem for the prime-order group instantiation of each system, using assumptions of comparable complexity to those used in the composite-order setting. Our conversion of the last two systems to prime-order groups answers a problem posed by Groth and Sahai
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