Efficient software implementation of AES on 32-bit platforms

Rijndael is the winner algorithm of the AES contest; therefore it should become the most used symmetric-key cryptographic algorithm. One important application of this new standard is cryptography on smart cards. In this paper we present an optimisation of the Rijndael algorithm to speed up execution on 32-bits processors with memory constraints, such as those used in smart cards. First a theoretical analysis of the Rijndael algorithm and of the proposed optimisation is discussed, and then simulation results of the optimised algorithm on different processors are presented and compared with other reference implementations, as known from the technical literature

Parallel hardware architectures for the cryptographic Tate pairing

Identity-based cryptography uses pairing functions, which are sophisticated bilinear maps defined on elliptic curves. Computing pairings efficiently in software is presently a relevant research topic. Since such functions are very complex and slow in software, dedicated hard- ware (HW) implementations are worthy of being stud- ied, but presently only very preliminary research is avail- able. This work affords the problem of designing paral- lel dedicated HW architectures, i.e.,co-processors, for the Tate pairing, in the case of the Duursma-Lee algorithm in characteristic 3. Formal scheduling methodologies are applied to carry out an extensive exploration of the archi- tectural solution space, evaluating the obtained structures by means of different figures of merit such as computation time, circuit area and combinations thereof.Comparisons with the (few) existing proposals are carried out, show- ing that a large space exists for the efficient parallelHW computation of pairings

Robust Global Motion Estimation with Matrix Completion

In this paper we address the problem of estimating the attitudes and positions of a set of cameras in an external coordinate system. Starting from a conventional global structure-from-motion pipeline, we present some substantial advances. In order to detect outlier relative rotations extracted from pairs of views, we improve a state-of-the-art algorithm based on cycle consistency, by introducing cycle bases. We estimate the angular attitudes of the cameras by proposing a novel gradient descent algorithm based on low-rank matrix completion, that naturally copes with the case of missing data. As for position recovery, we analyze an existing technique from a theoretical point of view, providing some insights on the conditions that guarantee solvability. We provide experimental results on both synthetic and real image sequences for which ground truth calibration is provided

Automatic 3DS Conversion of Historical Aerial Photographs

In this paper we present a method for the generation of 3D stereo (3DS) pairs from sequences of historical aerial photographs. The goal of our work is to provide a stereoscopic display when the existing exposures are in a monocular sequence. Each input image is processed using its neighbours and a synthetic image is rendered, which, together with the original one, form a stereo pair. Promising results on real images taken from a historical photo archive are shown, that corroborate the viability of generating 3DS data from monocular footage

Building a biomimetic membrane for neutron reflectivity investigation : complexity, asymmetry and contrast

The preparation and investigation of model membranes is deserving growing interest both for the physics of complex systems, and for biology. The need of simplified models should preserve mimicking the qualifying characteristics of biological membranes, and keep non-invasive and detailed description. As a main feature, biological membranes are non-homogeneous in the disposition of components, both in the lateral and in the transverse direction. We prepared asymmetric supported membranes containing GM1 ganglioside in biomimetic proportion according to different protocols. Then, we studied their internal structure by neutron reflectometry, providing few-Angstrom sensitivity in the cross direction meanwhile avoiding radiation damage. This technique can also be profitably applied to study interactions at the membrane surface. The best protocol has proven to be the Langmuir-Blodgett/Langmuir-Schaefer depositions. Notably, also the simpler and most accessible protocol of vesicle fusion was found to be suitable for straightforward and good quality deposition of compositionally asymmetric membranes

Packetizing scalable streams in heterogenus peer-to-peer networks

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Probing the polymer-electrode interface using neutron reflection

We demonstrate that neutron reflection (NR) can be used to characterize polymer films deposited on indium tin oxide (ITO). When the chloro precursor to poly[2-(2(')-ethylhexyloxy)5-methoxy-1,4-phenylenevinylene] (MEHPPV) was spin-coated onto ITO NR revealed that between the ITO and the uniform polymer layer was a 20 Angstrom thick low contact zone. We found that the conversion of the chloro precursor to MEHPPV at 180 degreesC under vacuum gave a uniform film of MEHPPV with the layer of low contact between the polymer and ITO remaining. Finally, the NR profile suggests that the blueshift in the MEHPPV absorption spectrum on ITO when compared to quartz is due to polymer morphology and not incomplete conversion. (C) 2003 American Institute of Physics

Dynamics of viscous amphiphilic films supported by elastic solid substrates

The dynamics of amphiphilic films deposited on a solid surface is analyzed for the case when shear oscillations of the solid surface are excited. The two cases of surface- and bulk shear waves are studied with film exposed to gas or to a liquid. By solving the corresponding dispersion equation and the wave equation while maintaining the energy balance we are able to connect the surface density and the shear viscocity of a fluid amphiphilic overlayer with experimentally accessible damping coefficients, phase velocity, dissipation factor and resonant frequency shifts of shear waves.Comment: 19 pages, latex, 3 figures in eps-forma

Relating the physical structure and optical properties of conjugated polymers using neutron reflectivity in combination with photoluminescence spectroscopy

Understanding the effect of physical structure and the role of interfaces is critical for gaining insight into the optoelectronic properties of conjugated polymers and their behavior in semiconductor devices such as organic light-emitting diodes and photovoltaic cells. We have developed an in situ neutron reflection measurement that allows the direct relationship between film photoluminescence and structure to be studied. In addition, we have found that by judicious deuteration of the conjugated polymers, the polymer/indium tin oxide (ITO) interface can be probed. Critically for both poly[2-(2-d(17)-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] and poly[9,9(')-(2-d(17)-ethylhexyl)-2,6-fluorene] of thickness of order 140-150 nm on ITO, we found that a thermally stable low-density layer of 20 A thickness was present between the polymer film and the ITO. The presence of the low-contact layer means that measurements involving these two families of polymers directly deposited onto ITO may need re-evaluating, and suggests why poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) may be so beneficial for polymer light-emitting diodes. (C) 2004 American Institute of Physics

Membrane restructuring following in situ sialidase digestion of gangliosides : complex model bilayers by synchrotron radiation reflectivity

Synchrotron radiation reflectometry was used to access the transverse structure of model membranes under the action of the human sialidase NEU2, down to the \uc5ngstr\uf6m length scale. Model membranes were designed to mimic the lipid composition of so-called Glycosphingolipids Enriched Microdomains (GEMs), which are membrane platforms specifically enriched in cholesterol and sphingolipids, and where also typical signalling molecules are hosted. Gangliosides, glycosphingolipids containing one or more sialic acid residues, are asymmetrically embedded in GEMs, in the outer membrane leaflet where gangliosides are claimed to interact directly with growth-factor receptors, modulating their activation and then the downstream intracellular signalling pathways. Thus, membrane dynamics and signalling could be strongly influenced by the activity of enzymes regulating the membrane ganglioside composition, including sialidases. Our results, concerning the structure of single membranes undergoing in-situ enzymatic digestion, show that the outcome of the sialidase action is not limited to the emergence of lower-sialylated ganglioside species. In fact, membrane reshaping occurs, involving a novel arrangement of the headgroups on its surface. Thus, sialidase activity reveals to be a potential tool to control dynamically the structural properties of the membrane external leaflet of living cells, influencing both the morphology of the close environment and the extent of interaction among active molecules belonging to signalling platforms