103 research outputs found
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Side channel attack resistant elliptic curves cryptosystem on multi-cores for power efficiency
The Advent of multi-cores allows programs to be executed much faster than before. Cryptoalgorithms use long-bit words thus parallelizing these operations on multi-cores will achieve significant performance improvement. However, not all long-bit word operations in cryptosystems are suitable for parallel execution on multi-cores. In particular, long-bit words used in Elliptic Curves Cryptography (ECC) do not efficiently divide by the system word size. This causes some of the cores to be idle, which makes it vulnerable for attackers to guess how many operations occurred and thus what field size is being used.
Multiplication is the most important part of public key cryptosystems. Long-bit word multiplication operations are needed for encryption and decryption. J. Fan et al. proposed using Montgomery multiplication on multi-cores using GF(2²⁵⁶) [25, 26], which is suitable for comput-er systems with 16-bit or 32-bit word size. Fan‟s Montgomery multiplication is suitable for most RSA. However, in ECC, some GFs will cause idle cores. For example, suppose GF(2¹³¹) is used (which is one of the recommended word size by NIST) on a quad-core with a 32-bit word size, which requires [132/32] =5 iterations with the last iteration requiring just a 3-bit operation. This cause three of the cores to be idle during this time causing needless power consumption. The most general and the easiest way to make side channel attacks difficult is to insert dummy instructions to cover the idle processors. However, dummy instructions result in extra workloads that lead to performance degradation and increases in power consumption. In this thesis, we will present a multiplier adjuster technique to improve the execution time and the power consumption for the last unbalanced iteration. By appropriately applying dummy instructions between point-addition and point-doubling operations, a balanced point operation can be achieved in ECC. The performance and power-efficiency of the proposed method on multi-cores are analyzed for each GF used in ECC
Dynamic Characteristics of Customer Participation: Based on Job Demand and Resource Model
Based on a Job Demands-Resources (JD-R) model, this study advances and empirically tests a conceptual model proposing the relationship between perceived customer participation (PCP), frontline employee's work engagement and employee's job performance (job satisfaction, organizational commitment, and organizational citizenship behavior). This study suggests an inverted U-shaped relationship between perceived customer participation and work engagement. In this research, customer orientation (CO) and frontline employee-customer fit (PCF) are suggested as moderators. As a personal resource, CO has direct effect on work engagement. As an environment resource, PCF also show positive relationship with work engagement. Based on the JD-R model, CO and PCF enhance the positive relationship and buffer the negative relationship between frontline employee PCP and work engagement. Internal and external benefits of frontline employee's work engagement are also investigated. The findings suggest the dynamic characteristics oBusiness Administration (MBA
The formation of the brightest cluster galaxy and intracluster light in cosmological N-body simulations with the Galaxy Replacement Technique
We investigate the formation channels of the intracluster light (ICL) and the
brightest cluster galaxy (BCG) in clusters at . For this, we perform
multi-resolution cosmological N-body simulations using the "Galaxy Replacement
Technique" (GRT). We study the formation channels of the ICL and BCG as a
function of distance from the cluster center and the dynamical state of the
clusters at . To do this, we trace back the stars of the ICL and BCG, and
identify the stellar components in which they existed when they first fell into
the clusters. We find that the progenitors of the ICL and BCG in the central
region of the cluster fell earlier and with a higher total mass ratio of the
progenitors to the cluster compared to the outer region. This causes a negative
radial gradient in the infall time and total mass ratio of the progenitors.
Although stellar mass of the progenitors does not show the same radial gradient
in all clusters, massive galaxies ()
are the dominant formation channel of the ICL and BCG for all clusters, except
for our most relaxed cluster. For clusters that are dynamically more unrelaxed,
we find that the progenitors of the ICL and BCG fall into their clusters more
recently, and with a higher mass and mass ratio. Furthermore, we find that the
diffuse material of massive galaxies and group-mass halos that is formed by
pre-processing contributes significantly to the ICL in the outer region of the
unrelaxed clusters.Comment: 18 pages, 8 figures, 4 tables. Accepted for publication in The
Astrophysical Journal, December 3rd, 202
Comparison of spatial distributions of Intracluster light and Dark Matter
In a galaxy cluster, the relative spatial distributions of dark matter,
member galaxies, gas, and intracluster light (ICL) may connote their mutual
interactions over the cluster evolution. However, it is a challenging problem
to provide a quantitative measure for the shape matching between two
multi-dimensional scalar distributions. We present a novel methodology, named
the {\em Weighted Overlap Coefficient (WOC)}, to quantify the similarity of
2-dimensional spatial distributions. We compare the WOC with a standard method
known as the Modified Hausdorff Distance (MHD). We find that our method is
robust, and performs well even with the existence of multiple sub-structures.
We apply our methodology to search for a visible component whose spatial
distribution resembled with that of dark matter. If such a component could be
found to trace the dark matter distribution with high fidelity for more relaxed
galaxy clusters, then the similarity of the distributions could also be used as
a dynamical stage estimator of the cluster. We apply the method to six galaxy
clusters at different dynamical stages simulated within the GRT simulation,
which is an N-body simulation using the galaxy replacement technique. Among the
various components (stellar particles, galaxies, ICL), the ICL+ brightest
cluster galaxy (BCG) component most faithfully trace the dark matter
distribution. Among the sample galaxy clusters, the relaxed clusters show
stronger similarity in the spatial distribution of the dark matter and ICL+BCG
than the dynamically young clusters. While the MHD results show weaker trend
with the dynamical stages.Comment: 17 pages, 8 figures, accepted in ApJ
BCG alignment with the Locations of Cluster Members and the Large Scale Structure out to 10 R
Using a sample of clusters, each with typically
spectroscopically confirmed cluster members, we search for a signal of
alignment between the Position Angle (PA) of the Brightest Cluster Galaxy (BCG)
and the distribution of cluster members on the sky about the cluster centre out
to projected distances of 3~R. The deep spectroscopy, combined with
corrections for spectroscopic incompleteness, makes our sample ideal to
determine alignment signal strengths. We also use an SDSS based skeleton of the
filamentary Large Scale Structure (LSS), and measure BCG alignment with the
location of the LSS skeleton segments on the sky out to projected distances of
10~R. The alignment signal is measured using three separate statistical
measures; Rao's spacing test (U), Kuiper's V parameter (V), and the Binomial
probability test (P). The significance of the BCG alignment signal with both
cluster members and LSS segments is extremely high (1 in a million chance or
less to be drawn randomly from a uniform distribution). We investigate a wide
set of parameters that may influence the strength of the alignment signal.
Clusters with more elliptical-shaped BCGs show stronger alignment with both
their cluster members and LSS segments. Also, selecting clusters with closely
connected filaments, or using a luminosity-weighted LSS skeleton, increases the
alignment signal significantly. Alignment strength decreases with increasing
projected distance. Combined, these results provide strong evidence for the
growth of clusters and their BCGs by preferential feeding along the direction
of the filaments in which they are embedded.Comment: 21 pages, 5 tables, 5 figures ,Accepted to MNRAS, August 202
An Extensive Catalog of Early-type Dwarf Galaxies in the Local Universe: Morphology and Environment
We present an extensive catalog of 5405 early-type dwarf (dE) galaxies
located in the various environments, i.e., clusters, groups and fields, of the
local universe ( 0.01). The dEs are selected through visual inspection
of the Legacy survey's -- combined tri-color images. The inspected
area, covering a total sky area of 7643 deg, encompasses two local
clusters, Virgo and Fornax, 265 groups, and the regions around 586 field
galaxies of 21 mag. The catalog aims to be one of the most
extensive and publicly accessible collections of data on dE, despite its
complex completeness limits that may not accurately represent its statistical
completeness. The strength of the catalog lies in the morphological
characteristics, including nucleated, tidal, and ultradiffuse dE. The two
clusters contribute nearly half (2437 out of 5405) dEs, and the 265 groups
contribute 2103 dEs. There are 864 dEs in 586 fields, i.e., ~1.47 dEs per
field. Using a standard definition commonly used in literature, we identify 100
ultra-diffuse galaxies (UDGs), which take ~2% of the dE population. We find
that 40% of our sample dEs harbor a central nucleus, and among the UDG
population, a majority, 79%, are nonnucleated. About 1.3 of dEs suffer from
ongoing tidal disturbance by nearby massive galaxies, and only 0.03% show the
sign of recent dwarf-dwarf mergers. The association between dEs and their
nearest bright neighbor galaxies suggests that dEs are more likely created
where their neighbors are non-star-forming ones.Comment: Accepted for publication in ApJ
SALM5 trans-synaptically interacts with LAR-RPTPs in a splicing-dependent manner to regulate synapse development
Synaptogenic adhesion molecules play critical roles in synapse formation. SALM5/Lrfn5, a SALM/Lrfn family adhesion molecule implicated in autism spectrum disorders (ASDs) and schizophrenia, induces presynaptic differentiation in contacting axons, but its presynaptic ligand remains unknown. We found that SALM5 interacts with the Ig domains of LAR family receptor protein tyrosine phosphatases (LAR-RPTPs; LAR, PTPδ, and PTPσ). These interactions are strongly inhibited by the splice insert B in the Ig domain region of LAR-RPTPs, and mediate SALM5-dependent presynaptic differentiation in contacting axons. In addition, SALM5 regulates AMPA receptor-mediated synaptic transmission through mechanisms involving the interaction of postsynaptic SALM5 with presynaptic LAR-RPTPs. These results suggest that postsynaptic SALM5 promotes synapse development by trans-synaptically interacting with presynaptic LAR-RPTPs and is important for the regulation of excitatory synaptic strength
Genomic diversity of Mycobacterium avium subsp. paratuberculosis: pangenomic approach for highlighting unique genomic features with newly constructed complete genomes
Mycobacterium avium subsp. paratuberculosis (MAP) is a causative agent of Johne's disease, which is a chronic granulomatous enteropathy in ruminants. Determining the genetic diversity of MAP is necessary to understand the epidemiology and biology of MAP, as well as establishing disease control strategies. In the present study, whole genome-based alignment and comparative analysis were performed using 40 publicly available MAP genomes, including newly sequenced Korean isolates. First, whole genome-based alignment was employed to identify new genomic structures in MAP genomes. Second, the genomic diversity of the MAP population was described by pangenome analysis. A phylogenetic tree based on the core genome and pangenome showed that the MAP was differentiated into two major types (C- and S-type), which was in keeping with the findings of previous studies. However, B-type strains were discriminated from C-type strains. Finally, functional analysis of the pangenome was performed using three virulence factor databases (i.e., PATRIC, VFDB, and Victors) to predict the phenotypic diversity of MAP in terms of pathogenicity. Based on the results of the pangenome analysis, we developed a real-time PCR technique to distinguish among S-, B- and C-type strains. In conclusion, the results of our study suggest that the phenotypic differences between MAP strains can be explained by their genetic polymorphisms. These results may help to elucidate the diversity of MAP, extending from genomic features to phenotypic traits
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