Efficient and secure digital signature algorithm (DSA)

The digital signature is used to ensure the integrity of messages as well as the authentication and non-repudiation of users. Today it has a very important role in information security. Digital signature is used in various fields such as e-commerce and e-voting, health, internet of things (IOT). Many digital signature schemes have been proposed, depending on the computational cost and security level. In this paper, we analyzed a recently proposed digital signature scheme based on the discrete logarithm problem (DLP). Our analysis shows that the scheme is not secure against the repeated random number attack to determine the secret keys of the signer. To overcome this problem, we propose a new improvement of the digital signature scheme

Oxinium femoral head damage generated by a metallic foreign body within the polyethylene cup following recurrent dislocation episodes

SummaryOxinium femoral heads are supposed to be more scratch-resistant thanks to their oxidized layer. However, damages to this thin layer can jeopardize implant's properties. Following revision total hip arthroplasty performed for recurrent posterior dislocations, the Oxinium femoral head initially implanted was observed to be dramatically damaged. A metallic foreign body from a trochanteric fixation wire was found within the polyethylene cup. Only few cases of damaged Oxinium femoral heads have been reported and all were related to either dislocation or reduction of THA. The aim of this report is to describe a non-reported mechanism of damaged Oxinium femoral head due to a broken trochanteric fixation wire device. Any broken metallic wire from a transtrochanteric approach should be carefully followed to detect migration within the polyethylene cup. If such a migration occurs, revision surgery should be rapidly scheduled

A Novel Approach for Enhancing Routing in Wireless Sensor Networks using ACO Algorithm

Wireless Sensors Network (WSN) is an emergent technology that aims to offer innovative capacities. In the last decade, the use of these networks increased in various fields like military, science, and health due to their fast and inexpressive deployment and installation. However, the limited sensor battery lifetime poses many technical challenges and affects essential services like routing. This issue is a hot topic of search, many researchers have proposed various routing protocols aimed at reducing the energy consumption in WSNs. The focus of this work is to investigate the effectiveness of integrating ACO algorithm with routing protocols in WSNs. Moreover, it presents a novel approach inspired by ant colony optimization (ACO) to be deployed as a new routing protocol that addresses key challenges in wireless sensor networks. The proposed protocol can significantly minimize nodes energy consumption, enhance the network lifetime, reduce latency, and expect performance in various scenarios

Improved Convergence Bounds For Operator Splitting Algorithms With Rare Extreme Errors

In this paper, we improve upon our previous work[24,22] and establish convergence bounds on the objective function values of approximate proximal-gradient descent (AxPGD), approximate accelerated proximal-gradient descent (AxAPGD) and approximate proximal ADMM (AxWLM-ADMM) schemes. We consider approximation errors that manifest rare extreme events and we propagate their effects through iterations. We establish probabilistic asymptotic and non-asymptotic convergence bounds as functions of the range (upper/lower bounds) and variance of approximation errors. We use the derived bound to assess AxPGD in a sparse model predictive control of a spacecraft system and compare its accuracy with previously derived bounds

A Low-Power Hardware-Friendly Optimisation Algorithm With Absolute Numerical Stability and Convergence Guarantees

We propose Dual-Feedback Generalized Proximal Gradient Descent (DFGPGD) as a new, hardware-friendly, operator splitting algorithm. We then establish convergence guarantees under approximate computational errors and we derive theoretical criteria for the numerical stability of DFGPGD based on absolute stability of dynamical systems. We also propose a new generalized proximal ADMM that can be used to instantiate most of existing proximal-based composite optimization solvers. We implement DFGPGD and ADMM on FPGA ZCU106 board and compare them in light of FPGA's timing as well as resource utilization and power efficiency. We also perform a full-stack, application-to-hardware, comparison between approximate versions of DFGPGD and ADMM based on dynamic power/error rate trade-off, which is a new hardware-application combined metric

The connection between stellar mass, age and quenching timescale in massive quiescent galaxies at z≃1z \simeq 1

We present a spectro-photometric study of a mass-complete sample of quiescent galaxies at $1.0 < z < 1.3$ with $\mathrm{log_{10}}(M_{\star}/\mathrm{M_{\odot}}) \geq 10.3$ drawn from the VANDELS survey, exploring the relationship between stellar mass, age and star-formation history. Within our sample of 114 galaxies, we derive a stellar-mass vs stellar-age relation with a slope of $1.20^{+0.28}_{-0.27}$ Gyr per decade in stellar mass. When combined with recent literature results, we find evidence that the slope of this relation remains consistent over the redshift interval $0<z<4$. The galaxies within the VANDELS quiescent display a wide range of star-formation histories, with a mean star-formation timescale of $1.5\pm{0.1}$ Gyr and a mean quenching timescale of $1.4\pm{0.1}$ Gyr. We also find a large scatter in the quenching timescales of the VANDELS quiescent galaxies, in agreement with previous evidence that galaxies at $z \sim 1$ cease star formation via multiple mechanisms. We then focus on the oldest galaxies in our sample, finding that the number density of galaxies that quenched before $z = 3$ with stellar masses $\mathrm{log_{10}}(M_{\star}/\mathrm{M_{\odot}}) \geq 10.6$ is $1.12_{-0.72}^{+1.47} \times 10^{-5} \ \mathrm{Mpc}^{-3}$. Although uncertain, this estimate is in good agreement with the latest observational results at $3<z<4$, tentatively suggesting that neither rejuvenation nor merger events are playing a major role in the evolution of the oldest massive quiescent galaxies within the redshift interval $1<z<3$.Comment: Accepted for publication in MNRAS, 11 pages, 6 figure

A combined VANDELS and LEGA-C study: the evolution of quiescent galaxy size, stellar mass, and age from z = 0.6 to z = 1.3

We study the relationships between stellar mass, size and age within the quiescent population, using two mass-complete spectroscopic samples with $\mathrm{log_{10}}(M_{\star}/\mathrm{M_{\odot}})>10.3$, taken from VANDELS at $1.0<z<1.3$, and LEGA-C at $0.6<z<0.8$. Using robust D$_{n}$4000 values, we demonstrate that the well-known 'downsizing' signature is already in place by $z\simeq1.1$, with D$_{n}$4000 increasing by $\simeq0.1$ across a $\simeq$ 1 dex mass interval for both VANDELS and LEGA-C. We then proceed to investigate the evolution of the quiescent galaxy stellar mass-size relation from $z\simeq1.1$ to $z\simeq0.7$. We find the median size increases by a factor of $1.9\pm{0.1}$ at $\mathrm{log_{10}}(M_{\star}/\mathrm{M_{\odot}})=10.5$, and see tentative evidence for flattening of the relation, finding slopes of $\alpha=0.72\pm0.06$ and $\alpha=$ $0.56\pm0.04$ for VANDELS and LEGA-C respectively. We finally split our sample into galaxies above and below our fitted mass-size relations, to investigate how size and D$_{n}$4000 correlate. For LEGA-C, we see a clear difference, with larger galaxies found to have smaller D$_{n}$4000 at fixed stellar mass. Due to the faintness and smaller numbers of the VANDELS sample, we cannot confirm whether a similar relation exists at $z\simeq1.1$. We consider whether differences in stellar age or metallicity are most likely to drive this size-D$_{n}$4000 relation, finding that any metallicity differences are unlikely to fully explain the observed offset, meaning smaller galaxies must be older than their larger counterparts. We find the observed evolution in size, mass and D$_{n}$4000 across the $\simeq2$ Gyr from $z\sim1.1$ to $z\sim0.7$ can be explained by a simple toy model in which VANDELS galaxies evolve passively, whilst experiencing a series of minor mergers.Comment: 14 pages, 9 figures, submitted to MNRA

A combined VANDELS and LEGA-C study: the evolution of quiescent galaxy size, stellar mass, and age from z = 0.6 to z = 1.3

We study the relationships between stellar mass, size, and age within the quiescent population, using two mass-complete spectroscopic samples with log10(M⊙/M⊙) &gt; 10.3, taken from VANDELS at 1.0 &lt; z &lt; 1.3, and LEGA-C at 0.6 &lt; z &lt; 0.8. Using robust Dn4000 values, we demonstrate that the well-known 'downsizing' signature is already in place by z 1.1, with Dn4000 increasing by 0.1 across a 1 dex mass interval for both VANDELS and LEGA-C. We then proceed to investigate the evolution of the quiescent galaxy stellar mass-size relation from z -1.1 to z -0.7. We find the median size increases by a factor of 1.9 ± 0.1 at log10(M⊙/M⊙) = 10.5, and see tentative evidence for flattening of the relation, finding slopes of α = 0.72 ± 0.06 and α =\0.56\pm 0.04 for VANDELS and LEGA-C, respectively. We finally split our sample into galaxies above and below our fitted mass-size relations, to investigate how size and Dn4000 correlate. For LEGA-C, we see a clear difference, with larger galaxies found to have smaller Dn4000 at fixed stellar mass. Due to the faintness and smaller numbers of the VANDELS sample, we cannot confirm whether a similar relation exists at z -1.1. We consider whether differences in stellar age or metallicity are most likely to drive this size-Dn4000 relation, finding that any metallicity differences are unlikely to fully explain the observed offset, meaning smaller galaxies must be older than their larger counterparts. We find the observed evolution in size, mass, and Dn4000 across the -2 Gyr from z ∼1.1 to z ∼0.7 can be explained by a simple toy model in which VANDELS galaxies evolve passively whilst experiencing a series of minor mergers