1,721,006 research outputs found
Digital Nonlinear Oscillators: A Novel Class of Circuits for the Design of Entropy Sources in Programmable Logic Devices
Full text linkIn recent years, cybersecurity is gaining more and more importance. Cryptography is used in numerous applications, such as authentication and encryption of data in communications, access control to restricted or protected areas, electronic payments. It is safe to assume that the presence of cryptographic systems in future technologies will become increasingly pervasive, leading to a greater demand for energy efficiency, hardware reliability, integration, portability, and security.
However, this pervasiveness introduces new challenges: the implementation of conventional cryptographic standards approved by NIST requires the achievement of performance in terms of timing, chip area, power and resource consumption that are not compatible with reduced complexity hardware devices, such as IoT systems. In response to this limitation, lightweight cryptography comes into play - a branch of cryptography that provides tailor-made solutions for resource-limited devices.
One of the fundamental classes of cryptographic hardware primitives is represented by Random Number Generators (RNGs), that is, systems that provide sequences of integers that are supposed to be unpredictable.
The circuits and systems that implement RNGs can be divided into two categories, namely Pseudo Random Number Generators (PRNGs) and True Random Number Generators (TRNGs).
PRNGs are deterministic and possibly periodic finite state machines, capable of generating sequences that appear to be random. In other words, a PRNG is a device that generates and repeats a finite random sequence, saved in memory, or generated by calculation.
A TRNG, on the other hand, is a device that generates random numbers based on real stochastic physical processes. Typically, a hardware TRNG consists of a mixed-signal circuit that is classified according to the stochastic process on which it is based. Specifically, the most used sources of randomness are chaotic circuits, high jitter oscillators, circuits that measure other stochastic processes.
A chaotic circuit is an analog or mixed-signal circuit in which currents and voltages vary over time based on certain mathematical properties. The evolution over time of these currents and voltages can be interpreted as the evolution of the state of a chaotic nonlinear dynamical system.
Jitter noise can instead be defined as the deviation of the output signal of an oscillator from its true periodicity, which causes uncertainty in its low-high and high-low transition times.
Other possible stochastic processes that a TRNG can use may involve radioactive decay, photon detection, or electronic noise in semiconductor devices.
TRNG proposals presented in the literature are typically designed in the form of Application Specific Integrated Circuits (ASICs). On the other hand, in recent years more and more researchers are exploring the possibility of designing TRNGs in Programmable Logic Devices (PLDs). A PLD offers, compared to an ASIC, clear advantages in terms of cost and versatility. At the same time, however, there is currently a widespread lack of trust in these PLD-based architectures, particularly due to strong cryptographic weaknesses found in Ring Oscillator-based solutions.
The goal of this thesis is to show how this mistrust does not depend on poor performance in cryptographic terms of solutions for the generation of random numbers based on programmable digital technologies, but rather on a still immature approach in the study of TRNG architectures designed on PLDs.
During the thesis chapters a new class of nonlinear circuits based on digital hardware is introduced that can be used as entropy sources for TRNGs implemented in PLDs, identified by the denomination of Digital Nonlinear Oscillators (DNOs).
In Chapter 2 a novel class of circuits that can be used to design entropy sources for True Random Number Generation, called Digital Nonlinear Oscillators (DNOs), is introduced. DNOs constitute nonlinear dynamical systems capable of supporting complex dynamics in the time-continuous domain, although they are based on purely digital hardware. By virtue of this characteristic, these circuits are suitable for their implementation on Programmable Logic Devices. By focusing the analysis on Digital Nonlinear Oscillators implemented in FPGAs, a preliminary comparison is proposed between three different circuit topologies referable to the introduced class, to demonstrate how circuits of this type can have different characteristics, depending on their dynamical behavior and the hardware implementation.
In Chapter 3 a methodology for the analysis and design of Digital Nonlinear Oscillators based on the evaluation of their electronics aspects, their dynamical behavior, and the information they can generate is formalized. The presented methodology makes use of different tools, such as figures of merit, simplified dynamical models, advanced numerical simulations and experimental tests carried out through implementation on FPGA. Each of these tools is analyzed both in its theoretical premises and through explanatory examples.
In Chapter 4 the analysis and design methodologies of Digital Nonlinear Oscillators formalized in Chapter 3 are used to describe the complete workflow followed for the design of a novel DNO topology. This DNO is characterized by chaotic dynamical behaviors and can achieve high performance in terms of generated entropy, downstream of a reduced hardware complexity and high sampling frequencies. By exploiting the simplified dynamical model, the advanced numerical simulations in Cadence Virtuoso and the FPGA implementation, the presented topology is extensively analyzed both from a theoretical point of view (notable circuit sub-elements that make up the topology, bifurcation diagrams, internal periodicities) and from an experimental point of view (generated entropy, source autocorrelation, sensitivity to routing, application of standard statistical tests).
In Chapter 5 an algorithm, called Maximum Worst-Case Entropy Selector (MWCES), that aims to identify, within a set of entropy sources, which offers the best performance in terms of worst-case entropy, also known in literature as "min-entropy", is presented. This algorithm is designed to be implemented in low-complexity digital architectures, suitable for lightweight cryptographic applications, thus allowing online maximization of the performance of a random number generation system based on Digital Nonlinear Oscillators. This chapter presents the theoretical premises underlying the algorithm formulation, some notable examples of its generic application and, finally, considerations related to its hardware implementation in FPGA
wPip Wolbachia contribution to Aedes albopictus SIT performance: Advantages under intensive rearing
No full textAs a part of a project aiming at the suppression of the mosquito vector Aedes albopictus, a specific Ae. albopictus line producing sterile males, ARwP, was tested for its suitability to intense rearing conditions compatible with mass production and field release. This line was developed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development thanks to the artificial infection with a heterologous Wolbachia strain, resulting in a bidirectional incompatibility pattern with wild-type Ae. albopictus. ARwP was reared under Standard Operating Procedures at the Centro Agricoltura Ambiente and compared with a wild-type strain in terms of time of pupation onset, production of male pupae in the following 24 h and mechanical sexing efficacy. Mating competitiveness of ARwP males was also evaluated in comparison with irradiated wild-type males in large field enclosures. ARwP males demonstrated a significantly shorter time of pupation onset, a higher rate of production of male pupae in the following 24 h and a lower percentage of residual contaminant females when applying mechanical sexing procedures. In addition, ARwP males were more efficient than wild-types in competing for wild-type females in large enclosures, thus inducing a level of sterility significantly higher than that expected for an equal mating competitiveness. These results encourage the use of this Ae. albopictus strain as suppression tool against Ae. albopictus based on considerations thoroughly discussed in the manuscript
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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