Digital signatures, which take the properties of classical signatures, are used to secure the actual content of documents, which can be modified during transmission over an insecure channel. The problems of security and protection of communicating participants are solved by cryptographic techniques. Identity verification, message integrity, credibility, the ownership of documents, and the secure transmission of information over an unsecured channel, are all dealt with in secure communications - Public Key Infrastructure, which uses digital signatures. Nowadays digital signatures are often used to secure data in communication over an unsecured channel. The aim of the following master’s thesis is to familiarize readers with the necessary technological aspects of digital signatures, as well as their advantages and disadvantages. By the time digital signatures are being used they will have to be improved and modified to be secure against more sophisticated attacks. In this paper, proposals of new efficient digital signature schemes and their comparison with current ones are described. Also are examined their implications for computationally weak devices, or deployment in low speed channel transmission systems. After an explanation of cryptography and a description of its basic subjects, digital signatures are introduced. The first chapter describes the possible formatting and architecture of the digital signature. The second part of this master’s thesis is about current digital signature schemes and their properties. Chapter 3 describes some proposals of new efficient digital signature schemes and their comparison to those currently in use. In the practical part, the implementations (in the environment .NET in C#) of two effective digital signature schemes as part of a client-server application are presented and described (Chapter 4). In the last chapter the comparison and analysis of the implemented signature schemes are provided.

Perhaps the most flexible synopsis of a database is a random sample of the data; such samples are widely used to speed up processing of analytic queries and data-mining tasks, enhance query optimization, and facilitate information integration. In this paper, we study methods for incrementally maintaining a uniform random sample of the items in a dataset in the presence of an arbitrary sequence of insertions and deletions. For “stable” datasets whose sizeremains roughly constant over time, we provide a novel sampling scheme, called “random pairing” (RP) which maintains a bounded-size uniform sample by using newly inserted data items to compensate for previous deletions. The RP algorithm is the first extension of the almost 40-year-old reservoir sampling algorithm to handle deletions. Experiments show that, when dataset-size fluctuations over time are not too extreme, RP is the algorithm of choice with respect to speed and sample-size stability. For “growing” datasets, we consider algorithms for periodically “resizing” a bounded-size random sample upwards. We prove that any such algorithm cannot avoid accessing the base data, and provide a novel resizing algorithm that minimizes the time needed to increase the sample size.

Background: RNA has been recognized as a key player in cellular regulation in recent years. In many cases, non-coding RNAs exert their function by binding to other nucleic acids, as in the case of microRNAs and snoRNAs. The specificity of these interactions derives from the stability of inter-molecular base pairing. The accurate computational treatment of RNA-RNA binding therefore lies at the heart of target prediction algorithms. Methods: The standard dynamic programming algorithms for computing secondary structures of linear single-stranded RNA molecules are extended to the co-folding of two interacting RNAs. Results: We present a program, RNAcofold, that computes the hybridization energy and base pairing pattern of a pair of interacting RNA molecules. In contrast to earlier approaches, complex internal structures in both RNAs are fully taken into account. RNAcofold supports the calculation of the minimum energy structure and of a complete set of suboptimal structures in an energy band above the ground state. Furthermore, it provides an extension of McCaskill's partition function algorithm to compute base pairing probabilities, realistic interaction energies, and equilibrium concentrations of duplex structures.

The science of behavior analysis is most notably recognized for its work with individuals with Autism Spectrum Disorder (ASD) and the development of language in individuals with and without ASD. As an extension of a behavior-analytic approach to language, Relational Frame Theory (RFT) posits that relating between stimuli is foundational for human language and cognition. This modern-day account of human verbal events also includes psychological distress, which is frequently experienced among family members of individuals with ASD. The effects of Acceptance and Commitment Therapy (ACT), which is derived from RFT, have been evaluated with caregivers of individuals with ASD and demonstrated empirical support. Despite all these advancements, researchers have not adequately considered cultural and linguistic factors in the provision of these approaches for diverse populations, such as Hispanics/Latinxs. Moreover, there is a paucity of research using such scientific approaches for caregivers and siblings of individuals with ASD. Considering that Hispanics/Latinxs are a growing population in the United States, behavior-analytic interventions should be culturally adapted. The purpose of this study was to culturally adapt treatments rooted in the science of human behavior specifically for Hispanic/Latinx families that care for a child with ASD. Specifically, sociocultural factors and Hispanic/Latinx cultural values were considered in the development of such interventions to promote the skill set and well-being of the family as a unit. In the first experiment, the evaluation of SPOP in transferring relational frames from Spanish to English in Hispanic/Latinx children with ASD was examined. Here, the language of instruction (i.e., English vs. Spanish) differed for participants, depending on their primary languages. SPOP demonstrated effectiveness for some relations with one participant, however, direct training was employed to teach correct relational responding. In the second experiment, the effects of culturally adapted ACT were evaluated on statements of psychological flexibility and inflexibility, and self-report measures for Spanish-speaking Hispanic/Latinx caregivers of children with ASD. Results demonstrated higher percentages of statements of psychological flexibility across all conditions, and a statistically significant difference in self-reported thought suppression post-treatment. Finally, the third experiment compared the effects of culturally adapted family-based ACT and non-culturally adapted non-family-based ACT on self-monitored committed actions and self-report measures for Hispanic/Latinx siblings of children with ASD. Results indicated statistically significant differences in reported committed actions before and after treatment, with changes in self-report measures post-treatment. Together, these experiments demonstrate the clinical and social significance of taking cultural and linguistic factors of diverse populations into consideration with behavior-analytic services.

The Chow/Van der Waerden approach to algebraic cycles via resultants is elaborated and used to give a purely algebraic proof for the algebraicity of the complex suspension over arbitrary fields. The algebraicity of the join pairing on Chow varieties then follows over the complex numbers. The approach implies a more algebraic proof of Lawson´s complex suspension theorem in characteristic 0. The continuity of the action of the linear isometries operad on the group completion of the stable Chow variety is a consequence. Further Hoyt´s proof of the independence of the algebraic-continuous homeomorphism type of Chow varieties on embeddings is rectified and worked out over arbitrary fields.

In two experiments, second-order conditioned taste aversion techniques were employed to develop aversions in rats, with a geotactic-excitation procedure as the independent variable. Periodic tilting of an experimental apparatus resulted in angular orientation changes of all subjects located within compartments of the chamber. The effect was excitation of geotactic behaviors, expressed as locomotor activity within the confines of these compartments. In the first experiment, two groups of rats (n = 6) were exposed to experimental protocols which were identical with the exception of the independent variable. Three conditioning trials were presented, separated by five to seven days, within which strychnine injections preceded LiCl injections by 15 minutes. A treatment trial was presented five days following the last drug pairing, in which a novel flavor was available in lieu of tap water. Immediately following the 10-min water-access period, an injection of the CS-drug was administered. Testing for evidence of second-order CTA was conducted via presentation of the flavored solution on the fifth day following treatment. statistically significant results were obtained in terms of Learned Aversion Ratios and CTA Suppression Ratios. A second experiment was conducted in an attempt to isolate the influence of the excitation procedures with other drug-pairings. Five groups of rats (n = 6 in each group) were run in which hypertonic saline was paired with LiCl, strychnine, or hypertonic saline. Combinations of saline and the US-drugs were tested with and without the excitation procedures. A no-injection group (n = 6) received exposure to the flavor stimulus followed only by the excitation procedure. Results obtained on the Learned Aversion Ratios were statistically significant and in the predicted direction. The excitation group in which saline had been paired with LiCl showed a significant aversion ratio compared to the appropriate control groups, the Saline-Saline Group and the No-Injection Group. The Saline-Strychnine Excitation Group also showed a significant Learned Aversion Ratio compared to its respective control group and to the No-Injection Excitation Group. The implications of these results for such issues as stimulus equipotentiality, avfail, and research methodology and CTA research in general may provide additional foundations for future research in this experimental area.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18060号 / 理博第3938号 / 新制||理||1567(附属図書館) / 30918 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 石田 憲二, 教授 前野 悦輝, 教授 松田 祐司 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The purpose of the present thesis is to investigate the effects of interactions in interferometers in the integer quantum Hall regime. The behaviour of electrons in condensed matter systems is mostly determined by the repulsive Coulomb interaction. However, under special circumstances the Coulomb interaction can be effectively attractive, giving rise to electron-pairing in unconventional superconductors and specifically designed mesoscopic setups. In particular, electron interactions can play a crucial role in quantum Hall systems, leading for instance to the emergence of quasi-particles with fractional charge and anyonic statistics. Quantum Hall Fabry-Pérot interferometers (FPI) have attracted increasing attention due to their ability to probe such exotic physics. In addition, such interferometers are affected by electron interactions themselves in unexpected ways. For example, experimental evidence for electron-pairing in a quantum Hall FPI was recently found. Interactions play a crucial role in quantum Hall FPI, and a deeper investigation of their effects is necessary in order to reach a better understanding of these systems. We start by analysing the magnetic field and gate voltage dependence of the longitudinal resistance in an electronic FPI, taking into account the interactions between an outer-most interfering edge mode, an inner non-interfering edge mode and the bulk. For weak bulk-edge coupling and sufficiently strong inter-edge interaction, we obtain that the interferometer operates in the Aharonov-Bohm regime with a flux periodicity halved with respect to the usual expectation, as recently observed. We do not find evidence for a connection between a reduced flux period and electron pairing, though. Then, we compute electron shot noise of an integer quantum Hall FPI in the limit of strong backscattering in the presence of a inter-edge repulsive interaction. We find that the Fano factor for strong edge-edge coupling is considerably enhanced with respect to the Fano factor of a non-interacting interferometer, indicating a significant correlation between the tunnelling of subsequent electrons. In particular, we find a two-fold enhanced Fano factor for some parameters, indicative of electron pairing as found experimentally. We interpret this result in terms of a dynamical attraction between electrons taking place in the interfering edge via the exchange of neutral inter-edge plasmons. We argue that our results for interferometers in the strong backscattering limit are related to an enhancement of shot noise observed experimentally in more open devices.

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Wireless sensor network (WSN) nodes communicate securely using pre-installed cryptographic keys. Although key pre-installation makes nodes less expensive, the technical process of installing keys prevents average users from deploying and controlling their own WSNs. Wireless pairing enables users to set up WSNs without pre-installing keys, but current pairing techniques introduce numerous concerns regarding security, hardware expense, and usability. This thesis introduces dynamic Near Field Communication (NFC) pairing, a new pairing technique designed for WSNs. This pairing overcomes the limitations of both key pre-installation and current pairing techniques. Dynamic NFC pairing is as secure as using pre-installed keys, requires only inexpensive NFC hardware, and is easy to use since the user simply holds nodes close together to add them to a network. A sample application shows the power of dynamic NFC pairing. The user adds sensors and actuators to a WSN by holding each node close to a central node or network coordinator. Data readings stream instantly from each sensor to a web page where the user may view data as well as click buttons to cause events to occur on the actuators. This happens quickly and securely without exposing the user to the complexity of cryptographic keys.