Bryophytes from Jalapão, state of Tocantins, northern Brazil

Although occupying almost half the area of Brazil, the northern region of the country remains poorly known bryologically. In an attempt to help remedy this problem, a collecting trip was made to Jalapão Desert, located in the state of Tocantins. A total of 22 taxa were found, 21 are new occurrences to the state and three are new to the northern region of Brazil. Bryum caespiticium Hedw. is listed for the second time from Brazil. A list of the taxa with references of descriptions and illustrations are provided.Embora ocupe quase metade da área do pais, a região norte do Brasil, continua sendo pouco conhecida do ponto de vista briológico. A fim de contribuir com o conhecimento sobre a brioflora da area, uma viajem de coleta foi feita a região do Jalapão, localizado no estado do Tocantins. Um total de 22 taxa foram encontrados, 21 novas ocorrências para o estado e três novas para a região norte. Bryum caespiticium Hedw. é citado pela segunda vez para o Brasil. É fornecida uma lista dos taxa com referências de descrições e ilustrações

A Fault Analytic Method against HB+

The search for lightweight authentication protocols suitable for low-cost RFID tags constitutes an active and challenging research area. In this context, a family of protocols based on the LPN problem has been proposed: the so-called HB-family. Despite the rich literature regarding the cryptanalysis of these protocols, there are no published results about the impact of fault analysis over them. The purpose of this paper is to fill this gap by presenting a fault analytic method against a prominent member of the HB-family: HB+ protocol. We demonstrate that the fault analysis model can lead to a flexible and effective attack against HB-like protocols, posing a serious threat over them

Commitment and Oblivious Transfer in the Bounded Storage Model with Errors

The bounded storage model restricts the memory of an adversary in a cryptographic protocol, rather than restricting its computational power, making information theoretically secure protocols feasible. We present the first protocols for commitment and oblivious transfer in the bounded storage model with errors, i.e., the model where the public random sources available to the two parties are not exactly the same, but instead are only required to have a small Hamming distance between themselves. Commitment and oblivious transfer protocols were known previously only for the error-free variant of the bounded storage model, which is harder to realize

On the Commitment Capacity of Unfair Noisy Channels

Noisy channels are a valuable resource from a cryptographic point of view. They can be used for exchanging secret-keys as well as realizing other cryptographic primitives such as commitment and oblivious transfer. To be really useful, noisy channels have to be consider in the scenario where a cheating party has some degree of control over the channel characteristics. Damg\r{a}rd et al. (EUROCRYPT 1999) proposed a more realistic model where such level of control is permitted to an adversary, the so called unfair noisy channels, and proved that they can be used to obtain commitment and oblivious transfer protocols. Given that noisy channels are a precious resource for cryptographic purposes, one important question is determining the optimal rate in which they can be used. The commitment capacity has already been determined for the cases of discrete memoryless channels and Gaussian channels. In this work we address the problem of determining the commitment capacity of unfair noisy channels. We compute a single-letter characterization of the commitment capacity of unfair noisy channels. In the case where an adversary has no control over the channel (the fair case) our capacity reduces to the well-known capacity of a discrete memoryless binary symmetric channel

Direct computation of asymptotic states for ratcheting prevention in elastoplasticity

This thesis summarizes three contributions to improve design accounting elastoplasticity under cyclic loads. (i) The development of a direct method to compute the asymptotic steady-state solution in ideal elastoplasticity. Validation examples show that the method is fast and accurate. The performance ranges from one to two orders of magnitude higher than incremental analysis. (ii) The performance allowed the development of a direct strategy to identify the structural ratchet-limit. The procedure applies to periodical loads and has no limitations on the number of applied loads. (iii) The upgrade of the asymptotic solution method with nonlinear kinematic hardening, which is required to model the Baushinger effect and material ratcheting. To the author knowledge, this is the first direct method for steadystate solution with this capability. Comparison with step-by-step solutions shows a increase in performance of one order of magnitude, at least.Esta tese descreve três contribuições relacioadas a estruturas elastoplasticas sob carregamento cíclico. (i) O desenvolvimento de um método direto para determinação de resposta assintótica em elastoplasticidade ideal. Exemplos de validação demonstram que o método é rápido e preciso. O incremento de desempenho registrado foi de uma a duas ordens de grandeza superior à integração incremental. (ii) O desempenho permitiu o desenvolvimento de uma estratégia direta para identificação do limite de ratcheting estrutural. O procedimento é aplicável para cargas cíclicas e não possui limitação no número de cargas aplicadas. (iii) A extensão do método de resposta assintótica contemplando encruamento não linear que é requerido para modelagem do efeito Baushinger e ratcheting material. De conhecimento do autor, este é o primeiro método direto com tal capacidade. A comparação com análise incremental demonstra um aumento de desempenho de ao menos uma ordem de grandeza

A CCA2 Secure Variant of the McEliece Cryptosystem

The McEliece public-key encryption scheme has become an interesting alternative to cryptosystems based on number-theoretical problems. Differently from RSA and ElGa- mal, McEliece PKC is not known to be broken by a quantum computer. Moreover, even tough McEliece PKC has a relatively big key size, encryption and decryption operations are rather efficient. In spite of all the recent results in coding theory based cryptosystems, to the date, there are no constructions secure against chosen ciphertext attacks in the standard model - the de facto security notion for public-key cryptosystems. In this work, we show the first construction of a McEliece based public-key cryptosystem secure against chosen ciphertext attacks in the standard model. Our construction is inspired by a recently proposed technique by Rosen and Segev

On the Oblivious Transfer Capacity of Generalized Erasure Channels against Malicious Adversaries

Noisy channels are a powerful resource for cryptography as they can be used to obtain information-theoretically secure key agreement, commitment and oblivious transfer protocols, among others. Oblivious transfer (OT) is a fundamental primitive since it is complete for secure multi-party computation, and the OT capacity characterizes how efficiently a channel can be used for obtaining string oblivious transfer. Ahlswede and Csisz\'{a}r (\emph{ISIT'07}) presented upper and lower bounds on the OT capacity of generalized erasure channels (GEC) against passive adversaries. In the case of GEC with erasure probability at least 1/2, the upper and lower bounds match and therefore the OT capacity was determined. It was later proved by Pinto et al. (\emph{IEEE Trans. Inf. Theory 57(8)}) that in this case there is also a protocol against malicious adversaries achieving the same lower bound, and hence the OT capacity is identical for passive and malicious adversaries. In the case of GEC with erasure probability smaller than 1/2, the known lower bound against passive adversaries that was established by Ahlswede and Csisz\'{a}r does not match their upper bound and it was unknown whether this OT rate could be achieved against malicious adversaries as well. In this work we show that there is a protocol against malicious adversaries achieving the same OT rate that was obtained against passive adversaries. In order to obtain our results we introduce a novel use of interactive hashing that is suitable for dealing with the case of low erasure probability ($p^* <1/2$)

Liberty and creativity in music education teachers graduation: reality or utopia? A portuguese case study

In Portugal, the curricular guidelines for Basic Music Education presuppose the development of pedagogical experiences that enhance the liberty and creativity of the students, who should be able to improvise and compose musical pieces through the combination of several musical elements, manipulating gradually more complex techniques and technologies (Ministry of Education, 2018). However, we believe that ew Music Education teachers eel confident and capable to promote such pedagogical experiences, perhaps because they are highly challenging, since they involve student's cognitive, physical-motor, and creative abilities (Heble & Laver, 2016). This communication aims to address some issues about the meaning and importance that uture Music Education teachers (finalist students o a Master's in Basic Music Education Teaching) attribute to improvisation, composition and, inherently, to liberty and creativity in musical teaching-learning processes. At the same time, we intend to find out i musical liberty and creativity in Music was present in their raduation and i they intend to work it in future Music Education contexts. Based on the intrinsic case study method (Stake, 1995), this study covers finalists o the Basic Music Education Teaching master’s degree of a Portuguese Superior School of Education (n=8). The data collection took place through the application of an individual questionnaire and a focus group interview. The results obtained indicate that, in accordance with the established by the Ministry of Music Education (2018), the future Music Education teachers attribute high value and relevance to musical improvisation and composition and, therefore, to liberty and creativity in Music Education, denoting that these same aspects could (and should) be much more present in their graduationinfo:eu-repo/semantics/acceptedVersio

Privacy-preserving scoring of tree ensembles : a novel framework for AI in healthcare

Machine Learning (ML) techniques now impact a wide variety of domains. Highly regulated industries such as healthcare and finance have stringent compliance and data governance policies around data sharing. Advances in secure multiparty computation (SMC) for privacy-preserving machine learning (PPML) can help transform these regulated industries by allowing ML computations over encrypted data with personally identifiable information (PII). Yet very little of SMC-based PPML has been put into practice so far. In this paper we present the very first framework for privacy-preserving classification of tree ensembles with application in healthcare. We first describe the underlying cryptographic protocols that enable a healthcare organization to send encrypted data securely to a ML scoring service and obtain encrypted class labels without the scoring service actually seeing that input in the clear. We then describe the deployment challenges we solved to integrate these protocols in a cloud based scalable risk-prediction platform with multiple ML models for healthcare AI. Included are system internals, and evaluations of our deployment for supporting physicians to drive better clinical outcomes in an accurate, scalable, and provably secure manner. To the best of our knowledge, this is the first such applied framework with SMC-based privacy-preserving machine learning for healthcare