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

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

Melhora na qualidade do sono em pacientes com rinossinusite crônica submetidos à cirurgia endoscópica nasal : uma revisão sistemática com meta-análise

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Medicina, Programa de Pós-Graduação em Ciências Médicas, 2017.Introdução: A rinossinusite crônica pode acarretar má qualidade do sono nos indivíduos acometidos. A cirurgia endoscópica nasal tem sido indicada para pacientes com rinossinusite crônica, resultando em melhora da qualidade de vida, mas ainda é desconhecido se há uma melhora similar na qualidade do sono após o procedimento cirúrgico. Objetivo: Avaliar qualidade do sono de pacientes com rinossinusite crônica após submetidos à cirurgia endoscópica nasal. Métodos: A busca na literatura foi realizada em bases de dados indexadas, Medline (via PubMed), Embase, Lilacs, SciELO, Google Scholar, Web of Science, Scopus, Cochrane Library, CAPES, Clinical Trials e na literatura cinzenta. Foram incluídos estudos que informassem a qualidade do sono dos pacientes com rinossinusite crônica após a cirurgia endoscópica nasal por meio de questionários de qualidade de vida, como o SNOT-20 (SinoNasal Outcome Test-20) e SNOT-22 (Sino-Nasal Outcome Test-22). A seleção dos estudos e a extração dos dados foram realizadas por dois pesquisadores de modo independente. A metaanálise foi realizada por meio do pacote estatístico STATA, versão 11. Resultados: Ao total, 4 estudos e 509 indivíduos foram incluídos na revisão sistemática. A melhora da qualidade do sono foi observada em 90% dos pacientes. Houve melhora em média de 57 a 67% em cada um dos cinco sintomas relacionados à qualidade do sono. Esses resultados da meta-análise apresentaram alta heterogeneidade. Conclusão: Esta revisão mostra que uma grande porcentagem de pessoas relata melhora na qualidade do sono após cirurgia endoscópica nasal.Introduction: Chronic rhinosinusitis can lead to poor sleep quality in affected individuals. Endoscopic nasal surgery has been indicated for patients with chronic rhinosinusitis, resulting in improved quality of life, but it is still unknown if there is a similar improvement in sleep quality after the surgical procedure. Study Objectives: To evaluate the sleep quality of patients with chronic rhinosinusitis after undergoing endoscopic sinus surgery. Methods: The literature search was conducted in the indexed databases Medline (via PubMed), Embase, Lilacs, SciELO, Google Scholar, Web of Science, Scopus, CAPES, Cochrane Library, Clinical Trials and in the grey literature. It included studies that reported the sleep quality of patients with chronic rhinosinusitis after undergoing endoscopic sinus surgery based on questionnaires assessing quality of life, such as the SNOT-20 (Sino-Nasal Outcome Test-20) and SNOT-22 (Sino-Nasal Outcome Test-22). Two researchers independently conducted the study selection and data extraction. The meta-analysis was performed using the statistical package STATA, version 11. Results: Overall, 4 studies and 509 subjects were included in the systematic review. Improved sleep quality was observed in 90% of the patients. There was an improvement ,on average, from 57% to 67% in each of the five symptoms related to sleep quality. The results of the meta-analysis presented high heterogeneity. Conclusions: This review shows that a large percentage of people report improved sleep quality after endoscopic sinus surgery

"The Time of the Most Polar Bears": A Co-management Conflict in Nunavut

Since the 1990s, Inuit traditional knowledge (Inuit Qaujimajatuqangit) has taken on a substantial role in polar bear management in the Canadian territory of Nunavut through its direct use in quota-setting procedures. A co-management conflict has arisen from an increase of hunting quotas in January 2005 for Inuit living in the Baffin Bay and Western Hudson Bay polar bear population areas. The quotas were based on Inuit observations and their conclusion that these polar bear populations had increased. Scientific information suggests that climate change has concentrated polar bears in areas where humans are more likely to encounter them, but that the populations are in decline as a result of overhunting and climate-change effects on demographic rates. During consultations with wildlife managers and through other interviews in 2005, Inuit indicated their lack of support for quota reductions. Discussions with Inuit reveal two categories of problems that, though couched in the polar bear management issue, involve the co-management system and the integration of Inuit and scientific knowledge more generally. The first relates to direct observations of the environment by both Inuit and scientists and the synthesis of such information. The second relates to Inuit conceptualizations of human-animal relationships and the incorporation of scientific studies and management into that relationship. These problems reveal that differences between Inuit Qaujimajatuqangit and scientific knowledge are not fully understood and accounted for within the co-management system and that the system does not effectively integrate Inuit cultural views into management.Depuis les années 1990, les connaissances traditionnelles des Inuits (Inuit Qaujimajatuqangit) jouent un grand rôle dans la gestion des ours polaires du territoire canadien du Nunavut et ce, grâce au recours direct aux quotas. Un conflit de co-gestion s’est déclaré en raison de l’augmentation des quotas de chasse en janvier 2005 chez les Inuits vivant dans les régions peuplées d’ours polaires de la baie de Baffin et de l’ouest de la baie d’Hudson. Les quotas avaient été établis en fonction des observations faites par les Inuits et de leur conclusion selon laquelle les populations d’ours polaires étaient à la hausse. Pour leur part, les données scientifiques laissent entendre que le changement climatique a fait en sorte que les ours polaires se concentrent dans des régions où les humains sont plus susceptibles de les rencontrer, mais que les populations connaissent une diminution en raison de la chasse abusive et des effets du changement climatique sur les taux démographiques. Dans le cadre de consultations avec des gestionnaires de la faune et d’entrevues réalisées en 2005, les Inuits ont mentionné qu’ils n’appuyaient pas la réduction des quotas. D’après les discussions entretenues avec les Inuits, les problèmes font partie de deux catégories même si celles-ci relèvent toutes deux de l’enjeu de la gestion des ours polaires, soit le système de co-gestion, ainsi que l’intégration des connaissances des Inuits et des connaissances scientifiques de manière plus générale. Le premier problème a trait aux observations directes de l’environnement réalisées tant par les Inuits que par les scientifiques, ainsi qu’à la synthèse de cette information. Le deuxième problème se rapporte aux conceptualisations des Inuits en matière de relations entre les humains et les animaux ainsi qu’à l’intégration des études scientifiques et de la gestion à cette relation. Ces problèmes révèlent que les différences entre les connaissances inuites (Qaujimajatuqangit) et les connaissances scientifiques ne sont pas entièrement comprises et considérées dans le cadre du système de co-gestion, et que le système n’intègre pas efficacement les points de vue culturels des Inuits à la gestion

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

Two Great Black-backed Gulls, Larus marinus, Kill Male Longtailed Duck, Clangula hyemalis

At Presqu’ile Point, Presqu’ile Provincial Park, Ontario on 23 March 2003, while interpreting the waterfowl migration for park visitors, we witnessed two adult Great Black-backed Gulls attack and kill a male Long-tailed Duck

A Survey on Design and Implementation of Protected Searchable Data in the Cloud

While cloud computing has exploded in popularity in recent years thanks to the potential efficiency and cost savings of outsourcing the storage and management of data and applications, a number of vulnerabilities that led to multiple attacks have deterred many potential users. As a result, experts in the field argued that new mechanisms are needed in order to create trusted and secure cloud services. Such mechanisms would eradicate the suspicion of users towards cloud computing by providing the necessary security guarantees. Searchable Encryption is among the most promising solutions - one that has the potential to help offer truly secure and privacy-preserving cloud services. We start this paper by surveying the most important searchable encryption schemes and their relevance to cloud computing. In light of this analysis we demonstrate the inefficiencies of the existing schemes and expand our analysis by discussing certain confidentiality and privacy issues. Further, we examine how to integrate such a scheme with a popular cloud platform. Finally, we have chosen - based on the findings of our analysis - an existing scheme and implemented it to review its practical maturity for deployment in real systems. The survey of the field, together with the analysis and with the extensive experimental results provides a comprehensive review of the theoretical and practical aspects of searchable encryption

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 ($p^* <1/2$)