Página 1 dos resultados de 41 itens digitais encontrados em 0.000 segundos

‣ Reforço da privacidade através do controlo da pegada digital

Macedo, Ricardo Joaquim Pereira de
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em //2013 Português
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Dissertação de mestrado em Engenharia Informática; Atualmente existe ainda uma relação assimétrica entre os utilizadores e os fornecedores de serviços disponibilizados pela internet. É prática comum, aquando da apresentação de um serviço, que o utilizador seja questionado sobre a aceitação, ou não, de um conjunto de políticas referentes ao uso de informação privada facultada ao fornecedor (por exemplo, a morada, o número de telefone, preferências, etc...). Geralmente os utilizadores aceitam a política com base na confiança que têm no fornecedor e/ou no contrato formal que lhes é apresentado. Os casos de violação de privacidade por parte de alguns fornecedores de serviços, vendendo ou facultando informação privada sobre os seus clientes a outros, são amplamente conhecidos e resultam em grande medida da falta de controlo que os utilizadores finais têm sobre a informação que entregam aos fornecedores. Este problema também tem grande impacto no ambiente empresarial. Quase toda a informação de uma organização é guardada em claro. Mesmo que esta seja guardada num local seguro, aqueles que conhecerem bem o sistema poderão ter indevidamente acesso a informação privada da organização. Além disto...

‣ Generation of cDNA expression libraries enriched for in-frame sequences

Davis, Claytus A.; Benzer, Seymour
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 18/03/1997 Português
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Bacterial cDNA expression libraries are made to reproduce protein sequences present in the mRNA source tissue. However, there is no control over which frame of the cDNA is translated, because translation of the cDNA must be initiated on vector sequence. In a library of nondirectionally cloned cDNAs, only some 8% of the protein sequences produced are expected to be correct. Directional cloning can increase this by a factor of two, but it does not solve the frame problem. We have therefore developed and tested a library construction methodology using a novel vector, pKE-1, with which translation in the correct reading frame confers kanamycin resistance on the host. Following kanamycin selection, the cDNA libraries contained 60–80% open, in-frame clones. These, compared with unselected libraries, showed a 10-fold increase in the number of matches between the cDNA-encoded proteins made by the bacteria and database protein sequences. cDNA sequencing programs will benefit from the enrichment for correct coding sequences, and screening methods requiring protein expression will benefit from the enrichment for authentic translation products.

‣ Arylamidase of Neisseria catarrhalis

Behal, Francis J.; Cox, Sidney T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1968 Português
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Neisseria catarrhalis produces arylamidase intracellularly and is one of the gram-negative bacteria producing exceptionally large amounts of this enzyme.In general, gram-positive bacteria do not produce this enzyme. Arylamidase from N. catarrhalis was purified by salt fractionation, chromatography, and density gradient ultracentrifugation. Its sedimentation coefficient was 6.6; l-alanine-β-naphthylamide (βNA) was the most rapidly hydrolyzed amino acid-βNA. The enzyme had pKe values of 6.1 and 8.7 and pKes values of 7.1 and 7.9; only those amino acid-βNA compounds of the l configuration were susceptible to hydrolysis. Arylamidase catalyzed stepwise hydrolysis of dipeptide-βNA, beginning with the N-terminal residue. Substrates having amino acid residues with larger R groups, such as leucine, interacted much more effectively with enzyme. The significance of the predominate occurrence of arylamidase activity in gram-negative bacteria and the role of this enzyme in the physiology of these organisms remain unclear. It has been established, however, that arylamidase is distinct from leucine aminopeptidase.

‣ Aspartate carbamoyltransferase from rat liver

Bresnick, E.; Mossé, Helena
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1966 Português
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1. Aspartate-carbamoyltransferase activity was concentrated from rat-liver preparations. Only l-aspartate, β-benzyl-l-aspartate and β-erythro-hydroxy-dl-aspartate were carbamoylated enzymically. The Km for l-aspartate and carbamoyl phosphate have been determined by three methods: colorimetric procedure, radioactive assay with [14C]aspartate and an assay with [14C]carbamoyl phosphate. 2. The Km for aspartate has been determined as a function of the pH; the pK of the functional group at the active site of the enzyme, pKe, was at pH9·0. Enzymic activity was diminished in the presence of N-ethylmaleimide, p-hydroxymercuribenzoate and the heavy metals Ag+, Hg2+, or Zn2+. The inhibitions could be prevented by mercaptoethanol. These findings suggested the association of a thiol group with the enzymic activity. 3. Enzymic activity was also decreased by sodium lauryl sulphate, urea and dioxan. Competitive inhibition (with l-aspartate) was manifested by maleate, succinate, oxaloacetate, β-erythro-hydroxy-dl-aspartate and β-benzyl-l-aspartate. The Ki for most of these inhibitions has been determined. 4. The properties of the liver enzyme are compared with those of Escherichia coli aspartate carbamoyltransferase and the implications of the findings are discussed.

‣ Multicenter dizygotic twin cohort study confirms two linkage susceptibility loci for body mass index at 3q29 and 7q36 and identifies three further potential novel loci

Kettunen, J; Perola, M; Martin, NG; Cornes, BK; Wilson, SG; Montgomery, GW; Benyamin, B; Harris, JR; Boomsma, D; Willemsen, G; Hottenga, J-J; Slagboom, PE; Christensen, K; Kyvik, KO; Sørensen, TIA; Pedersen, NL; Magnusson, PKE; Andrew, T; Spector, TD; Wi
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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‣ Effects of Enzyme Treated Palm Kernel Expeller on Metabolizable Energy, Growth Performance, Villus Height and Digesta Viscosity in Broiler Chickens

Saenphoom, P.; Liang, J. B.; Ho, Y. W.; Loh, T. C.; Rosfarizan, M.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /04/2013 Português
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This study examined whether pre-treating palm kernel expeller (PKE) with exogenous enzyme would degrade its fiber content; thus improving its metabolizable energy (ME), growth performance, villus height and digesta viscosity in broiler chickens fed diets containing PKE. Our results showed that enzyme treatment decreased (p<0.05) hemicellulose and cellulose contents of PKE by 26.26 and 32.62%, respectively; and improved true ME (TME) and its nitrogen corrected value (TMEn) by 38% and 33%, respectively, compared to the raw sample. Average daily gain (ADG), feed intake and feed conversion ratio (FCR) of chickens fed on different dietary treatments in the grower period were not significantly different. Although there was no difference in feed intake (p>0.05) among treatment groups in the finisher period, ADG of chickens in the control (PKE-free diet) was higher (p<0.05) than in all treatment groups fed either 20 or 30% PKE, irrespective of with or without enzyme treatment. However, ADG of birds fed with 20% PKE was higher than those fed with 30% PKE. The FCR of chickens in the control was the lowest (2.20) but not significantly different from those fed 20% PKE diets while birds in the 30% PKE diets recorded higher (p>0.05) FCR. The intestinal villus height and crypt depth (duodenum...

‣ Standardized Total Tract Digestibility of Phosphorus in Copra Expellers, Palm Kernel Expellers, and Cassava Root Fed to Growing Pigs

Son, A. R.; Shin, S. Y.; Kim, B. G.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /11/2013 Português
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An experiment was conducted to determine the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of phosphorus (P) in copra expellers (CE), palm kernel expellers (PKE), and cassava root (CR). Eight barrows (initial BW of 40.0 kg, SD = 4.5) were individually housed in metabolism crates. A replicated 4×3 incomplete Latin square design was employed involving 4 dietary treatments, 3 periods, and 8 animals. Three experimental diets contained 40% CE, PKE or CR as the only source of P. A P-free diet mainly based on corn starch, sucrose, and gelatin was also prepared to estimate the basal endogenous loss of P. The marker-to-marker method was used for fecal collection. Values for the ATTD of P in the CE and PKE were greater than in the CR (46.0 and 39.7 vs −14.0%; p<0.05). However, the STTD of P did not differ greatly among the test ingredients (56.5, 49.0, and 43.2% in the CE, PKE, and CR, respectively). In conclusion, the ATTD of P values in CE and PKE were greater than that in CR, but the STTD of P did not differ greatly among CE, PKE, and CR.

‣ Effect of modified hold-relax stretching and static stretching on hamstring muscle flexibility

Ahmed, Hashim; Iqbal, Amir; Anwer, Shahnawaz; Alghadir, Ahmad
Fonte: The Society of Physical Therapy Science Publicador: The Society of Physical Therapy Science
Tipo: Artigo de Revista Científica
Português
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[Purpose] The aim of present study was to compare the effectiveness of modified hold-relax stretching and static stretching in improving the hamstring muscle flexibility. [Subjects and Methods] Forty-five male subjects with hamstring tightness were included in this study. The subjects were randomly placed into three groups: the modified hold-relax stretching, static stretching and control groups. The modified hold-relax stretching group performed 7 seconds of isometric contraction and then relaxed for 5 seconds, and this was repeated five times daily for five consecutive days. The static stretching group received 10 minutes of static stretching with the help of a pulley and weight system for five consecutive days. The control group received only moist heat for 20 minutes for five consecutive days. A baseline reading of passive knee extension (PKE) was taken prior to the intervention; rest measurements were taken immediate post intervention on day 1, day 3, day 5, and after a 1 week follow-up, i.e., at the 12th day. [Results] On comparing the baseline readings of passive knee extension (PKE), there was no difference noted between the three groups. On comparing the posttest readings on day 5 between the 3 groups, a significant difference was noted. However...

‣ Effects of Supplemental Beta-mannanase on Digestible Energy and Metabolizable Energy Contents of Copra Expellers and Palm Kernel Expellers Fed to Pigs

Kwon, W. B.; Kim, B. G.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /07/2015 Português
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The purpose of this study was to determine the effect of β-mannanase supplementation on digestible energy (DE) and metabolizable energy (ME) contents of copra expellers (CE) and palm kernel expellers (PKE) fed to pigs. Six barrows with an initial body weight of 38.0 kg (standard deviation = 1.5) were randomly allotted to a 6×6 Latin square design with 6 dietary treatments and 6 periods. Six experimental diets were prepared in a 3×2 factorial treatment arrangement with 3 diets of a corn-soybean meal-based diet, a CE 30% diet, and a PKE 30% diet and with 2 concentrations of supplemental β-mannanase at 0 or 2,400 U/kg. All diets had the same proportion of corn:soybean meal ratio at 2.88:1. The marker-to-marker procedure was used for fecal and urine collection with 4-d adaptation and 5-d collection periods. No interactive effects were observed between diet and β-mannanase on energy digestibility and DE and ME contents of experimental diets. However, diets containing CE or PKE had less (p<0.05) DE and ME contents compared with the corn-soybean meal-based diet. The DE and ME contents in CE and PKE were not affected by supplemental β-mannanase. Taken together, we failed to find the effect of β-mannanase supplementation on energy utilization in CE and PKE fed to pigs.

‣ Effects of Palm Kernel Expellers on Growth Performance, Nutrient Digestibility, and Blood Profiles of Weaned Pigs

Seo, J.; Kim, W.; Kim, J.; Kim, J. K.; Kim, S. C.; Jang, Y.; Jang, K.; Kim, K.; Kim, B.; Park, S.; Park, I.; Kim, M. K.; Seo, K. S.; Kim, H. B.; Kim, I. H.; Seo, S.; Song, M.
Fonte: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST) Publicador: Asian-Australasian Association of Animal Production Societies (AAAP) and Korean Society of Animal Science and Technology (KSAST)
Tipo: Artigo de Revista Científica
Publicado em /07/2015 Português
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This experiment was conducted to investigate the effects of palm kernel expellers on growth performance, nutrient digestibility, and blood profiles of weaned pigs. A total of 88 weaned pigs (6.94±0.76 kg body weight [BW]; 28 d old) were randomly allotted to 2 dietary treatments (4 pigs/pen; 11 replicates/treatment) in a randomized complete block design (sex as a block). The dietary treatments were a typical nursery diet based on corn and soybean meal (CON) and CON added with 20% of palm kernel expellers (PKE). Pigs were fed for 6 wk using a 3-phase feeding program with declining diet complexity and with phases of 1, 2, and 3 wk, respectively. Blood was collected from randomly selected 2 pigs in each pen before weaning and on d 7 after weaning. Pigs were fed respective dietary treatments containing 0.2% chromic oxide from d 29 to 35 after weaning. Fecal samples were collected from randomly selected 2 pigs in each pen daily for the last 3 days after the 4-d adjustment period. Measurements were growth performances, digestibility of dry matter, nitrogen and energy, white and red blood cell counts, packed cell volume, and incidence of diarrhea. The PKE increased average daily gain (ADG) (246 vs 215 g/d; p = 0.06) and average daily feed intake (ADFI) (470 vs 343 g/d; p<0.05) and decreased gain-to-feed ratio (G:F) (0.522 vs 0.628 g/g; p<0.05) during phase 2 compared with CON...

‣ The effect of warm-up, static stretching and dynamic stretching on hamstring flexibility in previously injured subjects

O'Sullivan, Kieran; Murray, Elaine; Sainsbury, David
Fonte: BioMed Central Ltd Publicador: BioMed Central Ltd
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
Português
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peer-reviewed; Background: Warm-up and stretching are suggested to increase hamstring flexibility and reduce the risk of injury. This study examined the short-term effects of warm-up, static stretching and dynamic stretching on hamstring flexibility in individuals with previous hamstring injury and uninjured controls. Methods: A randomised crossover study design, over 2 separate days. Hamstring flexibility was assessed using passive knee extension range of motion (PKE ROM). 18 previously injured individuals and 18 uninjured controls participated. On both days, four measurements of PKE ROM were recorded: (1) at baseline; (2) after warm-up; (3) after stretch (static or dynamic) and (4) after a 15-minute rest. Participants carried out both static and dynamic stretches, but on different days. Data were analysed using Anova. Results: Across both groups, there was a significant main effect for time (p < 0.001). PKE ROM significantly increased with warm-up (p < 0.001). From warm-up, PKE ROM further increased with static stretching (p = 0.04) but significantly decreased after dynamic stretching (p = 0.013). The increased flexibility after warm-up and static stretching reduced significantly (p < 0.001) after 15 minutes of rest, but remained significantly greater than at baseline (p < 0.001). Between groups...

‣ "Proposta de esquemas de criptografia e de assinatura sob modelo de criptografia de chave pública sem certificado" ; "Proposal for encryption and signature schemes under certificateless public key cryptography model"

Goya, Denise Hideko
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/06/2006 Português
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Sob o modelo de criptografia de chave pública baseada em identidades (ID-PKC), a própria identidade dos usuários é usada como chave pública, de modo a dispensar a necessidade de uma infra-estrutura de chaves públicas (ICP), na qual o gerenciamento de certificados digitais é complexo. Por outro lado, sistemas nesse modelo requerem uma entidade capaz de gerar chaves secretas. Essa entidade é conhecida por PKG (Private Key Generator); ela possui uma chave-mestra e mantém custódia das chaves secretas geradas a partir dessa chave-mestra. Naturalmente, a custódia de chaves é indesejável em muitas aplicações. O conceito de Criptografia de Chave Pública sem Certificado, ou Certificateless Public Key Cryptography (CL-PKC), foi proposto para que a custódia de chaves fosse eliminada, mantendo, porém, as características de interesse: a não necessidade de uma ICP e a eliminação de certificados digitais. CL-PKC deixa de ser um sistema baseado em identidades, pois é introduzida uma chave pública, gerada a partir de uma informação secreta do usuário. Nesta dissertação, apresentamos a construção de dois esquemas, um CL-PKE e um CL-PKS, baseados em emparelhamentos bilineares sobre curvas elípticas. Ambas propostas: (1) eliminam custódia de chaves; (2) dispensam certificados digitais; (3) são mais eficientes...

‣ Paired kidney exchange transplantation: Maximizing the donor pool

Jha, P. K.; Sethi, S.; Bansal, S. B.; Jain, M.; Sharma, R.; Phanish, M. K.; Duggal, R.; Ahlawat, R.; Kher, V.
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
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In the last decade, paired kidney exchange (PKE) transplantation has gained popularity worldwide as a viable alternative for end stage renal disease (ESRD) patients who have incompatible or sensitized donors. This study presents our experience with PKE transplantation and compares outcome between PKE and non-PKE renal transplant recipients. Between February 2010 and November 2013, 742 transplants were performed, of which 26 (3.5%) were PKE transplantations. All were two-way exchanges. PKE recipients were significantly older than non-PKE (46.73 ± 9.71 vs. 40.08 ± 13.36 years; P = 0.012) while donor ages were comparable. PKE patients had significantly higher number of HLA mismatches (5.03 ± 1.14 vs. 3.49 ± 1.57; P < 0.0001). After a median follow-up of 20 months (range: 3–47 months), there was no significant difference in patient survival (PKE 96.16% vs. non-PKE 96.65%; P = 0.596) and death censored graft survival (PKE 96.16% vs. non-PKE 96.37%; P = 1). Mean serum creatinine at 1 month and at last follow-up was lower in PKE versus non-PKE group (0.98 ± 0.33 vs. 1.3 ± 0.61 mg/dl; P = 0.008 and 0.96 ± 0.30 vs. 1.27 ± 0.57 mg/dl, P = 0.006, respectively). Biopsy proven acute rejection rate was 11.5% in PKE group and 16.89% in non-PKE patients (P = 0.6). To conclude...

‣ Quantum public-key cryptosystems based on induced trapdoor one-way transformations

Yang, Li; Liang, Min; Li, Bao; Hu, Lei; Feng, Deng-Guo
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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A concept named induced trapdoor one-way quantum transformation (OWQT) has been introduced, and a theoretical framework of public-key encryption (PKE) of quantum message is presented based on it. Then several kinds of quantum public-key encryption (QPKE) protocols, such as quantum version PKE of RSA, ElGamal, Goldwasser-Micali, elliptic curve, McEliece, Niederreiter and Okamoto-Tanaka-Uchiyama, are given within this framework. Though all of these protocols are only computationally secure, the last three are probably secure in post-quantum era. Besides, theoretical frameworks for public-key authentication and signature of quantum message are also given based on the induced trapdoor OWQT. As examples, a public-key authentication protocol of quantum message based on SN-S authentication scheme and two quantum digital signature protocols based on RSA and McEliece algorithms respectively are presented.; Comment: 26 pages, 1 figures

‣ Tilted loop currents in cuprate superconductors

Yakovenko, Victor M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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The paper briefly surveys theoretical models for the polar Kerr effect (PKE) and time-reversal symmetry breaking in the pseudogap phase of cuprate superconductors. By elimination, the most promising candidate is the tilted loop-current model, obtained from the Simon-Varma model by tilting one triangular loop up and another one down toward the apical oxygens. The model is consistent with the PKE, spin-polarized neutron scattering, and optical anisotropy measurements. Spontaneous currents in this model flow between the in-plane and apical oxygens in such a manner that each oxygen belongs to one current loop. This loop-current pattern is similar to the spin order in the magnetoelectric antiferromagnet Cr2O3, where the PKE is observed experimentally. By analogy, it should be possible to train the PKE sign in the cuprates magnetoelectrically. Several experiments are proposed to confirm the loop-current order: the magnetic-field-induced polarity, the nonlinear anomalous Hall effect, and the second-harmonic generation.; Comment: 8 pages, 8 figures, submitted to Physica B, proceedings of ECRYS-2014 conference; v.2 references added and updated

‣ Evidence for broken time-reversal symmetry in the superconducting phase of URu$_2$Si$_2$

Schemm, E. R.; Baumbach, R. E.; Tobash, P. H.; Ronning, F.; Bauer, E. D.; Kapitulnik, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Recent experimental and theoretical interest in the superconducting phase of the heavy fermion material URu$_2$Si$_2$ has led to a number of proposals in which the superconducting order parameter breaks time-reversal symmetry (TRS). In this study we measured polar Kerr effect (PKE) as a function of temperature for several high-quality single crystals of URu$_2$Si$_2$. We find an onset of PKE below the superconducting transition that is consistent with a TRS-breaking order parameter. This effect appears to be independent of an additional, possibly extrinsic, PKE generated above the hidden order transition at $T_{HO}=17.5$ K, and contains structure below $T_c$ suggestive of additional physics within the superconducting state.; Comment: 5 pages, 5 figures

‣ An Efficient CCA2-Secure Variant of the McEliece Cryptosystem in the Standard Model

Rastaghi, Roohallah
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Recently, a few chosen-ciphertext secure (CCA2-secure) variants of the McEliece public-key encryption (PKE) scheme in the standard model were introduced. All the proposed schemes are based on encryption repetition paradigm and use general transformation from CPA-secure scheme to a CCA2-secure one. Therefore, the resulting encryption scheme needs \textit{separate} encryption and has \textit{large} key size compared to the original scheme, which complex public key size problem in the code-based PKE schemes. Thus, the proposed schemes are not sufficiently efficient to be used in practice. In this work, we propose an efficient CCA2-secure variant of the McEliece PKE scheme in the standard model. The main novelty is that, unlike previous approaches, our approach is a generic conversion and can be applied to \textit{any} one-way trapdoor function (OW-TDF), the lowest-level security notion in the context of public-key cryptography, resolving a big fundamental and central problem that has remained unsolved in the past two decades.; Comment: Submited. arXiv admin note: text overlap with arXiv:1205.5224 by other authors

‣ Intrinsic and extrinsic origins of the polar Kerr effect in a chiral p-wave superconductor

Goryo, Jun
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Recently, the measurement of the polar Kerr effect (PKE) in the quasi two-dimensional superconductor Sr2RuO4, which is motivated to observe the chirality of px + i py-wave pairing, has been reported. We clarify that the PKE has intrinsic and extrinsic (disorder-induced) origins. The extrinsic contribution would be dominant in the PKE experiment.; Comment: 7 pages, to be published in Mod. Phys. Lett. B

‣ URDP: General Framework for Direct CCA2 Security from any Lattice-Based PKE Scheme

Rastaghi, Roohallah
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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Design efficient lattice-based cryptosystem secure against adaptive chosen ciphertext attack (IND-CCA2) is a challenge problem. To the date, full CCA2-security of all proposed lattice-based PKE schemes achieved by using a generic transformations such as either strongly unforgeable one-time signature schemes (SU-OT-SS), or a message authentication code (MAC) and weak form of commitment. The drawback of these schemes is that encryption requires "separate encryption". Therefore, the resulting encryption scheme is not sufficiently efficient to be used in practice and it is inappropriate for many applications such as small ubiquitous computing devices with limited resources such as smart cards, active RFID tags, wireless sensor networks and other embedded devices. In this work, for the first time, we introduce an efficient universal random data padding (URDP) scheme, and show how it can be used to construct a "direct" CCA2-secure encryption scheme from "any" worst-case hardness problems in (ideal) lattice in the standard model, resolving a problem that has remained open till date. This novel approach is a "black-box" construction and leads to the elimination of separate encryption, as it avoids using general transformation from CPA-secure scheme to a CCA2-secure one. IND-CCA2 security of this scheme can be tightly reduced in the standard model to the assumption that the underlying primitive is an one-way trapdoor function.; Comment: arXiv admin note: text overlap with arXiv:1302.0347...

‣ Quantum McEliece public-key encryption scheme

Yang, Li; Liang, Min
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/01/2015 Português
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This paper investigates a quantum version of McEliece public-key encryption (PKE) scheme, and analyzes its security. As is well known, the security of classical McEliece PKE is not stronger than the onewayness of related classical one-way function. We prove the security of quantum McEliece PKE ranks between them. Moreover, we propose the double-encryption technique to improve its security, and the security of the improved scheme is proved to be between the original scheme and the quantum one-time pad.; Comment: 18pages, no figures