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Attack intensity of Corythucha ciliata (Hemiptera, Tingidae) on Platanus spp. in an urban area in Portugal: a comparison between pruned and unpruned trees.

Gonçalves, Ana; Santos, Sónia A.P.; Pinto, M. Alice
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
26.07%
Corythucha ciliata (Say, 1832), commonly known as sycamore lace bug (SLB), is an insect species native to North America. Since its accidental introduction in Europe (through Italy) in 1964, it has expanded across most European countries. The arrival of SLB in Portugal is uncertain but its distribution is wide. Sycamore (Platanus spp.), the only host of SLB, is one of the most widespread and important urban tree species in Portugal. It provides a wide range of environmental, social and economical benefits, which have been threatened by the invasion of this pest. SLB damages trees by feeding on the underside of the leaves causing discoloration and eventually premature senescence. While the long-term effect of SLB on the health of urban trees is yet to be fully assessed, there is compelling evidence that pruning further increases SLB damage. In this study we assessed the impact of pruning on the attack intensity of SLB. To test the hypothesis that pruning promotes the invasion of SLB, we compared the intensity of attack of pruned trees with unpruned trees. We collected sycamore leaves from pruned and unpruned trees and then assessed the intensity of attack by scaling damage by visual rating. Our findings show that pruned trees exhibit significantly higher attack intensities than unpruned trees (p < 0...

The general mechanisms of attack of nitrogen nucleophiles on carbonyl compounds: facts that determine the change of the rate-pH profiles

Brighente,Inês Maria Costa; Yunes,Rosendo Augusto
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/1997 EN
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36.04%
It have been described a general mechanism for the attack step of the reactions between nitrogen nucleophiles and carbonyl compounds to form a neutral tetrahedral addition intermediate. This general mechanism is based on the relative importance of the "concerted" hydronium-ion catalyzed attack of the nitrogen base on the carbonyl compound with respect to the "step wise" mechanism that involves the previous formation of a zwitterionic tetrahedral intermediate (T±) and the posterior proton transfer to it from the hydronium-ion. The relative importance of this pathway gives origin to three kinds of profile rates vs pH for these reactions. On the other hand, the importance of the "stepwise" mechanism was attributed to a dependence on the stability of the T± intermediate that is related to the pKa of the nitrogen base and the Kad (the equilibrium constant for the formation of the neutral tetrahedral addition intermediate (T0)). The comparison of the reactions of p-chlorobenzaldehyde and norcamphor with different nitrogen nucleophiles led to the observation that the general mechanism depends on each type of carbonyl compound. This is due to the great influence of the steric and electronic effects of the compounds structure, and the fact that the pKa value of the nitrogen base...

Demographic characteristics of patients with severe life threatening asthma: comparison with asthma deaths.

Richards, G. N.; Kolbe, J.; Fenwick, J.; Rea, H. H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1993 EN
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BACKGROUND--Studies of mortality from asthma have suggested that a very severe asthma attack identifies a group at greatly increased risk of subsequent death from the disease. This study compares the demographic characteristics of asthmatic patients who required management in an intensive care unit for a severe life threatening attack between 1981 and 1987 with a group who died of asthma between 1980 and 1986. The outcome of the group admitted to an intensive care unit is described. METHODS--The groups comprised all cases aged between 15 and 49 years arising from the Auckland Area Health Board (AAHB) population who required admission to an intensive care unit for asthma between 1981 and 1987 (n = 413) and all deaths from asthma in those aged 15 to 49 years arising from the New Zealand population between 1980 and 1986 (n = 466). Details of age, sex, and information on the day and month of the attack were collected. For the group requiring admission to an intensive care unit, outcome in terms of mortality and readmission to intensive care was determined. RESULTS--The age distributions of the two groups were dissimilar, with the severe life threatening attack group having an excess of asthmatic patients under 30 years old. The distribution of events by calendar month was uniform in both groups...

Left and right heart haemodynamics during spontaneous angina pectoris. Comparison between angina with ST segment depression and angina with ST segment elevation.

Guazzi, M; Polese, A; Fiorentini, C; Magrini, F; Olivari, M T; Bartorelli, C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1975 EN
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26.04%
The function of both right and left sides of the heart was studied during spontaneous attacks of angina pectoris at rest in 7 patients showing ST depression (type I) and 4 showing ST elevation (type II) during the attack. In none of the 44 type I attacks and 29 type II attacks which were recorded did circulatory changes; the latter were different in the two groups. Type I attacks showed: a) a brief fall in arterial pressure, accompanied by b) a rise of right atrial and pulmonary wedge pressures and c) a decrease of cardiac output, right and left stroke work, the mean rate of systolic ejection, and indirect left ventricular pre-ejection dP/dt. In the course of the attack a hypertensive phase followed, which was paralleled by an increase of heart rate, cardiac output, left and right stroke work, and mean systolic ejection rate, left dP/dt; right atrial pressure and wedge pressure remained raised. All of the circulatory functions started to revert towards the pre-attack levels coincident with the waning phase of the electrocardiographic alteration, the latter occurring either spontaneously or after nitroglycerin. Type II attacks for the entire duration of the electrocardiographic changes showed: a) a reduction of arterial pressure, cardiac output...

Oral contraception and risk of a cerebral thromboembolic attack: results of a case-control study.

Lidegaard, O
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 10/04/1993 EN
Relevância na Pesquisa
26.14%
OBJECTIVE--To assess the risk of cerebral thromboembolism in women using low dose oral contraceptives. DESIGN--A retrospective case-control study. SETTING--All Danish medical, neurological, neurosurgical, and gynaecological departments. SUBJECTS--All 794 women in Denmark aged 15-44 who had suffered a cerebral thromboembolic attack during 1985-9 and 1588 age matched randomly selected controls. RESULTS--Of 692/1584 case/control questionnaires sent out, 590/1396 (85.3%/88.1%) were returned. Among the cases, 15 refused to participate, 69 had a revised or unreliable diagnosis, 40 had had thromboembolic disease previously, 13 were pregnant, and 152 had a disease predisposing to a cerebral thromboembolic attack. Of the 323 cases without a known predisposition, 320 reported use or non-use of oral contraception. Among the 1396 controls, eight refused to participate, were mentally retarded, or lived abroad; 18 returned an uncompleted questionnaire; 17 had had thromboembolic disease previously; 31 were pregnant; and 130 had a disease predisposing to a cerebral thromboembolic attack. Thus 1198 non-predisposed controls were available, among whom 1197 reported use or non-use of oral contraception. Among the 320 cases, 116 (36.3%) were oral contraceptive users at the time of the cerebral thromboembolic attack. By comparison there were 191 users (16.0%) among the 1197 controls...

Case-control study of severe life threatening asthma (SLTA) in adults: demographics, health care, and management of the acute attack

Kolbe, J; Fergusson, W; Vamos, M; Garrett, J
Fonte: BMJ Group Publicador: BMJ Group
Tipo: Artigo de Revista Científica
Publicado em /12/2000 EN
Relevância na Pesquisa
26.28%
BACKGROUND—Severe life threatening asthma (SLTA) is important in its own right and as a proxy for asthma death. In order to target hospital based intervention strategies to those most likely to benefit, risk factors for SLTA among those admitted to hospital need to be identified. A case-control study was undertaken to determine whether, in comparison with patients admitted to hospital with acute asthma, those with SLTA have different sociodemographic and clinical characteristics, evidence of inadequate ongoing medical care, barriers to health care, or deficiencies in management of the acute attack.
METHODS—Seventy seven patients with SLTA were admitted to an intensive care unit (pH 7.17 (0.15), PaCO2 10.7 (5.0) kPa) and 239 matched controls (by date of index attack) with acute asthma were admitted to general medical wards. A questionnaire was administered 24-48 hours after admission.
RESULTS—The risk of SLTA in comparison with other patients admitted with acute asthma increased with age (odds ratio (OR) 1.04/year, 95% CI 1.01 to 1.07) and was less for women (OR 0.36, 95% CI 0.20to 0.68). These variables were controlled for in all subsequent analyses. There were no differences in other sociodemographic features. Cases were more likely to have experienced a previous SLTA (OR 2.04...

DMP: Detouring Using Multiple Paths against Jamming Attack for Ubiquitous Networking System

Kim, Mihui; Chae, Kijoon
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 12/04/2010 EN
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26.07%
To successfully realize the ubiquitous network environment including home automation or industrial control systems, it is important to be able to resist a jamming attack. This has recently been considered as an extremely threatening attack because it can collapse the entire network, despite the existence of basic security protocols such as encryption and authentication. In this paper, we present a method of jamming attack tolerant routing using multiple paths based on zones. The proposed scheme divides the network into zones, and manages the candidate forward nodes of neighbor zones. After detecting an attack, detour nodes decide zones for rerouting, and detour packets destined for victim nodes through forward nodes in the decided zones. Simulation results show that our scheme increases the PDR (Packet Delivery Ratio) and decreases the delay significantly in comparison with rerouting by a general routing protocol on sensor networks, AODV (Ad hoc On Demand Distance Vector), and a conventional JAM (Jammed Area Mapping) service with one reroute.

Knowledge of Signs and Symptoms of Heart Attack and Stroke among Singapore Residents

Quah, Joy Li Juan; Yap, Susan; Cheah, Si Oon; Ng, Yih Yng; Goh, E. Shaun; Doctor, Nausheen; Leong, Benjamin Sieu-Hon; Tiah, Ling; Chia, Michael Yih Chong; Ong, Marcus Eng Hock
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.12%
Aim. To determine the level of knowledge of signs and symptoms of heart attack and stroke in Singapore resident population, in comparison to the global community. Methods. A population based, random sample of 7,840 household addresses was selected from a validated national sampling frame. Each participant was asked eight questions on signs and symptoms of heart attack and 10 questions on stroke. Results. The response rate was 65.2% with 4,192 respondents. The level of knowledge for preselected, common signs and symptoms of heart attack and stroke was 57.8% and 57.1%, respectively. The respondents scored a mean of 5.0 (SD 2.4) out of 8 for heart attack, while they scored a mean of 6.8 (SD 2.9) out of 10 for stroke. Respondents who were ≥50 years, with lower educational level, and unemployed/retired had the least knowledge about both conditions. The level of knowledge of signs and symptoms of heart attack and stroke in Singapore is comparable to USA and Canada. Conclusion. We found a comparable knowledge of stroke and heart attack signs and symptoms in the community to countries within the same economic, educational, and healthcare strata. However older persons, those with lower educational level and those who are unemployed/retired...

Single nucleotide polymorphisms of cathepsin S and the risks of asthma attack induced by acaroid mites

Li, Chaopin; Chen, Qi; Jiang, Yuxin; Liu, Zhiming
Fonte: e-Century Publishing Corporation Publicador: e-Century Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 15/01/2015 EN
Relevância na Pesquisa
26.14%
To investigate association between the three single nucleotide polymorphisms (SNPs, rs146456111, rs143154304 and rs147260142) in cathepsin S (Cat S) and the risks of allergic asthma attack induced by the acaroid mites in the Chinese population. A case-control study was performed in 412 cases and 454 volunteers/controls to evaluate the effects of three SNPs in Cat S on the risks of asthma attack. The genotypes were determined using polymerase chain reaction (PCR) and cleaved amplification polymorphism sequence-tagged sites (PCR-RFLP). The frequencies of genotypes and alleles in these SNPs in the asthmatic group were also analyzed between the two groups. The locus of rs146456111 in Cat S gene, the allele frequency of A and C in asthmatic group were significantly different from the control group (χ2 = 184.425, P = 0.000), and the difference was significant regarding the distribution of the genotypes (AA, AC, and CC) between asthmatic subjects and normal controls (χ2 = 177.915, P = 0.000). Logistic regression analysis revealed that the AC, CC, and AC + CC genotypes were significantly increased with the risk of asthma (AC vs. AA, OR = 4.013, 95% CI = 2.989-4.751, P = 0.000; CC vs. AA, OR = 3.167, 95% CI = 2.483-3.785, P = 0.000; AC + CC vs. AA...

Comparison of Methods for Estimation of Attacking Adult Populations of Dendroctonus frontalis

Linit, M. J.; Stephen, F. M.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica Formato: text/html
EN
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36%
Attacking adult populations of the southern pine beetle in loblolly pine, Pinus taeda L., were measured by using 3 estimation procedures; X-ray analysis, bark dissection to locate attacking adults, and bark dissection to locate the entry point of each attack. Comparison of mean attack density indicates the different methods to be equally reliable estimators.

Effect of juncture fillets on double-delta wings undergoing sideslip at high angles of attack

Chang, Wen-Huan
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
26.1%
A flow visualization study of the vortical flow over a baseline double-delta wing model and a diamond-fillet double-delta wing model both with sharp leading edges was conducted in the Naval Postgraduate School water tunnel using the dye-injection technique. The main focus of this study was to observe the effect of juncture fillet on the vortex core trajectory, and vortex burst location on the wing surface at high angles of attack with sideslip angles. The data reported in this thesis is believed to be the first of its kind on the effect of juncture fillets on double-delta wings undergoing sideslip at high angles of attack. The results indicate that the strake vortex burst point moves upstream with increasing angle of attack at zero sideslip angle; but at constant angle of attack the windward side strake vortex burst location moves upstream and inboard while the leeward side vortex burst point moves downstream and outboard with increasing sideslip angle. Comparison of test results between the baseline model and the diamond-fillet model indicates a clear delay for the latter model in terms of both vortex core trajectory and breakdown location at high angles of attack with and without sideslip angle. The vortex breakdown data for the diamond-fillet model implies lift augmentation during sideslip motion...

Cost-Effectiveness Comparison of Response Strategies to a Large-Scale Anthrax Attack on the Chicago Metropolitan Area: Impact of Timing and Surge Capacity

Kyriacou, Demetrios N.; Dobrez, Debra; Parada, Jorge P.; Steinberg, Justin M.; Kahn, Adam; Bennett, Charles L.; Schmitt, Brian P.
Fonte: Mary Ann Liebert, Inc. Publicador: Mary Ann Liebert, Inc.
Tipo: Artigo de Revista Científica
Publicado em /09/2012 EN
Relevância na Pesquisa
26.14%
Rapid public health response to a large-scale anthrax attack would reduce overall morbidity and mortality. However, there is uncertainty about the optimal cost-effective response strategy based on timing of intervention, public health resources, and critical care facilities. We conducted a decision analytic study to compare response strategies to a theoretical large-scale anthrax attack on the Chicago metropolitan area beginning either Day 2 or Day 5 after the attack. These strategies correspond to the policy options set forth by the Anthrax Modeling Working Group for population-wide responses to a large-scale anthrax attack: (1) postattack antibiotic prophylaxis, (2) postattack antibiotic prophylaxis and vaccination, (3) preattack vaccination with postattack antibiotic prophylaxis, and (4) preattack vaccination with postattack antibiotic prophylaxis and vaccination. Outcomes were measured in costs, lives saved, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs). We estimated that postattack antibiotic prophylaxis of all 1,390,000 anthrax-exposed people beginning on Day 2 after attack would result in 205,835 infected victims, 35,049 fulminant victims, and 28,612 deaths. Only 6,437 (18.5%) of the fulminant victims could be saved with the existing critical care facilities in the Chicago metropolitan area. Mortality would increase to 69...

Does immune activation continue during an attack-free period in familial Mediterranean fever?

MUSABAK, U; SENGUL, A; OKTENLI, C; PAY, S; YESILOVA, Z; KENAR, L; SANISOGLU, S Y; INAL, A; TUZUN, A; ERDIL, A; BAGCI, S
Fonte: Blackwell Science Inc Publicador: Blackwell Science Inc
Tipo: Artigo de Revista Científica
Publicado em /12/2004 EN
Relevância na Pesquisa
26.17%
Although some information is available regarding immune activation in familial Mediterranean fever (FMF), little is known about either peripheral blood T cell activation marker expression or the T cell proliferative response to phytohaemagglutinin (PHA). In the present study, we aimed to investigate the percentages of peripheral blood lymphocyte subsets, T cell expression of cellular activation markers (CD25, CD69, HLA-DR), the T cell response to PHA and serum levels of soluble interleukin-2 receptor (sIL-2R) and interleukin (IL)-10 in patients with FMF. Forty patients with FMF were enrolled into the study. Control groups were sex- and age-matched and consisted of 20 healthy blood donors and 15 patients with inactive Behçet's disease. The patients with FMF in an attack period had higher levels of sIL-2R than those in an attack-free period, and also in comparison with both control groups. The levels of sIL-2R were also found to be higher in patients with FMF in an attack-free period than those in both control groups. The mean levels of IL-10 were found to be lower in patients with FMF in an attack-free period than those in an attack period and were also lower than those in the healthy controls. In an acute attack period, the absolute counts of CD3+HLA-DR+...

Protection against the man-in-the-middle-attack for the Kirchhoff-loop-Johnson(-like)-noise cipher and expansion by voltage-based security

Kish, Laszlo B.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.12%
It is shown that the original Kirchhoff-loop-Johnson(-like)-noise (KLJN) cipher is naturally protected against the man-in-the-middle (MITM) attack, if the eavesdropper is using resistors and noise voltage generators just like the sender and the receiver. The eavesdropper can extract zero bit of information before she is discovered. However, when the eavesdropper is using noise current generators, though the cipher is protected, the eavesdropper may still be able to extract one bit of information while she is discovered. For enhanced security, we expand the KLJN cipher with the comparison of the instantaneous voltages via the public channel. In this way, the sender and receiver has a full control over the security of measurable physical quantities in the Kirchhoff-loop. We show that when the sender and receiver compare not only their instantaneous current data but also their instantaneous voltage data then the zero-bit security holds even for the noise current generator case. We show that the original KLJN scheme is also zero-bit protected against that type of MITM attack when the eavesdropper uses voltage noise generators, only. In conclusion, within the idealized model scheme, the man-in-the-middle-attack does not provide any advantage compared to the regular attack considered earlier. The remaining possibility is the attack by a short...

Comment on "Fault-Tolerate Quantum Private Comparison Based on GHZ States and ECC"

Ji, Sai; Wang, Fang; Liu, Wen-Jie; Liu, Chao; Wang, Hai-Bin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/05/2014
Relevância na Pesquisa
26.08%
A two-party quantum private comparison scheme using GHZ states and error-correcting code (ECC) was introduced in Li et al.'s paper [Int. J. Theor. Phys. 52: 2818-2815, 2013], which holds the capability of fault-tolerate and could be performed in a none-ideal scenario. However, this study points out there exists a fatal loophole under a special attack, namely the twice-Hadamard-CNOT attack. A malicious party may intercept the other's particles, ?rstly executes the Hadamard operations on these intercepted particles and his (her) own ones respectively, and then sequentially performs twice CNOT operations on them and the auxiliary particles prepared in advance. As a result, the secret input will be revealed without being detected through measuring the auxiliary particles. For resisting this special attack, an improvement is proposed by applying a permutation operator before TP sends the particle sequences to all the participants.; Comment: 8 pages, 1 figure

Comparative Resilience Notions and Vertex Attack Tolerance of Scale-Free Networks

Matta, John; Borwey, Jeffrey; Ercal, Gunes
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 31/03/2014
Relevância na Pesquisa
26.18%
We are concerned with an appropriate mathematical measure of resilience in the face of targeted node attacks for arbitrary degree networks, and subsequently comparing the resilience of different scale-free network models with the proposed measure. We strongly motivate our resilience measure termed \emph{vertex attack tolerance} (VAT), which is denoted mathematically as $\tau(G) = \min_{S \subset V} \frac{|S|}{|V-S-C_{max}(V-S)|+1}$, where $C_{max}(V-S)$ is the largest connected component in $V-S$. We attempt a thorough comparison of VAT with several existing resilience notions: conductance, vertex expansion, integrity, toughness, tenacity and scattering number. Our comparisons indicate that for artbitrary degree distributions VAT is the only measure that fully captures both the major \emph{bottlenecks} of a network and the resulting \emph{component size distribution} upon targeted node attacks (both captured in a manner proportional to the size of the attack set). For the case of $d$-regular graphs, we prove that $\tau(G) \le d\Phi(G)$, where $\Phi(G)$ is the conductance of the graph $G$. Conductance and expansion are well-studied measures of robustness and bottlenecks in the case of regular graphs but fail to capture resilience in the case of highly heterogeneous degree graphs. Regarding comparison of different scale-free graph models...

Efficient Detection of Sybil Attack Based on Cryptography in Vanet

Rahbari, Mina; Jamali, Mohammad Ali Jabreil
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/12/2011
Relevância na Pesquisa
26.12%
Vehicular communications play a substantial role in providing safety transportation by means of safety message exchange. Researchers have proposed several solutions for securing safety messages. Protocols based on a fixed key infrastructure are more efficient in implementation and maintain stronger security in comparison with dynamic structures. The purpose of this paper present a method based on a fixed key infrastructure for detection impersonation attack, in other words, Sybil attack, in the vehicular ad hoc network. This attack, puts a great impact on performance of the network. The proposed method, using an cryptography mechanism to detection Sybil attack. Finally, using Mat lab simulator the results of this approach are reviewed, This method it has low delay for detection Sybil attack, because most operations are done in Certification Authority, so this proposed schema is a efficient method for detection Sybil attack.

Same Initial States Attack in Yang et al.'s Quantum Private Comparison Protocol and the Improvement

Liu, Wen-Jie; Liu, Chao; Liu, Zhi-Hao; Liu, Jing-Fa; Geng, Huan-Tong
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/12/2013
Relevância na Pesquisa
26.19%
In Yang et al.'s literatures (J. Phys. A: Math. 42, 055305, 2009; J. Phys. A:Math. 43, 209801, 2010), a quantum private comparison protocol based on Bell states and hash function is proposed, which aims to securely compare the equality of two participants' information with the help of a dishonest third party (TP). However, this study will point out their protocol cannot resist a special kind of attack, TP's same initial states attack, which is presented in this paper. That is, the dishonest TP can disturb the comparison result without being detected through preparing the same initial states. Finally, a simple improvement is given to avoid the attack.; Comment: 7pages,1 figure

Cryptanalysis of the efficient two-party quantum private comparison protocol with decoy photons and two-photon entanglement

Sun, Zhiwei; Long, Dongyang
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/04/2012
Relevância na Pesquisa
26.05%
We analyze the security of the efficient two-party quantum private comparison protocol with decoy photons and two-photon entanglement. It is shown that the compromised third party (TP) can obtain the final comparison result without introducing any detectable errors in the standard semi-honest model. The attack strategy is discussed in detail and an improvement of this protocol is demonstrated. The idea of our attack might be instructive for the cryptanalysis of quantum cryptographic schemes.; Comment: 5 pages

Genetic algorithms in cryptography; GAs in cryptography

Delman, Bethany
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado Formato: 539124 bytes; 1220359 bytes; 1220123 bytes; 1003907 bytes; 19284 bytes; 537 bytes; 539 bytes; 1727 bytes; 19168 bytes; 19630 bytes; 19149 bytes; 21868 bytes; 21147 bytes; 23856 bytes; 31031 bytes; 6479 bytes; 6943 bytes; 20517 bytes; 5083 bytes; 6691 byte
EN_US
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Genetic algorithms (GAs) are a class of optimization algorithms. GAs attempt to solve problems through modeling a simplified version of genetic processes. There are many problems for which a GA approach is useful. It is, however, undetermined if cryptanalysis is such a problem. Therefore, this work explores the use of GAs in cryptography. Both traditional cryptanalysis and GA-based methods are implemented in software. The results are then compared using the metrics of elapsed time and percentage of successful decryptions. A determination is made for each cipher under consideration as to the validity of the GA-based approaches found in the literature. In general, these GA-based approaches are typical of the field. Of the genetic algorithm attacks found in the literature, totaling twelve, seven were re-implemented. Of these seven, only three achieved any success. The successful attacks were those on the transposition and permutation ciphers by Matthews [20], Clark [4], and Gr¨undlingh and Van Vuuren [13], respectively. These attacks were further investigated in an attempt to improve or extend their success. Unfortunately, this attempt was unsuccessful, as was the attempt to apply the Clark [4] attack to the monoalphabetic substitution cipher and achieve the same or indeed any level of success. Overall...