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Rigorously analyzed algorithms for the discrete logarithm problem in quadratic number fieldsVollmer, Ulrich. January 1900 (has links) (PDF)
Darmstadt, Techn. University, Diss., 2003.
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Public key cryptography theory and practice /Möller, Bodo. January 2003 (has links) (PDF)
Darmstadt, Techn. University, Diss., 2003.
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Scalable symmetric block ciphers based on group basesČanda, Valér. January 2001 (has links) (PDF)
Essen, University, Diss., 2001.
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New public-key cryptosystems with fast decryptionTakagi, Tsuyoshi. January 2001 (has links) (PDF)
Darmstadt, Techn. University, Diss., 2001.
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Polly two - a public key cryptosystem based on Polly crackerLe, Van-Ly. January 2003 (has links) (PDF)
Bochum, University, Diss., 2003.
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Contributions to provable security and efficient cryptographySchmidt-Samoa, Katja. Unknown Date (has links)
Techn. University, Diss., 2006--Darmstadt.
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Key Account Management process : En jämförande studie av stora och små företagMahdi, Rafal, Nilsson, Sofia January 2015 (has links)
Titel: Key Account Management process Nivå: C-uppsats inom ämnet företagsekonomi Författare: Rafal Mahdi & Sofia Nilsson Handledare: Akmal Hyder & Zahra Ahmadi Syfte: Syftet med denna studie är att jämföra hur en KAM-process kan skilja sig mellan stora och små företag inom B2B marknad. Datum: 2015-06-03 Metod: Studien bygger på en abduktiv ansats. Vi utför en multipelfallstudie med en kvalitativ forskningsdesign. Kvalitativa semi-strukturerade intervjuer genomförs och utformas med hjälp av en operationalisering som grundar sig i den vetenskapliga teorin. Intervjuerna har spelats in och noga transkriberats för att sedan lyfta fram den mest väsentliga informationen de bidrog till, i förhållande till studiens syfte. Informationen har analyserats och diskuterats för att därefter presentera en slutsats som besvarar studiens frågeställningar och syfte. Resultat & Slutsats: Studien visar att den presenterade KAM processen tillämpas av samtliga fallföretag i studien. Vi fann dock att det förekommer märkbara skillnader i hur fallföretagen arbetar för att identifiera och analysera nyckelkunder, uppnå engagemang, förtroende och tillfredställelse till sina nyckelkunder i den presenterade KAM processen. Förslag till vidare forskning: Vidare forskning kan göras utifrån de begränsningar som vi fann i denna studie. Den första begränsningen är antalet företag som deltog i studien och därmed kan vidare forskning utföra en liknande studie med fler fallföretag. Den andra begräsningen är att endast en teoretisk modell av KAM processen studeras i denna studie. Vidare forskning kan därmed utföra en studie där fler modeller av KAM processen jämförs. I vår KAM process har vi använt ett begränsat antal faktorer, denna begränsning skulle kunna överträffas genom att inkludera fler faktorer som är viktiga för att tillämpa och förstå KAM processen. Uppsatsens bidrag: Studien visar om samma KAM process kan tillämpas i både stora och små företag samt vilka eventuella skillnader som kan uppstå däremellan.
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Failure analysis of ultra-high molecular weight polyethyelene acetabular cupsBurger, N.D.L (Nicolaas Daniel Lombard) 14 December 2006 (has links)
Owing to the crippling nature of arthritis, surgeons have been trying for well over a century to successfully treat this debilitating disease particularly when attacking the hip joint. In the early 1970s, Sir John Charnley started with total hip replacement as a solution to this ever-increasing problem. Many different designs were developed but all the designs revolved around a femoral stem, femoral head and acetabular component. Independent of the design, longevity of the implant remains a problem. The major cause of replacements, according to various hip registers, is due to aseptic loosening resulting from osteolysis. According to these registers, the average in-vivo life of a hip replacement is approximately 12 years. The main aim of this study was to determine the root cause of mechanical failure of the acetabular cups and to determine the origin of the excessive amount of ultra-high molecular weight polyethylene (UHMWPE) wear debris floating in the joint resulting in osteolysis. During the study, various techniques were used to investigate the acetabular components to try to establish the root cause of mechanical failure. These techniques included: 1. Visual inspection 2. Investigation making use of dye penetrant spray 3. Investigation under stereo microscope 4. Investigation making use of a scanning electron microscope 5. Electrophoresis 6. Mass-spectrometric analysis 7. Analysis of the synovial fluid on high-frequency linear-oscillation machine (SRV). The wear debris retrieved from the scar tissue surrounding the joints of a number of patients was also analysed. Apart from the obvious defects such as mechanical damage due to impingement, the main defect on which this study focuses is the wear patches found on the inside of the acetabular components. The wear areas were presented as areas where the surface layer of the UHMWPE was ripped off by adhering to the rotating femoral head. This type of failure is possible if localised overheating takes place resulting in the material either adhering to the rotating femoral head or the material being squeezed out under the prevailing pressure. Both these mechanisms were confirmed by the wear debris retrieved from the scar tissue, being either droplets of UHMWPE or whisker-like wear products. To confirm the existence of elevated temperatures the brown discolouring on the inside of the acetabular cups was analysed, making use of electrophoresis, mass-spectrometric analysis and scanning electron microscope recordings. In this part of the study, it was confirmed that localised temperatures on the bearing surface had reached at least 60°C during in-vivo service. This temperature was confirmed by inserting a thermocouple just under the surface of an acetabular cup and then measuring the temperature while in-vitro testing was taking place on a hip simulator. The wear debris as retrieved was also duplicated in laboratory experiments while the temperature on the surface of an acetabular cup was monitored. It was established that wear particles similar in shape and size were formed at temperatures in excess of 90°C. At temperatures above 50°C the UHMWPE had visually shown extensive increase in creep, indicating that at these temperatures the material softens sufficiently for this type of debris to be generated The overheating as described can also only occur if there is a lack of lubrication in the bearing couple. The synovial fluid from 12 patients was retrieved during revision surgery. This synovial fluid was then tested on a high-frequency linear-oscillation machine (Optimol SRV test machine) to determine the lubricity characteristics of the synovial fluid as retrieved. It was discovered that the load-carrying capability of the synovial fluid did not comply with the minimum requirements for a fluid to function as a lubricant. The final conclusion of this study is that excessive amounts of wear debris are generated due to the localised overheating of the bearing couple as a result of insufficient lubrication. The localised heat build-up results in excessive amounts of wear debris being generated and deposited in the joint area resulting in osteolysis. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2005. / Mechanical and Aeronautical Engineering / unrestricted
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RESEARCH OF SECURITY HARDWARE IN PKI SYSTEMWenhua, Qi, Qishan, Zhang, Hailong, Liu 10 1900 (has links)
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Security hardware based on asymmetric algorithm is the key component of Public Key Infrastructure (PKI), which decides the safety and performance of system. Security device in server or client have some common functions. We designed the client token and cryptographic server to improve the performance of PKI, and got obvious effect.
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Key establishment --- security models, protocols and usageUstaoglu, Berkant January 2008 (has links)
Key establishment is the process whereby two or more parties derive a shared
secret, typically used for subsequent confidential communication. However,
identifying the exact security requirements for key establishment protocols is
a non-trivial task. This thesis compares, extends and merges existing security
definitions and models for key establishment protocols.
The primary focus is on two-party key agreement schemes in the public-key
setting. On one hand new protocols are proposed and analyzed in the existing
Canetti-Krawzcyk model. On the other hand the thesis develops a security model
and novel definition that capture the essential security attributes of the
standardized Unified Model key agreement protocol. These analyses lead to the
development of a new security model and related definitions that combine and
extend the Canetti-Krawzcyk pre- and post- specified peer models in terms of
provided security assurances.
The thesis also provides a complete analysis of a one-pass key establishment
scheme. There are security goals that no one-pass key establishment scheme can
achieve, and hence the two-pass security models and definitions need to be
adapted for one-pass protocols. The analysis provided here includes
the description of the required modification to the underlying security model.
Finally, a complete security argument meeting these altered conditions is
presented as evidence supporting the security of the one-pass scheme.
Lastly, validation and reusing short lived key pairs are related to
efficiency, which is a major objective in practice. The thesis considers the
formal implication of omitting validation steps and reusing short lived key
pairs. The conclusions reached support the generally accepted cryptographic
conventions that incoming messages should not be blindly trusted and extra
care should be taken when key pairs are reused.
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