Dieser Vortrag gibt eine kleine Uebersicht ueber die Einsatzmoeglichkeiten von Linux im Netz - sowohl als Client als auch als Server.

Purpose: Due to the current climate crisis and the fact that the food industry accounts for a third of all greenhouse gas emissions, it is more important than ever that green initiatives in the food industry flourish. In recent years new food sources (NFS) have emerged as a consequence of trying to shift the world's consumption behaviours and making the food industry more sustainable. However, NFS companies are generally small companies with scarce resources and difficulties in expanding. Thus, the purpose of this report is to investigate which capabilities are necessary in order to succeed with a sustainable expansion within the New Food Sources industry, and to develop a framework that puts the capabilities in relation to different stages of sustainable expansion.  Method: In order to investigate these main areas, a multiple case study in the NFS sector has been conducted where several companies have been interviewed to enable the identification of success factors that enable a sustainable expansion. A total of 21 interviews were held with the case companies, people from the traditional source companies (e.g., traditional dairy corporations), and people with expertise within the field of NFS were interviewed. The interviews were later on analyzed through a thematic method.  Findings: The study resulted in identifying five stages of sustainability work that acts as drivers for sustainable expansion. Further, eight categories of capabilities were identified in order to reach the driver for sustainable expansion. The capabilities were then ranked in a gradual manner, from fundamental to gaining competitive advantage. Lastly, the five stages of sustainable expansion were linked to the capabilities, providing a roadmap for what capabilities that are necessary in each stage in order to proceed with a sustainable expansion.  Theoretical and managerial contributions: This study provides a sustainable perspective on expansions within NFS companies, meaning that the focus is not only economic growth but also how the company contributes to the society as a whole and how it affects the world. Furthermore, these insights have resulted in a roadmap that can be applied by managers in NFS- producing companies to get a better understanding of what capabilities that are essential in each stage of sustainability work. This will help managers in NFS companies to navigate through expansions and will help them understand what to focus on.

An understanding of Input/Output data access patterns of applications is useful in several situations. First, gaining an insight into what applications are doing with their data at a semantic level helps in designing efficient storage systems. Second, it helps to create benchmarks that mimic realistic application behavior closely. Third, it enables autonomic systems as the information obtained can be used to adapt the system in a closed loop. All these use cases require the ability to extract the application-level semantics of I/O operations. Methods such as modifying application code to associate I/O operations with semantic tags are intrusive. It is well known that network file system traces are an important source of information that can be obtained non-intrusively and analyzed either online or offline. These traces are a sequence of primitive file system operations and their parameters. Simple counting, statistical analysis or deterministic search techniques are inadequate for discovering application-level semantics in the general case, because of the inherent variation and noise in realistic traces. In this paper, we describe a trace analysis methodology based on Profile Hidden Markov Models. We show that the methodology has powerful discriminatory capabilities that enables it to recognize applications based on the patterns in the traces, and to mark out regions in a long trace that encapsulate sets of primitive operations that represent higher-level application actions. It is robust enough that it can work around discrepancies between training and target traces such as in length and interleaving with other operations. We demonstrate the feasibility of recognizing patterns based on a small sampling of the trace, enabling faster trace analysis. Preliminary experiments show that the method is capable of learning accurate profile models on live traces in an online setting. We present a detailed evaluation of this methodology in a UNIX environment using NFS traces of selected commonly used applications such as compilations as well as on industrial strength benchmarks such as TPC-C and Postmark, and discuss its capabilities and limitations in the context of the use cases mentioned above.

Large sparse matrices arise in many applications, especially in the major problems of Cryptography of factoring integers and computing discrete logarithms. We focus attention on such matrices called sieve matrices generated after the sieving stage of the algorithms for integer factoring. We need to solve large sparse system of equations Bx = 0, with sieve matrices B arising in this context. The traditional Gaussian elimination, with a cubic run time, is not efficient for handling such matrices. Better algorithms for such input matrices are the quadratic runtime algorithms based on Block Lanczos(BL) or Wiedemann techniques. Of these two, BL is even better for large integer factoring algorithms. We carry out an efficient implementation of the Block Lanczos algorithm for finding the vectors in the null space of the the sieve matrix. We report our test results using our implementation for matrices of sizes up to 106. We plan to use this implementation in our ongoing projects on factoring the large RSA challenge integers of sizes 640 bits(called RSA-640) and beyond. So it is useful to exploit possible parallelism. We propose a scheme for parallelizing certain steps of the Block Lanczos method, taking advantage of structural properties of the sieve matrix. The sizes of matrices arising in integer factoring context are quite large. Hence we also discuss some techniques that are used to reduce the size of the sieve matrix. We also consider the last stage of the NFS Algorithm for finding square roots of large algebraic numbers and outline a sketch of our algorithm.

Virtualization is a technique that allows several virtual machines (VMs) to run on a single physical machine (PM) by adding a virtualization layer above the physical host's hardware. Many virtualization products allow a VM be migrated from one PM to other PM without interrupting the services running on the VM. This is called live migration and offers many potential advantages like server consolidation, reduced energy consumption, disaster recovery, reliability, and efficient workflows such as "Follow-the-Sun''. At present, the advantages of VM live migration are limited to Local Area Networks (LANs) as migrations over Wide Area Networks (WAN) offer lower performance due to IP address changes in the migrating VMs and also due to large network latency. For scenarios which require migrations, shared storage solutions like iSCSI (block storage) and NFS (file storage) are used to store the VM's disk to avoid the high latencies associated with disk state migration when private storage is used. When using iSCSI or NFS, all the disk I/O operations generated by the VM are encapsulated and carried to the shared storage over the IP network. The underlying latency in WAN will effect the performance of application requesting the disk I/O from the VM. In this thesis our objective was to determine the performance of shared and private storage when VMs are live migrated in networks with high latency, with WANs as the typical case. To achieve this objective, we used Iometer, a disk benchmarking tool, to investigate the I/O performance of iSCSI and NFS when used as shared storage for live migrating Xen VMs over emulated WANs. In addition, we have configured the Distributed Replicated Block Device (DRBD) system to provide private storage for our VMs through incremental disk replication. Then, we have studied the I/O performance of the private storage solution in the context of live disk migration and compared it to the performance of shared storage based on iSCSI and NFS. The results from our testbed indicate that the DRBD-based solution should be preferred over the considered shared storage solutions because DRBD consumed less network bandwidth and has a lower maximum I/O response time.

Vortragsfolge Prof. Uwe Huebner: Metacomputing - neue Aufgabenverteilung im Netz Dr. Wolfgang Riedel: Was nuetzt uns SGML Sven Graupner: What's up in Operating System Research Sven Koehler: IP Security (nach RFC 1825) Holger Trapp: Kryptographisch gesicherte Kommunikation und Datenhaltung Dr. Joerg Anders: ATM-Eine kritische Betrachtung Guenther Fischer: Cacheserver-Hierarchien Frank Richter: Ein neuer WWW-Server fuer www.tu-chemnitz.de Steffen Brose: Web-Zugang zu DQS Jens Kraizci, Volker Holfeld: Wie weiter mit dem CSN? Jan Wunderlich: Harvest Michael Hasenstein: Datenbank-Klienten auf Java-Basis Andreas Koehler: Form-based File Upload in HTML Gerd Heide: BROADWAY - Interaktivitaet im WWW mittels X-Protokoll Matthias Ehrig: NFS 2 - Moeglichkeiten und Grenzen Ronald Koehler: NFS 3 Christoph Ziegler: HSM - Was verbirgt sich dahinter? Kai Zscheile: Hardware-Loesungen fuer HSM Matthias Clauss: Vergleich und Bewertung von HSM-Loesungen Thomas Mueller: Fileserving an der TUCZ Karsten Baensch: AFS-Loesung fuer die Softwareumgebung der Parsytec-Maschinen Joern Wohlrab: Alternative verteilte Filesysteme Jens Junghaenel: Integration von PC's mittels Samba Merten Schumann: Archivierung elektronisch publizierter Dokumente Michael Tautenhahn: Fast Ethernet Jens Wagner: Firmenadressverwaltung am URZ Dr . Wolfgang Riedel: Neues aus der TeX-Welt (METAPOST, lyx) Carsten Mund: Untersuchung von Einflussfaktoren auf SPEC CINT- und CFP-Benchmarks

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Compte tenu du récent taux alarmant d'épuisement des réserves de combustibles fossiles et de l'augmentation drastique des niveaux de CO2 dans l'atmosphère qui a conduit au réchauffement de la planète et à des changements climatiques sévères, l'exploitation de toutes sortes d'énergies renouvelables a été la Parmi les principales priorités de la recherche Champs à travers le monde. L'une des nombreuses voies de ce genre est la réduction du CO2 aux combustibles utilisant des énergies renouvelables, plus communément appelées cellules photoélectro-catalytiques (PEC). Des essais expérimentaux sur la réduction du CO2 ont été réalisés sur différents types de catalyseurs dans les deux cellules (Conçu par un laboratoire) afin de comprendre la sélectivité, la productivité et les produits de réaction obtenus. Des essais expérimentaux ont été réalisés sur différents types de catalyseurs à la fois dans les cellules en phase gazeuse et en phase liquide pour comprendre la sélectivité, la productivité et les produits de réaction obtenus. Pour les études sur la réduction EC du CO2 en phase gazeuse, une série d'électrodes (à base de nanoparticules (NPs) de Cu, Fe, Pt et CuFe déposées sur des nanotubes de carbone ou de noir de carbone puis placées à l'interface entre une membrane Nafion et Une électrode à couche de diffusion de gaz). Les résultats démontrent le type divers de produits formés et leurs productivités. Dans des conditions sans électrolyte, la formation de produits ≥C1 tels que l'éthanol, l'acétone et l'isopropanol a été observée la plus élevée étant pour Fe et suivie de près par Pt. Pour améliorer Combustibles nets, un ensemble différent d'électrodes a été préparé sur la base de revêtements MOF de type imidazolate de type zéolitique substitué (SIM-1) (Fe-CNT, Pt-CNT et CuFe-CNT basés sur MOF) Et Pt-MOF a montré des carburants améliorés. En se reportant aux études sur la réduction EC du CO2 dans une cellule en phase liquide, un ensemble similaire d'électrodes a été prepare (NP - Cu, Fe, Pt, Ru, Co déposées sur des nanotubes de carbone ou du noir de carbone ont). Pour les conditions de phase liquide, en termes de produits C nets, les électrodes catalytiques à base de Pt sont en tête de la catégorie, suivies de près par Ru et Cu, tandis que Fe a obtenu la position la plus basse. Le mécanisme réactionnel sous-jacent probable a également été fourni. Afin d'améliorer encore les performances, on a synthétisé des NP de metal (Ru, Fe, Pt et Cu) de différentes tailles en utilisant différentes techniques de synthèse: (i) l'itinéraire d'imprégnation (ImR) pour obtenir des NP dans la plage de tailles de 10 à 50 nm; (Ii) Approche organométallique (OM) pour synthétiser des NPs uniformes et ultrafines dans la plage de tailles de 1-5 nm. Fe ont été synthétisés par une nouvelle voie de synthèse et des conditions pour atteindre des NP de 1 à 3 nm. (Iii) Approche de haut en bas de Nanowire pour obtenir des NP de cuivre ultrafin dans la plage de taille de 2-3,8 nm. Les améliorations apportées à la productivité du carburant se sont révélées être de 5 à 30 fois plus élevées pour les petites NP sur les NP plus importantes et, en outre, une charge réduite de 10 à 1-2% en poids. Un autre ensemble d'électrodes à base de nano-mousses (Cu NF et Fe NF sur Feuille de Cu, Feuille de Foie, Al Foil, Inconel foil et Al grid / mesh) préparés par électrodéposition ont également été étudiés afin d'améliorer encore la conversion de CO2 / carburant. Après, l'optimisation du dépôt et de la tension à l'aide de la voltamétrie cyclique, les carburants se sont améliorés de 2 à 10 fois par rapport aux combustibles nets les plus élevés obtenus à l'aide d'électrodes CNT dopées à base de NP / In view of the recent alarming rate of depletion of fossil fuel reserves and the drastic rise in the CO2 levels in the atmosphere leading to global warming and severe climate changes, tapping into all kinds of renewable energy sources has been among the top priorities in the research fields across the globe. One of the many such pathways is CO2 reduction to fuels using renewable energies, more commonly referred as photo-electro-catalytic (PEC) cells. Experimental tests were carried out on various types of catalysts in both the gas and liquid phase cells (lab-designed) to understand the different selectivity, productivity and the reaction products obtained. For the studies on the EC reduction of CO2 in gas phase cell, a series of electrodes (based on Cu, Fe, Pt and Cu/Fe metal nanoparticles – NPs - deposited on carbon nanotubes – CNTs - or carbon black and then placed at the interface between a Nafion membrane and a gas-diffusion-layer) were prepared. Under gas phase, the formation of ≥C1 products (such as ethanol, acetone and isopropanol) were observed, the highest being for Fe and closely followed by Pt, evidencing that also non-noble metals can be used as efficient catalysts under these conditions. To enhance the net fuels, a different set of electrodes were also prepared based on substituted Zeolitic Imidazolate (SIM-1) type MOF coatings (MOF-based Fe-CNTs, Pt-CNTs and Cu/Fe-CNTs) and Pt-MOF showed improved fuels. Moving to the studies on the EC reduction of CO2 in liquid phase cell, a similar set of electrodes were prepared (metal NPs of Cu, Fe, Pt, Ru and Co deposited on CNTs or carbon black). For liquid phase conditions, in terms of net C-products, catalytic electrodes based on Pt topped the class, closely followed by Ru and Cu, while Fe got the lowest position. The probable underlying reaction mechanism was also provided. In order to improve further the performances, varied sized metal NPs (Ru, Fe, Pt and Cu) have been synthesized using different techniques: (i) impregnation (ImR) route to achieve NPs in the size range of 10-50 nm; (ii) organometallic (OM) approach to synthesize uniform and ultrafine NPs in the size range of 1-5 nm (i.e., Fe NPs were synthesized through a novel synthesis route to attain 1-3 nm NPs); (iii) Nanowire (NW) top-down approach to obtain ultrafine copper metal NPs in the size range of 2-3.8 nm. The enhancements in the fuel productivity were found to be 5-30 times higher for the smaller metal NPs over the larger metal NPs and moreover, with reduced metal loading from 10 to 1-2 wt %. A different set of electrodes based on nano-foams (Cu NF and Fe NF on Cu foil, Fe foil, Al foil, Inconel foil and Al grid/mesh) prepared via electro-deposition were also investigated, to further improve CO2 to fuels conversion. After, optimization of deposition and voltage using cyclic voltammetry, the fuels improved by 2-10 times over the highest net fuels achieved using metal NPs doped CNT electrodes

Πολλά κρυπτογραφικά σχήματα δημόσιου κλειδιού βασίζονται στο γεγονός ότι είναι υπολογιστικά δύσκολο να παραγοντοποιήσουμε μεγάλους ακέραιους αριθμούς. Ο ταχύτερος, και ταυτόχρονα πολυπλοκότερος, κλασσικός αλγόριθμος που είναι γνωστός μέχρι σήμερα για την παραγοντοποίηση ακεραίων μήκους άνω των 110 δεκαδικών ψηφίων είναι ο General Number Field Sieve (GNFS). Ο αλγόριθμος αυτός είναι ο καρπός πολλών ετών έρευνας, κατά τη διάρκεια της οποίας παράγονταν ολοένα και ταχύτεροι αλγόριθμοι για να καταλήξουμε μέχρι στιγμής στον αλγόριθμο GNFS. Πρωταρχικός σκοπός της παρούσης μεταπτυχιακής εργασίας είναι η παρουσίαση του θεωρητικού μαθηματικού υπόβαθρου πάνω στο οποίο βασίζεται ο GNFS καθώς και η ακολουθιακή υλοποίηση της βασικής εκδοχής του αλγορίθμου. Ως γλώσσα υλοποίησης επιλέχθηκε η C++. Η υλοποίηση έγινε σε συνεργασία με τον συμφοιτητή μου και αγαπητό φίλο Χρήστο Μπακογιάννη, όπου στα πλαίσια της μεταπτυχιακής του εργασίας πραγματοποιήθηκε η μεταφορά της ακολουθιακής υλοποίησης του αλγορίθμου σε παράλληλο κατανεμημένο περιβάλλον χρησιμοποιώντας το Message Passing Interface (MPI). Ο πηγαίος κώδικας της υλοποίησης καθώς και σχετικές πληροφορίες υπάρχουν online στη σελίδα http://kmgnfs.cti.gr. Σημειώνεται πως για την ευκολότερη και απρόσκοπτη ανάγνωση της εργασίας αυτής, ο αναγνώστης θα πρέπει να έχει ένα βαθμό εξοικείωσης με βασικές έννοιες της θεωρίας αριθμών, της αλγεβρικής θεωρίας αριθμών και της γραμμικής άλγεβρας. / Many public-key cryptosystems build their security on our inability to factor very large integers. The General Number Field Sieve (GNFS) is the most efficient, and at the same time most complex, classical known algorithm for factoring integers larger than 110 digits. This algorithm is the result of many years of research, during which, faster and faster algorithms were developed finally winding up to the development of the GNFS. The main purpose of this master thesis is the presentation of the mathematical ideas, on which the GNFS was developed, as well as a sequential implementation of the basic version of the algorithm. C++ was the language of choice. The implementation took place in collaboration with my colleague and dear friend Christos Bakogiannis, where as part of his master thesis, a distributed implementation of the algorithm using Message Passing Interface (MPI) was also developed. The source code of the implementations is publicly available and can be found online at http://kmgnfs.cti.gr. It is presumed that the reader is familiar with basic concepts of number theory, algebraic number theory and linear algebra.

This paper follows up the factorization of integers. Factorization is the most popular and used method for RSA cryptoanalysis. The SIQS was chosen as a factorization method that will be used in this paper. Although SIQS is the fastest method (up to 100 digits), it can't be effectively computed at polynomial time, so it's needed to look up for options, how to speed up the method as much as possible. One of the possible ways is paralelization. In this case OpenMP was used. Other possible way is optimalization. The goal of this paper is also to show, how easily is possible to use paralelizion and thanks to detailed analyzation the source codes one can reach relatively large speed up. Used method of iterative optimalization showed itself as a very effective tool. Using this method the implementation of SIQS achieved almost 100 multiplied speed up and at some parts of the code even more.