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During the previous decades, the upcoming demand for security in the digital world, e.g., the Internet, lead to numerous groundbreaking research topics in the field of cryptography. This thesis focuses on the design and analysis of cryptographic primitives and schemes to be used for authentication of data and communication endpoints, i.e., users. It is structured into three parts, where we present the first freely scalable multi-block-length block-cipher-based compression function (Counter-bDM) in the first part. The presented design is accompanied by a thorough security analysis regarding its preimage and collision security. The second and major part is devoted to password hashing. It is motivated by the large amount of leaked password during the last years and our discovery of side-channel attacks on scrypt – the first modern password scrambler that allowed to parameterize the amount of memory required to compute a password hash. After summarizing which properties we expect from a modern password scrambler, we (1) describe a cache-timing attack on scrypt based on its password-dependent memory-access pattern and (2) outline an additional attack vector – garbage-collector attacks – that exploits optimization which may disregard to overwrite the internally used memory. Based on our observations, we introduce Catena – the first memory-demanding password-scrambling framework that allows a password-independent memory-access pattern for resistance to the aforementioned attacks. Catena was submitted to the Password Hashing Competition (PHC) and, after two years of rigorous analysis, ended up as a finalist gaining special recognition for its agile framework approach and side-channel resistance. We provide six instances of Catena suitable for a variety of applications. We close the second part of this thesis with an overview of modern password scramblers regarding their functional, security, and general properties; supported by a brief analysis of their resistance to garbage-collector attacks. The third part of this thesis is dedicated to the integrity (authenticity of data) of nonce-based authenticated encryption schemes (NAE). We introduce the so-called j-IV-Collision Attack, allowing to obtain an upper bound for an adversary that is provided with a first successful forgery and tries to efficiently compute j additional forgeries for a particular NAE scheme (in short: reforgeability). Additionally, we introduce the corresponding security notion j-INT-CTXT and provide a comparative analysis (regarding j-INT-CTXT security) of the third-round submission to the CAESAR competition and the four classical and widely used NAE schemes CWC, CCM, EAX, and GCM.
One of the frequently examined design principles recommendations in multimedia learning is the personalization principle. Based on empirical evidence this principle states that using personalised messages in multimedia learning is more beneficial than using formal language (e.g. using ‘you’ instead of ‘the’). Although there is evidence that these slight changes in regard to the language style affect learning, motivation and the perceived cognitive load, it remains unclear, (1) whether the positive effects of personalised language can be transferred to all kinds of content of learning materials (e.g. specific potentially aversive health issues) and (2) which are the underlying processes (e.g. attention allocation) of the personalization effect. German university students (N= 37) learned symptoms and causes of cerebral haemorrhages either with a formal or a personalised version of the learning material. Analysis revealed comparable results to the few existing previous studies, indicating an inverted personalization effect for potentially aversive learning material. This effect was specifically revealed in regard to decreased average fixation duration and the number of fixations exclusively on the images in the personalised compared to the formal version. This result can be seen as indicators for an inverted effect of personalization on the level of visual attention.
Die Idee eines neuen Munizipalismus wird in den linken sozialen Bewegungen Europas und darüber hinaus breit diskutiert. Munizipalistische Bewegungen streben es an, kommunale Regierungen zu übernehmen oder zu beeinflussen, um lokale Institutionen (wieder) gemeinwohlorientiert auszurichten, ein neues Verhältnis zwischen kommunalen Regierungen und sozialen Bewegungen zu schaffen und so die Art wie Politik gestaltet wird von unten her zu demokratisieren und institutionelle Rahmenbedingungen zu verändern. Sie entstehen in Reaktion auf die aktuelle ökonomische und politische Krise – ebenso wie neue rechte und rechtspopulistische Bewegungen, als deren Gegenpart sie sich verstehen. Mit Mut und konkreten Utopien will man der multiplen städtischen Krise begegnen, statt mit Angst und Angstmacherei wie rechte Bewegungen. Deshalb trafen sich im Juni 2017 über 600 Vertreter_innen dieser munizipalistischen Bewegungen auf Einladung Barcelona en Comús.
Das rezensierte Buch stellt die zweite Publikation von Jörg Friedrich und seinem Team zum Thema Architektur und Flüchtlinge dar. Darin werden vor allem Entwurfsvorschläge für eine hybride Stadt vorgestellt, für die eine multifunktionale Nutzung von Raum als Grundidee vorgeschlagen wird. Zudem diskutieren konzeptionelle Beiträge des Bandes, wie nach der ‚Willkommenskultur’ im Jahr 2015 eine längerfristige Perspektive für Integration eingenommen werden kann. Der Band fordert ein größeres Engagement der Architektur und einen interdisziplinären Diskurs ein, der sich der vielfältigen Aufgaben der Flüchtlingsintegration annimmt.
Dieser Artikel analysiert, in welcher Weise sich die Weltkunstausstellung documenta 14 mit dem öffentlichen Raum in Kassel auseinandersetzte. Als Kritik an globalen Unrechtszuständen konzipiert, ging die diesjährige Documenta nicht auf die lokalen Umstände in Kassel ein und benutzte die Stadt stattdessen als Bühne. Statt sich mit den konkreten Prozessen vor Ort auseinanderzusetzen, wie die Ausstellung dies in Athen getan hat, wird die Tradition der Documenta gebrochen, einen Beitrag zur gesellschaftlichen Stadtentwicklung leisten zu wollen.
The building sector is responsible for a large share of human environmental impacts. Architects and planners are the key players for reducing the environmental impacts of buildings, as they define them to a large extent. Life Cycle Assessment (LCA) allows for the holistic environmental analysis of a building. However, it is currently not employed to improve the environmental performance of buildings during the design process, although the potential for optimization is greatest there. One main reason is the lack of an adequate means of applying LCA in the architectural design process. As such, the main objective of this thesis is to develop a method for environmental building design optimization that is applicable in the design process. The key concept proposed in this thesis is to combine LCA with parametric design, because it proved to have a high potential for design optimization.
The research approach includes the analysis of the characteristics of LCA for buildings and the architectural design stages to identify the research gap, the establishment of a requirement catalogue, the development of a method based on a digital, parametric model, and an evaluation of the method.
An analysis of currently available approaches for LCA of buildings indicates that they are either holistic but very complex or simple but not holistic. Furthermore, none of them provide the opportunity for optimization in the architectural design process, which is the main research gap. The requirements derived from the analysis have been summarized in the form of a catalogue. This catalogue can be used to evaluate both existing approaches and potential methods developed in the future. In this thesis, it served as guideline for the development of the parametric method – Parametric Life Cycle Assessment (PLCA). The unique main feature of PLCA is that embodied and operational environmental impact are calculated together. In combination with the self-contained workflow of the method, this provides the basis for holistic, time-efficient environmental design optimization. The application of PLCA to three examples indicated that all established mandatory requirements are met. In all cases, environmental impact could be significantly reduced. In comparison to conventional approaches, PLCA was shown to be much more time-efficient.
PLCA allows architects to focus on their main task of designing the building, and finally makes LCA practically useful as one of several criteria for design optimization. With PLCA, the building design can be time-efficiently optimized from the beginning of the most influential early design stages, which has not been possible until now. PLCA provides a good starting point for further research. In the future, it could be extended by integrating the social and economic aspects of sustainability.
Hochschulwege 2015
(2017)
Die in diesem Tagungsband zusammengeführten Beiträge beschäftigen sich mit dem Spannungsfeld, das sich zwischen externen Förderprogrammen, Veränderungsprojekten und den Zielen, Strukturen und Bedingungen der jeweiligen Hochschule ergibt. In diesem Spannungsfeld kommt es unweigerlich zu Reibungen, da vorhandene Strukturen und Ziele in Konflikt mit neuen Vorhaben und Ideen geraten. Ein Teil der Projekte stellt allein durch ihr finanzielles Volumen und die daraus resultierende Wirkkraft die tradierten Verhältnisse zwischen Lehre, Forschung und den wissenschaftsstützenden Bereichen in Frage und teils auf den Kopf. Die leitenden Fragen der Tagung und der hier versammelten Beiträge waren daher: Wie bringen Hochschulen ihre individuellen Ziele mit denen der bundesweiten Programme oder länderspezfifischer Fördermaßnahmen überein? Wie gehen Hochschulen mit ihren Projekten um? Wie vollzieht sich Veränderung an den Hochschulen? Und schließlich: Was bleibt von den Impulsen, die Projekte setzen? Die in diesem Tagungsband versammelten Beiträge geben darauf erste, auf dem bisherigen Erfahrungswissen basierende Antworten. Sie setzen sich intensiv mit den Faktoren auseinander, die den Erfolg von Veränderungsprozessen und Projekten befördern oder behindern können und leiten daraus Empfehlungen für Gestaltungsprozesse an Hochschulen ab.
The high resource demand of the building sector clearly indicates the need to search for alternative, renewable and energy-efficient materials. This work presents paper-laminated sandwich elements with a core of corrugated paperboard that can serve as architectural components with a load-bearing capacity after a linear folding process. Conventional methods either use paper tubes or glued layers of honeycomb panels. In contrast, the folded components are extremely lightweight, provide the material strength exactly where it is statically required and offer many possibilities for design variants. After removing stripes of the paper lamination, the sandwich can be folded in a linear way at this position. Without the resistance of the missing paper, the sandwich core can be easily compressed. The final angle of the folding correlates with the width of the removed paper stripe. As such, this angle can be described by a simple geometric equation. The geometrical basis for the production of folded sandwich elements was established and many profile types were generated such as triangular, square or rectangular shapes. The method allows the easy planning and fast production of components that can be used in the construction sector. A triangle profile was used to create a load-bearing frame as supporting structure for an experimental building. This first permanent building completely made of corrugated cardboard was evaluated in a two-year test to confirm the efficiency of the developed components. In addition to the frame shown in this paper, large-scale sandwich elements with a core of folded components can be used to fabricate lightweight ceilings and large-scale sandwich components. The method enables the efficient production of linearly folded cardboard elements which can replace normal wooden components like beams, pillars or frames and bring a fully recycled material in the context of architectural construction.
Since the end of the 1950s, Italy has focused part of its modernization on the erection of public works. Due to corruption, mafia, and further malpractice, this form of development has occasionally failed, producing a high number of constructions that have remained unfinished for decades. In 2007, the group of artists Alterazioni Video constructed an informal survey in the form of an on-line tool open to public contributions, which revealed that there are 395 unfinished public works in Italy from which 156, approximately 39.5%, are located in Sicily alone. In view of such a statistic, Alterazioni Video opted to coin the term ‘Incompiuto Siciliano’ – literally ‘Sicilian Incompletion’ – to refer to unfinished public works as a formal architectural style. This re-interpretation, which aims to convey the recovered dignity of these ‘modern ruins’, considers unfinished public works a type of heritage with the potential to represent the entirety of Italian society. Furthermore, it goes as far as to say an unfinished public work is ‘Incompiuto Siciliano’ despite being located in another of the Italian regions.
This doctoral dissertation embraces the artists’ argument to develop a complete study of Incompiuto Siciliano by embedding this architectural style/artistic project within the main debates on modern ruins at present. This is important because it is expected to contribute to the revalorization and eventual recommissioning of unfinished sites by validating Incompiuto Siciliano in the realm of academia. Furthermore, this work aspires to be a worthwhile source of information for future investigations dealing with cultural interpretations of incompletion in any other context – a not unreasonable goal considering how unfinished works are one of the key urban topics after the 2008 financial crisis. Hence, this doctoral dissertation uses Incompiuto Siciliano to discuss a different perspective in each of the five chapters and, though these can be read as independent contributions, the objective is that all chapters read together, form a clear, concise, continuous unit. And so it must be said this is not a dissertation about unfinished public works in Italy; this is a dissertation about Incompiuto Siciliano as an artistic response to unfinished public works in Italy – which clearly requires an interdisciplinary analysis involving Urban Studies, Cultural Geography, Contemporary Archaeology, Critical Heritage and Visual Arts.
Die Arbeit beschäftigt sich mit den Auswirkungen des Baus von neuen Stadtautobahnen in Santiago de Chile. Ziel der Studie ist, die Veränderungen im Segregationsmuster der Hauptstadt Chiles, die durch den Bau dieser Autobahnen entstanden sind, zu beschreiben.
Die Arbeit betrachtet die Entstehung von Segregationsmustern als kulturell-historisches Phänomen urbaner Bedeutung, weswegen die Entwicklung der Stadt Santiago und deren Segregationsmuster nicht nur aus der Perspektive der Stadtsoziologie und der Stadtgeographie, sondern auch aus einer historischen Perspektive analysiert wird. Dabei liegt der Schwerpunkt der Arbeit auf der Wechselbeziehung zwischen Verkehrsinfrastruktur und sozial-räumlicher Verteilung der verschiedenen sozialen Gruppen.
Die Entstehung der neuen Stadtautobahnen in Santiago de Chile lässt sich nur durch eine mehrdimensionale Betrachtung erklären. Diese Bauten und die besondere Art in der sie gebaut und betrieben werden, konnten nur durch die Einführung von Konzessionsmechanismen innerhalb einer neoliberalen Markwirtschaft entstehen. In diesem sozial-ökonomischer Rahmen, bei dem die Bürger lediglich als potenzielle Kunden betrachtet werden, sind die Infrastrukturbauten – darunter auch die Stadtautobahnen – maßgeschneiderte Produkte für eine Minderheit. Dieses Konzept hat gravierende Folgen für das Sozialgefüge der Stadt Santiago.
Die Folgen der Einführung der Stadtautobahnen auf das Segregationsmuster und das Sozialgefüge der Hauptstadt Chiles werden anhand zweier Fallstudien veranschaulicht. Mittels einer mehrschichtigen qualitativen Methodik werden die Auswirkungen des Baus von Stadtautobahnen im Armenviertel »Santo Tomás« des südlichen Stadtbezirk »La Pintana« und im elitären »Condominio La Reserva« im nördlichen Ausdehnungsgebiet »Chacabuco« analysiert.
Anschließend wird ein neues Beschreibungsmodell für die lateinamerikanische Stadt vorgeschlagen; das »symbiotische Stadtmodell« stützt sich zum größten Teil auf den Ausbau des Autobahnnetzes.