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See detailIs Eve nearby? Analysing protocols under the distant-attacker assumption
Gil Pons, Reynaldo UL; Horne, Ross James UL; Mauw, Sjouke UL et al

in IEEE Computer Security Foundations Symposium, August 7 - 10, 2022, Haifa, Israel (2022)

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See detailLe Centenaire et les nouveaux médias
Clavert, Frédéric UL

in Weinrich, Arndt; Patin, Nicolas (Eds.) Quel Bilan Scientifique pour le Centenaire de 1914-1918? (2022)

This chapter assesses the general and academic uses of social media (most particularly twitter) during the Centenary of the First World War.

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See detailFrom gravity to string topology
Merkoulov (merkulov), Serguei UL

E-print/Working paper (2022)

The chain gravity properad introduced earlier by the author acts on the cyclic Hochschild of any cyclic A∞ algebra equipped with a scalar product of degree −d. In particular, it acts on the cyclic ... [more ▼]

The chain gravity properad introduced earlier by the author acts on the cyclic Hochschild of any cyclic A∞ algebra equipped with a scalar product of degree −d. In particular, it acts on the cyclic Hochschild complex of any Poincare duality algebra of degree d, and that action factors through a quotient dg properad ST3−d of ribbon graphs which is in focus of this paper. We show that its cohomology properad H∙(ST3−d) is highly non-trivial and that it acts canonically on the reduced equivariant homology H¯S1∙(LM) of the loop space LM of any simply connected d-dimensional closed manifold M. By its very construction, the string topology properad H∙(ST3−d) comes equipped with a morphism from the gravity properad which is fully determined by the compactly supported cohomology of the moduli spaces Mg,n of stable algebraic curves of genus g with marked points. This result gives rise to new universal operations in string topology as well as reproduces in a unified way several known constructions: we show that (i) H∙(ST3−d) is also a properad under the properad of involutive Lie bialgebras in degree 3−d whose induced action on H¯S1∙(LM) agrees precisely with the famous purely geometric construction of M. Chas and D. Sullivan, (ii) H∙(ST3−d) is a properad under the properad of homotopy involutive Lie bialgebras in degree 2−d; (iii) E. Getzler's gravity operad injects into H∙(ST3−d) implying a purely algebraic counterpart of the geometric construction of C. Westerland establishing an action of the gravity operad on H¯S1∙(LM). [less ▲]

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See detailSecurity, Scalability and Privacy in Applied Cryptography
Vitto, Giuseppe UL

Doctoral thesis (2022)

In the modern digital world, cryptography finds its place in countless applications. However, as we increasingly use technology to perform potentially sensitive tasks, our actions and private data attract ... [more ▼]

In the modern digital world, cryptography finds its place in countless applications. However, as we increasingly use technology to perform potentially sensitive tasks, our actions and private data attract, more than ever, the interest of ill-intentioned actors. Due to the possible privacy implications of cryptographic flaws, new primitives’ designs need to undergo rigorous security analysis and extensive cryptanalysis to foster confidence in their adoption. At the same time, implementations of cryptographic protocols should scale on a global level and be efficiently deployable on users’ most common devices to widen the range of their applications. This dissertation will address the security, scalability and privacy of cryptosystems by presenting new designs and cryptanalytic results regarding blockchain cryptographic primitives and public-key schemes based on elliptic curves. In Part I, I will present the works I have done in regards to accumulator schemes. More precisely, in Chapter 2, I cryptanalyze Au et al. Dynamic Universal Accumulator, by showing some attacks which can completely take over the authority who manages the accumulator. In Chapter 3, I propose a design for an efficient and secure accumulator-based authentication mechanism, which is scalable, privacy-friendly, lightweight on the users’ side, and suitable to be implemented on the blockchain. In Part II, I will report some cryptanalytical results on primitives employed or considered for adoption in top blockchain-based cryptocurrencies. In particular, in Chapter 4, I describe how the zero-knowledge proof system and the commitment scheme adopted by the privacy-friendly cryptocurrency Zcash, contain multiple subliminal channels which can be exploited to embed several bytes of tagging information in users’ private transactions. In Chapter 5, instead, I report the cryptanalysis of the Legendre PRF, employed in a new consensus mechanism considered for adoption by the blockchain-based platform Ethereum, and attacks for further generalizations of this pseudo-random function, such as the Higher-Degree Legendre PRF, the Jacobi Symbol PRF, and the Power-Residue PRF. Lastly, in Part III, I present my line of research on public-key primitives based on elliptic curves. In Chapter 6, I will describe a backdooring procedure for primes so that whenever they appear as divisors of a large integer, the latter can be efficiently factored. This technique, based on elliptic curves Complex Multiplication theory, enables to eventually generate non-vulnerable certifiable semiprimes with unknown factorization in a multi-party computation setting, with no need to run a statistical semiprimality test common to other protocols. In Chapter 7, instead, I will report some attack optimizations and specific implementation design choices that allow breaking a reduced-parameters instance, proposed by Microsoft, of SIKE, a post-quantum key-encapsulation mechanism based on isogenies between supersingular elliptic curves. [less ▲]

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See detailDie Grenzen aufgezeigt:Technische Innovation und räumliche Abstraktion am Beispiel früher Landkarten der Grenzregion zwischen dem Herzogtum Luxemburg und dem Kurfürstentum Trier
Solchenbach, Karl UL

in Schröder, Lina; Wegewitz, Markus (Eds.) Europäische Grenzregionen. Neue Wege im Umgang mit historischen Raum- und Grenzkonzeptionen in der Geschichtswissenschaft (2022)

Die Ausbildung und Verfestigung der kurtrierischen und luxemburgischen Landesherrschaften war im 14. Jahrhundert weitgehend zum Abschluss gekommen. Die Transformation vom Personenverbands- zum ... [more ▼]

Die Ausbildung und Verfestigung der kurtrierischen und luxemburgischen Landesherrschaften war im 14. Jahrhundert weitgehend zum Abschluss gekommen. Die Transformation vom Personenverbands- zum Flächenstaat frühneuzeitlicher Prägung hatte die Ausbildung einer zunehmend deutlicheren Grenze zwischen beiden Territorien zur Folge. Ebenso formierte sich auch eine Grenze im Grenzraum mit Frankreich und Lothringen. Die vereinfachende Darstellung komplexer teils überlagerter Grenzzonen in Form von abstrahierenden Linien musste von den zeitgenössischen Kartographen jedoch erst noch entwickelt werden. Die älteste regionale Karte mit einer angedeuteten partiellen Grenzmarkierung stammt aus dem Jahr 1555. Eine zunehmende Professionalisierung der Kartographie gelang ab der zweiten Hälfte des 16. Jahrhunderts durch Landesaufnahmen, initiiert von den jeweiligen Landesherren. Die Intention der Auftraggeber war dabei ähnlich: einerseits sollte das jeweilige Territorium durch die Karte möglichst als geschlossen beherrschter Raum dargestellt werden, andererseits galt es, die bisher nur verbal beschriebenen teils strittigen Grenzen als abstrakte Linien deutlich sichtbar zu machen. Die Karten der Landesaufnahmen waren zunächst geheim, dennoch fanden sie bereits nach wenigen Jahren Eingang in die Atlanten von Ortelius, de Jode und Mercator. Diese beeinflussten wiederum die Karten der Region in den späteren Atlanten der niederländischen, französischen und süddeutschen Kartenverleger. Der Beitrag beschreibt, ab wann und in welcher Form Grenzen in frühen Karten (16.-18. Jahrhundert) dargestellt wurden. Besonders in den Blick genommen wird der Prozess der Ausbildung von Linien zur abstrakten Darstellung unklarer, teils strittiger Grenzräume sowie die zunehmende Professionalisierung und Genauigkeit in der kartographischen Darstellung durch Vermessungen im Feld. [less ▲]

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See detailKernel Regression over Graphs using Random Fourier Features
Elias, Vitor R.M.; Gogineni, Vinay C.; Alves Martins, Wallace UL et al

in IEEE Transactions on Signal Processing (2022)

This paper proposes efficient batch-based and online strategies for kernel regression over graphs (KRG). The proposed algorithms do not require the input signal to be a graph signal, whereas the target ... [more ▼]

This paper proposes efficient batch-based and online strategies for kernel regression over graphs (KRG). The proposed algorithms do not require the input signal to be a graph signal, whereas the target signal is defined over the graph. We first use random Fourier features (RFF) to tackle the complexity issues associated with kernel methods employed in the conventional KRG. For batch-based approaches, we also propose an implementation that reduces complexity by avoiding the inversion of large matrices. Then, we derive two distinct online strategies using RFF, namely, the mini-batch gradient KRG (MGKRG) and the recursive least squares KRG (RLSKRG). The stochastic gradient KRG (SGKRG) is introduced as a particular case of the MGKRG. The MGKRG and the SGKRG are low-complexity algorithms that employ stochastic gradient approximations in the regression-parameter update. The RLSKRG is a recursive implementation of the RFF-based batch KRG. A detailed stability analysis is provided for the proposed online algorithms, including convergence conditions in both mean and mean-squared senses. A discussion on complexity is also provided. Numerical simulations include a synthesized-data experiment and real-data experiments on temperature prediction, brain activity estimation, and image reconstruction. Results show that the RFF-based batch implementation offers competitive performance with a reduced computational burden when compared to the conventional KRG. The MGKRG offers a convenient trade-off between performance and complexity by varying the number of mini-batch samples. The RLSKRG has a faster convergence than the MGKRG and matches the performance of the batch implementation. [less ▲]

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See detailHow Germany achieved a record share of renewables during the COVID-19 pandemic while relying on the European interconnected power network
Halbrügge, Stephanie; Buhl, Hans Ulrich; Fridgen, Gilbert UL et al

in Energy (2022)

In 2020, Germany reached a maximum share of 50.5% intermittent renewables in electricity generation. Such a high share results in an increasing need for flexibility measures such as international ... [more ▼]

In 2020, Germany reached a maximum share of 50.5% intermittent renewables in electricity generation. Such a high share results in an increasing need for flexibility measures such as international transmission flexibility, i.e., electricity imports and exports. In fact, during the COVID-19 pandemic, Germany changed from a former electricity net exporter to a net importer. This paper, therefore, analyzes what we can learn from the resulting development of German electricity imports as a flexibility measure from a market, environmental, and network perspective. We analyze data on electricity imports/exports, generation, prices, and interconnection capacities of 38 bidding zones, respectively 11 countries within the ENTSO-E. In particular, we formulate three hypotheses to partition our overarching research question. Our results reveal that from a market perspective, Germany's increased need for transmission flexibility did not generally result in increased prices for German electricity imports. Also, from an environmental perspective, Germany increasingly relied on electricity imports from countries that exhibited a lower share of renewables. Finally, during the COVID-19 pandemic some of Germany's interconnection capacities to its neighboring countries exhibited a higher utilization. In view of our results, German policymakers may reflect on decarbonization policies considering a holistic European perspective. [less ▲]

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See detailHeterogeneous Innovation over the Business Cycle
Manso, Gustavo; Balsmeier, Benjamin UL; Fleming, Lee

in Review of Economics and Statistics (2022)

Schumpeter (1939) claims that recessions are periods of “creative destruction,” concentrating innovation that is useful for the long-term growth of the economy. However previous research finds that ... [more ▼]

Schumpeter (1939) claims that recessions are periods of “creative destruction,” concentrating innovation that is useful for the long-term growth of the economy. However previous research finds that standard measures of firms’ innovation, such as R&D expenditures or raw patent counts, concentrate in booms. We argue that these measures do not capture shifts in firms’ innovative search strategies. We contemplate firms’ choice between exploration vs. exploitation over the business cycle and find evidence with more nuanced measures of patent characteristics that firms shift towards exploration during contractions and exploitation during expansions, with a stronger effect for firms in more cyclical industries. [less ▲]

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See detailPUBA: Privacy-Preserving User-Data Bookkeeping and Analytics
Fetzer, Valerie; Keller, Marcel; Maier, Sven et al

in Proceedings on Privacy Enhancing Technologies (2022), 2022(2),

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See detailImpact of COVID-19 Pandemic on (Health) Care Situation of People with Parkinson’s Disease in Germany (Care4PD)
Fründt, Odette; Hanff, Anne-Marie UL; Mai, Tobias et al

in Brain Sciences (2022), 12(1 62),

The Care4PD study examined the impact of the COVID-19 pandemic on the care situation of people (PwP) with Parkinson’s disease in Germany. A comprehensive, nationwide, anonymous questionnaire for PwP was ... [more ▼]

The Care4PD study examined the impact of the COVID-19 pandemic on the care situation of people (PwP) with Parkinson’s disease in Germany. A comprehensive, nationwide, anonymous questionnaire for PwP was distributed by the members’ journal of the German Parkinson’s Disease Association and in several PD specialized in- and outpatient institutions. PwP subjectively evaluated their general care situation and individual impairments during the pandemic. We analyzed 1269 eligible out of 1437 returned questionnaires (88.3%) and compared PwP with (p-LTC) and without (np-LTC) professional long-term care. Both groups rated the general pandemic-related consequences as being rather mild to moderate (e.g., worsening of symptom or concerns). However, familial/social contact restrictions were indicated as most compromising, whereas access to outpatient professional health care providers was less affected. PwP with professional LTC reported more impairment than those without. COVID-19 vaccination rates and acceptance were generally high (p-LTC: 64.3%, np-LTC: 52.3%) at the time of the study, but realization of sanitary measures—especially wearing masks as a patient during care sessions—still needs to be improved. Technical options for telemedicine were principally available but only rarely used. Altogether, during the COVID-19 pandemic, PwP in Germany seemed to have a relatively stable health care access, at least in outpatient settings, while mainly social isolation compromised them. The p-LTC group was more impaired in everyday live compared with the np-LTC group. [less ▲]

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See detailGuide to the writing of law for the Social and Solidarity Economy
Hiez, David UL

Book published by SSE International Forum (2022)

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See detailLinguistische Begriffsarbeit ‘Populismus’
Sieburg, Heinz UL

in Dembeck, Till; Fohrmann, Jürgen (Eds.) Die Rhetorik des Populismus und das Populäre. Körperschaftsbildungen in der Gesellschaft (2022)

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See detailPréface à Z. Mchirgui, L’accord exclusif d’élection de for à travers la Convention de La Haye de 2005
Cuniberti, Gilles UL

in Mchirgui, Zohra (Ed.) L’accord exclusif d’élection de for à travers la Convention de La Haye de 2005 (2022)

Detailed reference viewed: 44 (0 UL)
See detailIn conversation with our young researchers: Yimin Zhang
Zhang, Yimin UL

Article for general public (2022)

In this editorial project, I'm invited to introduce my doctoral research as well as my trajectory as a young researcher in Luxembourg.

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See detailBedrohte Sieger. Populismus und Glaubenskrieg im Rolandslied des Pfaffen Konrad
Bendheim, Amelie UL

in Dembeck, Till; Fohrmann, Jürgen (Eds.) Die Rhetorik des Populismus und das Populäre. Körperschaftsbildungen in der Gesellschaft (2022)

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See detailA restless badit approach for capacitated condition based maintenance scheduling
Demirci, Ece; Arts, Joachim UL; Van Houtum, Geert-Jan

E-print/Working paper (2022)

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See detailHigher Supergeometry and Mathematical Physics
Ibarguengoytia, Eduardo UL

Doctoral thesis (2022)

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See detailMetaheuristics-based Exploration Strategies for Multi-Objective Reinforcement Learning
Felten, Florian UL; Danoy, Grégoire; Talbi, El-Ghazali UL et al

in Proceedings of the 14th International Conference on Agents and Artificial Intelligence (2022)

The fields of Reinforcement Learning (RL) and Optimization aim at finding an optimal solution to a problem, characterized by an objective function. The exploration-exploitation dilemma (EED) is a well ... [more ▼]

The fields of Reinforcement Learning (RL) and Optimization aim at finding an optimal solution to a problem, characterized by an objective function. The exploration-exploitation dilemma (EED) is a well known subject in those fields. Indeed, a consequent amount of literature has already been proposed on the subject and shown it is a non-negligible topic to consider to achieve good performances. Yet, many problems in real life involve the optimization of multiple objectives. Multi-Policy Multi-Objective Reinforcement Learning (MPMORL) offers a way to learn various optimised behaviours for the agent in such problems. This work introduces a modular framework for the learning phase of such algorithms, allowing to ease the study of the EED in Inner- Loop MPMORL algorithms. We present three new exploration strategies inspired from the metaheuristics domain. To assess the performance of our methods on various environments, we use a classical benchmark - the Deep Sea Treasure (DST) - as well as propose a harder version of it. Our experiments show all of the proposed strategies outperform the current state-of-the-art ε-greedy based methods on the studied benchmarks. [less ▲]

Detailed reference viewed: 148 (44 UL)