Quantum Attacks on Mersenne Number Cryptosystems

Mersenne number based cryptography was introduced by Aggarwal et al. as a potential post- quantum cryptosystem in 2017. Shortly after the publication Beunardeau et al. propose a lattice based attack significantly reducing the security margins. During the NIST post-quantum project Aggarwal et al. and Szepieniec introduced a new form of Mersenne number based cryptosystems which remain secure in the presence of the lattice reduction attack. The cryptoschemes make use of error correcting codes and have a low but non-zero probability of failure during the decoding phase. In the event of a decoding failure information about the secret key may be leaked and may allow for new attacks. In the first part of this work, we analyze the Mersenne number cryptosystem and NIST submission Ramstake and identify approaches to exploit the information leaked by decoding failures. We describe different attacks on a weakened variant of Ramstake. Furthermore we pair the decoding failures with a timing attack on the code from the submission package. Both our attacks significantly reduce the security margins compared to the best known generic attack. However, our results on the weakened variant do not seem to carry over to the unweakened cryptosystem. It remains an open question whether the information flow from decoding failures can be exploited to break Ramstake. In the second part of this work we analyze the Groverization of the lattice reduction attack by Beunardeau et al.. The incorporation of classical search problem into a quantum framework promises a quadratic speedup potentially reducing the security margin by half. We give an explicit description of the quantum circuits resulting from the translation of the classical attack. This description contains, to the best of our knowledge, the first in depth description and analysis of a quantum variant of the LLL algorithm. We show that the Groverized attack requires a large (but polynomial) overhead of quantum memory

“YourSights” – Konzeptionierung und Realisierung einer Geodaten-gestützten Informationsanwendung für Smartphones

Der Smartphone-Markt gehört zu einem der am stärksten wachsenden Märkte der heutigen Zeit. Zudem erfreuen sich Anwendungen mit soziotechnischen Aspekten wie YouTube und Facebook immer größer werdender Beliebtheit. Genau hier siedelt Your-Sights an. Dabei wurde im Rahmen eines Projekts eine Software für das Smartphone-Betriebssystem Android konzipiert und entwickelt, welche in der Lage ist Touren, bzw. eine Menge von Wegpunkten zu erstellen, wiederzugeben und zu verwalten. Neben obligatorischen GPS-Koordinaten können für jeden Wegpunkt textuelle und visuelle Informationen, in Form von Bildern, erfasst werden. Für die kartografische Darstellung wird auf das OpenStreetMap-Projekt zurückgegriffen. Im Rahmen dieser Bachelor-Thesis wird das Projekt fortgesetzt und auf die Konzeptio-nierung und Entwicklung einer Middleware eingegangen, welche eine Brücke zwischen den Anwendern und einer Datenbank bildet. Letztere dient nicht nur dem Austausch von Touren, sondern ermöglicht auch eine Kommunikation unter den Anwendern. Dabei wurde Wert auf die Evaluation einer adäquaten Kommunikationstechnologie für den Datenaustausch zwischen dem Anwender und der Middleware gelegt. Schließlich erfolgte der Einsatz des Java NIO-Frameworks Netty und die Entwicklung eines Kommunikationsprotokolls. Darüber hinaus wird auf notwendige Änderungen und Erweiterungen der Android-Applikation, als auch eine prototypische Entwicklung des Servers eingegangen.The smartphone market belongs to the strongly growing markets today. Furthermore are applications with socio-technical aspects enjoying great popularity. YourSights sets up at this point. In the context of a practical project, an Android-application has been designed and developed that is able to record, play and manage trips, which are represented as an amount of waypoints. Along with obligatory GPS coordinates, describing texts and pictures can be applied to a waypoint. For a cartographic representation Your-Sights reverts to the OpenStreetMap project. The project has been carried forward within the scope of this bachelor thesis. Conceptual design and development of a middleware, that connects the clients and a database, represents the central point of this paper. The last one not only serves the interchange of trips but also makes communication between users possible. It was attached importance to an evaluation of adequate communication technologies for data interchange. Finally the Java NIO framework Netty and a specially developed communication protocol was applied. Furthermore necessary changes and developments related to the android application and a prototypical server implementation are described

Unwinding Stochastic Order Flow: When to Warehouse Trades

We study how to unwind stochastic order flow with minimal transaction costs. Stochastic order flow arises, e.g., in the central risk book (CRB), a centralized trading desk that aggregates order flows within a financial institution. The desk can warehouse in-flow orders, ideally netting them against subsequent opposite orders (internalization), or route them to the market (externalization) and incur costs related to price impact and bid-ask spread. We model and solve this problem for a general class of in-flow processes, enabling us to study in detail how in-flow characteristics affect optimal strategy and core trading metrics. Our model allows for an analytic solution in semi-closed form and is readily implementable numerically. Compared with a standard execution problem where the order size is known upfront, the unwind strategy exhibits an additive adjustment for projected future in-flows. Its sign depends on the autocorrelation of orders; only truth-telling (martingale) flow is unwound myopically. In addition to analytic results, we present extensive simulations for different use cases and regimes, and introduce new metrics of practical interest

Uncertain Curve Simplification

We study the problem of polygonal curve simplification under uncertainty, where instead of a sequence of exact points, each uncertain point is represented by a region, which contains the (unknown) true location of the vertex. The regions we consider are disks, line segments, convex polygons, and discrete sets of points. We are interested in finding the shortest subsequence of uncertain points such that no matter what the true location of each uncertain point is, the resulting polygonal curve is a valid simplification of the original polygonal curve under the Hausdorff or the Fr\'echet distance. For both these distance measures, we present polynomial-time algorithms for this problem.Comment: 25 pages, 5 figure

Is functional status better in U.S. patients with cardiac disease than in their Canadian counterparts?

The raw images (available on request) have been captured using a Canon 8-15mm fisheye lens and therefore they have a wide field of view, which results in a dark image boundary as the lights did not illuminate the outer sectors well. The images in this dataset have then been undistorted to virtual images that an ideal perspective camera with only 90 degrees horizontal field of view would have seen from the same position. To achieve this, the color of each pixel in the ideal image is obtained by - computing the ray in space associated with this virtual pixel (using rectilinear un-projection) - projecting this ray into the original fisheye image (using equidistant projection), yielding a sub-pixel position - interpolating the colors of the neighboring pixels Technically, the undistortion has been performed using the tool https://svn.geomar.de/dsm-general/trunk/src/BIAS/Tools/biasproject.cpp (at revision 418, and earlier, compatible revisions). Manual image annotation is available here: https://annotate.geomar.de/volumes/24

Medición de la productividad en el área administrativa de compras y suministros de Comfamiliar Risaralda: una propuesta de mejora continua

Teniendo en cuenta que la productividad es uno de los pilares para el desarrollo empresarial y que esta se relaciona directamente con el progreso de la sociedad, se ha definido la productividad como objeto de estudio de este proyecto. Es así como, este trabajo pretende ofrecer una visión de la productividad y desempeño actual del proceso de Compras y Suministros de Comfamiliar Risaralda, apoyándose en la herramienta DMAIC para identificar los principales factores que inciden de manera negativa y positiva en la misma y ofrecer una propuesta de mejora para los aspectos identificados. Inicialmente, se realiza la caracterización del proceso a través del estudio de la documentación del proceso, entrevistas no estructuradas al personal del proceso y el análisis de los indicadores del proceso. También se ofrece un diagrama que permita visualizar la cadena de valor y el movimiento de información a través de los diferentes integrantes del proceso. Luego de esta descripción y tomando como base la información de histórica de compras, se definen las líneas sobre las cuales se enfocará el estudio. Después de definir las líneas se labora una matriz de evaluación para que sea diligenciada por los procesos que mayor interacción tienen con el proceso de compras. A partir de los resultados anteriores se realizan una encuesta al personal del proceso de Compras y Suministros que enfatiza las posibles falencias, oportunidad de mejora y cuellos de botella que presenta el proceso. Finalmente, se elabora una propuesta de mejora con base en los aspectos identificados durante el trabajo. También se dan las conclusiones obtenidas a partir del estudio y se ofrecen las recomendaciones identificadas por el equipo de trabajo