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t-Private and t-Secure Auctions

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Journal of Computer Science & Technology 2008年第5期23卷 694-710页

作者： Markus Hinkelmann Andreas Jakoby Peer Stechert institut für Theoretische informatik Universitt zu Lübeck Germany Fachgruppe Didaktik der informatik und E-Learning Universitt Siegen Germany

In most of the auction systems the values of bids are known to the auctioneer. This allows him to manipulate the outcome of the auction. Hence, one might be interested in hiding these values. Some cryptographically secure protocols for electronic auctions have been presented in the last decade. Our work extends these protocols in several ways. On the basis of garbled circuits, i.e., encrypted circuits, we present protocols for sealed-bid auctions that fulfill the following requirements： 1） protocols are information-theoretically t-private for honest but curious parties; 2） the number of bits that can be learned by malicious adversaries is bounded by the output length of the auction; 3） the computational requirements for participating parties are very low： only random bit choices and bitwise computation of the XOR-function are necessary. Note that one can distinguish between the protocol that generates a garbled circuit for an auction and the protocol to evaluate the auction. In this paper we address both problems. We will present a t-private protocol for the construction of a garbled circuit that reaches the lower bound of 2t ＋ 1 parties, and Finally, we address the problem of bid changes in an auction. a more randomness efficient protocol for （t ＋ 1）^2 parties

关键词： multi-party private and secure computation garbled circuits private auctions

Berry-Esseen bounds and moderate deviations for the norm, entries and spectral radius of products of positive random matrices

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Science China Mathematics 2024年第3期67卷 627-646页

作者： Hui Xiao Ion Grama Quansheng Liu institut fur Mathematik und Angewandte informatik Universitat HildesheimHildesheim 31141Germany Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China LMBA Universite Bretagne SudCNRS UMR 6205Vannes F-56000France

Let(g_(n))_(n≥1) be a sequence of independent and identically distributed positive random d×d matrices and consider the matrix product G_(n)=g_(n)…g_*** suitable conditions,we establish the Berry-Esseen bounds on the rate of convergence in the central limit theorem and Cramer-type moderate deviation expansions,for any matrix norm ‖G_(n)‖ of G_(n),its entries G_(n)^(i,j) and its spectral radius ρ(G_(n)).Extended versions of their joint law with the direction of the random walk G_(n)x are also established,where x is a starting point in the unit sphere of R~d.

关键词： Berry-Esseen bound Cramér-type moderate deviation product of random matrices operator norm entry spectral radius

A Prototype Expert System for Automatic Generation of Image Processing Programs

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Journal of Computer Science & Technology 1991年第3期6卷 296-300页

作者：宋茂强 FelixGrimm HorstBunke Beijing University of Posts and Telecommunications Beijing 100088 institut fuer informatik Universitaet BernSwitzerland

A prototype expert system for generating image processing programs using the subroutine pack- age SPIDER is described in this *** on an interactive dialog,the system can generate a complete application program using S... 详细信息

关键词： A Prototype Expert System for Automatic Generation of Image Processing Programs

The Dichotomy Between Traces on d-sets Г in R^n and the Density of D(R^n\Г) in Function Spaces

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Acta Mathematica Sinica,English Series 2008年第4期24卷 539-554页

作者： Hans TRIEBEL Mathematisches institut Fakultt fr Mathematik und InformatikFriedrich-Schiller-Universitt JenaD-07737 JenaGermany

A space Apq^s （R^n） with A ： B or A = F and s ∈R, 0 〈 p, q 〈 ∞ either has a trace in Lp（Г）, where Г is a compact d-set in R^n with 0 〈 d 〈 n, or D（R^n／Г） is dense in it. Related dichotomy numbers are ... 详细信息

A space Apq^s （R^n） with A ： B or A = F and s ∈R, 0 〈 p, q 〈 ∞ either has a trace in Lp（Г）, where Г is a compact d-set in R^n with 0 〈 d 〈 n, or D（R^n／Г） is dense in it. Related dichotomy numbers are introduced and calculated.

关键词： function spaces d-sets fractals traces

Approximation Algorithms for 3D Orthogonal Knapsack

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Journal of Computer Science & Technology 2008年第5期23卷 749-762页

作者： Florian Diedrich Rolf Harren Klaus Jansen Ralf Thle Henning Thomas institute of Computer Science University of Kiel Max-Planck-institut für informatik Campus E1466123 Saarbrücken Germany Department of Computer Science ETH ZurichZurich Switzerland

We study non-overlapping axis-parallel packings of 3D boxes with profits into a dedicated bigger box where rotation is either forbidden or permitted, and we wish to maximize the total profit. Since this optimization problem is NP-hard, we focus on approximation algorithms. We obtain fast and simple algorithms for the non-rotational scenario with approximation ratios 9 ＋ ε and 8 ＋ ε, as well as an algorithm with approximation ratio 7 ＋ ε that uses more sophisticated techniques; these are the smallest approximation ratios known for this problem. furthermore, we show how the used techniques can be adapted to the case where rotation by 90° either around the z-axis or around all axes is permitted, where we obtain algorithms with approximation ratios 6 ＋ ε and 5 ＋ ε, respectively. Finally our methods yield a 3D generalization of a packability criterion and a strip packing algorithm with absolute approximation ratio 29/4, improving the previously best known result of 45/4.

关键词： approximation algorithm computational and structural complexity geometric configurations

A Geometric Space-Time Multigrid Algorithm for the Heat Equation

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Numerical Mathematics(Theory,Methods and Applications) 2012年第1期5卷 110-130页

作者： Tobias Weinzierl Tobias Köppl institut für informatik Technische UniversitätMünchenBoltzmannstr.385748 GarchingGermany institut für Mathematik Technische UniversitätMünchenBoltzmannstr.385748 GarchingGermany

We study the time-dependent heat equation on its space-time domain that is discretised by a k-spacetree.k-spacetrees are a generalisation of the octree concept and are a discretisation paradigm yielding a multiscale representation of dynamically adaptive Cartesian grids with low memory *** paper presents a full approximation storage geometric multigrid implementation for this setting that combines the smoothing properties of multigrid for the equation’s elliptic operator with a multiscale solution propagation in *** the runtime and memory overhead for tackling the all-in-one space-time problem is bounded,the holistic approach promises to exhibit a better parallel scalability than classical time stepping,adaptive dynamic refinement in space and time fall naturally into place,as well as the treatment of periodic boundary conditions of steady cycle systems,on-time computational steering is eased as the algorithm delivers guesses for the solution’s long-term behaviour immediately,and,finally,backward problems arising from the adjoint equation benefit from the the solution being available for any point in space and time.

关键词： Adaptive Cartesian grids geometric multiscale methods heat equation octree spacetree space-time discretisation

Lacunary Measures and Self-similar Probability Measures in Function Spaces

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Acta Mathematicae Applicatae Sinica 2004年第4期 577-588页

作者： Hans TRIEBEL Friedrich-Schiller-Universitt Jena D-07740 Jena Germany Mathematisches institut Fakultt für Mathematik und informatik

The paper deals with multifractal quantities for some types of Radon measures,especiallyself-similar probability measures,and their relations to Besov spaces.

关键词： Multifractal quantities Self-similar probability measures Besov spaces

Concealed Integrity Monitoring for Wireless Sensor Networks

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Wireless Sensor Network 2011年第1期3卷 10-17页

作者： Bjorn Stelte Thomas Bühring institut für Technische informatik Universitat der Bundeswehr MünchenNeubibergGermany

Nowadays, sensor networks are widely installed around the world. Typical sensors provide data for healthcare, energy management, environmental monitoring, etc. In the future sensors will become a part of critical infrastructures. In such a scenario the network operator has to monitor the integrity of the network devices, otherwise the trustworthiness of the whole system is questionable. The problem is that every integrity protocol needs a secure channel between the devices. Therefore, we will introduce a covert channel for hidden transportation of integrity monitoring messages. The covert channel enables us to hide integrity check messages embedded into regular traffic without giving potential attackers a hint on the used integrity protocol.

关键词： Covert Channel Integrity Monitoring Wireless Sensor Network

Social Choice Meets Graph Drawing: How to Get Subexponential Time Algorithms for Ranking and Drawing Problems

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Tsinghua Science and Technology 2014年第4期19卷 374-386页

作者： Henning Fernau Fedor V.Fomin Daniel Lokshtanov Matthias Mnich Geevarghese Philip Saket Saurabh FB 4-Abteilung informatikwissenschaften Universitt Trier D-54286 TrierGermany the Department of Informatics University of Bergen N-5020 Bergen Norway Max-Planck-institut fr informatik D-66123 Saarbrcken Germany the institute of Mathematical Sciences Chennai - 600113 India

We analyze a common feature of p-Kemeny AGGregation（p-KAGG） and p-One-Sided Crossing Minimization（p-OSCM） to provide new insights and findings of interest to both the graph drawing community and the social choice community. We obtain parameterized subexponential-time algorithms for p-KAGG—a problem in social choice theory—and for p-OSCM—a problem in graph drawing. These algorithms run in time O＊（2O（√k log k））,where k is the parameter, and significantly improve the previous best algorithms with running times O.1.403k/and O.1.4656k/, respectively. We also study natural ＂above-guarantee＂ versions of these problems and show them to be fixed parameter tractable. In fact, we show that the above-guarantee versions of these problems are equivalent to a weighted variant of p-directed feedback arc set. Our results for the above-guarantee version of p-KAGG reveal an interesting contrast. We show that when the number of ＂votes＂ in the input to p-KAGG is odd the above guarantee version can still be solved in time O＊（2O（√k log k））, while if it is even then the problem cannot have a subexponential time algorithm unless the exponential time hypothesis fails（equivalently, unless FPT D M[1]）.

关键词： Kemeny aggregation one-sided crossing minimization parameterized complexity subexponential-time algorithms social choice theory graph drawing directed feedback arc set