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Title: Online Sorted Range Reporting

We study the following extension of the static one-dimensional range reporting problem. For an array A of n elements, build a data structure that supports the query: Given two indices i=j and an integer k, report the k smallest elements in the sub array A[i..j] in sorted order. We present a static data structure that uses O(n) words of space, supports queries in O(k) time, and can be constructed in O(n log n) time on the RAM model. We also extend the data structure to solve the online version of the problem where the elements in A[i..j] are reported in sorted order one-by-one, each element being reported in O(1) worst-case time. The data structure has applications to e.g. top-k queries in databases, prioritized suffix tree reporting, and three-sided planar sorted range reporting.

Joint work with Brodal, Fagerberg and López-Ortiz.

Host: Gerth Stølting Brodal

Privacy-enhancing first-price auctions using rational cryptography

We consider enhancing a sealed-bid single-item auction with privacy concerns, our assumption being that bidders primarily care about monetary payoff and secondarily worry about exposing information about their type to other players and learning information about other players types. To treat privacy explicitly within the game theoretic context, we put forward a novel hybrid utility model that considers both fiscal and privacy components in the players payoffs.
We show how to use rational cryptography to approximately implement a given ex interim indi- vidually strictly rational equilibrium of such an auction (or any game with a winner) without a trusted mediator through a cryptographic protocol that uses only point-to-point authenticated channels between the players. By ex interim individually strictly rational we mean that, given its type and before making its move, each player has a strictly positive expected utility, i.e., it becomes the winner of the auction with positive probability. By approximately implement we mean that, under cryptographic assump- tions, running the protocol is a computational Nash equilibrium with a payoff profile negligibly close to the original equilibrium.

In addition the protocol has the stronger property that no collusion, of any size, can obtain more by deviating in the implementation than by deviating in the ideal mediated setting which the mechanism was designed in. Also, despite the non-symmetric payoffs profile, the protocol always correctly terminates.

Joint work with Nikolaos Triandopoulos and Peter Bro Miltersen.

Kommunikation og præsentationsteknik

Som iværksætter har du brug for at kunne kommunikere klart og præcist. Både når salgsmødet skal i hus, og når du skal præsentere din virksomhed for kunder eller samarbejdspartnere. Få inspiration til din personlige kommunikation. Oplægget vil fokusere på forskellige typer af målgrupper, sprogbrug, disponering af stof, visuelle teknikker og kropssprog.

En række kognitivt begrundede principper for design er relevante på tværs af forskellige former for anvendt semiotik som f.eks. ved analyse og ”design” af film, multimedier, og tekniske grænseflader. Tre sådanne principper er (a) nødvendigheden af at forstå mening som organiseret på flere niveauer, (b) nødvendigheden af at forstå forskellige repræsentationsformer som noget der bærer en egen mening på tværs af forskellige medier, (c) nødvendigheden af at forstå mening som distribueret for så vidt vi vil forstå hvordan ”brugere” er involveret i disse medier og grænseflader.

Der er en hel masse at holde styr på, når du skal starte egen virksomhed. Få mere viden om valg af virksomhedsform, registrering af virksomheden, konkurrenceklausuler, skat, finansiering, den daglige drift, økonomisk styring, bogføring og regnskab.