Thore Thießen

dblp:297/3677 · DBLP profile ↗
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2ranked-venue papers
2as first author
2since 2021 · last 2024
0009-0002-9902-3853ORCID · verified

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Theory of computation · 2 · 2 first-author · 2 since 2021
YearPublicationVenuePosition
2024 Optimal Offline ORAM with Perfect Security via Simple Oblivious Priority Queues
Thore Thießen, Jan Vahrenhold
ISAAC1
2022 Klee's Measure Problem Made Oblivious
abstract
Abstract We study Klee’s measure problem — computing the volume of the union of n axis-parallel hyperrectangles in $$\mathbb {R}^d$$ R d — in the oblivious RAM (ORAM) setting. For this, we modify Chan’s algorithm [12] to guarantee memory access patterns and control flow independent of the input; this makes the resulting algorithm applicable to privacy-preserving computation over outsourced data and (secure) multi-party computation. For $$d = 2$$ d = 2 , we develop an oblivious version of Chan’s algorithm that runs in expected $$\mathcal {O}(n \log ^{5/3} n)$$ O ( n log 5 / 3 n ) time for perfect security or $$\mathcal {O}(n \log ^{3/2} n)$$ O ( n log 3 / 2 n ) time for computational security, thus improving over optimal general transformations. For $$d \ge 3$$ d ≥ 3 , we obtain an oblivious version with perfect security while maintaining the $$\mathcal {O}(n^{d/2})$$ O ( n d / 2 ) runtime, i. e., without any overhead. Generalizing our approach, we derive a technique to transform divide-and-conquer algorithms that rely on linear-scan processing into oblivious counterparts. As such, our results are of independent interest for geometric divide-and-conquer algorithms that maintain an order over the input. We apply our technique to two such algorithms and obtain efficient oblivious counterparts of algorithms for inversion counting and computing a closest pair in two dimensions.
Thore Thießen, Jan Vahrenhold
LATIN1