5 Search Results for "Ben-Kiki, Oren"


Document
Computational Social Dynamics (Dagstuhl Seminar 22452)

Authors: Martin Hoefer, Sigal Oren, Roger Wattenhofer, and Giovanna Varricchio

Published in: Dagstuhl Reports, Volume 12, Issue 11 (2023)


Abstract
This report documents the program and outcomes of Dagstuhl Seminar 22452 "Computational Social Dynamics". The seminar addressed social and dynamic problems in the field of algorithmic game theory, and their implications in numerous applications, such as fair division, financial networks, or behavioral game theory. We summarize organizational aspects of the seminar, the talk abstracts, and the problems that were discussed in the open problem sessions.

Cite as

Martin Hoefer, Sigal Oren, Roger Wattenhofer, and Giovanna Varricchio. Computational Social Dynamics (Dagstuhl Seminar 22452). In Dagstuhl Reports, Volume 12, Issue 11, pp. 28-44, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@Article{hoefer_et_al:DagRep.12.11.28,
  author =	{Hoefer, Martin and Oren, Sigal and Wattenhofer, Roger and Varricchio, Giovanna},
  title =	{{Computational Social Dynamics (Dagstuhl Seminar 22452)}},
  pages =	{28--44},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2023},
  volume =	{12},
  number =	{11},
  editor =	{Hoefer, Martin and Oren, Sigal and Wattenhofer, Roger and Varricchio, Giovanna},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.12.11.28},
  URN =		{urn:nbn:de:0030-drops-178346},
  doi =		{10.4230/DagRep.12.11.28},
  annote =	{Keywords: algorithmic game theory, behavioral economics, fair division, financial networks, social networks}
}
Document
Static vs. Adaptive Security in Perfect MPC: A Separation and the Adaptive Security of BGW

Authors: Gilad Asharov, Ran Cohen, and Oren Shochat

Published in: LIPIcs, Volume 230, 3rd Conference on Information-Theoretic Cryptography (ITC 2022)


Abstract
Adaptive security is a highly desirable property in the design of secure protocols. It tolerates adversaries that corrupt parties as the protocol proceeds, as opposed to static security where the adversary corrupts the parties at the onset of the execution. The well-accepted folklore is that static and adaptive securities are equivalent for perfectly secure protocols. Indeed, this folklore is backed up with a transformation by Canetti et al. (EUROCRYPT'01), showing that any perfectly secure protocol that is statically secure and satisfies some basic requirements is also adaptively secure. Yet, the transformation results in an adaptively secure protocol with inefficient simulation (i.e., where the simulator might run in super-polynomial time even if the adversary runs just in polynomial time). Inefficient simulation is problematic when using the protocol as a sub-routine in the computational setting. Our main question is whether an alternative efficient transformation from static to adaptive security exists. We show an inherent difficulty in achieving this goal generically. In contrast to the folklore, we present a protocol that is perfectly secure with efficient static simulation (therefore also adaptively secure with inefficient simulation), but for which efficient adaptive simulation does not exist (assuming the existence of one-way permutations). In addition, we prove that the seminal protocol of Ben-Or, Goldwasser and Wigderson (STOC'88) is secure against adaptive, semi-honest corruptions with efficient simulation. Previously, adaptive security of the protocol, as is, was only known either for a restricted class of circuits, or for all circuits but with inefficient simulation.

Cite as

Gilad Asharov, Ran Cohen, and Oren Shochat. Static vs. Adaptive Security in Perfect MPC: A Separation and the Adaptive Security of BGW. In 3rd Conference on Information-Theoretic Cryptography (ITC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 230, pp. 15:1-15:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


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@InProceedings{asharov_et_al:LIPIcs.ITC.2022.15,
  author =	{Asharov, Gilad and Cohen, Ran and Shochat, Oren},
  title =	{{Static vs. Adaptive Security in Perfect MPC: A Separation and the Adaptive Security of BGW}},
  booktitle =	{3rd Conference on Information-Theoretic Cryptography (ITC 2022)},
  pages =	{15:1--15:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-238-9},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{230},
  editor =	{Dachman-Soled, Dana},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITC.2022.15},
  URN =		{urn:nbn:de:0030-drops-164933},
  doi =		{10.4230/LIPIcs.ITC.2022.15},
  annote =	{Keywords: secure multiparty computation, perfect security, adaptive security, BGW protocol}
}
Document
Mechanism Design with Moral Bidders

Authors: Shahar Dobzinski and Sigal Oren

Published in: LIPIcs, Volume 215, 13th Innovations in Theoretical Computer Science Conference (ITCS 2022)


Abstract
A rapidly growing literature on lying in behavioral economics and psychology shows that individuals often do not lie even when lying maximizes their utility. In this work, we attempt to incorporate these findings into the theory of mechanism design. We consider players that have a preference for truth-telling and will only lie if their benefit from lying is sufficiently larger than the loss of the others. To accommodate such players, we introduce α-moral mechanisms, in which the gain of a player from misreporting his true value, comparing to truth-telling, is at most α times the loss that the others incur due to misreporting. Note that a 0-moral mechanism is a truthful mechanism. We develop a theory of moral mechanisms in the canonical setting of single-item auctions within the "reasonable" range of α, 0 ≤ α ≤ 1. We identify similarities and disparities to the standard theory of truthful mechanisms. In particular, we show that the allocation function does not uniquely determine the payments and is unlikely to admit a simple characterization. In contrast, recall that monotonicity characterizes the allocation function of truthful mechanisms. Our main technical effort is invested in determining whether the auctioneer can exploit the preference for truth-telling of the players to extract more revenue comparing to truthful mechanisms. We show that the auctioneer can indeed extract more revenue when the values of the players are correlated, even when there are only two players. However, we show that truthful mechanisms are revenue-maximizing even among moral ones when the values of the players are independently drawn from certain identical distributions (e.g., the uniform and exponential distributions). A by-product of our proof that optimal moral mechanisms are truthful is an alternative proof to Myerson’s optimal truthful mechanism characterization in the settings that we consider. We flesh out this approach by providing an alternative proof that does not involve moral mechanisms to Myerson’s characterization of optimal truthful mechanisms to all settings in which the values are independently drawn from regular distributions (not necessarily identical).

Cite as

Shahar Dobzinski and Sigal Oren. Mechanism Design with Moral Bidders. In 13th Innovations in Theoretical Computer Science Conference (ITCS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 215, pp. 55:1-55:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)


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@InProceedings{dobzinski_et_al:LIPIcs.ITCS.2022.55,
  author =	{Dobzinski, Shahar and Oren, Sigal},
  title =	{{Mechanism Design with Moral Bidders}},
  booktitle =	{13th Innovations in Theoretical Computer Science Conference (ITCS 2022)},
  pages =	{55:1--55:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-217-4},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{215},
  editor =	{Braverman, Mark},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2022.55},
  URN =		{urn:nbn:de:0030-drops-156513},
  doi =		{10.4230/LIPIcs.ITCS.2022.55},
  annote =	{Keywords: Mechanism Design, Cognitive Biases, Revenue Maximization}
}
Document
Time-Space Tradeoffs for Finding a Long Common Substring

Authors: Stav Ben-Nun, Shay Golan, Tomasz Kociumaka, and Matan Kraus

Published in: LIPIcs, Volume 161, 31st Annual Symposium on Combinatorial Pattern Matching (CPM 2020)


Abstract
We consider the problem of finding, given two documents of total length n, a longest string occurring as a substring of both documents. This problem, known as the Longest Common Substring (LCS) problem, has a classic 𝒪(n)-time solution dating back to the discovery of suffix trees (Weiner, 1973) and their efficient construction for integer alphabets (Farach-Colton, 1997). However, these solutions require Θ(n) space, which is prohibitive in many applications. To address this issue, Starikovskaya and Vildhøj (CPM 2013) showed that for n^{2/3} ≤ s ≤ n, the LCS problem can be solved in 𝒪(s) space and 𝒪̃(n²/s) time. Kociumaka et al. (ESA 2014) generalized this tradeoff to 1 ≤ s ≤ n, thus providing a smooth time-space tradeoff from constant to linear space. In this paper, we obtain a significant speed-up for instances where the length L of the sought LCS is large. For 1 ≤ s ≤ n, we show that the LCS problem can be solved in 𝒪(s) space and 𝒪̃(n²/(L⋅s) +n) time. The result is based on techniques originating from the LCS with Mismatches problem (Flouri et al., 2015; Charalampopoulos et al., CPM 2018), on space-efficient locally consistent parsing (Birenzwige et al., SODA 2020), and on the structure of maximal repetitions (runs) in the input documents.

Cite as

Stav Ben-Nun, Shay Golan, Tomasz Kociumaka, and Matan Kraus. Time-Space Tradeoffs for Finding a Long Common Substring. In 31st Annual Symposium on Combinatorial Pattern Matching (CPM 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 161, pp. 5:1-5:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


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@InProceedings{bennun_et_al:LIPIcs.CPM.2020.5,
  author =	{Ben-Nun, Stav and Golan, Shay and Kociumaka, Tomasz and Kraus, Matan},
  title =	{{Time-Space Tradeoffs for Finding a Long Common Substring}},
  booktitle =	{31st Annual Symposium on Combinatorial Pattern Matching (CPM 2020)},
  pages =	{5:1--5:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-149-8},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{161},
  editor =	{G{\o}rtz, Inge Li and Weimann, Oren},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CPM.2020.5},
  URN =		{urn:nbn:de:0030-drops-121302},
  doi =		{10.4230/LIPIcs.CPM.2020.5},
  annote =	{Keywords: longest common substring, time-space tradeoff, local consistency, periodicity}
}
Document
Optimal Packed String Matching

Authors: Oren Ben-Kiki, Philip Bille, Dany Breslauer, Leszek Gasieniec, Roberto Grossi, and Oren Weimann

Published in: LIPIcs, Volume 13, IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2011)


Abstract
In the packed string matching problem, each machine word accomodates alpha characters, thus an n-character text occupies n/alpha memory words. We extend the Crochemore-Perrin constant-space O(n)-time string matching algorithm to run in optimal O(n/alpha) time and even in real-time, achieving a factor alpha speedup over traditional algorithms that examine each character individually. Our solution can be efficiently implemented, unlike prior theoretical packed string matching work. We adapt the standard RAM model and only use its AC0 instructions (i.e. no multiplication) plus two specialized AC0 packed string instructions. The main string-matching instruction is available in commodity processors (i.e. Intel's SSE4.2 and AVX Advanced String Operations); the other maximal-suffix instruction is only required during pattern preprocessing. In the absence of these two specialized instructions, we propose theoretically-efficient emulation using integer multiplication (not AC0) and table lookup.

Cite as

Oren Ben-Kiki, Philip Bille, Dany Breslauer, Leszek Gasieniec, Roberto Grossi, and Oren Weimann. Optimal Packed String Matching. In IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2011). Leibniz International Proceedings in Informatics (LIPIcs), Volume 13, pp. 423-432, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2011)


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@InProceedings{benkiki_et_al:LIPIcs.FSTTCS.2011.423,
  author =	{Ben-Kiki, Oren and Bille, Philip and Breslauer, Dany and Gasieniec, Leszek and Grossi, Roberto and Weimann, Oren},
  title =	{{Optimal Packed String Matching}},
  booktitle =	{IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2011)},
  pages =	{423--432},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-34-7},
  ISSN =	{1868-8969},
  year =	{2011},
  volume =	{13},
  editor =	{Chakraborty, Supratik and Kumar, Amit},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2011.423},
  URN =		{urn:nbn:de:0030-drops-33558},
  doi =		{10.4230/LIPIcs.FSTTCS.2011.423},
  annote =	{Keywords: String matching, bit parallelism, real time, space efficiency}
}
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