2 Search Results for "Boer, Alexander"

Document
DOI: 10.4230/LIPIcs.FUN.2021.17
Foundations for Actively Secure Card-Based Cryptography

Authors: Alexander Koch and Stefan Walzer

Published in: LIPIcs, Volume 157, 10th International Conference on Fun with Algorithms (FUN 2021) (2020)

Abstract
Card-based cryptography, as first proposed by den Boer [den Boer, 1989], enables secure multiparty computation using only a deck of playing cards. Many protocols as of yet come with an “honest-but-curious” disclaimer. However, modern cryptography aims to provide security also in the presence of active attackers that deviate from the protocol description. In the few places where authors argue for the active security of their protocols, this is done ad-hoc and restricted to the concrete operations needed, often using additional physical tools, such as envelopes or sliding cover boxes. This paper provides the first systematic approach to active security in card-based protocols. The main technical contribution concerns shuffling operations. A shuffle randomly permutes the cards according to a well-defined distribution but hides the chosen permutation from the players. We show how the large and natural class of uniform closed shuffles, which are shuffles that select a permutation uniformly at random from a permutation group, can be implemented using only a linear number of helping cards. This ensures that any protocol in the model of Mizuki and Shizuya [Mizuki and Shizuya, 2014] can be realized in an actively secure fashion, as long as it is secure in this abstract model and restricted to uniform closed shuffles. Uniform closed shuffles are already sufficient for securely computing any circuit [Mizuki and Sone, 2009]. In the process, we develop a more concrete model for card-based cryptographic protocols with two players, which we believe to be of independent interest.
Cite as

Alexander Koch and Stefan Walzer. Foundations for Actively Secure Card-Based Cryptography. In 10th International Conference on Fun with Algorithms (FUN 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 157, pp. 17:1-17:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{koch_et_al:LIPIcs.FUN.2021.17,
  author =	{Koch, Alexander and Walzer, Stefan},
  title =	{{Foundations for Actively Secure Card-Based Cryptography}},
  booktitle =	{10th International Conference on Fun with Algorithms (FUN 2021)},
  pages =	{17:1--17:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-145-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{157},
  editor =	{Farach-Colton, Martin and Prencipe, Giuseppe and Uehara, Ryuhei},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.FUN.2021.17},
  URN =		{urn:nbn:de:0030-drops-127786},
  doi =		{10.4230/LIPIcs.FUN.2021.17},
  annote =	{Keywords: Card-Based Protocols, Card Shuffling, Secure Multiparty Computation, Active Security, Cryptography without Computers}
}
Document
DOI: 10.4230/OASIcs.CMN.2014.182
Legal Knowledge Conveyed by Narratives: Towards a Representational Model

Authors: Giovanni Sileno, Alexander Boer, and Tom van Engers

Published in: OASIcs, Volume 41, 2014 Workshop on Computational Models of Narrative

Abstract
The paper investigates a representational model for narratives, aiming to facilitate the acquisition of the systematic core of stories concerning legal cases, i.e. the set of causal and temporal relationships that govern the world in which the narrated scenario takes place. At the discourse level, we consider narratives as sequences of "messages" collected in an "observation", including descriptions of agents, of agents' behaviour and of "mechanisms" relative to physical, mental and institutional domains. At the content level, stories correspond to synchronizations of embodied "agent-roles" scripts. Following this approach, the "Pierson v Post" case is analyzed in detail and represented as a Petri net.
Cite as

Giovanni Sileno, Alexander Boer, and Tom van Engers. Legal Knowledge Conveyed by Narratives: Towards a Representational Model. In 2014 Workshop on Computational Models of Narrative. Open Access Series in Informatics (OASIcs), Volume 41, pp. 182-191, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)

Copy BibTex To Clipboard

@InProceedings{sileno_et_al:OASIcs.CMN.2014.182,
  author =	{Sileno, Giovanni and Boer, Alexander and van Engers, Tom},
  title =	{{Legal Knowledge Conveyed by Narratives: Towards a Representational Model}},
  booktitle =	{2014 Workshop on Computational Models of Narrative},
  pages =	{182--191},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-71-2},
  ISSN =	{2190-6807},
  year =	{2014},
  volume =	{41},
  editor =	{Finlayson, Mark A. and Meister, Jan Christoph and Bruneau, Emile G.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.CMN.2014.182},
  URN =		{urn:nbn:de:0030-drops-46567},
  doi =		{10.4230/OASIcs.CMN.2014.182},
  annote =	{Keywords: story representation, story acquisition, legal narratives, knowledge representation, agent-roles, causation, expectations, agent-based modeling, petri}
}
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