Multiparty Computation with Covert Security and Public Verifiability

Peter Scholl*, Mark Simkin, Luisa Siniscalchi

*Corresponding author for this work

Research output: Contribution to book/anthology/report/proceedingArticle in proceedingsResearchpeer-review

Abstract

Multiparty computation protocols (MPC) are said to be secure against covert adversaries if the honest parties are guaranteed to detect any misbehavior by the malicious parties with a constant probability. Protocols that, upon detecting a cheating attempt, additionally allow the honest parties to compute certificates, which enable third parties to be convinced of the malicious behavior of the accused parties, are called publicly verifiable. In this work, we make several contributions to the domain of MPC with security against covert adversaries. We identify a subtle flaw in a protocol of Goyal, Mohassel, and Smith (Eurocrypt 2008), meaning that their protocol does not allow to identify a cheating party, and show how to fix their original construction to obtain security against covert adversaries. We present generic compilers that transform arbitrary passively secure preprocessing protocols, i.e. protocols where the parties have no private inputs, into protocols that are secure against covert adversaries and publicly verifiable. Using our compiler, we construct the first efficient variants of the BMR and the SPDZ protocols that are secure and publicly verifiable against a covert adversary that corrupts all but one party, and also construct variants with covert security and identifiable abort. We observe that an existing impossibility result by Ishai, Ostrovsky, and Seyalioglu (TCC 2012) can be used to show that there exist certain functionalities that cannot be realized by parties, that have oracle-access to broadcast and arbitrary two-party functionalities, with information-theoretic security against a covert adversary.

Original languageEnglish
Title of host publication3rd Conference on Information-Theoretic Cryptography, ITC 2022
EditorsDana Dachman-Soled
PublisherSchloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
Publication dateJul 2022
Article number8
ISBN (Electronic)9783959772389
DOIs
Publication statusPublished - Jul 2022
Event3rd Conference on Information-Theoretic Cryptography, ITC 2022 - Cambridge, United States
Duration: 5 Jul 20227 Jul 2022

Conference

Conference3rd Conference on Information-Theoretic Cryptography, ITC 2022
Country/TerritoryUnited States
CityCambridge
Period05/07/202207/07/2022
SeriesLeibniz International Proceedings in Informatics, LIPIcs
Volume230
ISSN1868-8969

Keywords

  • covert security
  • Multi-party computation
  • public verifiability

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