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Paper 2007/369

Universally Composable Multi-Party Computation with an Unreliable Common Reference String

Vipul Goyal and Jonathan Katz

Abstract

Universally composable multi-party computation has been studied in two settings: \begin{itemize} \item When a majority of participants are honest, universally composable multi-party computation is known to be possible without any assumptions. \item When honest participants are \emph{not} in the majority, universally composable multi-party computation is known to be impossible (under any cryptographic assumption) in the bare model. On the other hand, feasibility results have been obtained (under standard cryptographic assumptions) in various augmented models, the most popular of which posits the existence of a \emph{common references string} (CRS) available to all parties who are executing the protocol. \end{itemize} In either of the above settings, some \emph{assumption} regarding the protocol execution is made (i.e., that many parties are honest in the first case, or that a legitimately-chosen string is available in the second), and if this assumption is incorrect then all security is lost. A natural question is whether it is possible to design protocols giving \emph{some} assurance of security in case \emph{either one} of these assumptions holds, i.e., a single protocol (that uses a CRS) which is secure if \emph{either} at most $s$ players are dishonest \emph{or} if up to $t$ players are dishonest (with $t > s$) but the CRS is chosen in the proscribed manner. We show that such protocols exist if and only if $s+t < n$.

Metadata
Available format(s)
PDF
Category
Foundations
Publication info
Published elsewhere. TCC 2008
Contact author(s)
vipul @ cs ucla edu
History
2007-12-28: revised
2007-09-19: received
See all versions
Short URL
https://ia.cr/2007/369
License
Creative Commons Attribution
CC BY
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