International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Universally Composable Multiparty Computation with Partially Isolated Parties

Ivan Damgård
Jesper Buus Nielsen
Daniel Wichs
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Abstract: It is well known that universally composable multiparty computation cannot, in general, be achieved in the standard model without setup assumptions when the adversary can corrupt an arbitrary number of players. One way to get around this problem is by having a trusted third party generate some global setup such as a common reference string (CRS) or a public key infrastructure (PKI). Recently, an alternative solution was proposed by Katz in \cite{Katz}, suggesting that one may rely on physical assumptions rather than trusted third parties. Concretely, the solution assumed it physically possible to construct tamper proof hardware tokens which can be run in complete isolation from the surrounding environment. Here we improve upon the work of \cite{Katz} by constructing a scheme in which the tokens only need to be partially isolated and may have some {\em limited communication with the environment}. In addition we improve on Katz's work by presenting a scheme which is secure against \emph{adaptive adversaries} and is based on \emph{general cryptographic assumptions}. We also consider an alternative scenario, in which there are some trusted third parties but no single such party is trusted by all of the players. This compromise allows us to limit the use of the physical set-up and hence might be preferred in practice.
  title={Universally Composable Multiparty Computation with Partially Isolated Parties},
  booktitle={IACR Eprint archive},
  keywords={cryptographic protocols / multiparty computation, universal composability, physical assumptions},
  note={ 13803 received 22 Aug 2007, last revised 17 Oct 2007},
  author={Ivan Damgård and Jesper Buus Nielsen and Daniel Wichs},