**Efficient General-Adversary Multi-Party Computation**

*Martin Hirt and Daniel Tschudi*

**Abstract: **Secure multi-party computation (MPC) allows a set P of n players to evaluate a function f in presence of an adversary who corrupts a subset of the players. In this paper we consider active, general adversaries, characterized by a so-called adversary structure Z which enumerates all possible subsets of corrupted players. In particular for small sets of players general adversaries better capture real-world requirements than classical threshold adversaries.

Protocols for general adversaries are ``efficient'' in the sense that they require |Z|^O(1) bits of communication. However, as |Z| is usually very large (even exponential in n), the exact exponent is very relevant. In the setting with perfect security, the most efficient protocol known to date communicates |Z|^3 bits; we present a protocol for this setting which communicates |Z|^2 bits. In the setting with statistical security, |Z|^3 bits of communication is needed in general (whereas for a very restricted subclass of adversary structures, a protocol with communication |Z|^2 bits is known); we present a protocol for this setting (without limitations) which communicates |Z|^1 bits.

**Category / Keywords: **Secure Multiparty Computation, General Adversaries, Efficiency

**Original Publication**** (in the same form): **IACR-ASIACRYPT-2013

**Date: **received 6 Sep 2013

**Contact author: **tschudid at inf ethz ch

**Available format(s): **PDF | BibTeX Citation

**Version: **20130909:020254 (All versions of this report)

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