SFE and MPC separate
Speaker: Ueli Maurer , ETH- Zurich
Date: April 27 2007
Time: 10:30AM to 12:00PM
Location: 32-G449 Patil-Kiva
Contact: Be Blackburn, 3-6098, email@example.com
Secure function evaluation (SFE) allows a set of players to
compute an arbitrary agreed function of their private inputs, even if
an adversary may corrupt some of the players. Secure multi-party
computation (MPC) is a generalization allowing to perform an arbitrary
on-going (also called reactive or stateful) computation during which
players can receive outputs and provide new inputs at intermediate
stages. In both cases, the functionality is described by an algebraic
circuit over a finite field.
Three types of corruptions are usually considered: active, passive,
and fail corruptions. The adversary's corruption power is
characterized by a constraint on which players he can potentially
corrupt, and in which way. One is interested in the exact condition for
which SFE and MPC are possible. So far, only restricted settings were
considered where either the condition is a threshold condition or
where not all three corruption types were considered at the same
time. For all these models, the exact conditions are identical for
perfectly secure SFE and MPC.
We present a very simple approach to secure computation and, based on
it, establish the exact conditions for perfectly secure SFE and MPC
for the natural general adversary model allowing active, passive, and
fail corruptions of players. Surprisingly, these two conditions are
distinct, i.e., there exist adversaries against which secure SFE is
possible, but secure MPC is not possible.
This is joint work with Zuzana Beerliova-Trubiniova, Matthias Fitzi,
Martin Hirt, Vassilis Zikas.
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