Universally Composable Protocols with Relaxed Set-up Assumptions
Boaz Barak and Ran Canetti and Jesper Buus
Nielsen and Rafael Pass
Abstract
Known constructions for realizing general functionalities in the
universally composable security framework require that the
parties have access to a common reference string (CRS) that is
drawn {from} a pre-specified distribution in a trusted way.
Furthermore it is known that
realizing general functionalities in the plain model is not possible, even
if ideally authenticated communication is provided.
We propose alternative set-up assumptions and show that they
suffice for reproducing the general feasibility results obtainable
in the CRS model. These alternative assumptions have the flavor of
a ``public-key infrastructure'': parties have registered
public keys, no single registration authority needs to be fully
trusted, and no single piece of information has to be globally
trusted and available. In addition, unlike known protocols in the
CRS model, our protocols guarantee some basic level of security
even if the set-up assumption is violated.
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