[Busec] busec this week: Muthu Venkitasubramaniam (Thurs 11am @ CS137)

Ran Canetti canetti at bu.edu
Sun Apr 13 10:09:21 EDT 2014



This week we have a talk about concurrent computation by Muthu
Venkitasubramaniam from the University of Rochester. The talk will be at 
an *unusual time*, Thursday at 11am, at CS137 followed by lunch.

See you there!

Sharon



*****

Adaptive and Concurrent Secure Computation from New Adaptive,
Non-Malleable Commitments
Muthu Venkitasubramaniam
University of Rochester.
Thursday April 17, 2014
11-12:30

Abstract:
We present a unified approach for obtaining general secure computation
that achieves adaptive-Universally Composable (UC)-security.
Conceptually, our approach can be viewed as an adaptive analogue to the
recent work of Lin, Pass and Venkitasubramaniam [STOC ‘09], who
considered only static (i.e. non-adaptive) adversaries. Their main
insight was that the non-malleability requirement could be decoupled
from the simulation requirement to achieve UC-security. A main
conceptual contribution of this work is, quite surprisingly, that it is
still the case even when considering adaptive security. Using our
approach we essentially obtain all previous results on adaptive
concurrent secure computation, both in relaxed models (e.g.,
quasi-polynomial time simulation), as well as trusted setup models
(e.g., the CRS model, the imperfect CRS model). As a corollary we also
obtain the first adaptively secure multiparty computation protocol in
the plain model that is secure under bounded-concurrency.

A key element in our construction is a commitment scheme that satisfies
a strong definition of non- malleability. Our new primitive of
concurrent equivocal non-malleable commitments, intuitively, guarantees
that even when a man-in-the-middle adversary observes concurrent
equivocal commitments and decommitments, the binding property of the
commitments continues to hold for commitments made by the adversary.
This definition is stronger than previous ones, and may be of
independent interest. Previous constructions that satisfy our definition 
have been constructed in setup models, but either re- quire existence of 
stronger encryption schemes such as CCA-secure encryption or require 
independent “trapdoors” provided by the setup for every pair of parties 
to ensure non-malleability. A main technical contribution of this work 
is to provide a construction that eliminates these requirements and 
requires only a single trapdoor.

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