CIS Seminar - Dominique Unruh
Speaker: Dominique Unruh , Saarland University
Date: March 28 2008
Time: 10:30AM to 12:00PM
Location: G449 Patil/Kiva
Host: Dr. Y Dodis, NYU
Contact: Be Blackburn, 3-6098, imbe@mit.edu
Relevant URL: In a coercion attack, an attacker forces a basically honest party to
deviate from the protocol; the protocol is only considered secure if
the coerced party is able to follow its original protocol while making
the attacker believe that the party followed the attacker's
instructions.
We present an extension of the Universal Composability framework that
allows to model the security of cryptographic protocols against
coercion. The framework allows to model general protocol tasks as ideal
functionalities and guarantees secure composition.
Various degrees of incoercibility can be expressed, ranging from
deniability (where the honest party only has to deny after the
protocol execution that it performed some actions) to full
incoercibility (where the attacker may force the party to deviate from
the protocol to produce proofs of its actions).
We compare the framework with the Global UC framework by Canetti,
Dodis, Pass and Walfish which also models deniability. We argue that
the Global UC framework models deniability against an outside
adversary, while our framework models deniability or incoercibility
against an inside adversary partaking in the protocol.
Finally, we investigate composable incoercible commitments.
(Joint work with Jörn Müller-Quade.)
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