[Busec] busec today: Foteini Baldimtsi (Wed 10am)

Sharon Goldberg goldbe at cs.bu.edu
Wed Sep 17 08:09:44 EDT 2014

Today, our new postdoc, Foteini Baldimtsi, will be talking about
transferable e-cash.  And the Wed after that, Leo Rezyin will talk about
key derivation from noisy sources.  As usual, lunch is after the seminar,
and abstracts are below.

Hope you can make it!

BUsec Calendar:  http://www.bu.edu/cs/busec/
BUsec Mailing list: http://cs-mailman.bu.edu/mailman/listinfo/busec

The busec seminar gratefully acknowledges the support of BU's Center for
Reliable Information Systems and Cyber Security (RISCS).


Truly Anonymous Transferable E-Cash
Speaker: Foteini Baldimtsi. BU
Wednesday Sept 17, 2014  10-11am
Hariri Seminar Room, MCS180

Abstract:  Cryptographic e-cash allows off-line electronic transactions
between a bank, users and merchants in a secure and anonymous fashion. A
plethora of e-cash constructions has been proposed in the literature;
however, these traditional e-cash schemes only allow coins to be
transferred once between users and merchants. Ideally, we would like users
to be able to transfer coins between each other multiple times before
deposit, as happens with physical cash. “Transferable” e-cash schemes are
the solution to this problem. Unfortunately, the currently proposed schemes
are either not efficient at all, or do not achieve the desirable anonymity
properties without compromises, such as the existence of a judge,
responsible for persecuting double spenders, who can trace all coins and
users in the system. This paper presents the first efficient and fully
anonymous transferable e-cash scheme without a judge. We start by revising
the security and anonymity properties of transferable e-cash to capture
issues that were previously ignored. For our construction we use the
recently proposed malleable signatures by Chase et al. to allow secure and
anonymous transferring of the coins. Finally, we propose an independent,
efficient double spending detection mechanism and discuss possible real
world applications of our construction.

Joint work with: Melissa Chase, Georg Fuchsbauer, Markulf Kohlweiss


Title: Key Derivation From Noisy Sources With More Errors Than Entropy
Speaker: Leonid Reyzin, BU
Wednesday September 24, 10-11:30 am
Hariri Seminar Room, MCS180

Fuzzy extractors convert a noisy source of entropy (such as a visual
password, a biometric reading, or a physically unclonable function) into a
consistent uniformly distributed key. In the process of eliminating noise,
they lose some of the entropy of the original source. Specifically, to
tolerate t errors, most natural constructions lose at least as much entropy
as the logarithm of the volume of the ball of radius t. This loss is too
high for many practically important sources, which do not have sufficient
starting entropy to tolerate it.

We construct the first fuzzy extractors that work for a large class of
sources whose starting entropy is not high enough to tolerate such a loss.
Our constructions correct Hamming errors over a large alphabet and
(necessarily) impose certain restrictions on the distribution of the
source. Their security is computational; unlike information-theoretic
constructions, they are ``reusable''--i.e., permit multiple independent
enrollments of correlated readings.

We also explore the limits of achievable error-tolerance by fuzzy
extractors, showing that customization for a particular distribution can be
a powerful tool.

Joint work with Ran Canetti, Benjamin Fuller, Omer Paneth, and Adam Smith
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