Dear All,
Next weeks research day on Wednesday! will be at the Computer Science Building.
Speaker: Bhavana Kanukurthi (Boston University) Title: "Key Agreement from Close Secrets over Unsecured Channels" Time: 5 pm Place: IFW E44
Abstract:
Can you communicate securely with no public key infrastructure, strong secrets, and computational hardness assumptions? We consider information-theoretic key agreement between two parties sharing somewhat different versions of a secret w that has relatively little entropy. This setting arises, for example, when a trusted server stores the biometric of a user, and the user subsequently uses his fresh biometric reading to authenticate himself to the server. Such key agreement, also known as information reconciliation and privacy amplification over unsecured channels, was shown to be theoretically feasible by Renner and Wolf (Eurocrypt 2004), although no protocol that runs in polynomial time was described. We propose a protocol that is not only polynomial-time, but actually practical, requiring only a few seconds on consumer-grade computers.
Our protocol can be seen as an interactive version of robust fuzzy extractors (Dodis et al., Crypto 2006). While robust fuzzy extractors, due to their noninteractive nature, require w to have entropy at least half its length, we have no such constraint. In fact, unlike in prior solutions, in our solution the entropy loss is essentially unrelated to the length or the entropy of w, and depends only on the security parameter.
The paper appears in Eurocrypt 2009 and is available at http://eprint.iacr.org/2008/494. This is joint work with Leonid Reyzin.
Cheers,
Dejan
Hi all,
At the beginning of the week after SOLA, we will have three guests, namely Lorenzo Maccone from Torino as well as Nicolas Brunner and Paul Skrzypczyk from Bristol.
We have two talks on Tuesday, namely Lorenzo's at 4pm and Nicolas' at 5pm, both in IFW E44.
Below you find their titles, as well as the abstracts of the corresponding articles.
Have a nice evening! Stefan
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Lorenzo Maccone:
"A quantum solution to the arrow-of-time dilemma"
The arrow of time dilemma: the laws of physics are invariant for time inversion, whereas the familiar phenomena we see everyday are not (i.e. entropy increases). I show that, within a quantum mechanical framework, all phenomena which leave a trail of information behind (and hence can be studied by physics) are those where entropy necessarily increases or remains constant. All phenomena where the entropy decreases must not leave any information of their having happened. This situation is completely indistinguishable from their not having happened at all. In the light of this observation, the second law of thermodynamics is reduced to a mere tautology: physics cannot study those processes where entropy has decreased, even if they were commonplace.
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Nicolas Brunner:
"Emergence of Quantum Correlations from Non-Locality Swapping"
By studying generalized non-signalling theories, the hope is to find out what makes quantum mechanics so special. In the present paper, we revisit the paradigmatic model of non-signalling boxes and introduce the concept of a genuine box. This will allow us to present the first generalized non-signalling model featuring quantum-like dynamics. In particular, we present the coupler, a device enabling non-locality swapping, the analogue of quantum entanglement swapping, as well as teleportation. Remarkably, part of the boundary between quantum and post-quantum correlations emerges in our study.
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itp-quantumseminare@lists.phys.ethz.ch