6 research outputs found
Does the quantum collapse make sense? Quantum Mechanics vs Multisimultaneity in interferometer-series experiments
It is argued that the three assumptions of quantum collapse, one photon-one
count, and relativity of simultaneity cannot hold together: Nonlocal
correlations can depend on the referential frames of the beam-splitters but not
of the detectors. New experiments using interferometers in series are proposed
which make it possible to test Quantum Mechanics vs Multisimultaneity.Comment: 18 pages Latex, 2 eps figures. Archive adapted version of an article
accepted for publication in Physics Letters
Revisiting Deniability in Quantum Key Exchange via Covert Communication and Entanglement Distillation
We revisit the notion of deniability in quantum key exchange (QKE), a topic
that remains largely unexplored. In the only work on this subject by Donald
Beaver, it is argued that QKE is not necessarily deniable due to an
eavesdropping attack that limits key equivocation. We provide more insight into
the nature of this attack and how it extends to other constructions such as QKE
obtained from uncloneable encryption. We then adopt the framework for quantum
authenticated key exchange, developed by Mosca et al., and extend it to
introduce the notion of coercer-deniable QKE, formalized in terms of the
indistinguishability of real and fake coercer views. Next, we apply results
from a recent work by Arrazola and Scarani on covert quantum communication to
establish a connection between covert QKE and deniability. We propose DC-QKE, a
simple deniable covert QKE protocol, and prove its deniability via a reduction
to the security of covert QKE. Finally, we consider how entanglement
distillation can be used to enable information-theoretically deniable protocols
for QKE and tasks beyond key exchange.Comment: 16 pages, published in the proceedings of NordSec 201
Adaptively Secure Two-Party Computation with Erasures
In the setting of multiparty computation a set of parties with private inputs wish to compute some joint function of their inputs, whilst preserving certain security properties (like privacy and correctness). An adaptively secure protocol is one in which the security properties are preserved even if an adversary can adaptively and dynamically corrupt parties during a computation. This provides a high level of security, that is arguably necessary in today\u27s world of active computer break-ins. Until now, the work on adaptively secure multiparty computation has focused almost exclusively on the setting of an honest majority, and very few works have considered the honest minority and two-party cases. In addition, significant computational and communication costs are incurred by most protocols that achieve adaptive security.
In this work, we consider the two-party setting and assume that honest parties may \emph{erase} data. We show that in this model it is possible to securely compute any two-party functionality in the presence of \emph{adaptive semi-honest adversaries}. Furthermore, our protocol remains secure under concurrent general composition (meaning that it remains secure irrespective of the other protocols running together with it). Our protocol is based on Yao\u27s garbled-circuit construction and, importantly, is as efficient as the analogous protocol for static corruptions. We argue that the model of adaptive corruptions with erasures has been unjustifiably neglected and that it deserves much more attention
The Round Complexity of Secure Computation Against Covert Adversaries
We investigate the exact round complexity of secure multiparty computation (MPC) against *covert* adversaries who may attempt to cheat, but do not wish to be caught doing so. Covert adversaries lie in between semi-honest adversaries who follow protocol specification and malicious adversaries who may deviate arbitrarily.
Recently, two round protocols for semi-honest MPC and four round protocols for malicious-secure MPC were constructed, both of which are optimal. While these results can be viewed as constituting two end points of a security spectrum, we investigate the design of protocols that potentially span the spectrum.
Our main result is an MPC protocol against covert adversaries with variable round complexity: when the detection probability is set to the lowest setting, our protocol requires two rounds and offers same security as semi-honest MPC. By increasing the detecting probability, we can increase the security guarantees, with round complexity five in the extreme case. The security of our protocol is based on standard cryptographic assumptions.
We supplement our positive result with a negative result, ruling out *strict* three round protocols with respect to black-box simulation
Communication-Efficient Secure Logistic Regression
We present a new construction for secure logistic regression training, which enables two parties to train a model on private secret-shared data. Our goal is to minimize online communication and round complexity, while still allowing for an efficient offline phase. As part of our construction we develop many building blocks of independent interest. These include a new approximation technique for the sigmoid function, which results in a secure protocol with better communication; secure spline evaluation and secure powers computation protocols for fixed-point values; and a new comparison protocol that optimizes online communication. We also present a new two-party protocol for generating keys for distributed point functions (DPFs) over arithmetic sharing, where previous constructions do this only for Boolean outputs. We implement our protocol in an end-to-end system and benchmark its efficiency. We can securely evaluate a sigmoid in ms online time and KB of online communication. Our system can train a model over a database with samples and features with online communication of MB and online time of hours at the cost of c over WAN. Our benchmarks demonstrate that we reduce online communication over state of the art by for sigmoid and for logistic regression training
A precise computational approach to knowledge
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 100-103).The seminal work of Goldwasser, Micali and Rackoff put forward a computational approach to knowledge in interactive systems, providing the foundation of modern Cryptography. Their notion bounds the knowledge of a player in terms of his potential computational power (technically defined as polynomial-time computation). In this thesis, we put forward a stronger notion that precisely bounds the knowledge gained by a player in an interaction in terms of the actual computation he has performed (which can be considerably less than any arbitrary polynomial-time computation). Our approach not only remains valid even if P = NP, but is most meaningful when modeling knowledge of computationally easy properties. As such, it broadens the applicability of Cryptography and weakens the complexity theoretic assumptions on which Cryptography can be based.by Rafael Pass.Ph.D