23,508 research outputs found
Combinatorial Solutions Providing Improved Security for the Generalized Russian Cards Problem
We present the first formal mathematical presentation of the generalized
Russian cards problem, and provide rigorous security definitions that capture
both basic and extended versions of weak and perfect security notions. In the
generalized Russian cards problem, three players, Alice, Bob, and Cathy, are
dealt a deck of cards, each given , , and cards, respectively.
The goal is for Alice and Bob to learn each other's hands via public
communication, without Cathy learning the fate of any particular card. The
basic idea is that Alice announces a set of possible hands she might hold, and
Bob, using knowledge of his own hand, should be able to learn Alice's cards
from this announcement, but Cathy should not. Using a combinatorial approach,
we are able to give a nice characterization of informative strategies (i.e.,
strategies allowing Bob to learn Alice's hand), having optimal communication
complexity, namely the set of possible hands Alice announces must be equivalent
to a large set of -designs, where . We also provide some
interesting necessary conditions for certain types of deals to be
simultaneously informative and secure. That is, for deals satisfying
for some , where and the strategy is assumed to satisfy
a strong version of security (namely perfect -security), we show that and hence . We also give a precise characterization of informative
and perfectly -secure deals of the form satisfying involving -designs
Interaction in Quantum Communication
In some scenarios there are ways of conveying information with many fewer,
even exponentially fewer, qubits than possible classically. Moreover, some of
these methods have a very simple structure--they involve only few message
exchanges between the communicating parties. It is therefore natural to ask
whether every classical protocol may be transformed to a ``simpler'' quantum
protocol--one that has similar efficiency, but uses fewer message exchanges.
We show that for any constant k, there is a problem such that its k+1 message
classical communication complexity is exponentially smaller than its k message
quantum communication complexity. This, in particular, proves a round hierarchy
theorem for quantum communication complexity, and implies, via a simple
reduction, an Omega(N^{1/k}) lower bound for k message quantum protocols for
Set Disjointness for constant k.
Enroute, we prove information-theoretic lemmas, and define a related measure
of correlation, the informational distance, that we believe may be of
significance in other contexts as well.Comment: 35 pages. Uses IEEEtran.cls, IEEEbib.bst. Submitted to IEEE
Transactions on Information Theory. Strengthens results in quant-ph/0005106,
quant-ph/0004100 and an earlier version presented in STOC 200
A secure additive protocol for card players
Consider three players Alice, Bob and Cath who hold a, b and c cards,
respectively, from a deck of d=a+b+c cards. The cards are all different and
players only know their own cards. Suppose Alice and Bob wish to communicate
their cards to each other without Cath learning whether Alice or Bob holds a
specific card.
Considering the cards as consecutive natural numbers 0,1,..., we investigate
general conditions for when Alice or Bob can safely announce the sum of the
cards they hold modulo an appropriately chosen integer. We demonstrate that
this holds whenever a,b>2 and c=1. Because Cath holds a single card, this also
implies that Alice and Bob will learn the card deal from the other player's
announcement
The Road to Quantum Computational Supremacy
We present an idiosyncratic view of the race for quantum computational
supremacy. Google's approach and IBM challenge are examined. An unexpected
side-effect of the race is the significant progress in designing fast classical
algorithms. Quantum supremacy, if achieved, won't make classical computing
obsolete.Comment: 15 pages, 1 figur
Special Libraries, January 1958
Volume 49, Issue 1https://scholarworks.sjsu.edu/sla_sl_1958/1000/thumbnail.jp
Secure aggregation of distributed information: How a team of agents can safely share secrets in front of a spy
We consider the generic problem of Secure Aggregation of Distributed
Information (SADI), where several agents acting as a team have information
distributed among them, modeled by means of a publicly known deck of cards
distributed among the agents, so that each of them knows only her cards. The
agents have to exchange and aggregate the information about how the cards are
distributed among them by means of public announcements over insecure
communication channels, intercepted by an adversary "eavesdropper", in such a
way that the adversary does not learn who holds any of the cards. We present a
combinatorial construction of protocols that provides a direct solution of a
class of SADI problems and develop a technique of iterated reduction of SADI
problems to smaller ones which are eventually solvable directly. We show that
our methods provide a solution to a large class of SADI problems, including all
SADI problems with sufficiently large size and sufficiently balanced card
distributions
Special Libraries, October 1960
Volume 51, Issue 8https://scholarworks.sjsu.edu/sla_sl_1960/1007/thumbnail.jp
Special Libraries, October 1960
Volume 51, Issue 8https://scholarworks.sjsu.edu/sla_sl_1960/1007/thumbnail.jp
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