1,339 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
A geometric protocol for cryptography with cards
In the generalized Russian cards problem, the three players Alice, Bob and
Cath draw a,b and c cards, respectively, from a deck of a+b+c cards. Players
only know their own cards and what the deck of cards is. Alice and Bob are then
required to communicate their hand of cards to each other by way of public
messages. The communication is said to be safe if Cath does not learn the
ownership of any specific card; in this paper we consider a strengthened notion
of safety introduced by Swanson and Stinson which we call k-safety.
An elegant solution by Atkinson views the cards as points in a finite
projective plane. We propose a general solution in the spirit of Atkinson's,
although based on finite vector spaces rather than projective planes, and call
it the `geometric protocol'. Given arbitrary c,k>0, this protocol gives an
informative and k-safe solution to the generalized Russian cards problem for
infinitely many values of (a,b,c) with b=O(ac). This improves on the collection
of parameters for which solutions are known. In particular, it is the first
solution which guarantees -safety when Cath has more than one card
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
Unconditionally Secure Cryptography: Signature Schemes, User-Private Information Retrieval, and the Generalized Russian Cards Problem
We focus on three different types of multi-party cryptographic protocols. The first is in the area of unconditionally secure signature schemes, the goal of which is to provide users the ability to electronically sign documents without the reliance on computational assumptions needed in traditional digital signatures. The second is on cooperative protocols in which users help each other maintain privacy while querying a database, called user-private information retrieval protocols. The third is concerned with the generalized Russian cards problem, in which two card players wish to communicate their hands to each other via public announcements without the third player learning the card deal. The latter two problems have close ties to the field of combinatorial designs, and properly fit within the field of combinatorial cryptography. All of these problems have a common thread, in that they are grounded in the information-theoretically secure or unconditionally secure setting
Advanced Information Systems and Technologies
This book comprises the proceedings of the VI International Scientific Conference “Advanced Information Systems and Technologies, AIST-2018”. The proceeding papers cover issues related to system analysis and modeling, project management, information system engineering, intelligent data processing, computer networking and telecomunications, modern methods and information technologies of sustainable development. They will be useful for students, graduate students, researchers who interested in computer science
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