Non-interactive zero-knowledge (NIZK) systems are fundamental cryptographic primitives used in many constructions, including CCA2-secure cryptosystems, digital signatures, and various cryptographic protocols. What makes them especially attractive, is that they work equally well in a concurrent setting, which is notoriously hard for interactive zero-knowledge protocols. However, while for intera...

We consider the problem of Generic Repeated Coordination, of which Reliable Broadcast and Repeated Distributed Consensus are but two instances. We show that in the absence of in nite storage capacity, all problems in this class require perfect failure detectors, highlighting signi cant assumptions made by many protocols assuming reliable broadcast. Our work also shows that the usual reason used...

A c-ary Perfect Factor is a set of uniformly long cycles whose elements are drawn from a set of size c, in which every possible v-tuple of elements occurs exactly once. In the binary case, i.e. where c = 2, these perfect factors have previously been studied by Etzion, [2], who showed that the obvious necessary conditions for their existence are in fact sufficient. This result has recently been ...

different world views and philosophies in defining development problems and their solutions derive currently from different disciplines. they refer in many respects to the principle of cause-effect as a fundamental relationship between phenomena. the history of differing values and attitudes presented in management and design indicates the importance of this relationship. this sort of knowledge...

Kodaira and Néron classified and described the geometry of the special fibers of the Néron model of an elliptic curve defined over a discrete valuation ring with a perfect residue field. Tate described an algorithm to determine the special fiber type by manipulating the Weierstrass equation. In the case of non-perfect residue fields, we discover new fiber types which are not on the Kodaira-Néro...

This paper first extends the result of Blakley and Kabatianski [3] to general non-perfect SSS using information-theoretic arguments. Furthermore, we refine Okada and Kurosawa’s lower bound [12] into a much more precise information-theoretic characterization of non-perfect secret sharing idealness. In the light of this generalization, we establish that ideal schemes do not always have a matroida...

We investigate solutions of Einstein field equations for the nonstatic spherically symmetric perfect fluid case using different equations of state. The properties of an exact spherically symmetric perfect fluid solutions are obtained which contain shear. We obtain three different solutions out of these one turns out to be an incoherent dust solution and the other two are stiff matter solutions.

By using a recently introduced framework for non-perfect secret sharing, several known results on perfect secret sharing are generalized. Specifically, we discuss about ideal secret sharing schemes, constructions of efficient linear secret sharing schemes, and the search for lower bounds on the length of the shares. Similarly to perfect secret sharing, matroids and polymatroids are very useful ...

A secret sharing scheme is non-perfect if some subsets of participants that cannot recover the secret value have partial information about it. The information ratio of a secret sharing scheme is the ratio between the maximum length of the shares and the length of the secret. This work is dedicated to the search of bounds on the information ratio of non-perfect secret sharing schemes. To this en...