In this paper we show some e cient and unconditionally secure oblivious transfer reductions Our main tool is a class of functions that generalizes the Zig zag functions introduced by Brassard Crep eau and S antha in We show necessary and su cient conditions for the existence of such generalized functions and some characterizations in terms of well known combinatorial structures Moreover we poin...

In this paper, we consider three very important issues namely detection, identification and robustness of k-out-of-n secret sharing schemes against rushing cheaters who are allowed to submit (possibly forged) shares after observing shares of the honest users in the reconstruction phase. Towards this we present five different schemes. Among these, first we present two k-out-of-n secret sharing s...

One of the main open problems in secret sharing is the characterization of the access structures of ideal secret sharing schemes. Brickell and Davenport proved that every one of these ideal access structures is related in a certain way to a unique matroid. Specifically, they are matroid ports. In addition to the search of general results, this difficult open problem has been studied in previous...

A necessary and sufficient condition for the asymptotic idealness of the AsmuthBloom threshold secret sharing scheme is proposed. Apart from this, a comprehensive analysis of the known variants of the Asmuth-Bloom threshold secret sharing scheme is provided, clarifying the security properties achieved by each of them.

More and more metering schemes based on some special protocols or mechanisms are used to calculate the number of visits which a website receives in a certain time frame. Then, the amount of money that an advertiser pay to a website depends on this number of visits. Until now, many protocols were suggested for metering schemes in literature. However, the discussion mainly focused on the theory o...

Formulate the problem as follows. Split a file into n pieces so that it can be restored without any m parts (1<=m<=n). Such problems are called problems secret sharing. There exists a set of methods for solving such problems, but they all require a fairly large number of calculations applied to the problem posed above. The proposed method does not require calculations, and requires only the ope...

Visual secret sharing by using generalized random grids is a novel approach for generating nonexpansible shares by artfully utilizing various random variables. Stacking the shares together, secret image can be revealed. This paper proposes a 2 out of 3 visual multiple secret sharing method using generalized random grids. Three secret images (A, B, C) are used for generating three non-expansible...

We investigate whether two players in a long-run relationship can maintain cooperation when the details of the underlying game are unknown. Specifically, we consider a new class of repeated games with private monitoring, where an unobservable state of the world influences the payoff functions and/or the monitoring structure. Each player privately learns the state over time, but cannot observe w...

Starting from a new relation between graphs and secret sharing schemes introduced by Xiao, Liu and Zhang, we show a method to construct more general ideal homogeneous access structures. The method has some advantages: it efficiently gives an ideal homogeneous access structure for the desired rank, and some conditions can be imposed (such as forbidden or necessary subsets of players), even if th...