Two secret sharing schemes based on Boolean operations

Experiments in Musical Intelligence

Visual cryptography schemes allow the encoding of a secret image, consisting of black or white pixels, into n shares which are distributed to the participants. The shares are such that only qualified subsets of participants can 'visually' recover the secret image. The secret pixels are shared with techniques that subdivide each secret pixel into a certain number m, m ≥ 2 of subpixels. Such a parameter m is called pixel expansion. Recently Yang introduced a probabilistic model. In such a model the pixel expansion m is 1, that is, there is no pixel expansion. The reconstruction of the image however is probabilistic, meaning that a secret pixel will be correctly reconstructed only with a certain probability. In this paper we propose a generalization of the model proposed by Yang. In our model we fix the pixel expansion m ≥ 1 that can be tolerated and we consider probabilistic schemes attaining such a pixel expansion. For m = 1 our model reduces to the one of Yang. For big enough values of m, for which a deterministic scheme exists, our model reduces to the classical deterministic model. We show that between these two extremes one can trade the probability factor of the scheme with the pixel expansion. Moreover, we prove that there is a one-to-one mapping between deterministic schemes and probabilistic schemes with no pixel expansion, where contrast is traded for the probability factor.

Probabilistic Visual Cryptography Schemes

Distributed Computing Through Combinatorial Topology describes techniques for analyzing distributed algorithms based on award winning combinatorial topology research. The authors present a solid theoretical foundation relevant to many real systems reliant on parallelism with unpredictable delays, such as multicore microprocessors, wireless networks, distributed systems, and Internet protocols. Today, a new student or researcher must assemble a collection of scattered conference publications, which are typically terse and commonly use different notations and terminologies. This book provides a self-contained explanation of the mathematics to readers with computer science backgrounds, as well as explaining computer science concepts to readers with backgrounds in applied mathematics. The first section presents mathematical notions and models, including message passing and shared-memory systems, failures, and timing models. The next section presents core concepts in two chapters each: first, proving a simple result that lends itself to examples and pictures that will build up readers' intuition; then generalizing the concept to prove a more sophisticated result. The overall result weaves together and develops the basic concepts of the field, presenting them in a gradual and intuitively appealing way. The book's final section discusses advanced topics typically found in a graduate-level course for those who wish to explore further. Gathers knowledge otherwise spread across research and conference papers using consistent notations and a standard approach to facilitate understandingPresents unique insights applicable to multiple computing fields, including multicore microprocessors, wireless networks, distributed systems, and Internet protocols Synthesizes and distills material into a simple, unified presentation with examples, illustrations, and exercises

Distributed Computing Through Combinatorial Topology

Visual secret sharing by random grids revisited

Visual cryptography schemes allow the encoding of a secret image into shares, in the form of transparencies, which are distributed to the participants. The shares are such that only qualified subsets of participants can visually recover the secret image by superimposing the transparencies.

In this paper we study colored visual cryptography schemes. Most of previous work on colored visual cryptography allows the superposition of pixels having the same color assuming that the resulting pixel still has the same color. This is not what happens in reality since when superimposing two pixels of the same color one gets a darker version of that color, which effectively is a different color. Superimposing many pixels of the same color might result in a so dark version of the color that the resulting pixel might be not distinguishable from a black pixel.

Thus we propose a model where the reconstruction has to guarantee that the reconstructed secret pixel has the same color of the original one and not a darker version of it. We give a construction of c-color (k,n)-threshold visual cryptography schemes. Since we have to guarantee the reconstruction of the exact original color, in many cases our schemes have a bigger pixel expansion than previous ones. However, for the case of k = n, we get a smaller pixel expansion when compared with schemes that to do not guarantee the exact reconstruction of the original color. We also prove that, in the model introduced in this paper, our schemes for k = n have optimal pixel expansion.

Colored visual cryptography without color darkening

In this paper, we investigate the k-set consensus problem in asynchronous distributed systems. In this problem, each participating process begins the protocol with an input value and by the end of the protocol must decide on one value so that at most k total values are decided by all correct processes. We extend previous work by exploring several variations of the problem definition and model, including for the first time investigation of Byzantine failures. We show that the precise definition of the validity requirement, which characterizes what decision values are allowed as a function of the input values and whether failures occur, is crucial to the solvability of the problem. For example, we show that allowing default decisions in case of failures makes the problem solvable for most values of k despite a minority of failures, even in face of the most severe type of failures (Byzantine). We introduce six validity conditions for this problem (all considered in various contexts in the literature), and demarcate the line between possible and impossible for each case. In many cases, this line is different from the one of the originally studied k-set consensus problem.

On k-set consensus problems in asynchronous systems

We provide new bounds on the expected length L of a binary one-to-one code for a discrete random variable X with entropy H. We prove that L/spl ges/H-log(H+1)-Hlog(1+1/H). This bound improves on previous results. Furthermore, we provide upper bounds on the expected length of the best code as function of H and the most likely source letter probability.

New bounds on the expected length of one-to-one codes

Evolutionary algorithms mimic evolutionary behaviors in order to solve problems. They have been successfully applied in many areas and appear to have a special relationship with creative problems; ...

R. De Prisco

Papers

Probabilistic Visual Cryptography Schemes

Colored visual cryptography without color darkening

On k-set consensus problems in asynchronous systems

New bounds on the expected length of one-to-one codes

EvoComposer: An Evolutionary Algorithm for 4-Voice Music Compositions