Claudio Fontanari

Rectangular Thinned Arrays Based on McFarland Difference Sets

A new class of analytical rectangular thinned arrays with low peak sidelobe level (PSL) is introduced. The proposed synthesis technique exploits binary sequences derived from McFarland difference sets to design thinned layouts on a lattice of P × P(P+2) positions for any prime P. The pattern features of the arising massively-thinned arrangements characterized by only P × (P+1) active elements are discussed and the results of an extensive numerical analysis are presented to assess advantages and limitations of the McFarland-based arrays.

Watermarking Robustness Evaluation Based on Perceptual Quality via Genetic Algorithms

This paper presents a novel and flexible benchmarking tool based on genetic algorithms (GA) and designed to assess the robustness of any digital image watermarking system. The main idea is to evaluate robustness in terms of perceptual quality, measured by weighted peak signal-to-noise ratio. Through a stochastic approach, we optimize this quality metric, by finding the minimal degradation that needs to be introduced in a marked image in order to remove the embedded watermark. Given a set of attacks, chosen according to the considered application scenario, GA support the optimization of the parameters to be assigned to each processing operation, in order to obtain an unmarked image with perceptual quality as high as possible. Extensive experimental results demonstrate the effectiveness of the proposed evaluation tool.

An improved asymmetric watermarking scheme suitable for copy protection

A major limitation of some recently proposed asymmetric watermarking techniques based on linear algebra lies in the strong dependence of the watermark on the original image. The present correspondence suggests an alternative scheme that not only is secure against projection attack but also allows the insertion of arbitrary watermarking sequences

Digital Image Tracing by Sequential Multiple Watermarking

The possibility of adding several watermarks to the same image would enable many interesting applications such as multimedia document tracing, data usage monitoring, multiple property management. In this paper, we present a novel watermarking scheme which allows to insert and reliably detect multiple watermarks sequentially embedded into a digital image. The proposed method, based on elementary linear algebra, is asymmetric, secure under projection attack and robust against distortion due to basic operations such as storage, transmission, format conversion, etc

Moduli of curves and spin structures via algebraic geometry

GILBERTO BINI AND CLAUDIO FONTANARIAbstract. Here we investigate some birational properties of two collec-tions of moduli spaces, namely moduli spaces of (pointed) stable curvesand of (pointed) spin curves. In particular, we focus on vanishings ofHodge numbers of type (p,0) and on computations of the Kodaira di-mension. Our methods are purely algebro-geometric and rely on aninduction argument on the number of marked points and the genus ofthe curves (cf. [3]).

On the Birational Geometry of the Universal Picard Variety

We compute the Kodaira dimension of the univer- sal Picard variety Pd,g parameterizing line bundles of degree d on curves of genus g under the assumption that (d−g+1,2g−2) = 1. We also give partial results for arbitrary degrees d and we investi- gate for which degrees the universal Picard varieties are birational.

The Horace Method for Error-Correcting Codes: Mathematics Subject Classification (2000)

Here we apply the so-called Horace method for zero-dimensional schemes to error-correcting codes on complete intersections. In particular, we obtain sharper estimates on the minimum distance.

On the birational geometry of moduli spaces of pointed curves

Abstract We prove that the moduli space ℳ g,n of smooth curves of genus g with n marked points is rational for g = 6 and 1 ≤ n ≤ 8, and it is unirational for g = 8 and 1 ≤ n ≤ 11, g = 10 and 1 ≤ n ≤ 3, g = 12 and n = 1.

Hierarchical Secret Sharing in Ad Hoc Networks through Birkhoff Interpolation

Secret sharing schemes provide a natural way of addressing security issues in mobile ad hoc networks. This paper introduces a flexible framework for secure end-to-end transmission of confidential information which exploits multipath source routing and hierarchical shares distribution. Such a goal is achieved by designing a ideal, perfect, and eventually verifiable secret sharing scheme based on Birkhoff polynomial interpolation and by establishing suitable hierarchies among independent paths.

On Waring's problem for many forms and Grassmann defective varieties

Abstract This paper is devoted to the classical Waring type problem for several algebraic forms. Its geometric translation in terms of Grassmann defectivity for projective varieties yields the best possible solution whenever the number of polynomials is greater than the number of variables. In particular, together with a classical theorem of Alessandro Terracini, this result gives a complete answer to Warings problem for several ternary forms.