\documentclass[10pt]{article}

\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[italian]{babel}
\usepackage{a4wide}
\usepackage{url}

\newcommand{\esercizio}[1]{{\bf Esercizio #1.}\par}

\title{Sicurezza e Crittografia\\[2mm]{\small\emph{Anno Accademico 2010-2011}}\\[4mm] \textbf{Homework \NumeroHomework}}
\author{\Nome\ \Cognome, Matricola \Matricola}

%%%% Comandi da Modificare %%%
\newcommand{\NumeroHomework}{??}
\newcommand{\Cognome}{??}
\newcommand{\Nome}{??}
\newcommand{\Matricola}{??}

\begin{document}
\maketitle
%%%%%%%%%%%%%
\esercizio{1}
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??
\par\vspace{3mm}
%%%%%%%%%%%%%
\esercizio{2}
%%%%%%%%%%%%%
??
\par\vspace{3mm}
%%%%%%%%%%%%%
\esercizio{3}
%%%%%%%%%%%%%
??
\par\vspace{3mm}
\end{document}
