%% 
%%  A DANTE-Edition example
%% 
%%  Example 36-00-107 on page 814.
%% 
%%  Copyright (C) 2011 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{201.70511pt}
\setlength\parindent{0pt}

\usepackage{amsmath, amsthm, amssymb}
\usepackage{pst-node}
\newcommand {\card}[1]     {\lvert#1\rvert}
\newcommand {\eqobs}       {\equiv_{obs}}
\newcommand {\gameemph}[1] {{\color{blue} #1}}
\newcommand {\gen}[1]      {\langle#1\rangle}
\newcommand {\mybox}[1]    {\psshadowbox[linecolor=gray,shadowcolor=lightgray]{#1}}
\newcommand {\sel}         {\leftarrow}

\begin{document}
\rnode{game1}{\mybox{\small
      \begin{tabular}{llcl}
        let & ($e$, $d$)          & $\sel$ & \gameemph{:encGen ElGamal: $1^n$}\\
            & ($m_1$, $m_2$, $a$) & $\sel$ & :A: ($1^n$, $e$)\\
            & $c$                 & $\sel$ & \gameemph{:encEnc ElGamal: ($1^n$, $e$, $m_1$)}\\
        in  & \multicolumn{3}{l}{:A': ($1^n$, $m_1$, $m_2$, $a$, $e$, $c$)}\\
      \end{tabular}}}\\[1cm]
\hspace*{2cm}
\rnode{game2}{\mybox{\small
      \begin{tabular}{llcl}
        let & ($e$, $d$)          & $\sel$ & \gameemph{let $x$ $\sel$ fun(uniform, $\card{\gen{g_n}}$)}\\
            &                     &        & \gameemph{in ($g_n^x$, $x$)}\\
            & ($m_1$, $m_2$, $a$) & $\sel$ & :A: ($1^n$, $e$)\\
            & $c$                 & $\sel$ & \gameemph{let $y$ $\sel$ fun(uniform, $\card{\gen{g_n}}$)}\\
            &                     &        & \gameemph{in ($g_n^y$, $m_1 \times e^y$)}\\
        in  & \multicolumn{3}{l}{:A': ($1^n$, $m_1$, $m_2$, $a$, $e$, $c$)}\\
      \end{tabular}}}
  %Arrows
  \ncline{->}{game1}{game2}\ncput*{$\eqobs$}
\end{document}