+\documentclass[t]{beamer}
+\usetheme{Madrid}
+\usefonttheme[stillsansseriflarge, stillsansserifsmall]{serif}
+\usepackage[T1]{fontenc}
+\usepackage[utf8]{inputenc}
+\usepackage[palatino, helvetica, courier, maths = palatino]{mdwfonts}
+\usepackage{tikz}
+\usepackage{crypto, mdwmath}
+
+\newcommand{\E}{{\mathcal{E}}}
+
+\errorcontextlines=999
+
+\def\Wident{\Xid{W}{ident}}
+\def\Wkx{\Xid{W}{kx}}
+\def\Nupto#1{\{0, 1, \ldots, #1 - 1\}}
+\def\Bin{\{0, 1\}}
+\let\op\star
+\let\le\leqslant
+\let\ge\geqslant
+\let\epsilon\varepsilon
+
+\title{The Wrestlers Protocol}
+\subtitle{A simple, practical, secure, deniable protocol for key-exchange}
+\author{Mark Wooding}
+
+\newdimen\boxwd
+\newenvironment{protocol}[2]{%
+ \small
+ \begin{tikzpicture}[x = 1cm, y = -\baselineskip]
+ \tikzstyle{thoughts} = [text width = #1cm - 4mm, anchor = north]
+ \tikzstyle{alice} = [xshift = 12cm - #1cm/2]
+ \tikzstyle{bob} = [xshift = #1cm/2]
+ \tikzstyle{other} = [text = blue]
+ \tikzstyle{message} =
+ [xshift = #1cm + 2mm, x = 11.6cm - #1cm*2, draw, font = \footnotesize]
+ \draw [rounded corners, fill = blue!20]
+ (0, 0) rectangle +(#1, #2);
+ \draw [rounded corners, fill = red!20]
+ (12cm - #1cm, 0) rectangle +(#1, #2);
+ \path node [alice] at (0, 1) {\normalsize Alice}
+ node [bob] at (0, 1) {\normalsize Bob}
+ ;
+}{%
+ \end{tikzpicture}
+}