Mal eben copy'n'paste, denke mal die wichtigen Stellen editieren dürfte jetzt selbsterklärend sein 😉
\usepackage{color}
\definecolor{darkblue}{rgb}{0,0,.6}
\definecolor{darkred}{rgb}{.6,0,0}
\definecolor{darkgreen}{rgb}{0,.6,0}
\definecolor{red}{rgb}{.98,0,0}
\usepackage{listings}
\lstloadlanguages{Ruby,Java,SQL}
\lstset{numbers=left,stepnumber=1,frame=single,language=SQL,
basicstyle=\scriptsize\ttfamily,numberstyle=\scriptsize,
commentstyle=\upshape\ttfamily,
numbersep=7pt,tabsize=2,breaklines=false,
morecomment=[l]{//},showtabs=false,showspaces=false,
showstringspaces=false,extendedchars=true,inputencoding={utf8},
keywordstyle=\bfseries\color{darkblue},stringstyle=\color{darkred}}
\lstinputlisting[language=Ruby]{./kasiski.rb}