\documentclass[12pt]{article}
\usepackage{url,amsmath,setspace,amssymb}


\setlength{\oddsidemargin}{.25in}
\setlength{\evensidemargin}{.25in}
\setlength{\textwidth}{6.25in}
\setlength{\topmargin}{-0.4in}
\setlength{\textheight}{8.5in}

\newcommand{\heading}[5]{
   \renewcommand{\thepage}{#1-\arabic{page}}
   \noindent
   \begin{center}
   \framebox[\textwidth]{
     \begin{minipage}{0.9\textwidth} \onehalfspacing
       {\bf CSL 759 -- Cryptography and Network Security} \hfill #2

       {\centering \Large #5
       
       }\medskip

       {\it #3 \hfill #4}
     \end{minipage}
   }
   \end{center}
}

\newcommand{\handout}[3]{\heading{#1}{#2}{Instructor:
Shweta Agrawal}{Scribe: Your Name}{Lecture #1: #3}}

\setlength{\parindent}{0in}

\newcommand{\proof}{{\bf Proof. }} %% To begin a proof write \proof
\newcommand{\qed}{\mbox{}\hspace*{\fill}\nolinebreak\mbox{$\rule{0.6em}{0.6em}$}} %%to end your proof write $\qed$.
\newcommand{\ma}{{\mathcal A}}
\newcommand{\mf}{{\mathcal F}}
\newcommand{\hs}{\heartsuit}
\newcommand{\cs}{\clubsuit}
\newcommand{\noi}{\noindent}
\newtheorem{lemma}{Lemma}
\newtheorem{theorem}[lemma]{Theorem}
\newtheorem{definition}{Definition}
\newtheorem{proposition}{Proposition}
\bibliographystyle{plain}

\begin{document}
\handout{3}{Jan 20, 2009}{Something}
\section{Some section title}
\begin{definition} Some definition
\end{definition}

\begin{theorem}
Some theorem
\end{theorem}
\proof
Some proof
\qed
\end{document}