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+++ b/handout.tex	Tue Aug 08 18:54:58 2006 -0400
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+% two sided printing
+\documentclass[letterpaper,12pt]{article}
+
+\usepackage[reset,margin=1in]{geometry}
+\usepackage{url}
+\usepackage{epsfig}
+
+\title{\huge GPG\normalsize}
+\author{Josef ``Jeff'' Sipek $<$jeffpc@josefsipek.net$>$}
+\date{}
+\twocolumn
+\begin{document}
+\maketitle
+\vspace{0.75cm}
+
+\noindent\fbox{
+\begin{minipage}{0.9\linewidth}
+{\bf Cryptography}, n.
+
+The science which studies methods for encoding messages so
+that they can be read only by a person who knows the
+secret information required for decoding, called the key
+\end{minipage}
+}
+
+
+\section{History}
+\begin{itemize}
+	\item Caesar cipher -- used by Julius Caesar to deliver messages to
+	his generals. A simple substitution cipher which relied on the
+	illiteracy of majority of people.
+	\item ROT13 -- ``modern'' version of the Caesar cipher. It shifts
+	all characters by 13 instead of 3. Since there are only 26 letters
+	in the english alphabet, an interesting effect occurs: encryption
+	and decryption are one and the same operation!
+\end{itemize}
+
+\subsection{Symmetric ciphers}
+Both Caesar and ROT13 are \emph{symmetric} ciphers. That means that the same
+key is used during both encryption and decryption.
+
+Some modern symmetric ciphers include \emph{AES} and \emph{Blowfish}. Both
+of these ciphers, with a good key are \emph{effectively} unbreakable with
+today's technology \& mathematics.
+
+The only problem with symmetric ciphers is the fact that the key has to be
+agreed upon over a secure channel -- in-person meeting, trusted courier, etc.
+
+
+\section{Asymmetric ciphers}
+The solution to the problem is ``simple'' --- it is called \emph{asymetric}
+ciphers. Asymmetric ciphers consist of 2 keys. One \emph{private} and the
+other \emph{public}. The public key is exactly that, public. You can post it
+on your website and not worry about a thing. The private key should be kept
+secure at all times. The private key allows you to do all the cool things.
+:)
+
+\subsection{Generating a key-pair}
+Large random numbers are the basis of modern cryptography.
+
+\noindent
+\begin{minipage}{0.5\linewidth}
+\begin{center}
+\epsfig{file=Public_key_making.eps, scale=0.45}
+\end{center}
+\end{minipage}
+
+\newpage
+\subsection{Uses}
+Such key-pair can be used to:
+\begin{itemize}
+	\item Sign/Verify signature
+	\begin{itemize}
+		\item Sign with private key
+		\item Verify with public key
+	\end{itemize}
+\end{itemize}
+
+\noindent
+\begin{minipage}{0.5\linewidth}
+\begin{center}
+\epsfig{file=Public_key_signing.eps, scale=0.45}
+\end{center}
+\end{minipage}
+
+\begin{itemize}
+	\item Encrypt/Decrypt
+	\begin{itemize}
+		\item Encrypt with public key
+		\item Decrypt with private key
+	\end{itemize}
+\end{itemize}
+
+\noindent
+\begin{minipage}{0.5\linewidth}
+\begin{center}
+\epsfig{file=Public_key_encryption.eps, scale=0.45}
+\end{center}
+\end{minipage}
+
+\section{GPG commands}
+\noindent{\bf Generate a new key-pair}:\\
+\noindent{\texttt gpg --gen-key}\\
+
+\noindent{\bf Sign a file}:\\
+\noindent{\texttt gpg --clearsign \emph{filename}}\\
+\noindent{\texttt gpg -a --sign \emph{filename}}\\
+
+\noindent{\bf Verify a signature on a file}:\\
+\noindent{\texttt gpg --verify \emph{filename}}\\
+
+\noindent{\bf Encrypt a file}:\\
+\noindent{\texttt gpg --encrypt \emph{filename}}\\
+\noindent{\texttt gpg -a --encrypt \emph{filename}}\\
+
+\noindent{\bf Decrypt a file}:\\
+\noindent{\texttt gpg --decrypt \emph{filename}}\\
+
+\subsection{Nasty, eh?}
+Since using GPG directly is rather nasty, people have developed many
+GUI/console frontends, as well as integrated GPG functionality right into
+their applications. For example, Kmail, mutt, both integrate with GPG very
+nicely.
+
+\section{Resources}
+Images shamelessly stolen from Wikipedia.
+
+\begin{itemize}
+	\item Wikipedia \\
+		\url{http://en.wikipedia.org/wiki/Asymmetric_key_algorithm}
+	\item GNU Privacy Guard \\
+		\url{http://www.gnupg.org}
+	\item OpenPGP Message Format \\
+		\url{http://www.ietf.org/rfc/rfc2440.txt} 
+\end{itemize}
+
+\end{document}