Too many people are dangerously unaware that their email messages are sent  
across the world "in the clear" with no more protection than an open post
card in the traditional paper-based mail. For messages such as "Having a 
great time on vacation, wish you were here," probably no harm is done.  
But this same exposure exists also for more serious messages such as those 
containing contract negotiations, proprietary information, or your own 
copyrighted material that you send out for review.  Another description as
to why it is necessary to use encryption for email is here:
"http://www.pgp.net/pgpnet/pgp-faq/pgp-faq-general-questions.html#pgp-why"
The Carnegie Mellon CERT Coordination Center on their web site at
"http://www.cert.org/contact_cert/encryptmail.html" says: "We strongly urge 
you to encrypt sensitive information." You may rightly conclude that you 
are in good company using email encryption.

For your convenience, the GNU Privacy Guard (GnuPG) key in the file  
"marwalk@marwalk.com-public-key.txt" is the key to use in sending secure  
encrypted messages to me, Mark Caldwell Walker, at marwalk@marwalk.com.   
Another way to say this is that "marwalk@marwalk.com-public-key.txt" is my  
public key.  You can use this key to encrypt your messages to me.  Once you  
encrypt a message with my public key, I and only I am able to decrypt it;  
all others, including you, have an utterly minuscule chance of decrypting 
it even though it was you who encrypted it in the first place (you still 
will have your original message on your own computer though).

If you have and know how to use either Pretty Good Privacy (PGP) or GnuPG,  
feel free to import this key into your public keyring. The "fingerprint" of  
the key is in the file "key-fingerprint.txt" for you to use in verification  
that the key you import is in fact my public key.  If you already know me  
personally, feel free to contact me to see about a mutual "key signing party."

For anyone who has never used public key encryption, there is a wealth of 
help and information on the Internet.  I will not attempt to make this short 
note into a GnuPG tutorial, but I would be surprised if you did not find the 
requisite RTFM activity for GnuPG a pleasant experience.  The installation 
includes excellent "readme" and "man" files that are invaluable.

Enough of words, here's how to get going:

Get the install files from one of the links here:
"http://ftp.gnupg.org/GnuPG/" or
"http://www.gnupg.org/download/mirrors.html"
Go to the mirror nearest you, and get the latest version available (which  
might be at the bottom of the page).  For W32 binaries, it will have a file 
name something like: "gnupg-w32cli-1.4.2.exe" (or later version). The commands 
in the W32 installation are basically the same as the Unix flavor versions.
Get GnuPG for Mac OS X at "http://macgpg.sourceforge.net/"

Quickly satisfy your curiosity with the FAQ page at:
"http://www.gnupg.org/documentation/faqs.html"

Once you have generated your public key, you might wish to place it on a
public key server.  A well known server is at MIT: "http://pgp.mit.edu/"

If you at first have difficulty integrating GnuPG into your current email  
client, try just encrypting message files that you have written off line 
(be sure to "ASCII armor" them; RTFM to see how) and sending your encrypted 
files as attachments to your messages.  Most recipients should know what to 
do with them.

Changing to a GnuPG-friendly email client might help; Mozilla Thunderbird 
is an excellent choice among several, and installations are available for
OS X, Linux, as well as W32.  Thunderbird needs a plug-in, but it 
functions very well.  Get the "Enigmail" plug-in for Thunderbird at 
"http://enigmail.mozdev.org/download.html" and install it by using the 
"Tools --> Extensions --> Install" menu choices in Thunderbird.  With minimal 
tweaking, your GnuPG encryption capability will be seamlessly integrated 
into your Thunderbird email client.

There is a difference between PGP and the X.509 Certificates that you might
use in a large government or corporate organization.  So far there is little
if any compatibility between these systems.  A good description of the 
difference between PGP and X.509 is in an MS Word document at:
"http://csrc.nist.gov/ecforum/comments/Cybercash-comments.doc"
This still does not prevent you from enabling both systems on your email 
client and using the appropriate one for each respective recipient you email.

If you'd like to "geek-out" on things "encryption," two places to start are:
"http://www.pki-page.org/"
"http://www.pgp.net/pgpnet/pgp-faq/pgp-faq.html"

Regardless of its warts, public key encryption certainly beats whispering 
your intimate secrets with a hidden open microphone nearby.

Happy secure messaging,
Mark