PGP 5.0: The DOS Version
Follow these steps to install and use DOS version PGP 5.0. Remember: It’s all DOS, so you can’t have
filenames with more than 8 characters, and no more than 3 characters in the extension.
You will likely want to use your hard drive for all this. However, you might want to use a bootable
floppy disk that has an editor (such as notepad.exe or editor.com) on it. Keeping your PGP files and, in
particular, your encrypted private key, on a removable medium minimizes your security risk. (Note
that a USB Pen Drive might be a better choice. For example, you could store your files on a USB Pen
Drive and carry it on a chain around your neck wherever you go.)
Unless you create a configuration file, PGP will complain a lot about your not having one, but you can
get along just fine without one. See pgpcfg.doc for more information.
We assume here that you are Mary Smith, and you are communicating with John Smith.
INSTALLATION
1. Go to http://www.pgpi.com and click on download (the latest freeware PGP), then click on PGP, then
click on MS-DOS, then click on Download PGP 5.0i, then click on Norway, and download
pgp50ibi.zip.
2. Unzip pgp50ibi.zip, preferably to c:\pgp (or to a:\). Usually just double-clicking on it does the trick. If
you need unzipper, you can go to http://www.winzip.com/ and download an evaluation copy of WinZip
or you can go to http://www.stuffit.com/consumer.html and download a free copy of Stuffit.
3. Open a DOS window . Even better: Boot to DOS - since Windows saves temp files everywhere, you
might want it totally out of the picture.
4. Go to the PGP directory, using the DOS command: cd c:\pgp or cd a:\pgp
5. Install PGP by entering the DOS command (‘o’ = ‘old’): install o
6. You might want to check to make sure all the PGP files are here by entering: dir
The most important files are pgpo.exe (encryption/decryption) and pgpk.exe (key management).
7. To get a list of options, enter: pgpo –h and pgpk -h
CREATING YOUR PUBLIC KEY PAIR- Do this only once!
1. To create your public key pair, enter (‘k’ = key management; ‘g’ = generate): pgpk –g
a. You want a Diffie-Hellman key, so to the question about public key type, enter: 1
b. A pair of 1024-bit keys (public & private) will do, so for the next question, enter: 2
c. For a User ID, enter your name, for example, John Smith.
d. Enter whatever key validity length you want (0 = forever).
e. Enter a pass phrase. The longer the better. Spaces count. Case counts.
f. Finally, you click the keyboard randomly until told to stop. Then PGP will create your public key
pair. PGP will put your public key in the file PUBRING.PKR and your private key (encrypted with
your pass phrase) in the file SECRING.SKR. You can examine the contents of your public key ring
by entering (‘l’ = list): pgpk –l
DISTRIBUTING YOUR PUBLIC KEY
1. To extract your public key from PUBRING.PKR so you can email it to your friends, if your User ID is
Mary Smith, enter (‘x’ = extract a key; ‘o’ = output file to put it in):
pgpk –x “Mary Smith” –o msmith.key
a. You will get an error message, “Cannot open configuration file pgp.cfg” - ignore it.
2. To see your public key, enter: type msmith.key
a. If your correspondent is also using DOS PGP, simply attach the *.key file to an email
b. If your correspondent is using an email client that has PGP built in, you can copy the contents of the
*.key file to the Windows clipboard. Then run your email client, create an email to your friend, and
paste your key into the email body. Now the recipient can merely click a single button to decrypt
your message.
3. NOTE : At this point, all you can do is:
a. Send other people your public key (so they can send you messages).
b. Sign plain text messages with your secret key and send them to people. (See below.)
c. Wait for your correspondents to send you their public keys.
d. You CANNOT send any encrypted messages until someone sends you their public key.
