PGP: A Simple Usage Guide
David Endler
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The freeware program PGP (Pretty Good Privacy) has become the
standard for encrypting Internet email and verifying the
authenticity of the email's author. Use of PGP has been prompted by
the growing concern for privacy in the very non-private realm of
the Internet. The article, "PGP: A Simple Guide to Pretty Good
Privacy Setup," in the July issue of Sys Admin stepped
through the basic configuration of PGP. This article concludes the
two-part series by exploring PGP's use as an encryption and
document-signing tool. Several useful PGP commands are shown in the
accompanying sidebar.
Encrypting a File
After completing the initial setup discussed in the previous
article, you are ready to encrypt a file. Once you have added a
person's public key to your public key ring, you can encrypt a
message to them using that key. The syntax is pgp -e
filename. We will add the -a and -t options,
respectively, meaning that we want ASCII output and that we are
dealing with a plaintext input file that should be converted
accordingly. For example, see the following file called
file.text:
Hi there,
This is Dave sending you some email just so we can
test out one of the wonderful uses of PGP.
-dave
For the ease of example, I will encrypt the file to myself since
(a) I have the public key, and (b) I can illustrate decryption
later using the same message. I type:
% pgp -eta file.text
Recipients' public key(s) will be used to encrypt.
A user ID is required to select the recipient's public key.
Enter the recipient's user ID: endler
Key for user ID: David Endler <endler@eecs.t
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