Many tools that use cryptography on Linx revolve around PGP software standard (OpenPGP). The GNU Privacy Guard (GnuPG or GPG) is a popular free software implementation of this standard.
Before starting learning this useful tool to protect your own digital privacy, you might want to understand the algorithm / mechanism behind it:
Now you can start learning the basic usage of GNU
gpg(1), follow the following three
tutorials of this series:
Then you might be also interested in some of the applications of GnuPG:
I personally found the above two applications quite useful in system administration domain.