Good introduction to GPG concepts?

[Benjamin Esham]

Where can I find a fairly basic introduction to GPG concepts like trust 
models and
signatures?  I've been using GPG for personal use for five years, but 
somehow missed
some of the more basic concepts.  I took a look at the GPG Privacy 
Handbook, but it
looks like it hasn't been updated for six years.

Thanks for the help!

-- 
Benjamin D. Esham
bdesham at gmail.com  |  http://bdesham.net  |  AIM: bdesham128
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