How to set up signing/encryption with GnuPG? Some newbie questions

[Marius Hofert <marius.hofert@math.ethz.ch>]

Hi,

Although I found and read (not necessarily understood :-) ) the security related
parts of the Gnus manual (e.g., C-h i Gnus -> Security), I still have the
following questions concerning signing and encryption of messages with Gnus:

1) What is a useful/meaningful setup in ~/.gnus.el for obtaining enabling GnusPG
for PGP/MIME?
I figured the following to be useful:
(setq mm-verify-option 'always); always verify signed parts
(setq mm-decrypt-option 'always); always decrypt encrypted parts
(setq gnus-message-replysign t); gnus-message-replyencrypt, gnus-message-replysignencrypted are already t by default
I also found Gnus users who set
(setq gnus-treat-x-pgp-sig t)
but I could not find sufficient documentation of gnus-treat-x-pgp-sig to
determine whether this is useful.

2) Why are gnus-message-replyencrypt and gnus-message-replysignencrypted set to
t by default, but gnus-message-replysign defaults to nil? Has this been
forgotten in the recent change (see http://comments.gmane.org/gmane.emacs.gnus.general/75543)?

3) Is it "good practice" to always sign messages? AFAIK, this does not require
the recipient to deal with encryption, but he could at least check that the
message has the correct signature. How would one always sign messages in Gnus by
default?

4) Where are my private/public keys? I never saw them nor was asked to generate
them. 

5) Am I correct in that signing a message simply requires C-c C-m s p? (and
signing + encrypting C-c C-m c p?)

I tried to send a test mail to adele@gnupp.de (mentioned on the german wiki page
http://de.wikipedia.org/wiki/GNU_Privacy_Guard). I used C-c C-m c p. On sending
via C-c C-c, I received "No public key for <adele@gnupp.de>; skip it? (y or
n)". I chose 'y', since the public key will be sent by adele@gnupp.de. I then
obtained "mml2015-epg-encrypt: No recipient specified". What does this mean?

Cheers,

Marius

PS: I am working with Emacs 24 under Ubuntu 12.04 with Gnus v5.13.