GPG key error at apt-get

Depends:
# apt-get install debian-keyring debian-archive-keyring

If you get o follow error from an unofficial repository:

 W: GPG error: ftp://ftp.ragner.net etch Release: The following
 signatures couldn't be verified because the public key is not available:
 NO_PUBKEY 08GC463D1F41D098

Take the GPG key

# gpg --keyserver subkeys.pgp.net --recv-keys 08GC463D1F41D098

and add to apt

gpg --export --armor 08GC463D1F41D098 | sudo apt-key add -

End