See also: http://www.hackzine.org/register-apt-repository-key.html
Here is an useful script to register APT keys, to avoid the “There are no public key available for the following key IDs” warning message.
#!/bin/bash
# samu 2010-01-01
# (c) 2010 Samuele ~redShadow~ Santi
# redshadow&hackzine.org - http://www.hackzine.org
# Under Gnu GPL v3
KEYID="$1"
echo "Registering APT key $1..."
gpg --keyserver pgp.mit.edu --recv-keys "$KEYID"
gpg --export --armor "$KEYID" | apt-key add -
From: http://www.debian-administration.org/users/dkg/weblog/11
apt-get install debian-archive-keyring
or, if you have unstable repositories:
apt-get install debian-archive-keyring/unstable
Another method, is just to run:
apt-key update
“This will obtain the necessary keys and import them. No need to go through gpg directly”.
Anyways, this method will not always work.