#Lorsque :
root@monordi:~# aptitude update
W: GPG error: ftp://ftp.fr.debian.org Etch Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY <0123456789ABCDEF>

# faire :
root@monordi:~# gpg --keyserver <pgpkeys.mit.edu> --recv-key <0123456789ABCDEF>
root@monordi:~# gpg -a --export <0123456789ABCDEF> |apt-key add -
root@monordi:~# aptitude update

http://wiki.ombrenoire.net/Debian_-_GPG
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