Putem synaptica dodam repozitorij (url), kliknem na reload i maltretira me s nekim public key. Kako da sredim situaciju? (Pitanje ne može bit jednostavnije) 
pozdrav
zbunjeni
If you get errors about missing keys, lookup the key in this file
and run these commands (replace KEY with the key number):
gpg --keyserver subkeys.pgp.net --recv KEY
gpg --export --armor KEY | sudo apt-key add -
If you have a gpg key URL use (replace URL with the key address):
wget URL --quiet -O - | sudo apt-key add -
If you have a gpg key file use (replace FILE with the key file):
sudo apt-key add FILE
Thx
zbunjeni