Requires installation of untrusted packages "The action would require the installation of packages from not authenticated sources

Try this series of commands.......
Code:
sudo apt-get clean
Code:
cd /var/lib/apt
Code:
sudo mv lists lists.old
Code:
sudo mkdir -p lists/partial
Code:
sudo apt-get clean
Code:
sudo apt-get update
OR........... It may be worth removing/purging the faulty packages in terminal with:
Code:
sudo apt-get remove --purge packagename