The action would require the installation of packages from not authenticated sources.This is a common problem if 'Software Center' try to download from any 'unauthenticated' source.
And if you click on 'details' then it may show an another message:
libcddb2 libdvbpsi5 libebml0 libiso9660-7 liblua5.1-0
libmatroska0 libsdl-image1.2 libtar libupnp3 libvcdinfo0
Don't worry. Download your desired software using 'Synaptic' and update your system regularly. Problem will solved by itself. You do not need to do anything. Just stay calm.