how to fix this updates installation?
Requires installation of untrusted packages
The action would require the installation of packages from not authenticated sources.
Details : libnux-1.0-0 libnux-1.0-common
More often than not, I've found that this error results from corruption in the security keys associated with the upgrade sources. The easy way to fix this is as follows (hit Enter after each line, and don't type the $ or # symbols):
$ sudo -i
# apt-get clean
# cd /var/lib/apt
# mv lists lists.old
# mkdir -p lists/partial
# apt-get update