At the moment The Tor Project’s apt repository key is expired. You’ll see the following warning.
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://deb.torproject.org stable Release: The following signatures were invalid: KEYEXPIRED 1409325681 KEYEXPIRED 1409325681 KEYEXPIRED 1409325681 KEYEXPIRED 1409325681
W: Failed to fetch http://deb.torproject.org/torproject.org/dists/stable/Release
W: Some index files failed to download. They have been ignored, or old ones used instead.
Instructions how to update the operating system ( Security Guide - Whonix ) have been extended:
Documentation for updating ( https://www.whonix.org/wiki/Security_Guide#Updates ) has been extended: