I've checked several forums and sites for trying to fix this issue. This issue has been happening for the last three days. I'm a bit of a newbie to Linux but I think I've managed to narrow down where the issue is.
I've recently been getting an error like this
E: GPG error: http://arcgive.canonical.com raring Release: The following signatures were invalid: NODATA 1 NODATA 2
every time with "sudo apt-get update". Also been getting a red warning triangle warning me update information is outdated and may be caused by network issues or outdated repository. After some intense google searching a few people have had a similar issue but it seemed to be with 13.03.
From what I gather, I am missing GPG keys that is causing the issue (tried resetting them to default in the settings but no luck). There was a link to what appeared to be the PGP key for raring Release but I can't make heads or tails of what to do with it: http://archive.canonical.com/dists/raring/Release.gpg
I am really hoping someone here may know what to do.
Thank you for your help