I recently added clamav to my Ubuntu system. The next time I received a notice from the software center to update my system there were some updates from clamav. When trying to update this error message was returned:
The action would require the installation of packages from not authenticated sources.
What this means is that Ubuntu was unable to find a public key to authenticate against the code being requested making it an untrustworthy source.
Is this solution for you?
To determine if this solution will work for you fire up a terminal (“Applications > Accessories > Terminal”) and run:
sudo apt-get update
Among the messages outputted on the terminal, you will be looking for a message at the end with similar wording:
W: GPG error: http://ppa.launchpad.net natty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8AB767895ADC2037
Notice the hexadecimal number at the end (8AB767895ADC2037), this is the public key that is missing.
To fix this I ran the following command:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 8AB767895ADC2037
NOTICE: Your key(s) will most likely be different from mine. Use your key(s) not mine.
As with most problems in life, this one can be solved through Googling. Here are the resources that I used: