When running 'apt-get update', I encountered time out issues and this error:
W: GPG error: http://security.debian.org testing/updates Release:
The following signatures couldn't be verified
because the public key is not available: NO_PUBKEY A70DAF536070D3A1
A search came up with a solution at
FreeSpamFilter.org Forum Site. The site recommended the following commands (where the key is the
one from the above error message):
gpg --keyserver subkeys.pgp.net --recv-keys A70DAF536070D3A1
gpg --export A70DAF536070D3A1 | apt-key add -
Before running 'apt-get update' again, based upon comments from
Ubuntu Forums,
I also ran the following two commands:
apt-get clean
apt-get check
The update process now runs cleanly.