It seems the OBS Security key (keyid 79EAFD54) on keys.gnupg.net has expired (2011-Apr-2). Would it be possible for someone to update it?
I know an updated key has been generated (which expires 2013) as it can be found here:
Further details can be found via:
The Openvas-distro April 2011 Archive by thread
Basically the issue came to light when following instructions:
OpenVAS - OpenVAS - Open Vulnerability Assessment System Community Site