The following packages cannot be authenticated

[Jason Hsu <jhsu802701@jasonhsu.com>]

I'm working on the development of the next version of Swift Linux (http://www.swiftlinux.org , http://github.com/swiftlinux).  I'm now finding that when I try to add packages in a script with the "apt-get install -y <package>" command, I get an error messages "WARNING: The following packages cannot be authenticated!" and "There are problems and -y was used without --force-yes".

I know that I could add packages manually, but the two reasons not to are:
1.  I'm using these "apt-get install y <package>" commands in scripts.
2.  I know that I can use the --force-yes option, but is this actually safe?

A Google search yields more information than I can understand, but it sounds like my authentication key is not up-to-date.  How do I resolve this matter WITHOUT throwing security under the bus?

-- 
Jason Hsu <jhsu802701@jasonhsu.com>