Debian Etch: problems with unauthenticated packages

I upgraded Sarge (which I upgraded from Woody) to Etch using
apt-get dist-upgrade.

I also downloaded some packages with apt-get -dy install ...
and put them in a mirror with apt-move update.

Now my mirror appears useless as it is ignored when I do
apt-get update.

Earlier the system complained of unauthenticated packages.
At some point it stopped complaining but silently ignores
packages in the mirror!

Could anyone tell me how to get the contents of my mirror
authenticated using GPG so as to satisfy apt?