OK, So because of that I'm guessing you need an entry like:
gpg: key cxdfddey: "Local Repository Key"
blah blah blah.
So following the adage -- teach a man to fish ...
Googling "how to authenticate a local repository Debian"
(leave off the quotes in the search box.)
Returns, e.g.:
http://forums.debian.net/viewtopic.php?f=16&t=60560
http://www.kanotix.com/PNphpBB2-viewtopic-t-18541.html
https://wiki.debian.org/SecureApt
http://www.eyrie.org/~eagle/notes/debian/private-repo.html
http://linuxconfig.org/easy-way-to-create-a-debian-package-and-local-package-repository
http://ubuntuforums.org/archive/index.php/t-1664281.html
http://www.eucalyptus.com/download/euca2ools/1.3.1/debian
http://serverfault.com/questions/111885/securely-restrict-access-to-a-private-debian-repository
http://blog.jonliv.es/2011/04/26/creating-your-own-signed-apt-repository-and-debian-packages/
Another way is to just cut'n'paste the error/warning/ message into
google.