FedoraCore2 up2date: package zip-2.3-26.2 does't have a valid GPG signature

[videoproducer at att.net]

I completed a search of Fedora-list archive and found no match. Assistance in 
finding a solution to this problem is welcome. Perhaps an URL or short response 
to point me toward the solution?

-- start test of three error message windows --
Fedora 2 Core upgrade of 10-Nov-2004:
Up2date - Package Retreval

Retreiving: zip-2.3-26.2.i386.rpm a file compression packaging utility 
compatible with PKZIP.

The zip program is a compression and file packaging utility. Zip is analogous to 
a combonation of the UNIX tar and compress commands and is compatible with 
PKZIP, a compression and file packing program for MS-DOS systems.

QUESTION: The package zip-2.3-26.2 does not have a valid GPG signature.
It has been tampered with or corrupted. Continue?

-- end test of three error message windows --
Justin Swain