The Fedora Project recently re-signed all of its packages with a new key. Background details regarding the key change are found here. Contact the release engineering team via IRC in #fedora-devel (irc.freenode.org) or via email to firstname.lastname@example.org for more information.
We are in the final stages of testing on new builds of the fedora-release, PackageKit, gnome-packagekit and unique (new dependency for gnome-packagekit) packages. After we complete this testing, we will push updates to their appropriate locations and make them available for download. Users who perform a system update will receive these packages.
Once these initial packages are installed, the next update attempt will point to the new repositories utilizing the new signing key. Users must accept the new signing key the first time updates are downloaded. PackageKit prompts you whether or not to import the signing key. To accept the key, press y at the prompt.