Short tip: List imported RPM GPG keys
Sometimes it is sufficient to know which RPM GPG-Keys have been imported. You can get this information with the following command:
1# rpm -qa --qf '%{VERSION}-%{RELEASE} %{SUMMARY}\n' gpg-pubkey*
2c105b9de-4e0fd3a3 gpg(CentOS-6 Key (CentOS 6 Official Signing Key) <centos-6-key@centos.org>)
30608b895-4bd22942 gpg(EPEL (6) <epel@fedoraproject.org>)
4863a853d-4f55f54d gpg(Spacewalk <spacewalk-devel@redhat.com>)
566fd4949-4803fe57 gpg(VMware, Inc. -- Linux Packaging Key -- <linux-packages@vmware.com>)
The command lists all packages that are starting with the string gpg-pubkey - for each package the version, release and a summary is displayed. In the summary you might find a useful hint about the appropriate YUM repository.