Find key that signed a package?

[Frank Murphy]

How do I find\know the exact key that signed a package?

Have tried "rpm -Kv foo.rpm"
but it just bring backs back:
Header SHA1 digest: OK (yadayada)
     MD5 digest: OK (yadayada)

But what I'm looking for is to end up like:
https://fedoraproject.org/keys

Currently used keys
RPM-GPG-KEY-fedora-13-primary

       pub   4096R/E8E40FDE 2010-01-19
       Key fingerprint = 8E5F 73FF 2A18 1765 4D35  8FCA 7EDC 6AD6 E8E4 0FDE
uid                  Fedora (13) <fedora at fedoraproject.org>

-- 
Regards,

Frank Murphy
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Friend of Fedora