This is the package signature as generated by The GnuPG. This signature identifies the party that created the package. By verifying it you are sure that the package coming from a trustworty person or organization.
Here is the package signature:
-----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEABECAAYFAlAySyAACgkQqesEzEdeXBGbvQCeMxMvBoIsUmmciKMvAfU5GmnE d1gAn3SasouRdd40k/KP41DBOCm/D6IW =qsKe -----END PGP SIGNATURE-----
You can save this signature in a text file (e.g. graphviz-2.28.0-i486-1gds.txz.asc) in the same directory where the package file (graphviz-2.28.0-i486-1gds.txz) resides and you can verify it by issuing the following command:
gpg --verify graphviz-2.28.0-i486-1gds.txz.asc
NOTE: You need to import the public key of SlackPack first:
gpg --import KEY