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) iEYEABECAAYFAlCn+bsACgkQqesEzEdeXBGbkwCgkc++IIL4V0SLuaK/TP3Z7eoz incAn1A9Evru/U7Tum7CjxiSwcv4FNH6 =d6wP -----END PGP SIGNATURE-----
You can save this signature in a text file (e.g. libreoffice-helppack-bg-3.5.7-i686-1gds.txz.asc) in the same directory where the package file (libreoffice-helppack-bg-3.5.7-i686-1gds.txz) resides and you can verify it by issuing the following command:
gpg --verify libreoffice-helppack-bg-3.5.7-i686-1gds.txz.asc
NOTE: You need to import the public key of SlackPack first:
gpg --import KEY