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 v1.4.9 (GNU/Linux) iEYEABECAAYFAkn9yXcACgkQqesEzEdeXBF3mwCdFaDHmNjnABCdwNrLQV6sjhIy VCcAn08PwJOjntrge3ULXBpDjlg60fMg =cw97 -----END PGP SIGNATURE-----
You can save this signature in a text file (e.g. boost-1.39.0-i486-1gds.tgz.asc) in the same directory where the package file (boost-1.39.0-i486-1gds.tgz) resides and you can verify it by issuing the following command:
gpg --verify boost-1.39.0-i486-1gds.tgz.asc
NOTE: You need to import the public key of SlackPack first:
gpg --import KEY