How do I open a ".sig" file
 

I have a file called "hspell.tar.gz.sig" what app can I use to open it?

It probably shouldn't have the .sig extension.

.tar files are archived files
.gz files are gzipped (like windows zip) files

You can open your file by typing

tar xzf hspell.tar.gz.sig

on the commandline, if you have tar installed (which you almost certainly will).

Hey, isn't .sig the signature file that uses MD5 checksum? In that case, you need to use gpg to import the public key of the person/authority who has signed and use it to verify hspell.tar.gz . Read the gpg manual for more...

Good point. If it's an md5 checksum, you should have the other file (w/out the .sig) there as well and it can be opened as described above.

You don't need to use gpg to check md5 sums, just type md5sum hspell.tar.gz to see its md5sum and check that it is the same as the value in the .sig file (which can be viewed by 'cat hspell.tar.gz.sig'

Yeah, but it depends whether you have just a 128 bit MD5 checksum or a PGP/GPG signature in your hands. For the former, md5sum is fine but for the latter, I think you need gpg. Correct me if I'm wrong;)