where to know about .sign format?

[mines2s]

hi,
i am new to .sign format in linux i tried the google to find about it but i was not successful ,plz can some one tell me how to decompress the bz2.sign or
tell me aout the link to read about it.

[scientica]

I'm not sure if .sign is just one format, I think it's a de facto standad name for a signature file, it could contain some PGP/GPG sign key, some hashes (like MD5).
Simply it's a file containing some meta info on some file (generally if the file is something.bz2.sign it's the sign file for something.bz2).
it could also be a signature file with a signatur like bellow: